text:
#if defined(__GNUC__) || defined(__clang__)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wcast-qual"
#pragma GCC diagnostic ignored "-Wsign-conversion"
#pragma GCC diagnostic ignored "-Wsign-conversion"
#pragma GCC diagnostic ignored "-Wimplicit-int-float-conversion"
#pragma GCC diagnostic ignored "-Wcast-align"
#endif

#if defined(IMG_ONLY_JPEG) || defined(IMG_ONLY_PNG) ||                         \
    defined(IMG_ONLY_BMP) || defined(IMG_ONLY_TGA) || defined(IMG_ONLY_GIF) || \
    defined(IMG_ONLY_PSD) || defined(IMG_ONLY_HDR) || defined(IMG_ONLY_PIC) || \
    defined(IMG_ONLY_PNM) || defined(IMG_ONLY_ZLIB)
#ifndef IMG_ONLY_JPEG
#define IMG_NO_JPEG
#endif
#ifndef IMG_ONLY_PNG
#define IMG_NO_PNG
#endif
#ifndef IMG_ONLY_BMP
#define IMG_NO_BMP
#endif
#ifndef IMG_ONLY_PSD
#define IMG_NO_PSD
#endif
#ifndef IMG_ONLY_TGA
#define IMG_NO_TGA
#endif
#ifndef IMG_ONLY_GIF
#define IMG_NO_GIF
#endif
#ifndef IMG_ONLY_HDR
#define IMG_NO_HDR
#endif
#ifndef IMG_ONLY_PIC
#define IMG_NO_PIC
#endif
#ifndef IMG_ONLY_PNM
#define IMG_NO_PNM
#endif
#endif

#if defined(IMG_NO_PNG) && !defined(IMG_SUPPORT_ZLIB) && !defined(IMG_NO_ZLIB)
#define IMG_NO_ZLIB
#endif

#include <stdarg.h>
#include <stddef.h>  // ptrdiff_t on osx
#include <stdlib.h>
#include <string.h>
#include <limits.h>

#if !defined(IMG_NO_LINEAR) || !defined(IMG_NO_HDR)
#include <math.h>  // ldexp, pow
#endif

#ifndef IMG_NO_STDIO
#include <stdio.h>
#endif

#ifndef IMG_ASSERT
#include <assert.h>
#define IMG_ASSERT(x) assert(x)
#endif

#ifdef __cplusplus
#define IMG_EXTERN extern "C"
#else
#define IMG_EXTERN extern
#endif

#ifndef _MSC_VER
#ifdef __cplusplus
#define img_inline inline
#else
#define img_inline
#endif
#else
#define img_inline __forceinline
#endif

#ifndef IMG_NO_THREAD_LOCALS
#if defined(__cplusplus) && __cplusplus >= 201103L
#define IMG_THREAD_LOCAL thread_local
#elif defined(__GNUC__) && __GNUC__ < 5
#define IMG_THREAD_LOCAL __thread
#elif defined(_MSC_VER)
#define IMG_THREAD_LOCAL __declspec(thread)
#elif defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L && \
    !defined(__STDC_NO_THREADS__)
#define IMG_THREAD_LOCAL _Thread_local
#endif

#ifndef IMG_THREAD_LOCAL
#if defined(__GNUC__)
#define IMG_THREAD_LOCAL __thread
#endif
#endif
#endif

#ifdef _MSC_VER
typedef unsigned short img__uint16;
typedef signed short img__int16;
typedef unsigned int img__uint32;
typedef signed int img__int32;
#else
#include <stdint.h>
typedef uint16_t img__uint16;
typedef int16_t img__int16;
typedef uint32_t img__uint32;
typedef int32_t img__int32;
#endif

// should produce compiler error if size is wrong
typedef unsigned char validate_uint32[sizeof(img__uint32) == 4 ? 1 : -1];

#ifdef _MSC_VER
#define IMG_NOTUSED(v) (void)(v)
#else
#define IMG_NOTUSED(v) (void)sizeof(v)
#endif

#ifdef _MSC_VER
#define IMG_HAS_LROTL
#endif

#ifdef IMG_HAS_LROTL
#define img_lrot(x, y) _lrotl(x, y)
#else
#define img_lrot(x, y) (((x) << (y)) | ((x) >> (32 - (y))))
#endif

#if defined(IMG_MALLOC) && defined(IMG_FREE) && \
    (defined(IMG_REALLOC) || defined(IMG_REALLOC_SIZED))
// ok
#elif !defined(IMG_MALLOC) && !defined(IMG_FREE) && !defined(IMG_REALLOC) && \
    !defined(IMG_REALLOC_SIZED)
// ok
#else
#error \
    "Must define all or none of IMG_MALLOC, IMG_FREE, and IMG_REALLOC (or IMG_REALLOC_SIZED)."
#endif

#ifndef IMG_MALLOC
#define IMG_MALLOC(sz) malloc(sz)
#define IMG_REALLOC(p, newsz) realloc(p, newsz)
#define IMG_FREE(p) free(p)
#endif

#ifndef IMG_REALLOC_SIZED
#define IMG_REALLOC_SIZED(p, oldsz, newsz) IMG_REALLOC(p, newsz)
#endif

// x86/x64 detection
#if defined(__x86_64__) || defined(_M_X64)
#define IMG__X64_TARGET
#elif defined(__i386) || defined(_M_IX86)
#define IMG__X86_TARGET
#endif

#if defined(__GNUC__) && defined(IMG__X86_TARGET) && !defined(__SSE2__) && \
    !defined(IMG_NO_SIMD)
// gcc doesn't support sse2 intrinsics unless you compile with -msse2,
// which in turn means it gets to use SSE2 everywhere. This is unfortunate,
// but previous attempts to provide the SSE2 functions with runtime
// detection caused numerous issues. The way architecture extensions are
// exposed in GCC/Clang is, sadly, not really suited for one-file libs.
// New behavior: if compiled with -msse2, we use SSE2 without any
// detection; if not, we don't use it at all.
#define IMG_NO_SIMD
#endif

#if defined(__MINGW32__) && defined(IMG__X86_TARGET) && \
    !defined(IMG_MINGW_ENABLE_SSE2) && !defined(IMG_NO_SIMD)
// Note that __MINGW32__ doesn't actually mean 32-bit, so we have to avoid
// IMG__X64_TARGET
//
// 32-bit MinGW wants ESP to be 16-byte aligned, but this is not in the
// Windows ABI and VC++ as well as Windows DLLs don't maintain that invariant.
// As a result, enabling SSE2 on 32-bit MinGW is dangerous when not
// simultaneously enabling "-mstackrealign".
//
// See https://github.com/nothings/stb/issues/81 for more information.
//
// So default to no SSE2 on 32-bit MinGW. If you've read this far and added
// -mstackrealign to your build settings, feel free to #define
// IMG_MINGW_ENABLE_SSE2.
#define IMG_NO_SIMD
#endif

#if !defined(IMG_NO_SIMD) && \
    (defined(IMG__X86_TARGET) || defined(IMG__X64_TARGET))
#define IMG_SSE2
#include <emmintrin.h>

#ifdef _MSC_VER

#if _MSC_VER >= 1400  // not VC6
#include <intrin.h>   // __cpuid
static int
img__cpuid3(void) {
  int info[4];
  __cpuid(info, 1);
  return info[3];
}
#else
static int
img__cpuid3(void) {
  int res;
  __asm {
      mov  eax,1
      cpuid
      mov  res,edx
  }
  return res;
}
#endif

#define IMG_SIMD_ALIGN(type, name) __declspec(align(16)) type name

#if !defined(IMG_NO_JPEG) && defined(IMG_SSE2)
static int
img__sse2_available(void) {
  int info3 = img__cpuid3();
  return ((info3 >> 26) & 1) != 0;
}
#endif

#else  // assume GCC-style if not VC++
#define IMG_SIMD_ALIGN(type, name) type name __attribute__((aligned(16)))

#if !defined(IMG_NO_JPEG) && defined(IMG_SSE2)
static int
img__sse2_available(void) {
  // If we're even attempting to compile this on GCC/Clang, that means
  // -msse2 is on, which means the compiler is allowed to use SSE2
  // instructions at will, and so are we.
  return 1;
}
#endif

#endif
#endif

// ARM NEON
#if defined(IMG_NO_SIMD) && defined(IMG_NEON)
#undef IMG_NEON
#endif

#ifdef IMG_NEON
#include <arm_neon.h>
// assume GCC or Clang on ARM targets
#define IMG_SIMD_ALIGN(type, name) type name __attribute__((aligned(16)))
#endif

#ifndef IMG_SIMD_ALIGN
#define IMG_SIMD_ALIGN(type, name) type name
#endif

#ifndef IMG_MAX_DIMENSIONS
#define IMG_MAX_DIMENSIONS (1 << 24)
#endif

///////////////////////////////////////////////
//
//  img__context struct and start_xxx functions

// img__context structure is our basic context used by all images, so it
// contains all the IO context, plus some basic image information
typedef struct {
  img__uint32 img_x, img_y;
  int img_n, img_out_n;

  img_io_callbacks io;
  void *io_user_data;

  int read_from_callbacks;
  int buflen;
  img_uc buffer_start[128];
  int callback_already_read;

  img_uc *img_buffer, *img_buffer_end;
  img_uc *img_buffer_original, *img_buffer_original_end;
} img__context;

static void
img__refill_buffer(img__context *s);

// initialize a memory-decode context
static void
img__start_mem(img__context *s, img_uc const *buffer, int len) {
  s->io.read = NULL;
  s->read_from_callbacks = 0;
  s->callback_already_read = 0;
  s->img_buffer = s->img_buffer_original = (img_uc *)buffer;
  s->img_buffer_end = s->img_buffer_original_end = (img_uc *)buffer + len;
}

// initialize a callback-based context
static void
img__start_callbacks(img__context *s, img_io_callbacks *c, void *user) {
  s->io = *c;
  s->io_user_data = user;
  s->buflen = sizeof(s->buffer_start);
  s->read_from_callbacks = 1;
  s->callback_already_read = 0;
  s->img_buffer = s->img_buffer_original = s->buffer_start;
  img__refill_buffer(s);
  s->img_buffer_original_end = s->img_buffer_end;
}

#ifndef IMG_NO_STDIO

static int
img__stdio_read(void *user, char *data, int size) {
  return (int)fread(data, 1, size, (FILE *)user);
}

static void
img__stdio_skip(void *user, int n) {
  int ch;
  fseek((FILE *)user, n, SEEK_CUR);
  ch = fgetc((FILE *)user); /* have to read a byte to reset feof()'s flag */
  if (ch != EOF) {
    ungetc(ch, (FILE *)user); /* push byte back onto stream if valid. */
  }
}

static int
img__stdio_eof(void *user) {
  return feof((FILE *)user) || ferror((FILE *)user);
}

static img_io_callbacks img__stdio_callbacks = {
    img__stdio_read,
    img__stdio_skip,
    img__stdio_eof,
};

static void
img__start_file(img__context *s, FILE *f) {
  img__start_callbacks(s, &img__stdio_callbacks, (void *)f);
}

// static void stop_file(img__context *s) { }

#endif  // !IMG_NO_STDIO

static void
img__rewind(img__context *s) {
  // conceptually rewind SHOULD rewind to the beginning of the stream,
  // but we just rewind to the beginning of the initial buffer, because
  // we only use it after doing 'test', which only ever looks at at most 92
  // bytes
  s->img_buffer = s->img_buffer_original;
  s->img_buffer_end = s->img_buffer_original_end;
}

enum { IMG_ORDER_RGB, IMG_ORDER_BGR };

typedef struct {
  int bits_per_channel;
  int num_channels;
  int channel_order;
} img__result_info;

#ifndef IMG_NO_JPEG
static int
img__jpeg_test(img__context *s);
static void *
img__jpeg_load(img__context *s, int *x, int *y, int *comp, int req_comp,
               img__result_info *ri);
static int
img__jpeg_info(img__context *s, int *x, int *y, int *comp);
#endif

#ifndef IMG_NO_PNG
static int
img__png_test(img__context *s);
static void *
img__png_load(img__context *s, int *x, int *y, int *comp, int req_comp,
              img__result_info *ri);
static int
img__png_info(img__context *s, int *x, int *y, int *comp);
static int
img__png_is16(img__context *s);
#endif

#ifndef IMG_NO_BMP
static int
img__bmp_test(img__context *s);
static void *
img__bmp_load(img__context *s, int *x, int *y, int *comp, int req_comp,
              img__result_info *ri);
static int
img__bmp_info(img__context *s, int *x, int *y, int *comp);
#endif

#ifndef IMG_NO_TGA
static int
img__tga_test(img__context *s);
static void *
img__tga_load(img__context *s, int *x, int *y, int *comp, int req_comp,
              img__result_info *ri);
static int
img__tga_info(img__context *s, int *x, int *y, int *comp);
#endif

#ifndef IMG_NO_PSD
static int
img__psd_test(img__context *s);
static void *
img__psd_load(img__context *s, int *x, int *y, int *comp, int req_comp,
              img__result_info *ri, int bpc);
static int
img__psd_info(img__context *s, int *x, int *y, int *comp);
static int
img__psd_is16(img__context *s);
#endif

#ifndef IMG_NO_HDR
static int
img__hdr_test(img__context *s);
static float *
img__hdr_load(img__context *s, int *x, int *y, int *comp, int req_comp,
              img__result_info *ri);
static int
img__hdr_info(img__context *s, int *x, int *y, int *comp);
#endif

#ifndef IMG_NO_PIC
static int
img__pic_test(img__context *s);
static void *
img__pic_load(img__context *s, int *x, int *y, int *comp, int req_comp,
              img__result_info *ri);
static int
img__pic_info(img__context *s, int *x, int *y, int *comp);
#endif

#ifndef IMG_NO_GIF
static int
img__gif_test(img__context *s);
static void *
img__gif_load(img__context *s, int *x, int *y, int *comp, int req_comp,
              img__result_info *ri);
static void *
img__load_gif_main(img__context *s, int **delays, int *x, int *y, int *z,
                   int *comp, int req_comp);
static int
img__gif_info(img__context *s, int *x, int *y, int *comp);
#endif

#ifndef IMG_NO_PNM
static int
img__pnm_test(img__context *s);
static void *
img__pnm_load(img__context *s, int *x, int *y, int *comp, int req_comp,
              img__result_info *ri);
static int
img__pnm_info(img__context *s, int *x, int *y, int *comp);
#endif

static
#ifdef IMG_THREAD_LOCAL
    IMG_THREAD_LOCAL
#endif
    const char *img__g_failure_reason;

static const char *
img_failure_reason(void) {
  return img__g_failure_reason;
}

#ifndef IMG_NO_FAILURE_STRINGS
static int
img__err(const char *str) {
  img__g_failure_reason = str;
  return 0;
}
#endif

static void *
img__malloc(size_t size) {
  return IMG_MALLOC(size);
}

// stb_image uses ints pervasively, including for offset calculations.
// therefore the largest decoded image size we can support with the
// current code, even on 64-bit targets, is INT_MAX. this is not a
// significant limitation for the intended use case.
//
// we do, however, need to make sure our size calculations don't
// overflow. hence a few helper functions for size calculations that
// multiply integers together, making sure that they're non-negative
// and no overflow occurs.

// return 1 if the sum is valid, 0 on overflow.
// negative terms are considered invalid.
static int
img__addsizes_valid(int a, int b) {
  if (b < 0) return 0;
  // now 0 <= b <= INT_MAX, hence also
  // 0 <= INT_MAX - b <= INTMAX.
  // And "a + b <= INT_MAX" (which might overflow) is the
  // same as a <= INT_MAX - b (no overflow)
  return a <= INT_MAX - b;
}

// returns 1 if the product is valid, 0 on overflow.
// negative factors are considered invalid.
static int
img__mul2sizes_valid(int a, int b) {
  if (a < 0 || b < 0) return 0;
  if (b == 0) return 1;  // mul-by-0 is always safe
  // portable way to check for no overflows in a*b
  return a <= INT_MAX / b;
}

#if !defined(IMG_NO_JPEG) || !defined(IMG_NO_PNG) || !defined(IMG_NO_TGA) || \
    !defined(IMG_NO_HDR)
// returns 1 if "a*b + add" has no negative terms/factors and doesn't overflow
static int
img__mad2sizes_valid(int a, int b, int add) {
  return img__mul2sizes_valid(a, b) && img__addsizes_valid(a * b, add);
}
#endif

// returns 1 if "a*b*c + add" has no negative terms/factors and doesn't overflow
static int
img__mad3sizes_valid(int a, int b, int c, int add) {
  return img__mul2sizes_valid(a, b) && img__mul2sizes_valid(a * b, c) &&
         img__addsizes_valid(a * b * c, add);
}

// returns 1 if "a*b*c*d + add" has no negative terms/factors and doesn't
// overflow
#if !defined(IMG_NO_LINEAR) || !defined(IMG_NO_HDR)
static int
img__mad4sizes_valid(int a, int b, int c, int d, int add) {
  return img__mul2sizes_valid(a, b) && img__mul2sizes_valid(a * b, c) &&
         img__mul2sizes_valid(a * b * c, d) &&
         img__addsizes_valid(a * b * c * d, add);
}
#endif

#if !defined(IMG_NO_JPEG) || !defined(IMG_NO_PNG) || !defined(IMG_NO_TGA) || \
    !defined(IMG_NO_HDR)
// mallocs with size overflow checking
static void *
img__malloc_mad2(int a, int b, int add) {
  if (!img__mad2sizes_valid(a, b, add)) return NULL;
  return img__malloc(a * b + add);
}
#endif

static void *
img__malloc_mad3(int a, int b, int c, int add) {
  if (!img__mad3sizes_valid(a, b, c, add)) return NULL;
  return img__malloc(a * b * c + add);
}

#if !defined(IMG_NO_LINEAR) || !defined(IMG_NO_HDR)
static void *
img__malloc_mad4(int a, int b, int c, int d, int add) {
  if (!img__mad4sizes_valid(a, b, c, d, add)) return NULL;
  return img__malloc(a * b * c * d + add);
}
#endif

// img__err - error
// img__errpf - error returning pointer to float
// img__errpuc - error returning pointer to unsigned char

#ifdef IMG_NO_FAILURE_STRINGS
#define img__err(x, y) 0
#elif defined(IMG_FAILURE_USERMSG)
#define img__err(x, y) img__err(y)
#else
#define img__err(x, y) img__err(x)
#endif

#define img__errpf(x, y) ((float *)(size_t)(img__err(x, y) ? NULL : NULL))
#define img__errpuc(x, y) \
  ((unsigned char *)(size_t)(img__err(x, y) ? NULL : NULL))

static void
img_image_free(void *retval_from_img_load) {
  IMG_FREE(retval_from_img_load);
}

#ifndef IMG_NO_LINEAR
static float *
img__ldr_to_hdr(img_uc *data, int x, int y, int comp);
#endif

#ifndef IMG_NO_HDR
static img_uc *
img__hdr_to_ldr(float *data, int x, int y, int comp);
#endif

static int img__vertically_flip_on_load_global = 0;

static void
img_set_flip_vertically_on_load(int flag_true_if_should_flip) {
  img__vertically_flip_on_load_global = flag_true_if_should_flip;
}

#ifndef IMG_THREAD_LOCAL
#define img__vertically_flip_on_load img__vertically_flip_on_load_global
#else
static IMG_THREAD_LOCAL int img__vertically_flip_on_load_local,
    img__vertically_flip_on_load_set;

static void
img_set_flip_vertically_on_load_thread(int flag_true_if_should_flip) {
  img__vertically_flip_on_load_local = flag_true_if_should_flip;
  img__vertically_flip_on_load_set = 1;
}

#define img__vertically_flip_on_load                                     \
  (img__vertically_flip_on_load_set ? img__vertically_flip_on_load_local \
                                    : img__vertically_flip_on_load_global)
#endif  // IMG_THREAD_LOCAL

static void *
img__load_main(img__context *s, int *x, int *y, int *comp, int req_comp,
               img__result_info *ri, int bpc) {
  memset(ri, 0,
         sizeof(*ri));  // make sure it's initialized if we add new fields
  ri->bits_per_channel =
      8;  // default is 8 so most paths don't have to be changed
  ri->channel_order =
      IMG_ORDER_RGB;  // all current input & output are this, but this is here
                      // so we can add BGR order
  ri->num_channels = 0;

#ifndef IMG_NO_JPEG
  if (img__jpeg_test(s)) return img__jpeg_load(s, x, y, comp, req_comp, ri);
#endif
#ifndef IMG_NO_PNG
  if (img__png_test(s)) return img__png_load(s, x, y, comp, req_comp, ri);
#endif
#ifndef IMG_NO_BMP
  if (img__bmp_test(s)) return img__bmp_load(s, x, y, comp, req_comp, ri);
#endif
#ifndef IMG_NO_GIF
  if (img__gif_test(s)) return img__gif_load(s, x, y, comp, req_comp, ri);
#endif
#ifndef IMG_NO_PSD
  if (img__psd_test(s)) return img__psd_load(s, x, y, comp, req_comp, ri, bpc);
#else
  IMG_NOTUSED(bpc);
#endif
#ifndef IMG_NO_PIC
  if (img__pic_test(s)) return img__pic_load(s, x, y, comp, req_comp, ri);
#endif
#ifndef IMG_NO_PNM
  if (img__pnm_test(s)) return img__pnm_load(s, x, y, comp, req_comp, ri);
#endif

#ifndef IMG_NO_HDR
  if (img__hdr_test(s)) {
    float *hdr = img__hdr_load(s, x, y, comp, req_comp, ri);
    return img__hdr_to_ldr(hdr, *x, *y, req_comp ? req_comp : *comp);
  }
#endif

#ifndef IMG_NO_TGA
  // test tga last because it's a crappy test!
  if (img__tga_test(s)) return img__tga_load(s, x, y, comp, req_comp, ri);
#endif

  return img__errpuc("unknown image type",
                     "Image not of any known type, or corrupt");
}

static img_uc *
img__convert_16_to_8(img__uint16 *orig, int w, int h, int channels) {
  int i;
  int img_len = w * h * channels;
  img_uc *reduced;

  reduced = (img_uc *)img__malloc(img_len);
  if (reduced == NULL) return img__errpuc("outofmem", "Out of memory");

  for (i = 0; i < img_len; ++i)
    reduced[i] =
        (img_uc)((orig[i] >> 8) & 0xFF);  // top half of each byte is sufficient
                                          // approx of 16->8 bit scaling

  IMG_FREE(orig);
  return reduced;
}

static img__uint16 *
img__convert_8_to_16(img_uc *orig, int w, int h, int channels) {
  int i;
  int img_len = w * h * channels;
  img__uint16 *enlarged;

  enlarged = (img__uint16 *)img__malloc(img_len * 2);
  if (enlarged == NULL)
    return (img__uint16 *)img__errpuc("outofmem", "Out of memory");

  for (i = 0; i < img_len; ++i)
    enlarged[i] = (img__uint16)(
        (orig[i] << 8) +
        orig[i]);  // replicate to high and low byte, maps 0->0, 255->0xffff

  IMG_FREE(orig);
  return enlarged;
}

static void
img__vertical_flip(void *image, int w, int h, int bytes_per_pixel) {
  int row;
  size_t bytes_per_row = (size_t)w * bytes_per_pixel;
  img_uc temp[2048];
  img_uc *bytes = (img_uc *)image;

  for (row = 0; row < (h >> 1); row++) {
    img_uc *row0 = bytes + row * bytes_per_row;
    img_uc *row1 = bytes + (h - row - 1) * bytes_per_row;
    // swap row0 with row1
    size_t bytes_left = bytes_per_row;
    while (bytes_left) {
      size_t bytes_copy =
          (bytes_left < sizeof(temp)) ? bytes_left : sizeof(temp);
      memcpy(temp, row0, bytes_copy);
      memcpy(row0, row1, bytes_copy);
      memcpy(row1, temp, bytes_copy);
      row0 += bytes_copy;
      row1 += bytes_copy;
      bytes_left -= bytes_copy;
    }
  }
}

#ifndef IMG_NO_GIF
static void
img__vertical_flip_slices(void *image, int w, int h, int z,
                          int bytes_per_pixel) {
  int slice;
  int slice_size = w * h * bytes_per_pixel;

  img_uc *bytes = (img_uc *)image;
  for (slice = 0; slice < z; ++slice) {
    img__vertical_flip(bytes, w, h, bytes_per_pixel);
    bytes += slice_size;
  }
}
#endif

static unsigned char *
img__load_and_postprocess_8bit(img__context *s, int *x, int *y, int *comp,
                               int req_comp) {
  img__result_info ri;
  void *result = img__load_main(s, x, y, comp, req_comp, &ri, 8);

  if (result == NULL) return NULL;

  // it is the responsibility of the loaders to make sure we get either 8 or 16
  // bit.
  IMG_ASSERT(ri.bits_per_channel == 8 || ri.bits_per_channel == 16);

  if (ri.bits_per_channel != 8) {
    result = img__convert_16_to_8((img__uint16 *)result, *x, *y,
                                  req_comp == 0 ? *comp : req_comp);
    ri.bits_per_channel = 8;
  }

  // @TODO: move img__convert_format to here

  if (img__vertically_flip_on_load) {
    int channels = req_comp ? req_comp : *comp;
    img__vertical_flip(result, *x, *y, channels * sizeof(img_uc));
  }

  return (unsigned char *)result;
}

static img__uint16 *
img__load_and_postprocess_16bit(img__context *s, int *x, int *y, int *comp,
                                int req_comp) {
  img__result_info ri;
  void *result = img__load_main(s, x, y, comp, req_comp, &ri, 16);

  if (result == NULL) return NULL;

  // it is the responsibility of the loaders to make sure we get either 8 or 16
  // bit.
  IMG_ASSERT(ri.bits_per_channel == 8 || ri.bits_per_channel == 16);

  if (ri.bits_per_channel != 16) {
    result = img__convert_8_to_16((img_uc *)result, *x, *y,
                                  req_comp == 0 ? *comp : req_comp);
    ri.bits_per_channel = 16;
  }

  // @TODO: move img__convert_format16 to here
  // @TODO: special case RGB-to-Y (and RGBA-to-YA) for 8-bit-to-16-bit case to
  // keep more precision

  if (img__vertically_flip_on_load) {
    int channels = req_comp ? req_comp : *comp;
    img__vertical_flip(result, *x, *y, channels * sizeof(img__uint16));
  }

  return (img__uint16 *)result;
}

#if !defined(IMG_NO_HDR) && !defined(IMG_NO_LINEAR)
static void
img__float_postprocess(float *result, int *x, int *y, int *comp, int req_comp) {
  if (img__vertically_flip_on_load && result != NULL) {
    int channels = req_comp ? req_comp : *comp;
    img__vertical_flip(result, *x, *y, channels * sizeof(float));
  }
}
#endif

#ifndef IMG_NO_STDIO

#if defined(_MSC_VER) && defined(IMG_WINDOWS_UTF8)
IMG_EXTERN __declspec(dllimport) int __stdcall MultiByteToWideChar(
    unsigned int cp, unsigned long flags, const char *str, int cbmb,
    wchar_t *widestr, int cchwide);
IMG_EXTERN __declspec(dllimport) int __stdcall WideCharToMultiByte(
    unsigned int cp, unsigned long flags, const wchar_t *widestr, int cchwide,
    char *str, int cbmb, const char *defchar, int *used_default);
#endif

#if defined(_MSC_VER) && defined(IMG_WINDOWS_UTF8)
static int
img_convert_wchar_to_utf8(char *buffer, size_t bufferlen,
                          const wchar_t *input) {
  return WideCharToMultiByte(65001 /* UTF8 */, 0, input, -1, buffer,
                             (int)bufferlen, NULL, NULL);
}
#endif

static FILE *
img__fopen(char const *filename, char const *mode) {
  FILE *f;
#if defined(_MSC_VER) && defined(IMG_WINDOWS_UTF8)
  wchar_t wMode[64];
  wchar_t wFilename[1024];
  if (0 == MultiByteToWideChar(65001 /* UTF8 */, 0, filename, -1, wFilename,
                               sizeof(wFilename)))
    return 0;

  if (0 ==
      MultiByteToWideChar(65001 /* UTF8 */, 0, mode, -1, wMode, sizeof(wMode)))
    return 0;

#if _MSC_VER >= 1400
  if (0 != _wfopen_s(&f, wFilename, wMode)) f = 0;
#else
  f = _wfopen(wFilename, wMode);
#endif

#elif defined(_MSC_VER) && _MSC_VER >= 1400
  if (0 != fopen_s(&f, filename, mode)) f = 0;
#else
  f = fopen(filename, mode);
#endif
  return f;
}

static img_uc *
img_load(char const *filename, int *x, int *y, int *comp, int req_comp) {
  FILE *f = img__fopen(filename, "rb");
  unsigned char *result;
  if (!f) return img__errpuc("can't fopen", "Unable to open file");
  result = img_load_from_file(f, x, y, comp, req_comp);
  fclose(f);
  return result;
}

static img_uc *
img_load_from_file(FILE *f, int *x, int *y, int *comp, int req_comp) {
  unsigned char *result;
  img__context s;
  img__start_file(&s, f);
  result = img__load_and_postprocess_8bit(&s, x, y, comp, req_comp);
  if (result) {
    // need to 'unget' all the characters in the IO buffer
    fseek(f, -(int)(s.img_buffer_end - s.img_buffer), SEEK_CUR);
  }
  return result;
}

static img__uint16 *
img_load_from_file_16(FILE *f, int *x, int *y, int *comp, int req_comp) {
  img__uint16 *result;
  img__context s;
  img__start_file(&s, f);
  result = img__load_and_postprocess_16bit(&s, x, y, comp, req_comp);
  if (result) {
    // need to 'unget' all the characters in the IO buffer
    fseek(f, -(int)(s.img_buffer_end - s.img_buffer), SEEK_CUR);
  }
  return result;
}

static img_us *
img_load_16(char const *filename, int *x, int *y, int *comp, int req_comp) {
  FILE *f = img__fopen(filename, "rb");
  img__uint16 *result;
  if (!f) return (img_us *)img__errpuc("can't fopen", "Unable to open file");
  result = img_load_from_file_16(f, x, y, comp, req_comp);
  fclose(f);
  return result;
}

#endif  //! IMG_NO_STDIO

static img_us *
img_load_16_from_memory(img_uc const *buffer, int len, int *x, int *y,
                        int *channels_in_file, int desired_channels) {
  img__context s;
  img__start_mem(&s, buffer, len);
  return img__load_and_postprocess_16bit(&s, x, y, channels_in_file,
                                         desired_channels);
}

static img_us *
img_load_16_from_callbacks(img_io_callbacks const *clbk, void *user, int *x,
                           int *y, int *channels_in_file,
                           int desired_channels) {
  img__context s;
  img__start_callbacks(&s, (img_io_callbacks *)clbk, user);
  return img__load_and_postprocess_16bit(&s, x, y, channels_in_file,
                                         desired_channels);
}

static img_uc *
img_load_from_memory(img_uc const *buffer, int len, int *x, int *y, int *comp,
                     int req_comp) {
  img__context s;
  img__start_mem(&s, buffer, len);
  return img__load_and_postprocess_8bit(&s, x, y, comp, req_comp);
}

static img_uc *
img_load_from_callbacks(img_io_callbacks const *clbk, void *user, int *x,
                        int *y, int *comp, int req_comp) {
  img__context s;
  img__start_callbacks(&s, (img_io_callbacks *)clbk, user);
  return img__load_and_postprocess_8bit(&s, x, y, comp, req_comp);
}

#ifndef IMG_NO_GIF
static img_uc *
img_load_gif_from_memory(img_uc const *buffer, int len, int **delays, int *x,
                         int *y, int *z, int *comp, int req_comp) {
  unsigned char *result;
  img__context s;
  img__start_mem(&s, buffer, len);

  result =
      (unsigned char *)img__load_gif_main(&s, delays, x, y, z, comp, req_comp);
  if (img__vertically_flip_on_load) {
    img__vertical_flip_slices(result, *x, *y, *z, *comp);
  }

  return result;
}
#endif

#ifndef IMG_NO_LINEAR
static float *
img__loadf_main(img__context *s, int *x, int *y, int *comp, int req_comp) {
  unsigned char *data;
#ifndef IMG_NO_HDR
  if (img__hdr_test(s)) {
    img__result_info ri;
    float *hdr_data = img__hdr_load(s, x, y, comp, req_comp, &ri);
    if (hdr_data) img__float_postprocess(hdr_data, x, y, comp, req_comp);
    return hdr_data;
  }
#endif
  data = img__load_and_postprocess_8bit(s, x, y, comp, req_comp);
  if (data) return img__ldr_to_hdr(data, *x, *y, req_comp ? req_comp : *comp);
  return img__errpf("unknown image type",
                    "Image not of any known type, or corrupt");
}

static float *
img_loadf_from_memory(img_uc const *buffer, int len, int *x, int *y, int *comp,
                      int req_comp) {
  img__context s;
  img__start_mem(&s, buffer, len);
  return img__loadf_main(&s, x, y, comp, req_comp);
}

static float *
img_loadf_from_callbacks(img_io_callbacks const *clbk, void *user, int *x,
                         int *y, int *comp, int req_comp) {
  img__context s;
  img__start_callbacks(&s, (img_io_callbacks *)clbk, user);
  return img__loadf_main(&s, x, y, comp, req_comp);
}

#ifndef IMG_NO_STDIO
static float *
img_loadf(char const *filename, int *x, int *y, int *comp, int req_comp) {
  float *result;
  FILE *f = img__fopen(filename, "rb");
  if (!f) return img__errpf("can't fopen", "Unable to open file");
  result = img_loadf_from_file(f, x, y, comp, req_comp);
  fclose(f);
  return result;
}

static float *
img_loadf_from_file(FILE *f, int *x, int *y, int *comp, int req_comp) {
  img__context s;
  img__start_file(&s, f);
  return img__loadf_main(&s, x, y, comp, req_comp);
}
#endif  // !IMG_NO_STDIO

#endif  // !IMG_NO_LINEAR

// these is-hdr-or-not is defined independent of whether IMG_NO_LINEAR is
// defined, for API simplicity; if IMG_NO_LINEAR is defined, it always
// reports false!

static int
img_is_hdr_from_memory(img_uc const *buffer, int len) {
#ifndef IMG_NO_HDR
  img__context s;
  img__start_mem(&s, buffer, len);
  return img__hdr_test(&s);
#else
  IMG_NOTUSED(buffer);
  IMG_NOTUSED(len);
  return 0;
#endif
}

#ifndef IMG_NO_STDIO
static int
img_is_hdr(char const *filename) {
  FILE *f = img__fopen(filename, "rb");
  int result = 0;
  if (f) {
    result = img_is_hdr_from_file(f);
    fclose(f);
  }
  return result;
}

static int
img_is_hdr_from_file(FILE *f) {
#ifndef IMG_NO_HDR
  long pos = ftell(f);
  int ret;
  img__context s;
  img__start_file(&s, f);
  ret = img__hdr_test(&s);
  fseek(f, pos, SEEK_SET);
  return res;
#else
  IMG_NOTUSED(f);
  return 0;
#endif
}
#endif  // !IMG_NO_STDIO

static int
img_is_hdr_from_callbacks(img_io_callbacks const *clbk, void *user) {
#ifndef IMG_NO_HDR
  img__context s;
  img__start_callbacks(&s, (img_io_callbacks *)clbk, user);
  return img__hdr_test(&s);
#else
  IMG_NOTUSED(clbk);
  IMG_NOTUSED(user);
  return 0;
#endif
}

#ifndef IMG_NO_LINEAR
static float img__l2h_gamma = 2.2f, img__l2h_scale = 1.0f;

static void
img_ldr_to_hdr_gamma(float gamma) {
  img__l2h_gamma = gamma;
}
static void
img_ldr_to_hdr_scale(float scale) {
  img__l2h_scale = scale;
}
#endif

static float img__h2l_gamma_i = 1.0f / 2.2f, img__h2l_scale_i = 1.0f;

static void
img_hdr_to_ldr_gamma(float gamma) {
  img__h2l_gamma_i = 1 / gamma;
}
static void
img_hdr_to_ldr_scale(float scale) {
  img__h2l_scale_i = 1 / scale;
}

//////////////////////////////////////////////////////////////////////////////
//
// Common code used by all image loaders
//

enum { IMG__SCAN_load = 0, IMG__SCAN_type, IMG__SCAN_header };

static void
img__refill_buffer(img__context *s) {
  int n = (s->io.read)(s->io_user_data, (char *)s->buffer_start, s->buflen);
  s->callback_already_read += (int)(s->img_buffer - s->img_buffer_original);
  if (n == 0) {
    // at end of file, treat same as if from memory, but need to handle case
    // where s->img_buffer isn't pointing to safe memory, e.g. 0-byte file
    s->read_from_callbacks = 0;
    s->img_buffer = s->buffer_start;
    s->img_buffer_end = s->buffer_start + 1;
    *s->img_buffer = 0;
  } else {
    s->img_buffer = s->buffer_start;
    s->img_buffer_end = s->buffer_start + n;
  }
}

img_inline static img_uc
img__get8(img__context *s) {
  if (s->img_buffer < s->img_buffer_end) return *s->img_buffer++;
  if (s->read_from_callbacks) {
    img__refill_buffer(s);
    return *s->img_buffer++;
  }
  return 0;
}

#if defined(IMG_NO_JPEG) && defined(IMG_NO_HDR) && defined(IMG_NO_PIC) && \
    defined(IMG_NO_PNM)
// nothing
#else
img_inline static int
img__at_eof(img__context *s) {
  if (s->io.read) {
    if (!(s->io.eof)(s->io_user_data)) return 0;
    // if feof() is true, check if buffer = end
    // special case: we've only got the special 0 character at the end
    if (s->read_from_callbacks == 0) return 1;
  }

  return s->img_buffer >= s->img_buffer_end;
}
#endif

#if defined(IMG_NO_JPEG) && defined(IMG_NO_PNG) && defined(IMG_NO_BMP) && \
    defined(IMG_NO_PSD) && defined(IMG_NO_TGA) && defined(IMG_NO_GIF) &&  \
    defined(IMG_NO_PIC)
// nothing
#else
static void
img__skip(img__context *s, int n) {
  if (n == 0) return;  // already there!
  if (n < 0) {
    s->img_buffer = s->img_buffer_end;
    return;
  }
  if (s->io.read) {
    int blen = (int)(s->img_buffer_end - s->img_buffer);
    if (blen < n) {
      s->img_buffer = s->img_buffer_end;
      (s->io.skip)(s->io_user_data, n - blen);
      return;
    }
  }
  s->img_buffer += n;
}
#endif

#if defined(IMG_NO_PNG) && defined(IMG_NO_TGA) && defined(IMG_NO_HDR) && \
    defined(IMG_NO_PNM)
// nothing
#else
static int
img__getn(img__context *s, img_uc *buffer, int n) {
  if (s->io.read) {
    int blen = (int)(s->img_buffer_end - s->img_buffer);
    if (blen < n) {
      int ret, count;

      memcpy(buffer, s->img_buffer, blen);

      count = (s->io.read)(s->io_user_data, (char *)buffer + blen, n - blen);
      ret = (count == (n - blen));
      s->img_buffer = s->img_buffer_end;
      return ret;
    }
  }

  if (s->img_buffer + n <= s->img_buffer_end) {
    memcpy(buffer, s->img_buffer, n);
    s->img_buffer += n;
    return 1;
  } else
    return 0;
}
#endif

#if defined(IMG_NO_JPEG) && defined(IMG_NO_PNG) && defined(IMG_NO_PSD) && \
    defined(IMG_NO_PIC)
// nothing
#else
static int
img__get16be(img__context *s) {
  int z = img__get8(s);
  return (z << 8) + img__get8(s);
}
#endif

#if defined(IMG_NO_PNG) && defined(IMG_NO_PSD) && defined(IMG_NO_PIC)
// nothing
#else
static img__uint32
img__get32be(img__context *s) {
  img__uint32 z = img__get16be(s);
  return (z << 16) + img__get16be(s);
}
#endif

#if defined(IMG_NO_BMP) && defined(IMG_NO_TGA) && defined(IMG_NO_GIF)
// nothing
#else
static int
img__get16le(img__context *s) {
  int z = img__get8(s);
  return z + (img__get8(s) << 8);
}
#endif

#ifndef IMG_NO_BMP
static img__uint32
img__get32le(img__context *s) {
  img__uint32 z = img__get16le(s);
  return z + (img__get16le(s) << 16);
}
#endif

#define IMG__BYTECAST(x) \
  ((img_uc)((x)&255))  // truncate int to byte without warnings

#if defined(IMG_NO_JPEG) && defined(IMG_NO_PNG) && defined(IMG_NO_BMP) && \
    defined(IMG_NO_PSD) && defined(IMG_NO_TGA) && defined(IMG_NO_GIF) &&  \
    defined(IMG_NO_PIC) && defined(IMG_NO_PNM)
// nothing
#else
//////////////////////////////////////////////////////////////////////////////
//
//  generic converter from built-in img_n to req_comp
//    individual types do this automatically as much as possible (e.g. jpeg
//    does all cases internally since it needs to colorspace convert anyway,
//    and it never has alpha, so very few cases ). png can automatically
//    interleave an alpha=255 channel, but falls back to this for other cases
//
//  assume data buffer is malloced, so malloc a new one and free that one
//  only failure mode is malloc failing

static img_uc
img__compute_y(int r, int g, int b) {
  return (img_uc)(((r * 77) + (g * 150) + (29 * b)) >> 8);
}
#endif

#if defined(IMG_NO_PNG) && defined(IMG_NO_BMP) && defined(IMG_NO_PSD) && \
    defined(IMG_NO_TGA) && defined(IMG_NO_GIF) && defined(IMG_NO_PIC) && \
    defined(IMG_NO_PNM)
// nothing
#else
static unsigned char *
img__convert_format(unsigned char *data, int img_n, int req_comp,
                    unsigned int x, unsigned int y) {
  int i, j;
  unsigned char *good;

  if (req_comp == img_n) return data;
  IMG_ASSERT(req_comp >= 1 && req_comp <= 4);

  good = (unsigned char *)img__malloc_mad3(req_comp, x, y, 0);
  if (good == NULL) {
    IMG_FREE(data);
    return img__errpuc("outofmem", "Out of memory");
  }

  for (j = 0; j < (int)y; ++j) {
    unsigned char *src = data + j * x * img_n;
    unsigned char *dest = good + j * x * req_comp;

#define IMG__COMBO(a, b) ((a)*8 + (b))
#define IMG__CASE(a, b)  \
  case IMG__COMBO(a, b): \
    for (i = x - 1; i >= 0; --i, src += a, dest += b)
    // convert source image with img_n components to one with req_comp
    // components; avoid switch per pixel, so use switch per scanline and
    // massive macros
    switch (IMG__COMBO(img_n, req_comp)) {
      IMG__CASE(1, 2) {
        dest[0] = src[0];
        dest[1] = 255;
      }
      break;
      IMG__CASE(1, 3) { dest[0] = dest[1] = dest[2] = src[0]; }
      break;
      IMG__CASE(1, 4) {
        dest[0] = dest[1] = dest[2] = src[0];
        dest[3] = 255;
      }
      break;
      IMG__CASE(2, 1) { dest[0] = src[0]; }
      break;
      IMG__CASE(2, 3) { dest[0] = dest[1] = dest[2] = src[0]; }
      break;
      IMG__CASE(2, 4) {
        dest[0] = dest[1] = dest[2] = src[0];
        dest[3] = src[1];
      }
      break;
      IMG__CASE(3, 4) {
        dest[0] = src[0];
        dest[1] = src[1];
        dest[2] = src[2];
        dest[3] = 255;
      }
      break;
      IMG__CASE(3, 1) { dest[0] = img__compute_y(src[0], src[1], src[2]); }
      break;
      IMG__CASE(3, 2) {
        dest[0] = img__compute_y(src[0], src[1], src[2]);
        dest[1] = 255;
      }
      break;
      IMG__CASE(4, 1) { dest[0] = img__compute_y(src[0], src[1], src[2]); }
      break;
      IMG__CASE(4, 2) {
        dest[0] = img__compute_y(src[0], src[1], src[2]);
        dest[1] = src[3];
      }
      break;
      IMG__CASE(4, 3) {
        dest[0] = src[0];
        dest[1] = src[1];
        dest[2] = src[2];
      }
      break;
      default:
        IMG_ASSERT(0);
        IMG_FREE(data);
        IMG_FREE(good);
        return img__errpuc("unsupported", "Unsupported format conversion");
    }
#undef IMG__CASE
  }

  IMG_FREE(data);
  return good;
}
#endif

#if defined(IMG_NO_PNG) && defined(IMG_NO_PSD)
// nothing
#else
static img__uint16
img__compute_y_16(int r, int g, int b) {
  return (img__uint16)(((r * 77) + (g * 150) + (29 * b)) >> 8);
}
#endif

#if defined(IMG_NO_PNG) && defined(IMG_NO_PSD)
// nothing
#else
static img__uint16 *
img__convert_format16(img__uint16 *data, int img_n, int req_comp,
                      unsigned int x, unsigned int y) {
  int i, j;
  img__uint16 *good;

  if (req_comp == img_n) return data;
  IMG_ASSERT(req_comp >= 1 && req_comp <= 4);

  good = (img__uint16 *)img__malloc(req_comp * x * y * 2);
  if (good == NULL) {
    IMG_FREE(data);
    return (img__uint16 *)img__errpuc("outofmem", "Out of memory");
  }

  for (j = 0; j < (int)y; ++j) {
    img__uint16 *src = data + j * x * img_n;
    img__uint16 *dest = good + j * x * req_comp;

#define IMG__COMBO(a, b) ((a)*8 + (b))
#define IMG__CASE(a, b)  \
  case IMG__COMBO(a, b): \
    for (i = x - 1; i >= 0; --i, src += a, dest += b)
    // convert source image with img_n components to one with req_comp
    // components; avoid switch per pixel, so use switch per scanline and
    // massive macros
    switch (IMG__COMBO(img_n, req_comp)) {
      IMG__CASE(1, 2) {
        dest[0] = src[0];
        dest[1] = 0xffff;
      }
      break;
      IMG__CASE(1, 3) { dest[0] = dest[1] = dest[2] = src[0]; }
      break;
      IMG__CASE(1, 4) {
        dest[0] = dest[1] = dest[2] = src[0];
        dest[3] = 0xffff;
      }
      break;
      IMG__CASE(2, 1) { dest[0] = src[0]; }
      break;
      IMG__CASE(2, 3) { dest[0] = dest[1] = dest[2] = src[0]; }
      break;
      IMG__CASE(2, 4) {
        dest[0] = dest[1] = dest[2] = src[0];
        dest[3] = src[1];
      }
      break;
      IMG__CASE(3, 4) {
        dest[0] = src[0];
        dest[1] = src[1];
        dest[2] = src[2];
        dest[3] = 0xffff;
      }
      break;
      IMG__CASE(3, 1) { dest[0] = img__compute_y_16(src[0], src[1], src[2]); }
      break;
      IMG__CASE(3, 2) {
        dest[0] = img__compute_y_16(src[0], src[1], src[2]);
        dest[1] = 0xffff;
      }
      break;
      IMG__CASE(4, 1) { dest[0] = img__compute_y_16(src[0], src[1], src[2]); }
      break;
      IMG__CASE(4, 2) {
        dest[0] = img__compute_y_16(src[0], src[1], src[2]);
        dest[1] = src[3];
      }
      break;
      IMG__CASE(4, 3) {
        dest[0] = src[0];
        dest[1] = src[1];
        dest[2] = src[2];
      }
      break;
      default:
        IMG_ASSERT(0);
        IMG_FREE(data);
        IMG_FREE(good);
        return (img__uint16 *)img__errpuc("unsupported",
                                          "Unsupported format conversion");
    }
#undef IMG__CASE
  }

  IMG_FREE(data);
  return good;
}
#endif

#ifndef IMG_NO_LINEAR
static float *
img__ldr_to_hdr(img_uc *data, int x, int y, int comp) {
  int i, k, n;
  float *output;
  if (!data) return NULL;
  output = (float *)img__malloc_mad4(x, y, comp, sizeof(float), 0);
  if (output == NULL) {
    IMG_FREE(data);
    return img__errpf("outofmem", "Out of memory");
  }
  // compute number of non-alpha components
  if (comp & 1)
    n = comp;
  else
    n = comp - 1;
  for (i = 0; i < x * y; ++i) {
    for (k = 0; k < n; ++k) {
      output[i * comp + k] =
          (float)(pow(data[i * comp + k] / 255.0f, img__l2h_gamma) *
                  img__l2h_scale);
    }
  }
  if (n < comp) {
    for (i = 0; i < x * y; ++i) {
      output[i * comp + n] = data[i * comp + n] / 255.0f;
    }
  }
  IMG_FREE(data);
  return output;
}
#endif

#ifndef IMG_NO_HDR
#define img__float2int(x) ((int)(x))
static img_uc *
img__hdr_to_ldr(float *data, int x, int y, int comp) {
  int i, k, n;
  img_uc *output;
  if (!data) return NULL;
  output = (img_uc *)img__malloc_mad3(x, y, comp, 0);
  if (output == NULL) {
    IMG_FREE(data);
    return img__errpuc("outofmem", "Out of memory");
  }
  // compute number of non-alpha components
  if (comp & 1)
    n = comp;
  else
    n = comp - 1;
  for (i = 0; i < x * y; ++i) {
    for (k = 0; k < n; ++k) {
      float z =
          (float)pow(data[i * comp + k] * img__h2l_scale_i, img__h2l_gamma_i) *
              255 +
          0.5f;
      if (z < 0) z = 0;
      if (z > 255) z = 255;
      output[i * comp + k] = (img_uc)img__float2int(z);
    }
    if (k < comp) {
      float z = data[i * comp + k] * 255 + 0.5f;
      if (z < 0) z = 0;
      if (z > 255) z = 255;
      output[i * comp + k] = (img_uc)img__float2int(z);
    }
  }
  IMG_FREE(data);
  return output;
}
#endif

//////////////////////////////////////////////////////////////////////////////
//
//  "baseline" JPEG/JFIF decoder
//
//    simple implementation
//      - doesn't support delayed output of y-dimension
//      - simple interface (only one output format: 8-bit interleaved RGB)
//      - doesn't try to recover corrupt jpegs
//      - doesn't allow partial loading, loading multiple at once
//      - still fast on x86 (copying globals into locals doesn't help x86)
//      - allocates lots of intermediate memory (full size of all components)
//        - non-interleaved case requires this anyway
//        - allows good upsampling (see next)
//    high-quality
//      - upsampled channels are bilinearly interpolated, even across blocks
//      - quality integer IDCT derived from IJG's 'slow'
//    performance
//      - fast huffman; reasonable integer IDCT
//      - some SIMD kernels for common paths on targets with SSE2/NEON
//      - uses a lot of intermediate memory, could cache poorly

#ifndef IMG_NO_JPEG

// huffman decoding acceleration
#define FAST_BITS 9  // larger handles more cases; smaller stomps less cache

typedef struct {
  img_uc fast[1 << FAST_BITS];
  // weirdly, repacking this into AoS is a 10% speed loss, instead of a win
  img__uint16 code[256];
  img_uc values[256];
  img_uc size[257];
  unsigned int maxcode[18];
  int delta[17];  // old 'firstsymbol' - old 'firstcode'
} img__huffman;

typedef struct {
  img__context *s;
  img__huffman huff_dc[4];
  img__huffman huff_ac[4];
  img__uint16 dequant[4][64];
  img__int16 fast_ac[4][1 << FAST_BITS];

  // sizes for components, interleaved MCUs
  int img_h_max, img_v_max;
  int img_mcu_x, img_mcu_y;
  int img_mcu_w, img_mcu_h;

  // definition of jpeg image component
  struct {
    int id;
    int h, v;
    int tq;
    int hd, ha;
    int dc_pred;

    int x, y, w2, h2;
    img_uc *data;
    void *raw_data, *raw_coeff;
    img_uc *linebuf;
    short *coeff;          // progressive only
    int coeff_w, coeff_h;  // number of 8x8 coefficient blocks
  } img_comp[4];

  img__uint32 code_buffer;  // jpeg entropy-coded buffer
  int code_bits;            // number of valid bits
  unsigned char marker;     // marker seen while filling entropy buffer
  int nomore;               // flag if we saw a marker so must stop

  int progressive;
  int spec_start;
  int spec_end;
  int succ_high;
  int succ_low;
  int eob_run;
  int jfif;
  int app14_color_transform;  // Adobe APP14 tag
  int rgb;

  int scan_n, order[4];
  int restart_interval, todo;

  // kernels
  void (*idct_block_kernel)(img_uc *out, int out_stride, short data[64]);
  void (*YCbCr_to_RGB_kernel)(img_uc *out, const img_uc *y, const img_uc *pcb,
                              const img_uc *pcr, int count, int step);
  img_uc *(*resample_row_hv_2_kernel)(img_uc *out, img_uc *in_near,
                                      img_uc *in_far, int w, int hs);
} img__jpeg;

static int
img__build_huffman(img__huffman *h, int *count) {
  int i, j, k = 0;
  unsigned int code;
  // build size list for each symbol (from JPEG spec)
  for (i = 0; i < 16; ++i)
    for (j = 0; j < count[i]; ++j) h->size[k++] = (img_uc)(i + 1);
  h->size[k] = 0;

  // compute actual symbols (from jpeg spec)
  code = 0;
  k = 0;
  for (j = 1; j <= 16; ++j) {
    // compute delta to add to code to compute symbol id
    h->delta[j] = k - code;
    if (h->size[k] == j) {
      while (h->size[k] == j) h->code[k++] = (img__uint16)(code++);
      if (code - 1 >= (1u << j))
        return img__err("bad code lengths", "Corrupt JPEG");
    }
    // compute largest code + 1 for this size, preshifted as needed later
    h->maxcode[j] = code << (16 - j);
    code <<= 1;
  }
  h->maxcode[j] = 0xffffffff;

  // build non-spec acceleration table; 255 is flag for not-accelerated
  memset(h->fast, 255, 1 << FAST_BITS);
  for (i = 0; i < k; ++i) {
    int s = h->size[i];
    if (s <= FAST_BITS) {
      int c = h->code[i] << (FAST_BITS - s);
      int m = 1 << (FAST_BITS - s);
      for (j = 0; j < m; ++j) {
        h->fast[c + j] = (img_uc)i;
      }
    }
  }
  return 1;
}

// build a table that decodes both magnitude and value of small ACs in
// one go.
static void
img__build_fast_ac(img__int16 *fast_ac, img__huffman *h) {
  int i;
  for (i = 0; i < (1 << FAST_BITS); ++i) {
    img_uc fast = h->fast[i];
    fast_ac[i] = 0;
    if (fast < 255) {
      int rs = h->values[fast];
      int run = (rs >> 4) & 15;
      int magbits = rs & 15;
      int len = h->size[fast];

      if (magbits && len + magbits <= FAST_BITS) {
        // magnitude code followed by receive_extend code
        int k = ((i << len) & ((1 << FAST_BITS) - 1)) >> (FAST_BITS - magbits);
        int m = 1 << (magbits - 1);
        if (k < m) k += (~0U << magbits) + 1;
        // if the result is small enough, we can fit it in fast_ac table
        if (k >= -128 && k <= 127)
          fast_ac[i] = (img__int16)((k * 256) + (run * 16) + (len + magbits));
      }
    }
  }
}

static void
img__grow_buffer_unsafe(img__jpeg *j) {
  do {
    unsigned int b = j->nomore ? 0 : img__get8(j->s);
    if (b == 0xff) {
      int c = img__get8(j->s);
      while (c == 0xff) c = img__get8(j->s);  // consume fill bytes
      if (c != 0) {
        j->marker = (unsigned char)c;
        j->nomore = 1;
        return;
      }
    }
    j->code_buffer |= b << (24 - j->code_bits);
    j->code_bits += 8;
  } while (j->code_bits <= 24);
}

// (1 << n) - 1
static const img__uint32 img__bmask[17] = {0,    1,    3,     7,     15,   31,
                                           63,   127,  255,   511,   1023, 2047,
                                           4095, 8191, 16383, 32767, 65535};

// decode a jpeg huffman value from the bitstream
img_inline static int
img__jpeg_huff_decode(img__jpeg *j, img__huffman *h) {
  unsigned int temp;
  int c, k;

  if (j->code_bits < 16) img__grow_buffer_unsafe(j);

  // look at the top FAST_BITS and determine what symbol ID it is,
  // if the code is <= FAST_BITS
  c = (j->code_buffer >> (32 - FAST_BITS)) & ((1 << FAST_BITS) - 1);
  k = h->fast[c];
  if (k < 255) {
    int s = h->size[k];
    if (s > j->code_bits) return -1;
    j->code_buffer <<= s;
    j->code_bits -= s;
    return h->values[k];
  }

  // naive test is to shift the code_buffer down so k bits are
  // valid, then test against maxcode. To speed this up, we've
  // preshifted maxcode left so that it has (16-k) 0s at the
  // end; in other words, regardless of the number of bits, it
  // wants to be compared against something shifted to have 16;
  // that way we don't need to shift inside the loop.
  temp = j->code_buffer >> 16;
  for (k = FAST_BITS + 1;; ++k)
    if (temp < h->maxcode[k]) break;
  if (k == 17) {
    // error! code not found
    j->code_bits -= 16;
    return -1;
  }

  if (k > j->code_bits) return -1;

  // convert the huffman code to the symbol id
  c = ((j->code_buffer >> (32 - k)) & img__bmask[k]) + h->delta[k];
  IMG_ASSERT((((j->code_buffer) >> (32 - h->size[c])) &
              img__bmask[h->size[c]]) == h->code[c]);

  // convert the id to a symbol
  j->code_bits -= k;
  j->code_buffer <<= k;
  return h->values[c];
}

// bias[n] = (-1<<n) + 1
static const int img__jbias[16] = {0,     -1,    -3,     -7,    -15,   -31,
                                   -63,   -127,  -255,   -511,  -1023, -2047,
                                   -4095, -8191, -16383, -32767};

// combined JPEG 'receive' and JPEG 'extend', since baseline
// always extends everything it receives.
img_inline static int
img__extend_receive(img__jpeg *j, int n) {
  unsigned int k;
  int sgn;
  if (j->code_bits < n) img__grow_buffer_unsafe(j);

  sgn = (img__int32)j->code_buffer >> 31;  // sign bit is always in MSB
  k = img_lrot(j->code_buffer, n);
  if (n < 0 || n >= (int)(sizeof(img__bmask) / sizeof(*img__bmask))) return 0;
  j->code_buffer = k & ~img__bmask[n];
  k &= img__bmask[n];
  j->code_bits -= n;
  return k + (img__jbias[n] & ~sgn);
}

// get some unsigned bits
img_inline static int
img__jpeg_get_bits(img__jpeg *j, int n) {
  unsigned int k;
  if (j->code_bits < n) img__grow_buffer_unsafe(j);
  k = img_lrot(j->code_buffer, n);
  j->code_buffer = k & ~img__bmask[n];
  k &= img__bmask[n];
  j->code_bits -= n;
  return k;
}

img_inline static int
img__jpeg_get_bit(img__jpeg *j) {
  unsigned int k;
  if (j->code_bits < 1) img__grow_buffer_unsafe(j);
  k = j->code_buffer;
  j->code_buffer <<= 1;
  --j->code_bits;
  return k & 0x80000000;
}

// given a value that's at position X in the zigzag stream,
// where does it appear in the 8x8 matrix coded as row-major?
static const img_uc img__jpeg_dezigzag[64 + 15] = {
    0, 1, 8, 16, 9, 2, 3, 10, 17, 24, 32, 25, 18, 11, 4, 5, 12, 19, 26, 33, 40,
    48, 41, 34, 27, 20, 13, 6, 7, 14, 21, 28, 35, 42, 49, 56, 57, 50, 43, 36,
    29, 22, 15, 23, 30, 37, 44, 51, 58, 59, 52, 45, 38, 31, 39, 46, 53, 60, 61,
    54, 47, 55, 62, 63,
    // let corrupt input sample past end
    63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 63};

// decode one 64-entry block--
static int
img__jpeg_decode_block(img__jpeg *j, short data[64], img__huffman *hdc,
                       img__huffman *hac, img__int16 *fac, int b,
                       img__uint16 *dequant) {
  int diff, dc, k;
  int t;

  if (j->code_bits < 16) img__grow_buffer_unsafe(j);
  t = img__jpeg_huff_decode(j, hdc);
  if (t < 0) return img__err("bad huffman code", "Corrupt JPEG");

  // 0 all the ac values now so we can do it 32-bits at a time
  memset(data, 0, 64 * sizeof(data[0]));

  diff = t ? img__extend_receive(j, t) : 0;
  dc = j->img_comp[b].dc_pred + diff;
  j->img_comp[b].dc_pred = dc;
  data[0] = (short)(dc * dequant[0]);

  // decode AC components, see JPEG spec
  k = 1;
  do {
    unsigned int zig;
    int c, r, s;
    if (j->code_bits < 16) img__grow_buffer_unsafe(j);
    c = (j->code_buffer >> (32 - FAST_BITS)) & ((1 << FAST_BITS) - 1);
    r = fac[c];
    if (r) {               // fast-AC path
      k += (r >> 4) & 15;  // run
      s = r & 15;          // combined length
      j->code_buffer <<= s;
      j->code_bits -= s;
      // decode into unzigzag'd location
      zig = img__jpeg_dezigzag[k++];
      data[zig] = (short)((r >> 8) * dequant[zig]);
    } else {
      int rs = img__jpeg_huff_decode(j, hac);
      if (rs < 0) return img__err("bad huffman code", "Corrupt JPEG");
      s = rs & 15;
      r = rs >> 4;
      if (s == 0) {
        if (rs != 0xf0) break;  // end block
        k += 16;
      } else {
        k += r;
        // decode into unzigzag'd location
        zig = img__jpeg_dezigzag[k++];
        data[zig] = (short)(img__extend_receive(j, s) * dequant[zig]);
      }
    }
  } while (k < 64);
  return 1;
}

static int
img__jpeg_decode_block_prog_dc(img__jpeg *j, short data[64], img__huffman *hdc,
                               int b) {
  int diff, dc;
  int t;
  if (j->spec_end != 0)
    return img__err("can't merge dc and ac", "Corrupt JPEG");

  if (j->code_bits < 16) img__grow_buffer_unsafe(j);

  if (j->succ_high == 0) {
    // first scan for DC coefficient, must be first
    memset(data, 0, 64 * sizeof(data[0]));  // 0 all the ac values now
    t = img__jpeg_huff_decode(j, hdc);
    if (t == -1) return img__err("can't merge dc and ac", "Corrupt JPEG");
    diff = t ? img__extend_receive(j, t) : 0;

    dc = j->img_comp[b].dc_pred + diff;
    j->img_comp[b].dc_pred = dc;
    data[0] = (short)(dc << j->succ_low);
  } else {
    // refinement scan for DC coefficient
    if (img__jpeg_get_bit(j)) data[0] += (short)(1 << j->succ_low);
  }
  return 1;
}

// @OPTIMIZE: store non-zigzagged during the decode passes,
// and only de-zigzag when dequantizing
static int
img__jpeg_decode_block_prog_ac(img__jpeg *j, short data[64], img__huffman *hac,
                               img__int16 *fac) {
  int k;
  if (j->spec_start == 0)
    return img__err("can't merge dc and ac", "Corrupt JPEG");

  if (j->succ_high == 0) {
    int shift = j->succ_low;

    if (j->eob_run) {
      --j->eob_run;
      return 1;
    }

    k = j->spec_start;
    do {
      unsigned int zig;
      int c, r, s;
      if (j->code_bits < 16) img__grow_buffer_unsafe(j);
      c = (j->code_buffer >> (32 - FAST_BITS)) & ((1 << FAST_BITS) - 1);
      r = fac[c];
      if (r) {               // fast-AC path
        k += (r >> 4) & 15;  // run
        s = r & 15;          // combined length
        j->code_buffer <<= s;
        j->code_bits -= s;
        zig = img__jpeg_dezigzag[k++];
        data[zig] = (short)((r >> 8) << shift);
      } else {
        int rs = img__jpeg_huff_decode(j, hac);
        if (rs < 0) return img__err("bad huffman code", "Corrupt JPEG");
        s = rs & 15;
        r = rs >> 4;
        if (s == 0) {
          if (r < 15) {
            j->eob_run = (1 << r);
            if (r) j->eob_run += img__jpeg_get_bits(j, r);
            --j->eob_run;
            break;
          }
          k += 16;
        } else {
          k += r;
          zig = img__jpeg_dezigzag[k++];
          data[zig] = (short)(img__extend_receive(j, s) << shift);
        }
      }
    } while (k <= j->spec_end);
  } else {
    // refinement scan for these AC coefficients

    short bit = (short)(1 << j->succ_low);

    if (j->eob_run) {
      --j->eob_run;
      for (k = j->spec_start; k <= j->spec_end; ++k) {
        short *p = &data[img__jpeg_dezigzag[k]];
        if (*p != 0)
          if (img__jpeg_get_bit(j))
            if ((*p & bit) == 0) {
              if (*p > 0)
                *p += bit;
              else
                *p -= bit;
            }
      }
    } else {
      k = j->spec_start;
      do {
        int r, s;
        int rs = img__jpeg_huff_decode(
            j, hac);  // @OPTIMIZE see if we can use the fast path here,
                      // advance-by-r is so slow, eh
        if (rs < 0) return img__err("bad huffman code", "Corrupt JPEG");
        s = rs & 15;
        r = rs >> 4;
        if (s == 0) {
          if (r < 15) {
            j->eob_run = (1 << r) - 1;
            if (r) j->eob_run += img__jpeg_get_bits(j, r);
            r = 64;  // force end of block
          } else {
            // r=15 s=0 should write 16 0s, so we just do
            // a run of 15 0s and then write s (which is 0),
            // so we don't have to do anything special here
          }
        } else {
          if (s != 1) return img__err("bad huffman code", "Corrupt JPEG");
          // sign bit
          if (img__jpeg_get_bit(j))
            s = bit;
          else
            s = -bit;
        }

        // advance by r
        while (k <= j->spec_end) {
          short *p = &data[img__jpeg_dezigzag[k++]];
          if (*p != 0) {
            if (img__jpeg_get_bit(j))
              if ((*p & bit) == 0) {
                if (*p > 0)
                  *p += bit;
                else
                  *p -= bit;
              }
          } else {
            if (r == 0) {
              *p = (short)s;
              break;
            }
            --r;
          }
        }
      } while (k <= j->spec_end);
    }
  }
  return 1;
}

// take a -128..127 value and img__clamp it and convert to 0..255
img_inline static img_uc
img__clamp(int x) {
  // trick to use a single test to catch both cases
  if ((unsigned int)x > 255) {
    if (x < 0) return 0;
    if (x > 255) return 255;
  }
  return (img_uc)x;
}

#define img__f2f(x) ((int)(((x)*4096 + 0.5)))
#define img__fsh(x) ((x)*4096)

// derived from jidctint -- DCT_ISLOW
#define IMG__IDCT_1D(s0, s1, s2, s3, s4, s5, s6, s7)      \
  int t0, t1, t2, t3, p1, p2, p3, p4, p5, x0, x1, x2, x3; \
  p2 = s2;                                                \
  p3 = s6;                                                \
  p1 = (p2 + p3) * img__f2f(0.5411961f);                  \
  t2 = p1 + p3 * img__f2f(-1.847759065f);                 \
  t3 = p1 + p2 * img__f2f(0.765366865f);                  \
  p2 = s0;                                                \
  p3 = s4;                                                \
  t0 = img__fsh(p2 + p3);                                 \
  t1 = img__fsh(p2 - p3);                                 \
  x0 = t0 + t3;                                           \
  x3 = t0 - t3;                                           \
  x1 = t1 + t2;                                           \
  x2 = t1 - t2;                                           \
  t0 = s7;                                                \
  t1 = s5;                                                \
  t2 = s3;                                                \
  t3 = s1;                                                \
  p3 = t0 + t2;                                           \
  p4 = t1 + t3;                                           \
  p1 = t0 + t3;                                           \
  p2 = t1 + t2;                                           \
  p5 = (p3 + p4) * img__f2f(1.175875602f);                \
  t0 = t0 * img__f2f(0.298631336f);                       \
  t1 = t1 * img__f2f(2.053119869f);                       \
  t2 = t2 * img__f2f(3.072711026f);                       \
  t3 = t3 * img__f2f(1.501321110f);                       \
  p1 = p5 + p1 * img__f2f(-0.899976223f);                 \
  p2 = p5 + p2 * img__f2f(-2.562915447f);                 \
  p3 = p3 * img__f2f(-1.961570560f);                      \
  p4 = p4 * img__f2f(-0.390180644f);                      \
  t3 += p1 + p4;                                          \
  t2 += p2 + p3;                                          \
  t1 += p2 + p4;                                          \
  t0 += p1 + p3;

static void
img__idct_block(img_uc *out, int out_stride, short data[64]) {
  int i, val[64], *v = val;
  img_uc *o;
  short *d = data;

  // columns
  for (i = 0; i < 8; ++i, ++d, ++v) {
    // if all zeroes, shortcut -- this avoids dequantizing 0s and IDCTing
    if (d[8] == 0 && d[16] == 0 && d[24] == 0 && d[32] == 0 && d[40] == 0 &&
        d[48] == 0 && d[56] == 0) {
      //    no shortcut                 0     seconds
      //    (1|2|3|4|5|6|7)==0          0     seconds
      //    all separate               -0.047 seconds
      //    1 && 2|3 && 4|5 && 6|7:    -0.047 seconds
      int dcterm = d[0] * 4;
      v[0] = v[8] = v[16] = v[24] = v[32] = v[40] = v[48] = v[56] = dcterm;
    } else {
      IMG__IDCT_1D(d[0], d[8], d[16], d[24], d[32], d[40], d[48], d[56])
      // constants scaled things up by 1<<12; let's bring them back
      // down, but keep 2 extra bits of precision
      x0 += 512;
      x1 += 512;
      x2 += 512;
      x3 += 512;
      v[0] = (x0 + t3) >> 10;
      v[56] = (x0 - t3) >> 10;
      v[8] = (x1 + t2) >> 10;
      v[48] = (x1 - t2) >> 10;
      v[16] = (x2 + t1) >> 10;
      v[40] = (x2 - t1) >> 10;
      v[24] = (x3 + t0) >> 10;
      v[32] = (x3 - t0) >> 10;
    }
  }

  for (i = 0, v = val, o = out; i < 8; ++i, v += 8, o += out_stride) {
    // no fast case since the first 1D IDCT spread components out
    IMG__IDCT_1D(v[0], v[1], v[2], v[3], v[4], v[5], v[6], v[7])
    // constants scaled things up by 1<<12, plus we had 1<<2 from first
    // loop, plus horizontal and vertical each scale by sqrt(8) so together
    // we've got an extra 1<<3, so 1<<17 total we need to remove.
    // so we want to round that, which means adding 0.5 * 1<<17,
    // aka 65536. Also, we'll end up with -128 to 127 that we want
    // to encode as 0..255 by adding 128, so we'll add that before the shift
    x0 += 65536 + (128 << 17);
    x1 += 65536 + (128 << 17);
    x2 += 65536 + (128 << 17);
    x3 += 65536 + (128 << 17);
    // tried computing the shifts into temps, or'ing the temps to see
    // if any were out of range, but that was slower
    o[0] = img__clamp((x0 + t3) >> 17);
    o[7] = img__clamp((x0 - t3) >> 17);
    o[1] = img__clamp((x1 + t2) >> 17);
    o[6] = img__clamp((x1 - t2) >> 17);
    o[2] = img__clamp((x2 + t1) >> 17);
    o[5] = img__clamp((x2 - t1) >> 17);
    o[3] = img__clamp((x3 + t0) >> 17);
    o[4] = img__clamp((x3 - t0) >> 17);
  }
}

#ifdef IMG_SSE2
// sse2 integer IDCT. not the fastest possible implementation but it
// produces bit-identical results to the generic C version so it's
// fully "transparent".
static void
img__idct_simd(img_uc *out, int out_stride, short data[64]) {
  // This is constructed to match our regular (generic) integer IDCT exactly.
  __m128i row0, row1, row2, row3, row4, row5, row6, row7;
  __m128i tmp;

// dot product constant: even elems=x, odd elems=y
#define dct_const(x, y) _mm_setr_epi16((x), (y), (x), (y), (x), (y), (x), (y))

// out(0) = c0[even]*x + c0[odd]*y   (c0, x, y 16-bit, out 32-bit)
// out(1) = c1[even]*x + c1[odd]*y
#define dct_rot(out0, out1, x, y, c0, c1)        \
  __m128i c0##lo = _mm_unpacklo_epi16((x), (y)); \
  __m128i c0##hi = _mm_unpackhi_epi16((x), (y)); \
  __m128i out0##_l = _mm_madd_epi16(c0##lo, c0); \
  __m128i out0##_h = _mm_madd_epi16(c0##hi, c0); \
  __m128i out1##_l = _mm_madd_epi16(c0##lo, c1); \
  __m128i out1##_h = _mm_madd_epi16(c0##hi, c1)

// out = in << 12  (in 16-bit, out 32-bit)
#define dct_widen(out, in)                                              \
  __m128i out##_l =                                                     \
      _mm_srai_epi32(_mm_unpacklo_epi16(_mm_setzero_si128(), (in)), 4); \
  __m128i out##_h =                                                     \
      _mm_srai_epi32(_mm_unpackhi_epi16(_mm_setzero_si128(), (in)), 4)

// wide add
#define dct_wadd(out, a, b)                      \
  __m128i out##_l = _mm_add_epi32(a##_l, b##_l); \
  __m128i out##_h = _mm_add_epi32(a##_h, b##_h)

// wide sub
#define dct_wsub(out, a, b)                      \
  __m128i out##_l = _mm_sub_epi32(a##_l, b##_l); \
  __m128i out##_h = _mm_sub_epi32(a##_h, b##_h)

// butterfly a/b, add bias, then shift by "s" and pack
#define dct_bfly32o(out0, out1, a, b, bias, s)                               \
  {                                                                          \
    __m128i abiased_l = _mm_add_epi32(a##_l, bias);                          \
    __m128i abiased_h = _mm_add_epi32(a##_h, bias);                          \
    dct_wadd(sum, abiased, b);                                               \
    dct_wsub(dif, abiased, b);                                               \
    out0 =                                                                   \
        _mm_packs_epi32(_mm_srai_epi32(sum_l, s), _mm_srai_epi32(sum_h, s)); \
    out1 =                                                                   \
        _mm_packs_epi32(_mm_srai_epi32(dif_l, s), _mm_srai_epi32(dif_h, s)); \
  }

// 8-bit interleave step (for transposes)
#define dct_interleave8(a, b)  \
  tmp = a;                     \
  a = _mm_unpacklo_epi8(a, b); \
  b = _mm_unpackhi_epi8(tmp, b)

// 16-bit interleave step (for transposes)
#define dct_interleave16(a, b)  \
  tmp = a;                      \
  a = _mm_unpacklo_epi16(a, b); \
  b = _mm_unpackhi_epi16(tmp, b)

#define dct_pass(bias, shift)                        \
  {                                                  \
    /* even part */                                  \
    dct_rot(t2e, t3e, row2, row6, rot0_0, rot0_1);   \
    __m128i sum04 = _mm_add_epi16(row0, row4);       \
    __m128i dif04 = _mm_sub_epi16(row0, row4);       \
    dct_widen(t0e, sum04);                           \
    dct_widen(t1e, dif04);                           \
    dct_wadd(x0, t0e, t3e);                          \
    dct_wsub(x3, t0e, t3e);                          \
    dct_wadd(x1, t1e, t2e);                          \
    dct_wsub(x2, t1e, t2e);                          \
    /* odd part */                                   \
    dct_rot(y0o, y2o, row7, row3, rot2_0, rot2_1);   \
    dct_rot(y1o, y3o, row5, row1, rot3_0, rot3_1);   \
    __m128i sum17 = _mm_add_epi16(row1, row7);       \
    __m128i sum35 = _mm_add_epi16(row3, row5);       \
    dct_rot(y4o, y5o, sum17, sum35, rot1_0, rot1_1); \
    dct_wadd(x4, y0o, y4o);                          \
    dct_wadd(x5, y1o, y5o);                          \
    dct_wadd(x6, y2o, y5o);                          \
    dct_wadd(x7, y3o, y4o);                          \
    dct_bfly32o(row0, row7, x0, x7, bias, shift);    \
    dct_bfly32o(row1, row6, x1, x6, bias, shift);    \
    dct_bfly32o(row2, row5, x2, x5, bias, shift);    \
    dct_bfly32o(row3, row4, x3, x4, bias, shift);    \
  }

  __m128i rot0_0 = dct_const(img__f2f(0.5411961f),
                             img__f2f(0.5411961f) + img__f2f(-1.847759065f));
  __m128i rot0_1 = dct_const(img__f2f(0.5411961f) + img__f2f(0.765366865f),
                             img__f2f(0.5411961f));
  __m128i rot1_0 = dct_const(img__f2f(1.175875602f) + img__f2f(-0.899976223f),
                             img__f2f(1.175875602f));
  __m128i rot1_1 = dct_const(img__f2f(1.175875602f),
                             img__f2f(1.175875602f) + img__f2f(-2.562915447f));
  __m128i rot2_0 = dct_const(img__f2f(-1.961570560f) + img__f2f(0.298631336f),
                             img__f2f(-1.961570560f));
  __m128i rot2_1 = dct_const(img__f2f(-1.961570560f),
                             img__f2f(-1.961570560f) + img__f2f(3.072711026f));
  __m128i rot3_0 = dct_const(img__f2f(-0.390180644f) + img__f2f(2.053119869f),
                             img__f2f(-0.390180644f));
  __m128i rot3_1 = dct_const(img__f2f(-0.390180644f),
                             img__f2f(-0.390180644f) + img__f2f(1.501321110f));

  // rounding biases in column/row passes, see img__idct_block for explanation.
  __m128i bias_0 = _mm_set1_epi32(512);
  __m128i bias_1 = _mm_set1_epi32(65536 + (128 << 17));

  // load
  row0 = _mm_load_si128((const __m128i *)(data + 0 * 8));
  row1 = _mm_load_si128((const __m128i *)(data + 1 * 8));
  row2 = _mm_load_si128((const __m128i *)(data + 2 * 8));
  row3 = _mm_load_si128((const __m128i *)(data + 3 * 8));
  row4 = _mm_load_si128((const __m128i *)(data + 4 * 8));
  row5 = _mm_load_si128((const __m128i *)(data + 5 * 8));
  row6 = _mm_load_si128((const __m128i *)(data + 6 * 8));
  row7 = _mm_load_si128((const __m128i *)(data + 7 * 8));

  // column pass
  dct_pass(bias_0, 10)

  {
    // 16bit 8x8 transpose pass 1
    dct_interleave16(row0, row4);
    dct_interleave16(row1, row5);
    dct_interleave16(row2, row6);
    dct_interleave16(row3, row7);

    // transpose pass 2
    dct_interleave16(row0, row2);
    dct_interleave16(row1, row3);
    dct_interleave16(row4, row6);
    dct_interleave16(row5, row7);

    // transpose pass 3
    dct_interleave16(row0, row1);
    dct_interleave16(row2, row3);
    dct_interleave16(row4, row5);
    dct_interleave16(row6, row7);
  }

  // row pass
  dct_pass(bias_1, 17)

  {
    // pack
    __m128i p0 = _mm_packus_epi16(row0, row1);  // a0a1a2a3...a7b0b1b2b3...b7
    __m128i p1 = _mm_packus_epi16(row2, row3);
    __m128i p2 = _mm_packus_epi16(row4, row5);
    __m128i p3 = _mm_packus_epi16(row6, row7);

    // 8bit 8x8 transpose pass 1
    dct_interleave8(p0, p2);  // a0e0a1e1...
    dct_interleave8(p1, p3);  // c0g0c1g1...

    // transpose pass 2
    dct_interleave8(p0, p1);  // a0c0e0g0...
    dct_interleave8(p2, p3);  // b0d0f0h0...

    // transpose pass 3
    dct_interleave8(p0, p2);  // a0b0c0d0...
    dct_interleave8(p1, p3);  // a4b4c4d4...

    // store
    _mm_storel_epi64((__m128i *)out, p0);
    out += out_stride;
    _mm_storel_epi64((__m128i *)out, _mm_shuffle_epi32(p0, 0x4e));
    out += out_stride;
    _mm_storel_epi64((__m128i *)out, p2);
    out += out_stride;
    _mm_storel_epi64((__m128i *)out, _mm_shuffle_epi32(p2, 0x4e));
    out += out_stride;
    _mm_storel_epi64((__m128i *)out, p1);
    out += out_stride;
    _mm_storel_epi64((__m128i *)out, _mm_shuffle_epi32(p1, 0x4e));
    out += out_stride;
    _mm_storel_epi64((__m128i *)out, p3);
    out += out_stride;
    _mm_storel_epi64((__m128i *)out, _mm_shuffle_epi32(p3, 0x4e));
  }

#undef dct_const
#undef dct_rot
#undef dct_widen
#undef dct_wadd
#undef dct_wsub
#undef dct_bfly32o
#undef dct_interleave8
#undef dct_interleave16
#undef dct_pass
}

#endif  // IMG_SSE2

#ifdef IMG_NEON

// NEON integer IDCT. should produce bit-identical
// results to the generic C version.
static void
img__idct_simd(img_uc *out, int out_stride, short data[64]) {
  int16x8_t row0, row1, row2, row3, row4, row5, row6, row7;

  int16x4_t rot0_0 = vdup_n_s16(img__f2f(0.5411961f));
  int16x4_t rot0_1 = vdup_n_s16(img__f2f(-1.847759065f));
  int16x4_t rot0_2 = vdup_n_s16(img__f2f(0.765366865f));
  int16x4_t rot1_0 = vdup_n_s16(img__f2f(1.175875602f));
  int16x4_t rot1_1 = vdup_n_s16(img__f2f(-0.899976223f));
  int16x4_t rot1_2 = vdup_n_s16(img__f2f(-2.562915447f));
  int16x4_t rot2_0 = vdup_n_s16(img__f2f(-1.961570560f));
  int16x4_t rot2_1 = vdup_n_s16(img__f2f(-0.390180644f));
  int16x4_t rot3_0 = vdup_n_s16(img__f2f(0.298631336f));
  int16x4_t rot3_1 = vdup_n_s16(img__f2f(2.053119869f));
  int16x4_t rot3_2 = vdup_n_s16(img__f2f(3.072711026f));
  int16x4_t rot3_3 = vdup_n_s16(img__f2f(1.501321110f));

#define dct_long_mul(out, inq, coeff)                      \
  int32x4_t out##_l = vmull_s16(vget_low_s16(inq), coeff); \
  int32x4_t out##_h = vmull_s16(vget_high_s16(inq), coeff)

#define dct_long_mac(out, acc, inq, coeff)                          \
  int32x4_t out##_l = vmlal_s16(acc##_l, vget_low_s16(inq), coeff); \
  int32x4_t out##_h = vmlal_s16(acc##_h, vget_high_s16(inq), coeff)

#define dct_widen(out, inq)                               \
  int32x4_t out##_l = vshll_n_s16(vget_low_s16(inq), 12); \
  int32x4_t out##_h = vshll_n_s16(vget_high_s16(inq), 12)

// wide add
#define dct_wadd(out, a, b)                    \
  int32x4_t out##_l = vaddq_s32(a##_l, b##_l); \
  int32x4_t out##_h = vaddq_s32(a##_h, b##_h)

// wide sub
#define dct_wsub(out, a, b)                    \
  int32x4_t out##_l = vsubq_s32(a##_l, b##_l); \
  int32x4_t out##_h = vsubq_s32(a##_h, b##_h)

// butterfly a/b, then shift using "shiftop" by "s" and pack
#define dct_bfly32o(out0, out1, a, b, shiftop, s)              \
  {                                                            \
    dct_wadd(sum, a, b);                                       \
    dct_wsub(dif, a, b);                                       \
    out0 = vcombine_s16(shiftop(sum_l, s), shiftop(sum_h, s)); \
    out1 = vcombine_s16(shiftop(dif_l, s), shiftop(dif_h, s)); \
  }

#define dct_pass(shiftop, shift)                     \
  {                                                  \
    /* even part */                                  \
    int16x8_t sum26 = vaddq_s16(row2, row6);         \
    dct_long_mul(p1e, sum26, rot0_0);                \
    dct_long_mac(t2e, p1e, row6, rot0_1);            \
    dct_long_mac(t3e, p1e, row2, rot0_2);            \
    int16x8_t sum04 = vaddq_s16(row0, row4);         \
    int16x8_t dif04 = vsubq_s16(row0, row4);         \
    dct_widen(t0e, sum04);                           \
    dct_widen(t1e, dif04);                           \
    dct_wadd(x0, t0e, t3e);                          \
    dct_wsub(x3, t0e, t3e);                          \
    dct_wadd(x1, t1e, t2e);                          \
    dct_wsub(x2, t1e, t2e);                          \
    /* odd part */                                   \
    int16x8_t sum15 = vaddq_s16(row1, row5);         \
    int16x8_t sum17 = vaddq_s16(row1, row7);         \
    int16x8_t sum35 = vaddq_s16(row3, row5);         \
    int16x8_t sum37 = vaddq_s16(row3, row7);         \
    int16x8_t sumodd = vaddq_s16(sum17, sum35);      \
    dct_long_mul(p5o, sumodd, rot1_0);               \
    dct_long_mac(p1o, p5o, sum17, rot1_1);           \
    dct_long_mac(p2o, p5o, sum35, rot1_2);           \
    dct_long_mul(p3o, sum37, rot2_0);                \
    dct_long_mul(p4o, sum15, rot2_1);                \
    dct_wadd(sump13o, p1o, p3o);                     \
    dct_wadd(sump24o, p2o, p4o);                     \
    dct_wadd(sump23o, p2o, p3o);                     \
    dct_wadd(sump14o, p1o, p4o);                     \
    dct_long_mac(x4, sump13o, row7, rot3_0);         \
    dct_long_mac(x5, sump24o, row5, rot3_1);         \
    dct_long_mac(x6, sump23o, row3, rot3_2);         \
    dct_long_mac(x7, sump14o, row1, rot3_3);         \
    dct_bfly32o(row0, row7, x0, x7, shiftop, shift); \
    dct_bfly32o(row1, row6, x1, x6, shiftop, shift); \
    dct_bfly32o(row2, row5, x2, x5, shiftop, shift); \
    dct_bfly32o(row3, row4, x3, x4, shiftop, shift); \
  }

  // load
  row0 = vld1q_s16(data + 0 * 8);
  row1 = vld1q_s16(data + 1 * 8);
  row2 = vld1q_s16(data + 2 * 8);
  row3 = vld1q_s16(data + 3 * 8);
  row4 = vld1q_s16(data + 4 * 8);
  row5 = vld1q_s16(data + 5 * 8);
  row6 = vld1q_s16(data + 6 * 8);
  row7 = vld1q_s16(data + 7 * 8);

  // add DC bias
  row0 = vaddq_s16(row0, vsetq_lane_s16(1024, vdupq_n_s16(0), 0));

  // column pass
  dct_pass(vrshrn_n_s32, 10);

  // 16bit 8x8 transpose
  {
// these three map to a single VTRN.16, VTRN.32, and VSWP, respectively.
// whether compilers actually get this is another story, sadly.
#define dct_trn16(x, y)              \
  {                                  \
    int16x8x2_t t = vtrnq_s16(x, y); \
    x = t.val[0];                    \
    y = t.val[1];                    \
  }
#define dct_trn32(x, y)                                                \
  {                                                                    \
    int32x4x2_t t =                                                    \
        vtrnq_s32(vreinterpretq_s32_s16(x), vreinterpretq_s32_s16(y)); \
    x = vreinterpretq_s16_s32(t.val[0]);                               \
    y = vreinterpretq_s16_s32(t.val[1]);                               \
  }
#define dct_trn64(x, y)                                     \
  {                                                         \
    int16x8_t x0 = x;                                       \
    int16x8_t y0 = y;                                       \
    x = vcombine_s16(vget_low_s16(x0), vget_low_s16(y0));   \
    y = vcombine_s16(vget_high_s16(x0), vget_high_s16(y0)); \
  }

    // pass 1
    dct_trn16(row0, row1);  // a0b0a2b2a4b4a6b6
    dct_trn16(row2, row3);
    dct_trn16(row4, row5);
    dct_trn16(row6, row7);

    // pass 2
    dct_trn32(row0, row2);  // a0b0c0d0a4b4c4d4
    dct_trn32(row1, row3);
    dct_trn32(row4, row6);
    dct_trn32(row5, row7);

    // pass 3
    dct_trn64(row0, row4);  // a0b0c0d0e0f0g0h0
    dct_trn64(row1, row5);
    dct_trn64(row2, row6);
    dct_trn64(row3, row7);

#undef dct_trn16
#undef dct_trn32
#undef dct_trn64
  }

  // row pass
  // vrshrn_n_s32 only supports shifts up to 16, we need
  // 17. so do a non-rounding shift of 16 first then follow
  // up with a rounding shift by 1.
  dct_pass(vshrn_n_s32, 16);

  {
    // pack and round
    uint8x8_t p0 = vqrshrun_n_s16(row0, 1);
    uint8x8_t p1 = vqrshrun_n_s16(row1, 1);
    uint8x8_t p2 = vqrshrun_n_s16(row2, 1);
    uint8x8_t p3 = vqrshrun_n_s16(row3, 1);
    uint8x8_t p4 = vqrshrun_n_s16(row4, 1);
    uint8x8_t p5 = vqrshrun_n_s16(row5, 1);
    uint8x8_t p6 = vqrshrun_n_s16(row6, 1);
    uint8x8_t p7 = vqrshrun_n_s16(row7, 1);

    // again, these can translate into one instruction, but often don't.
#define dct_trn8_8(x, y)           \
  {                                \
    uint8x8x2_t t = vtrn_u8(x, y); \
    x = t.val[0];                  \
    y = t.val[1];                  \
  }
#define dct_trn8_16(x, y)                                                      \
  {                                                                            \
    uint16x4x2_t t = vtrn_u16(vreinterpret_u16_u8(x), vreinterpret_u16_u8(y)); \
    x = vreinterpret_u8_u16(t.val[0]);                                         \
    y = vreinterpret_u8_u16(t.val[1]);                                         \
  }
#define dct_trn8_32(x, y)                                                      \
  {                                                                            \
    uint32x2x2_t t = vtrn_u32(vreinterpret_u32_u8(x), vreinterpret_u32_u8(y)); \
    x = vreinterpret_u8_u32(t.val[0]);                                         \
    y = vreinterpret_u8_u32(t.val[1]);                                         \
  }

    // sadly can't use interleaved stores here since we only write
    // 8 bytes to each scan line!

    // 8x8 8-bit transpose pass 1
    dct_trn8_8(p0, p1);
    dct_trn8_8(p2, p3);
    dct_trn8_8(p4, p5);
    dct_trn8_8(p6, p7);

    // pass 2
    dct_trn8_16(p0, p2);
    dct_trn8_16(p1, p3);
    dct_trn8_16(p4, p6);
    dct_trn8_16(p5, p7);

    // pass 3
    dct_trn8_32(p0, p4);
    dct_trn8_32(p1, p5);
    dct_trn8_32(p2, p6);
    dct_trn8_32(p3, p7);

    // store
    vst1_u8(out, p0);
    out += out_stride;
    vst1_u8(out, p1);
    out += out_stride;
    vst1_u8(out, p2);
    out += out_stride;
    vst1_u8(out, p3);
    out += out_stride;
    vst1_u8(out, p4);
    out += out_stride;
    vst1_u8(out, p5);
    out += out_stride;
    vst1_u8(out, p6);
    out += out_stride;
    vst1_u8(out, p7);

#undef dct_trn8_8
#undef dct_trn8_16
#undef dct_trn8_32
  }

#undef dct_long_mul
#undef dct_long_mac
#undef dct_widen
#undef dct_wadd
#undef dct_wsub
#undef dct_bfly32o
#undef dct_pass
}

#endif  // IMG_NEON

#define IMG__MARKER_none 0xff
// if there's a pending marker from the entropy stream, return that
// otherwise, fetch from the stream and get a marker. if there's no
// marker, return 0xff, which is never a valid marker value
static img_uc
img__get_marker(img__jpeg *j) {
  img_uc x;
  if (j->marker != IMG__MARKER_none) {
    x = j->marker;
    j->marker = IMG__MARKER_none;
    return x;
  }
  x = img__get8(j->s);
  if (x != 0xff) return IMG__MARKER_none;
  while (x == 0xff) x = img__get8(j->s);  // consume repeated 0xff fill bytes
  return x;
}

// in each scan, we'll have scan_n components, and the order
// of the components is specified by order[]
#define IMG__RESTART(x) ((x) >= 0xd0 && (x) <= 0xd7)

// after a restart interval, img__jpeg_reset the entropy decoder and
// the dc prediction
static void
img__jpeg_reset(img__jpeg *j) {
  j->code_bits = 0;
  j->code_buffer = 0;
  j->nomore = 0;
  j->img_comp[0].dc_pred = j->img_comp[1].dc_pred = j->img_comp[2].dc_pred =
      j->img_comp[3].dc_pred = 0;
  j->marker = IMG__MARKER_none;
  j->todo = j->restart_interval ? j->restart_interval : 0x7fffffff;
  j->eob_run = 0;
  // no more than 1<<31 MCUs if no restart_interal? that's plenty safe,
  // since we don't even allow 1<<30 pixels
}

static int
img__parse_entropy_coded_data(img__jpeg *z) {
  img__jpeg_reset(z);
  if (!z->progressive) {
    if (z->scan_n == 1) {
      int i, j;
      IMG_SIMD_ALIGN(short, data[64]);
      int n = z->order[0];
      // non-interleaved data, we just need to process one block at a time,
      // in trivial scanline order
      // number of blocks to do just depends on how many actual "pixels" this
      // component has, independent of interleaved MCU blocking and such
      int w = (z->img_comp[n].x + 7) >> 3;
      int h = (z->img_comp[n].y + 7) >> 3;
      for (j = 0; j < h; ++j) {
        for (i = 0; i < w; ++i) {
          int ha = z->img_comp[n].ha;
          if (!img__jpeg_decode_block(z, data, z->huff_dc + z->img_comp[n].hd,
                                      z->huff_ac + ha, z->fast_ac[ha], n,
                                      z->dequant[z->img_comp[n].tq]))
            return 0;
          z->idct_block_kernel(
              z->img_comp[n].data + z->img_comp[n].w2 * j * 8 + i * 8,
              z->img_comp[n].w2, data);
          // every data block is an MCU, so countdown the restart interval
          if (--z->todo <= 0) {
            if (z->code_bits < 24) img__grow_buffer_unsafe(z);
            // if it's NOT a restart, then just bail, so we get corrupt data
            // rather than no data
            if (!IMG__RESTART(z->marker)) return 1;
            img__jpeg_reset(z);
          }
        }
      }
      return 1;
    } else {  // interleaved
      int i, j, k, x, y;
      IMG_SIMD_ALIGN(short, data[64]);
      for (j = 0; j < z->img_mcu_y; ++j) {
        for (i = 0; i < z->img_mcu_x; ++i) {
          // scan an interleaved mcu... process scan_n components in order
          for (k = 0; k < z->scan_n; ++k) {
            int n = z->order[k];
            // scan out an mcu's worth of this component; that's just determined
            // by the basic H and V specified for the component
            for (y = 0; y < z->img_comp[n].v; ++y) {
              for (x = 0; x < z->img_comp[n].h; ++x) {
                int x2 = (i * z->img_comp[n].h + x) * 8;
                int y2 = (j * z->img_comp[n].v + y) * 8;
                int ha = z->img_comp[n].ha;
                if (!img__jpeg_decode_block(z, data,
                                            z->huff_dc + z->img_comp[n].hd,
                                            z->huff_ac + ha, z->fast_ac[ha], n,
                                            z->dequant[z->img_comp[n].tq]))
                  return 0;
                z->idct_block_kernel(
                    z->img_comp[n].data + z->img_comp[n].w2 * y2 + x2,
                    z->img_comp[n].w2, data);
              }
            }
          }
          // after all interleaved components, that's an interleaved MCU,
          // so now count down the restart interval
          if (--z->todo <= 0) {
            if (z->code_bits < 24) img__grow_buffer_unsafe(z);
            if (!IMG__RESTART(z->marker)) return 1;
            img__jpeg_reset(z);
          }
        }
      }
      return 1;
    }
  } else {
    if (z->scan_n == 1) {
      int i, j;
      int n = z->order[0];
      // non-interleaved data, we just need to process one block at a time,
      // in trivial scanline order
      // number of blocks to do just depends on how many actual "pixels" this
      // component has, independent of interleaved MCU blocking and such
      int w = (z->img_comp[n].x + 7) >> 3;
      int h = (z->img_comp[n].y + 7) >> 3;
      for (j = 0; j < h; ++j) {
        for (i = 0; i < w; ++i) {
          short *data =
              z->img_comp[n].coeff + 64 * (i + j * z->img_comp[n].coeff_w);
          if (z->spec_start == 0) {
            if (!img__jpeg_decode_block_prog_dc(
                    z, data, &z->huff_dc[z->img_comp[n].hd], n))
              return 0;
          } else {
            int ha = z->img_comp[n].ha;
            if (!img__jpeg_decode_block_prog_ac(z, data, &z->huff_ac[ha],
                                                z->fast_ac[ha]))
              return 0;
          }
          // every data block is an MCU, so countdown the restart interval
          if (--z->todo <= 0) {
            if (z->code_bits < 24) img__grow_buffer_unsafe(z);
            if (!IMG__RESTART(z->marker)) return 1;
            img__jpeg_reset(z);
          }
        }
      }
      return 1;
    } else {  // interleaved
      int i, j, k, x, y;
      for (j = 0; j < z->img_mcu_y; ++j) {
        for (i = 0; i < z->img_mcu_x; ++i) {
          // scan an interleaved mcu... process scan_n components in order
          for (k = 0; k < z->scan_n; ++k) {
            int n = z->order[k];
            // scan out an mcu's worth of this component; that's just determined
            // by the basic H and V specified for the component
            for (y = 0; y < z->img_comp[n].v; ++y) {
              for (x = 0; x < z->img_comp[n].h; ++x) {
                int x2 = (i * z->img_comp[n].h + x);
                int y2 = (j * z->img_comp[n].v + y);
                short *data = z->img_comp[n].coeff +
                              64 * (x2 + y2 * z->img_comp[n].coeff_w);
                if (!img__jpeg_decode_block_prog_dc(
                        z, data, &z->huff_dc[z->img_comp[n].hd], n))
                  return 0;
              }
            }
          }
          // after all interleaved components, that's an interleaved MCU,
          // so now count down the restart interval
          if (--z->todo <= 0) {
            if (z->code_bits < 24) img__grow_buffer_unsafe(z);
            if (!IMG__RESTART(z->marker)) return 1;
            img__jpeg_reset(z);
          }
        }
      }
      return 1;
    }
  }
}

static void
img__jpeg_dequantize(short *data, img__uint16 *dequant) {
  int i;
  for (i = 0; i < 64; ++i) data[i] *= dequant[i];
}

static void
img__jpeg_finish(img__jpeg *z) {
  if (z->progressive) {
    // dequantize and idct the data
    int i, j, n;
    for (n = 0; n < z->s->img_n; ++n) {
      int w = (z->img_comp[n].x + 7) >> 3;
      int h = (z->img_comp[n].y + 7) >> 3;
      for (j = 0; j < h; ++j) {
        for (i = 0; i < w; ++i) {
          short *data =
              z->img_comp[n].coeff + 64 * (i + j * z->img_comp[n].coeff_w);
          img__jpeg_dequantize(data, z->dequant[z->img_comp[n].tq]);
          z->idct_block_kernel(
              z->img_comp[n].data + z->img_comp[n].w2 * j * 8 + i * 8,
              z->img_comp[n].w2, data);
        }
      }
    }
  }
}

static int
img__process_marker(img__jpeg *z, int m) {
  int L;
  switch (m) {
    case IMG__MARKER_none:  // no marker found
      return img__err("expected marker", "Corrupt JPEG");

    case 0xDD:  // DRI - specify restart interval
      if (img__get16be(z->s) != 4)
        return img__err("bad DRI len", "Corrupt JPEG");
      z->restart_interval = img__get16be(z->s);
      return 1;

    case 0xDB:  // DQT - define quantization table
      L = img__get16be(z->s) - 2;
      while (L > 0) {
        int q = img__get8(z->s);
        int p = q >> 4, sixteen = (p != 0);
        int t = q & 15, i;
        if (p != 0 && p != 1) return img__err("bad DQT type", "Corrupt JPEG");
        if (t > 3) return img__err("bad DQT table", "Corrupt JPEG");

        for (i = 0; i < 64; ++i)
          z->dequant[t][img__jpeg_dezigzag[i]] =
              (img__uint16)(sixteen ? img__get16be(z->s) : img__get8(z->s));
        L -= (sixteen ? 129 : 65);
      }
      return L == 0;

    case 0xC4:  // DHT - define huffman table
      L = img__get16be(z->s) - 2;
      while (L > 0) {
        img_uc *v;
        int sizes[16], i, n = 0;
        int q = img__get8(z->s);
        int tc = q >> 4;
        int th = q & 15;
        if (tc > 1 || th > 3) return img__err("bad DHT header", "Corrupt JPEG");
        for (i = 0; i < 16; ++i) {
          sizes[i] = img__get8(z->s);
          n += sizes[i];
        }
        L -= 17;
        if (tc == 0) {
          if (!img__build_huffman(z->huff_dc + th, sizes)) return 0;
          v = z->huff_dc[th].values;
        } else {
          if (!img__build_huffman(z->huff_ac + th, sizes)) return 0;
          v = z->huff_ac[th].values;
        }
        for (i = 0; i < n; ++i) v[i] = img__get8(z->s);
        if (tc != 0) img__build_fast_ac(z->fast_ac[th], z->huff_ac + th);
        L -= n;
      }
      return L == 0;
  }

  // check for comment block or APP blocks
  if ((m >= 0xE0 && m <= 0xEF) || m == 0xFE) {
    L = img__get16be(z->s);
    if (L < 2) {
      if (m == 0xFE)
        return img__err("bad COM len", "Corrupt JPEG");
      else
        return img__err("bad APP len", "Corrupt JPEG");
    }
    L -= 2;

    if (m == 0xE0 && L >= 5) {  // JFIF APP0 segment
      static const unsigned char tag[5] = {'J', 'F', 'I', 'F', '\0'};
      int ok = 1;
      int i;
      for (i = 0; i < 5; ++i)
        if (img__get8(z->s) != tag[i]) ok = 0;
      L -= 5;
      if (ok) z->jfif = 1;
    } else if (m == 0xEE && L >= 12) {  // Adobe APP14 segment
      static const unsigned char tag[6] = {'A', 'd', 'o', 'b', 'e', '\0'};
      int ok = 1;
      int i;
      for (i = 0; i < 6; ++i)
        if (img__get8(z->s) != tag[i]) ok = 0;
      L -= 6;
      if (ok) {
        img__get8(z->s);                             // version
        img__get16be(z->s);                          // flags0
        img__get16be(z->s);                          // flags1
        z->app14_color_transform = img__get8(z->s);  // color transform
        L -= 6;
      }
    }

    img__skip(z->s, L);
    return 1;
  }

  return img__err("unknown marker", "Corrupt JPEG");
}

// after we see SOS
static int
img__process_scan_header(img__jpeg *z) {
  int i;
  int Ls = img__get16be(z->s);
  z->scan_n = img__get8(z->s);
  if (z->scan_n < 1 || z->scan_n > 4 || z->scan_n > (int)z->s->img_n)
    return img__err("bad SOS component count", "Corrupt JPEG");
  if (Ls != 6 + 2 * z->scan_n) return img__err("bad SOS len", "Corrupt JPEG");
  for (i = 0; i < z->scan_n; ++i) {
    int id = img__get8(z->s), which;
    int q = img__get8(z->s);
    for (which = 0; which < z->s->img_n; ++which)
      if (z->img_comp[which].id == id) break;
    if (which == z->s->img_n) return 0;  // no match
    z->img_comp[which].hd = q >> 4;
    if (z->img_comp[which].hd > 3)
      return img__err("bad DC huff", "Corrupt JPEG");
    z->img_comp[which].ha = q & 15;
    if (z->img_comp[which].ha > 3)
      return img__err("bad AC huff", "Corrupt JPEG");
    z->order[i] = which;
  }

  {
    int aa;
    z->spec_start = img__get8(z->s);
    z->spec_end = img__get8(z->s);  // should be 63, but might be 0
    aa = img__get8(z->s);
    z->succ_high = (aa >> 4);
    z->succ_low = (aa & 15);
    if (z->progressive) {
      if (z->spec_start > 63 || z->spec_end > 63 ||
          z->spec_start > z->spec_end || z->succ_high > 13 || z->succ_low > 13)
        return img__err("bad SOS", "Corrupt JPEG");
    } else {
      if (z->spec_start != 0) return img__err("bad SOS", "Corrupt JPEG");
      if (z->succ_high != 0 || z->succ_low != 0)
        return img__err("bad SOS", "Corrupt JPEG");
      z->spec_end = 63;
    }
  }

  return 1;
}

static int
img__free_jpeg_components(img__jpeg *z, int ncomp, int why) {
  int i;
  for (i = 0; i < ncomp; ++i) {
    if (z->img_comp[i].raw_data) {
      IMG_FREE(z->img_comp[i].raw_data);
      z->img_comp[i].raw_data = NULL;
      z->img_comp[i].data = NULL;
    }
    if (z->img_comp[i].raw_coeff) {
      IMG_FREE(z->img_comp[i].raw_coeff);
      z->img_comp[i].raw_coeff = 0;
      z->img_comp[i].coeff = 0;
    }
    if (z->img_comp[i].linebuf) {
      IMG_FREE(z->img_comp[i].linebuf);
      z->img_comp[i].linebuf = NULL;
    }
  }
  return why;
}

static int
img__process_frame_header(img__jpeg *z, int scan) {
  img__context *s = z->s;
  int Lf, p, i, q, h_max = 1, v_max = 1, c;
  Lf = img__get16be(s);
  if (Lf < 11) return img__err("bad SOF len", "Corrupt JPEG");  // JPEG
  p = img__get8(s);
  if (p != 8)
    return img__err("only 8-bit",
                    "JPEG format not supported: 8-bit only");  // JPEG baseline
  s->img_y = img__get16be(s);
  if (s->img_y == 0)
    return img__err(
        "no header height",
        "JPEG format not supported: delayed height");  // Legal, but we don't
                                                       // handle it--but neither
                                                       // does IJG
  s->img_x = img__get16be(s);
  if (s->img_x == 0)
    return img__err("0 width", "Corrupt JPEG");  // JPEG requires
  if (s->img_y > IMG_MAX_DIMENSIONS)
    return img__err("too large", "Very large image (corrupt?)");
  if (s->img_x > IMG_MAX_DIMENSIONS)
    return img__err("too large", "Very large image (corrupt?)");
  c = img__get8(s);
  if (c != 3 && c != 1 && c != 4)
    return img__err("bad component count", "Corrupt JPEG");
  s->img_n = c;
  for (i = 0; i < c; ++i) {
    z->img_comp[i].data = NULL;
    z->img_comp[i].linebuf = NULL;
  }

  if (Lf != 8 + 3 * s->img_n) return img__err("bad SOF len", "Corrupt JPEG");

  z->rgb = 0;
  for (i = 0; i < s->img_n; ++i) {
    static const unsigned char rgb[3] = {'R', 'G', 'B'};
    z->img_comp[i].id = img__get8(s);
    if (s->img_n == 3 && z->img_comp[i].id == rgb[i]) ++z->rgb;
    q = img__get8(s);
    z->img_comp[i].h = (q >> 4);
    if (!z->img_comp[i].h || z->img_comp[i].h > 4)
      return img__err("bad H", "Corrupt JPEG");
    z->img_comp[i].v = q & 15;
    if (!z->img_comp[i].v || z->img_comp[i].v > 4)
      return img__err("bad V", "Corrupt JPEG");
    z->img_comp[i].tq = img__get8(s);
    if (z->img_comp[i].tq > 3) return img__err("bad TQ", "Corrupt JPEG");
  }

  if (scan != IMG__SCAN_load) return 1;

  if (!img__mad3sizes_valid(s->img_x, s->img_y, s->img_n, 0))
    return img__err("too large", "Image too large to decode");

  for (i = 0; i < s->img_n; ++i) {
    if (z->img_comp[i].h > h_max) h_max = z->img_comp[i].h;
    if (z->img_comp[i].v > v_max) v_max = z->img_comp[i].v;
  }

  // compute interleaved mcu info
  z->img_h_max = h_max;
  z->img_v_max = v_max;
  z->img_mcu_w = h_max * 8;
  z->img_mcu_h = v_max * 8;
  // these sizes can't be more than 17 bits
  z->img_mcu_x = (s->img_x + z->img_mcu_w - 1) / z->img_mcu_w;
  z->img_mcu_y = (s->img_y + z->img_mcu_h - 1) / z->img_mcu_h;

  for (i = 0; i < s->img_n; ++i) {
    // number of effective pixels (e.g. for non-interleaved MCU)
    z->img_comp[i].x = (s->img_x * z->img_comp[i].h + h_max - 1) / h_max;
    z->img_comp[i].y = (s->img_y * z->img_comp[i].v + v_max - 1) / v_max;
    // to simplify generation, we'll allocate enough memory to decode
    // the bogus oversized data from using interleaved MCUs and their
    // big blocks (e.g. a 16x16 iMCU on an image of width 33); we won't
    // discard the extra data until colorspace conversion
    //
    // img_mcu_x, img_mcu_y: <=17 bits; comp[i].h and .v are <=4 (checked
    // earlier) so these muls can't overflow with 32-bit ints (which we require)
    z->img_comp[i].w2 = z->img_mcu_x * z->img_comp[i].h * 8;
    z->img_comp[i].h2 = z->img_mcu_y * z->img_comp[i].v * 8;
    z->img_comp[i].coeff = 0;
    z->img_comp[i].raw_coeff = 0;
    z->img_comp[i].linebuf = NULL;
    z->img_comp[i].raw_data =
        img__malloc_mad2(z->img_comp[i].w2, z->img_comp[i].h2, 15);
    if (z->img_comp[i].raw_data == NULL)
      return img__free_jpeg_components(z, i + 1,
                                       img__err("outofmem", "Out of memory"));
    // align blocks for idct using mmx/sse
    z->img_comp[i].data =
        (img_uc *)(((size_t)z->img_comp[i].raw_data + 15) & ~15);
    if (z->progressive) {
      // w2, h2 are multiples of 8 (see above)
      z->img_comp[i].coeff_w = z->img_comp[i].w2 / 8;
      z->img_comp[i].coeff_h = z->img_comp[i].h2 / 8;
      z->img_comp[i].raw_coeff = img__malloc_mad3(
          z->img_comp[i].w2, z->img_comp[i].h2, sizeof(short), 15);
      if (z->img_comp[i].raw_coeff == NULL)
        return img__free_jpeg_components(z, i + 1,
                                         img__err("outofmem", "Out of memory"));
      z->img_comp[i].coeff =
          (short *)(((size_t)z->img_comp[i].raw_coeff + 15) & ~15);
    }
  }

  return 1;
}

// use comparisons since in some cases we handle more than one case (e.g. SOF)
#define img__DNL(x) ((x) == 0xdc)
#define img__SOI(x) ((x) == 0xd8)
#define img__EOI(x) ((x) == 0xd9)
#define img__SOF(x) ((x) == 0xc0 || (x) == 0xc1 || (x) == 0xc2)
#define img__SOS(x) ((x) == 0xda)

#define img__SOF_progressive(x) ((x) == 0xc2)

static int
img__decode_jpeg_header(img__jpeg *z, int scan) {
  int m;
  z->jfif = 0;
  z->app14_color_transform = -1;  // valid values are 0,1,2
  z->marker = IMG__MARKER_none;   // initialize cached marker to empty
  m = img__get_marker(z);
  if (!img__SOI(m)) return img__err("no SOI", "Corrupt JPEG");
  if (scan == IMG__SCAN_type) return 1;
  m = img__get_marker(z);
  while (!img__SOF(m)) {
    if (!img__process_marker(z, m)) return 0;
    m = img__get_marker(z);
    while (m == IMG__MARKER_none) {
      // some files have extra padding after their blocks, so ok, we'll scan
      if (img__at_eof(z->s)) return img__err("no SOF", "Corrupt JPEG");
      m = img__get_marker(z);
    }
  }
  z->progressive = img__SOF_progressive(m);
  if (!img__process_frame_header(z, scan)) return 0;
  return 1;
}

// decode image to YCbCr format
static int
img__decode_jpeg_image(img__jpeg *j) {
  int m;
  for (m = 0; m < 4; m++) {
    j->img_comp[m].raw_data = NULL;
    j->img_comp[m].raw_coeff = NULL;
  }
  j->restart_interval = 0;
  if (!img__decode_jpeg_header(j, IMG__SCAN_load)) return 0;
  m = img__get_marker(j);
  while (!img__EOI(m)) {
    if (img__SOS(m)) {
      if (!img__process_scan_header(j)) return 0;
      if (!img__parse_entropy_coded_data(j)) return 0;
      if (j->marker == IMG__MARKER_none) {
        // handle 0s at the end of image data from IP Kamera 9060
        while (!img__at_eof(j->s)) {
          int x = img__get8(j->s);
          if (x == 255) {
            j->marker = img__get8(j->s);
            break;
          }
        }
        // if we reach eof without hitting a marker, img__get_marker() below
        // will fail and we'll eventually return 0
      }
    } else if (img__DNL(m)) {
      int Ld = img__get16be(j->s);
      img__uint32 NL = img__get16be(j->s);
      if (Ld != 4) return img__err("bad DNL len", "Corrupt JPEG");
      if (NL != j->s->img_y) return img__err("bad DNL height", "Corrupt JPEG");
    } else {
      if (!img__process_marker(j, m)) return 0;
    }
    m = img__get_marker(j);
  }
  if (j->progressive) img__jpeg_finish(j);
  return 1;
}

// static jfif-centered resampling (across block boundaries)

typedef img_uc *(*resample_row_func)(img_uc *out, img_uc *in0, img_uc *in1,
                                     int w, int hs);

#define img__div4(x) ((img_uc)((x) >> 2))

static img_uc *
resample_row_1(img_uc *out, img_uc *in_near, img_uc *in_far, int w, int hs) {
  IMG_NOTUSED(out);
  IMG_NOTUSED(in_far);
  IMG_NOTUSED(w);
  IMG_NOTUSED(hs);
  return in_near;
}

static img_uc *
img__resample_row_v_2(img_uc *out, img_uc *in_near, img_uc *in_far, int w,
                      int hs) {
  // need to generate two samples vertically for every one in input
  int i;
  IMG_NOTUSED(hs);
  for (i = 0; i < w; ++i) out[i] = img__div4(3 * in_near[i] + in_far[i] + 2);
  return out;
}

static img_uc *
img__resample_row_h_2(img_uc *out, img_uc *in_near, img_uc *in_far, int w,
                      int hs) {
  // need to generate two samples horizontally for every one in input
  int i;
  img_uc *input = in_near;

  if (w == 1) {
    // if only one sample, can't do any interpolation
    out[0] = out[1] = input[0];
    return out;
  }

  out[0] = input[0];
  out[1] = img__div4(input[0] * 3 + input[1] + 2);
  for (i = 1; i < w - 1; ++i) {
    int n = 3 * input[i] + 2;
    out[i * 2 + 0] = img__div4(n + input[i - 1]);
    out[i * 2 + 1] = img__div4(n + input[i + 1]);
  }
  out[i * 2 + 0] = img__div4(input[w - 2] * 3 + input[w - 1] + 2);
  out[i * 2 + 1] = input[w - 1];

  IMG_NOTUSED(in_far);
  IMG_NOTUSED(hs);

  return out;
}

#define img__div16(x) ((img_uc)((x) >> 4))

static img_uc *
img__resample_row_hv_2(img_uc *out, img_uc *in_near, img_uc *in_far, int w,
                       int hs) {
  // need to generate 2x2 samples for every one in input
  int i, t0, t1;
  if (w == 1) {
    out[0] = out[1] = img__div4(3 * in_near[0] + in_far[0] + 2);
    return out;
  }

  t1 = 3 * in_near[0] + in_far[0];
  out[0] = img__div4(t1 + 2);
  for (i = 1; i < w; ++i) {
    t0 = t1;
    t1 = 3 * in_near[i] + in_far[i];
    out[i * 2 - 1] = img__div16(3 * t0 + t1 + 8);
    out[i * 2] = img__div16(3 * t1 + t0 + 8);
  }
  out[w * 2 - 1] = img__div4(t1 + 2);

  IMG_NOTUSED(hs);

  return out;
}

#if defined(IMG_SSE2) || defined(IMG_NEON)
static img_uc *
img__resample_row_hv_2_simd(img_uc *out, img_uc *in_near, img_uc *in_far, int w,
                            int hs) {
  // need to generate 2x2 samples for every one in input
  int i = 0, t0, t1;

  if (w == 1) {
    out[0] = out[1] = img__div4(3 * in_near[0] + in_far[0] + 2);
    return out;
  }

  t1 = 3 * in_near[0] + in_far[0];
  // process groups of 8 pixels for as long as we can.
  // note we can't handle the last pixel in a row in this loop
  // because we need to handle the filter boundary conditions.
  for (; i < ((w - 1) & ~7); i += 8) {
#if defined(IMG_SSE2)
    // load and perform the vertical filtering pass
    // this uses 3*x + y = 4*x + (y - x)
    __m128i zero = _mm_setzero_si128();
    __m128i farb = _mm_loadl_epi64((__m128i *)(in_far + i));
    __m128i nearb = _mm_loadl_epi64((__m128i *)(in_near + i));
    __m128i farw = _mm_unpacklo_epi8(farb, zero);
    __m128i nearw = _mm_unpacklo_epi8(nearb, zero);
    __m128i diff = _mm_sub_epi16(farw, nearw);
    __m128i nears = _mm_slli_epi16(nearw, 2);
    __m128i curr = _mm_add_epi16(nears, diff);  // current row

    // horizontal filter works the same based on shifted vers of current
    // row. "prev" is current row shifted right by 1 pixel; we need to
    // insert the previous pixel value (from t1).
    // "next" is current row shifted left by 1 pixel, with first pixel
    // of next block of 8 pixels added in.
    __m128i prv0 = _mm_slli_si128(curr, 2);
    __m128i nxt0 = _mm_srli_si128(curr, 2);
    __m128i prev = _mm_insert_epi16(prv0, t1, 0);
    __m128i next =
        _mm_insert_epi16(nxt0, 3 * in_near[i + 8] + in_far[i + 8], 7);

    // horizontal filter, polyphase implementation since it's convenient:
    // even pixels = 3*cur + prev = cur*4 + (prev - cur)
    // odd  pixels = 3*cur + next = cur*4 + (next - cur)
    // note the shared term.
    __m128i bias = _mm_set1_epi16(8);
    __m128i curs = _mm_slli_epi16(curr, 2);
    __m128i prvd = _mm_sub_epi16(prev, curr);
    __m128i nxtd = _mm_sub_epi16(next, curr);
    __m128i curb = _mm_add_epi16(curs, bias);
    __m128i even = _mm_add_epi16(prvd, curb);
    __m128i odd = _mm_add_epi16(nxtd, curb);

    // interleave even and odd pixels, then undo scaling.
    __m128i int0 = _mm_unpacklo_epi16(even, odd);
    __m128i int1 = _mm_unpackhi_epi16(even, odd);
    __m128i de0 = _mm_srli_epi16(int0, 4);
    __m128i de1 = _mm_srli_epi16(int1, 4);

    // pack and write output
    __m128i outv = _mm_packus_epi16(de0, de1);
    _mm_storeu_si128((__m128i *)(out + i * 2), outv);
#elif defined(IMG_NEON)
    // load and perform the vertical filtering pass
    // this uses 3*x + y = 4*x + (y - x)
    uint8x8_t farb = vld1_u8(in_far + i);
    uint8x8_t nearb = vld1_u8(in_near + i);
    int16x8_t diff = vreinterpretq_s16_u16(vsubl_u8(farb, nearb));
    int16x8_t nears = vreinterpretq_s16_u16(vshll_n_u8(nearb, 2));
    int16x8_t curr = vaddq_s16(nears, diff);  // current row

    // horizontal filter works the same based on shifted vers of current
    // row. "prev" is current row shifted right by 1 pixel; we need to
    // insert the previous pixel value (from t1).
    // "next" is current row shifted left by 1 pixel, with first pixel
    // of next block of 8 pixels added in.
    int16x8_t prv0 = vextq_s16(curr, curr, 7);
    int16x8_t nxt0 = vextq_s16(curr, curr, 1);
    int16x8_t prev = vsetq_lane_s16(t1, prv0, 0);
    int16x8_t next =
        vsetq_lane_s16(3 * in_near[i + 8] + in_far[i + 8], nxt0, 7);

    // horizontal filter, polyphase implementation since it's convenient:
    // even pixels = 3*cur + prev = cur*4 + (prev - cur)
    // odd  pixels = 3*cur + next = cur*4 + (next - cur)
    // note the shared term.
    int16x8_t curs = vshlq_n_s16(curr, 2);
    int16x8_t prvd = vsubq_s16(prev, curr);
    int16x8_t nxtd = vsubq_s16(next, curr);
    int16x8_t even = vaddq_s16(curs, prvd);
    int16x8_t odd = vaddq_s16(curs, nxtd);

    // undo scaling and round, then store with even/odd phases interleaved
    uint8x8x2_t o;
    o.val[0] = vqrshrun_n_s16(even, 4);
    o.val[1] = vqrshrun_n_s16(odd, 4);
    vst2_u8(out + i * 2, o);
#endif

    // "previous" value for next iter
    t1 = 3 * in_near[i + 7] + in_far[i + 7];
  }

  t0 = t1;
  t1 = 3 * in_near[i] + in_far[i];
  out[i * 2] = img__div16(3 * t1 + t0 + 8);

  for (++i; i < w; ++i) {
    t0 = t1;
    t1 = 3 * in_near[i] + in_far[i];
    out[i * 2 - 1] = img__div16(3 * t0 + t1 + 8);
    out[i * 2] = img__div16(3 * t1 + t0 + 8);
  }
  out[w * 2 - 1] = img__div4(t1 + 2);

  IMG_NOTUSED(hs);

  return out;
}
#endif

static img_uc *
img__resample_row_generic(img_uc *out, img_uc *in_near, img_uc *in_far, int w,
                          int hs) {
  // resample with nearest-neighbor
  int i, j;
  IMG_NOTUSED(in_far);
  for (i = 0; i < w; ++i)
    for (j = 0; j < hs; ++j) out[i * hs + j] = in_near[i];
  return out;
}

// this is a reduced-precision calculation of YCbCr-to-RGB introduced
// to make sure the code produces the same results in both SIMD and scalar
#define img__float2fixed(x) (((int)((x)*4096.0f + 0.5f)) << 8)
static void
img__YCbCr_to_RGB_row(img_uc *out, const img_uc *y, const img_uc *pcb,
                      const img_uc *pcr, int count, int step) {
  int i;
  for (i = 0; i < count; ++i) {
    int y_fixed = (y[i] << 20) + (1 << 19);  // rounding
    int r, g, b;
    int cr = pcr[i] - 128;
    int cb = pcb[i] - 128;
    r = y_fixed + cr * img__float2fixed(1.40200f);
    g = y_fixed + (cr * -img__float2fixed(0.71414f)) +
        ((cb * -img__float2fixed(0.34414f)) & 0xffff0000);
    b = y_fixed + cb * img__float2fixed(1.77200f);
    r >>= 20;
    g >>= 20;
    b >>= 20;
    if ((unsigned)r > 255) {
      if (r < 0)
        r = 0;
      else
        r = 255;
    }
    if ((unsigned)g > 255) {
      if (g < 0)
        g = 0;
      else
        g = 255;
    }
    if ((unsigned)b > 255) {
      if (b < 0)
        b = 0;
      else
        b = 255;
    }
    out[0] = (img_uc)r;
    out[1] = (img_uc)g;
    out[2] = (img_uc)b;
    out[3] = 255;
    out += step;
  }
}

#if defined(IMG_SSE2) || defined(IMG_NEON)
static void
img__YCbCr_to_RGB_simd(img_uc *out, img_uc const *y, img_uc const *pcb,
                       img_uc const *pcr, int count, int step) {
  int i = 0;

#ifdef IMG_SSE2
  // step == 3 is pretty ugly on the final interleave, and i'm not convinced
  // it's useful in practice (you wouldn't use it for textures, for example).
  // so just accelerate step == 4 case.
  if (step == 4) {
    // this is a fairly straightforward implementation and not super-optimized.
    __m128i signflip = _mm_set1_epi8(-0x80);
    __m128i cr_const0 = _mm_set1_epi16((short)(1.40200f * 4096.0f + 0.5f));
    __m128i cr_const1 = _mm_set1_epi16(-(short)(0.71414f * 4096.0f + 0.5f));
    __m128i cb_const0 = _mm_set1_epi16(-(short)(0.34414f * 4096.0f + 0.5f));
    __m128i cb_const1 = _mm_set1_epi16((short)(1.77200f * 4096.0f + 0.5f));
    __m128i y_bias = _mm_set1_epi8((char)(unsigned char)128);
    __m128i xw = _mm_set1_epi16(255);  // alpha channel

    for (; i + 7 < count; i += 8) {
      // load
      __m128i y_bytes = _mm_loadl_epi64((__m128i *)(y + i));
      __m128i cr_bytes = _mm_loadl_epi64((__m128i *)(pcr + i));
      __m128i cb_bytes = _mm_loadl_epi64((__m128i *)(pcb + i));
      __m128i cr_biased = _mm_xor_si128(cr_bytes, signflip);  // -128
      __m128i cb_biased = _mm_xor_si128(cb_bytes, signflip);  // -128

      // unpack to short (and left-shift cr, cb by 8)
      __m128i yw = _mm_unpacklo_epi8(y_bias, y_bytes);
      __m128i crw = _mm_unpacklo_epi8(_mm_setzero_si128(), cr_biased);
      __m128i cbw = _mm_unpacklo_epi8(_mm_setzero_si128(), cb_biased);

      // color transform
      __m128i yws = _mm_srli_epi16(yw, 4);
      __m128i cr0 = _mm_mulhi_epi16(cr_const0, crw);
      __m128i cb0 = _mm_mulhi_epi16(cb_const0, cbw);
      __m128i cb1 = _mm_mulhi_epi16(cbw, cb_const1);
      __m128i cr1 = _mm_mulhi_epi16(crw, cr_const1);
      __m128i rws = _mm_add_epi16(cr0, yws);
      __m128i gwt = _mm_add_epi16(cb0, yws);
      __m128i bws = _mm_add_epi16(yws, cb1);
      __m128i gws = _mm_add_epi16(gwt, cr1);

      // descale
      __m128i rw = _mm_srai_epi16(rws, 4);
      __m128i bw = _mm_srai_epi16(bws, 4);
      __m128i gw = _mm_srai_epi16(gws, 4);

      // back to byte, set up for transpose
      __m128i brb = _mm_packus_epi16(rw, bw);
      __m128i gxb = _mm_packus_epi16(gw, xw);

      // transpose to interleave channels
      __m128i t0 = _mm_unpacklo_epi8(brb, gxb);
      __m128i t1 = _mm_unpackhi_epi8(brb, gxb);
      __m128i o0 = _mm_unpacklo_epi16(t0, t1);
      __m128i o1 = _mm_unpackhi_epi16(t0, t1);

      // store
      _mm_storeu_si128((__m128i *)(out + 0), o0);
      _mm_storeu_si128((__m128i *)(out + 16), o1);
      out += 32;
    }
  }
#endif

#ifdef IMG_NEON
  // in this version, step=3 support would be easy to add. but is there demand?
  if (step == 4) {
    // this is a fairly straightforward implementation and not super-optimized.
    uint8x8_t signflip = vdup_n_u8(0x80);
    int16x8_t cr_const0 = vdupq_n_s16((short)(1.40200f * 4096.0f + 0.5f));
    int16x8_t cr_const1 = vdupq_n_s16(-(short)(0.71414f * 4096.0f + 0.5f));
    int16x8_t cb_const0 = vdupq_n_s16(-(short)(0.34414f * 4096.0f + 0.5f));
    int16x8_t cb_const1 = vdupq_n_s16((short)(1.77200f * 4096.0f + 0.5f));

    for (; i + 7 < count; i += 8) {
      // load
      uint8x8_t y_bytes = vld1_u8(y + i);
      uint8x8_t cr_bytes = vld1_u8(pcr + i);
      uint8x8_t cb_bytes = vld1_u8(pcb + i);
      int8x8_t cr_biased = vreinterpret_s8_u8(vsub_u8(cr_bytes, signflip));
      int8x8_t cb_biased = vreinterpret_s8_u8(vsub_u8(cb_bytes, signflip));

      // expand to s16
      int16x8_t yws = vreinterpretq_s16_u16(vshll_n_u8(y_bytes, 4));
      int16x8_t crw = vshll_n_s8(cr_biased, 7);
      int16x8_t cbw = vshll_n_s8(cb_biased, 7);

      // color transform
      int16x8_t cr0 = vqdmulhq_s16(crw, cr_const0);
      int16x8_t cb0 = vqdmulhq_s16(cbw, cb_const0);
      int16x8_t cr1 = vqdmulhq_s16(crw, cr_const1);
      int16x8_t cb1 = vqdmulhq_s16(cbw, cb_const1);
      int16x8_t rws = vaddq_s16(yws, cr0);
      int16x8_t gws = vaddq_s16(vaddq_s16(yws, cb0), cr1);
      int16x8_t bws = vaddq_s16(yws, cb1);

      // undo scaling, round, convert to byte
      uint8x8x4_t o;
      o.val[0] = vqrshrun_n_s16(rws, 4);
      o.val[1] = vqrshrun_n_s16(gws, 4);
      o.val[2] = vqrshrun_n_s16(bws, 4);
      o.val[3] = vdup_n_u8(255);

      // store, interleaving r/g/b/a
      vst4_u8(out, o);
      out += 8 * 4;
    }
  }
#endif

  for (; i < count; ++i) {
    int y_fixed = (y[i] << 20) + (1 << 19);  // rounding
    int r, g, b;
    int cr = pcr[i] - 128;
    int cb = pcb[i] - 128;
    r = y_fixed + cr * img__float2fixed(1.40200f);
    g = y_fixed + cr * -img__float2fixed(0.71414f) +
        ((cb * -img__float2fixed(0.34414f)) & 0xffff0000);
    b = y_fixed + cb * img__float2fixed(1.77200f);
    r >>= 20;
    g >>= 20;
    b >>= 20;
    if ((unsigned)r > 255) {
      if (r < 0)
        r = 0;
      else
        r = 255;
    }
    if ((unsigned)g > 255) {
      if (g < 0)
        g = 0;
      else
        g = 255;
    }
    if ((unsigned)b > 255) {
      if (b < 0)
        b = 0;
      else
        b = 255;
    }
    out[0] = (img_uc)r;
    out[1] = (img_uc)g;
    out[2] = (img_uc)b;
    out[3] = 255;
    out += step;
  }
}
#endif

// set up the kernels
static void
img__setup_jpeg(img__jpeg *j) {
  j->idct_block_kernel = img__idct_block;
  j->YCbCr_to_RGB_kernel = img__YCbCr_to_RGB_row;
  j->resample_row_hv_2_kernel = img__resample_row_hv_2;

#ifdef IMG_SSE2
  if (img__sse2_available()) {
    j->idct_block_kernel = img__idct_simd;
    j->YCbCr_to_RGB_kernel = img__YCbCr_to_RGB_simd;
    j->resample_row_hv_2_kernel = img__resample_row_hv_2_simd;
  }
#endif

#ifdef IMG_NEON
  j->idct_block_kernel = img__idct_simd;
  j->YCbCr_to_RGB_kernel = img__YCbCr_to_RGB_simd;
  j->resample_row_hv_2_kernel = img__resample_row_hv_2_simd;
#endif
}

// clean up the temporary component buffers
static void
img__cleanup_jpeg(img__jpeg *j) {
  img__free_jpeg_components(j, j->s->img_n, 0);
}

typedef struct {
  resample_row_func resample;
  img_uc *line0, *line1;
  int hs, vs;   // expansion factor in each axis
  int w_lores;  // horizontal pixels pre-expansion
  int ystep;    // how far through vertical expansion we are
  int ypos;     // which pre-expansion row we're on
} img__resample;

// fast 0..255 * 0..255 => 0..255 rounded multiplication
static img_uc
img__blinn_8x8(img_uc x, img_uc y) {
  unsigned int t = x * y + 128;
  return (img_uc)((t + (t >> 8)) >> 8);
}

static img_uc *
load_jpeg_image(img__jpeg *z, int *out_x, int *out_y, int *comp, int req_comp) {
  int n, decode_n, is_rgb;
  z->s->img_n = 0;  // make img__cleanup_jpeg safe

  // validate req_comp
  if (req_comp < 0 || req_comp > 4)
    return img__errpuc("bad req_comp", "Internal error");

  // load a jpeg image from whichever source, but leave in YCbCr format
  if (!img__decode_jpeg_image(z)) {
    img__cleanup_jpeg(z);
    return NULL;
  }

  // determine actual number of components to generate
  n = req_comp ? req_comp : z->s->img_n >= 3 ? 3 : 1;

  is_rgb = z->s->img_n == 3 &&
           (z->rgb == 3 || (z->app14_color_transform == 0 && !z->jfif));

  if (z->s->img_n == 3 && n < 3 && !is_rgb)
    decode_n = 1;
  else
    decode_n = z->s->img_n;

  // resample and color-convert
  {
    int k;
    unsigned int i, j;
    img_uc *output;
    img_uc *coutput[4] = {NULL, NULL, NULL, NULL};

    img__resample res_comp[4];

    for (k = 0; k < decode_n; ++k) {
      img__resample *r = &res_comp[k];

      // allocate line buffer big enough for upsampling off the edges
      // with upsample factor of 4
      z->img_comp[k].linebuf = (img_uc *)img__malloc(z->s->img_x + 3);
      if (!z->img_comp[k].linebuf) {
        img__cleanup_jpeg(z);
        return img__errpuc("outofmem", "Out of memory");
      }

      r->hs = z->img_h_max / z->img_comp[k].h;
      r->vs = z->img_v_max / z->img_comp[k].v;
      r->ystep = r->vs >> 1;
      r->w_lores = (z->s->img_x + r->hs - 1) / r->hs;
      r->ypos = 0;
      r->line0 = r->line1 = z->img_comp[k].data;

      if (r->hs == 1 && r->vs == 1)
        r->resample = resample_row_1;
      else if (r->hs == 1 && r->vs == 2)
        r->resample = img__resample_row_v_2;
      else if (r->hs == 2 && r->vs == 1)
        r->resample = img__resample_row_h_2;
      else if (r->hs == 2 && r->vs == 2)
        r->resample = z->resample_row_hv_2_kernel;
      else
        r->resample = img__resample_row_generic;
    }

    // can't error after this so, this is safe
    output = (img_uc *)img__malloc_mad3(n, z->s->img_x, z->s->img_y, 1);
    if (!output) {
      img__cleanup_jpeg(z);
      return img__errpuc("outofmem", "Out of memory");
    }

    // now go ahead and resample
    for (j = 0; j < z->s->img_y; ++j) {
      img_uc *out = output + n * z->s->img_x * j;
      for (k = 0; k < decode_n; ++k) {
        img__resample *r = &res_comp[k];
        int y_bot = r->ystep >= (r->vs >> 1);
        coutput[k] =
            r->resample(z->img_comp[k].linebuf, y_bot ? r->line1 : r->line0,
                        y_bot ? r->line0 : r->line1, r->w_lores, r->hs);
        if (++r->ystep >= r->vs) {
          r->ystep = 0;
          r->line0 = r->line1;
          if (++r->ypos < z->img_comp[k].y) r->line1 += z->img_comp[k].w2;
        }
      }
      if (n >= 3) {
        img_uc *y = coutput[0];
        if (z->s->img_n == 3) {
          if (is_rgb) {
            for (i = 0; i < z->s->img_x; ++i) {
              out[0] = y[i];
              out[1] = coutput[1][i];
              out[2] = coutput[2][i];
              out[3] = 255;
              out += n;
            }
          } else {
            z->YCbCr_to_RGB_kernel(out, y, coutput[1], coutput[2], z->s->img_x,
                                   n);
          }
        } else if (z->s->img_n == 4) {
          if (z->app14_color_transform == 0) {  // CMYK
            for (i = 0; i < z->s->img_x; ++i) {
              img_uc m = coutput[3][i];
              out[0] = img__blinn_8x8(coutput[0][i], m);
              out[1] = img__blinn_8x8(coutput[1][i], m);
              out[2] = img__blinn_8x8(coutput[2][i], m);
              out[3] = 255;
              out += n;
            }
          } else if (z->app14_color_transform == 2) {  // YCCK
            z->YCbCr_to_RGB_kernel(out, y, coutput[1], coutput[2], z->s->img_x,
                                   n);
            for (i = 0; i < z->s->img_x; ++i) {
              img_uc m = coutput[3][i];
              out[0] = img__blinn_8x8(255 - out[0], m);
              out[1] = img__blinn_8x8(255 - out[1], m);
              out[2] = img__blinn_8x8(255 - out[2], m);
              out += n;
            }
          } else {  // YCbCr + alpha?  Ignore the fourth channel for now
            z->YCbCr_to_RGB_kernel(out, y, coutput[1], coutput[2], z->s->img_x,
                                   n);
          }
        } else
          for (i = 0; i < z->s->img_x; ++i) {
            out[0] = out[1] = out[2] = y[i];
            out[3] = 255;  // not used if n==3
            out += n;
          }
      } else {
        if (is_rgb) {
          if (n == 1)
            for (i = 0; i < z->s->img_x; ++i)
              *out++ =
                  img__compute_y(coutput[0][i], coutput[1][i], coutput[2][i]);
          else {
            for (i = 0; i < z->s->img_x; ++i, out += 2) {
              out[0] =
                  img__compute_y(coutput[0][i], coutput[1][i], coutput[2][i]);
              out[1] = 255;
            }
          }
        } else if (z->s->img_n == 4 && z->app14_color_transform == 0) {
          for (i = 0; i < z->s->img_x; ++i) {
            img_uc m = coutput[3][i];
            img_uc r = img__blinn_8x8(coutput[0][i], m);
            img_uc g = img__blinn_8x8(coutput[1][i], m);
            img_uc b = img__blinn_8x8(coutput[2][i], m);
            out[0] = img__compute_y(r, g, b);
            out[1] = 255;
            out += n;
          }
        } else if (z->s->img_n == 4 && z->app14_color_transform == 2) {
          for (i = 0; i < z->s->img_x; ++i) {
            out[0] = img__blinn_8x8(255 - coutput[0][i], coutput[3][i]);
            out[1] = 255;
            out += n;
          }
        } else {
          img_uc *y = coutput[0];
          if (n == 1)
            for (i = 0; i < z->s->img_x; ++i) out[i] = y[i];
          else
            for (i = 0; i < z->s->img_x; ++i) {
              *out++ = y[i];
              *out++ = 255;
            }
        }
      }
    }
    img__cleanup_jpeg(z);
    *out_x = z->s->img_x;
    *out_y = z->s->img_y;
    if (comp)
      *comp =
          z->s->img_n >= 3 ? 3 : 1;  // report original components, not output
    return output;
  }
}

static void *
img__jpeg_load(img__context *s, int *x, int *y, int *comp, int req_comp,
               img__result_info *ri) {
  unsigned char *result;
  img__jpeg *j = (img__jpeg *)img__malloc(sizeof(img__jpeg));
  IMG_NOTUSED(ri);
  j->s = s;
  img__setup_jpeg(j);
  result = load_jpeg_image(j, x, y, comp, req_comp);
  IMG_FREE(j);
  return result;
}

static int
img__jpeg_test(img__context *s) {
  int r;
  img__jpeg *j = (img__jpeg *)img__malloc(sizeof(img__jpeg));
  j->s = s;
  img__setup_jpeg(j);
  r = img__decode_jpeg_header(j, IMG__SCAN_type);
  img__rewind(s);
  IMG_FREE(j);
  return r;
}

static int
img__jpeg_info_raw(img__jpeg *j, int *x, int *y, int *comp) {
  if (!img__decode_jpeg_header(j, IMG__SCAN_header)) {
    img__rewind(j->s);
    return 0;
  }
  if (x) *x = j->s->img_x;
  if (y) *y = j->s->img_y;
  if (comp) *comp = j->s->img_n >= 3 ? 3 : 1;
  return 1;
}

static int
img__jpeg_info(img__context *s, int *x, int *y, int *comp) {
  int result;
  img__jpeg *j = (img__jpeg *)(img__malloc(sizeof(img__jpeg)));
  j->s = s;
  result = img__jpeg_info_raw(j, x, y, comp);
  IMG_FREE(j);
  return result;
}
#endif

// public domain zlib decode    v0.2  Sean Barrett 2006-11-18
//    simple implementation
//      - all input must be provided in an upfront buffer
//      - all output is written to a single output buffer (can malloc/realloc)
//    performance
//      - fast huffman

#ifndef IMG_NO_ZLIB

// fast-way is faster to check than jpeg huffman, but slow way is slower
#define IMG__ZFAST_BITS 9  // accelerate all cases in default tables
#define IMG__ZFAST_MASK ((1 << IMG__ZFAST_BITS) - 1)

// zlib-style huffman encoding
// (jpegs packs from left, zlib from right, so can't share code)
typedef struct {
  img__uint16 fast[1 << IMG__ZFAST_BITS];
  img__uint16 firstcode[16];
  int maxcode[17];
  img__uint16 firstsymbol[16];
  img_uc size[288];
  img__uint16 value[288];
} img__zhuffman;

img_inline static int
img__bitreverse16(int n) {
  n = ((n & 0xAAAA) >> 1) | ((n & 0x5555) << 1);
  n = ((n & 0xCCCC) >> 2) | ((n & 0x3333) << 2);
  n = ((n & 0xF0F0) >> 4) | ((n & 0x0F0F) << 4);
  n = ((n & 0xFF00) >> 8) | ((n & 0x00FF) << 8);
  return n;
}

img_inline static int
img__bit_reverse(int v, int bits) {
  IMG_ASSERT(bits <= 16);
  // to bit reverse n bits, reverse 16 and shift
  // e.g. 11 bits, bit reverse and shift away 5
  return img__bitreverse16(v) >> (16 - bits);
}

static int
img__zbuild_huffman(img__zhuffman *z, const img_uc *sizelist, int num) {
  int i, k = 0;
  int code, next_code[16], sizes[17];

  // DEFLATE spec for generating codes
  memset(sizes, 0, sizeof(sizes));
  memset(z->fast, 0, sizeof(z->fast));
  for (i = 0; i < num; ++i) ++sizes[sizelist[i]];
  sizes[0] = 0;
  for (i = 1; i < 16; ++i)
    if (sizes[i] > (1 << i)) return img__err("bad sizes", "Corrupt PNG");
  code = 0;
  for (i = 1; i < 16; ++i) {
    next_code[i] = code;
    z->firstcode[i] = (img__uint16)code;
    z->firstsymbol[i] = (img__uint16)k;
    code = (code + sizes[i]);
    if (sizes[i])
      if (code - 1 >= (1 << i))
        return img__err("bad codelengths", "Corrupt PNG");
    z->maxcode[i] = code << (16 - i);  // preshift for inner loop
    code <<= 1;
    k += sizes[i];
  }
  z->maxcode[16] = 0x10000;  // sentinel
  for (i = 0; i < num; ++i) {
    int s = sizelist[i];
    if (s) {
      int c = next_code[s] - z->firstcode[s] + z->firstsymbol[s];
      img__uint16 fastv = (img__uint16)((s << 9) | i);
      z->size[c] = (img_uc)s;
      z->value[c] = (img__uint16)i;
      if (s <= IMG__ZFAST_BITS) {
        int j = img__bit_reverse(next_code[s], s);
        while (j < (1 << IMG__ZFAST_BITS)) {
          z->fast[j] = fastv;
          j += (1 << s);
        }
      }
      ++next_code[s];
    }
  }
  return 1;
}

// zlib-from-memory implementation for PNG reading
//    because PNG allows splitting the zlib stream arbitrarily,
//    and it's annoying structurally to have PNG call ZLIB call PNG,
//    we require PNG read all the IDATs and combine them into a single
//    memory buffer

typedef struct {
  img_uc *zbuffer, *zbuffer_end;
  int num_bits;
  img__uint32 code_buffer;

  char *zout;
  char *zout_start;
  char *zout_end;
  int z_expandable;

  img__zhuffman z_length, z_distance;
} img__zbuf;

img_inline static int
img__zeof(img__zbuf *z) {
  return (z->zbuffer >= z->zbuffer_end);
}

img_inline static img_uc
img__zget8(img__zbuf *z) {
  return img__zeof(z) ? 0 : *z->zbuffer++;
}

static void
img__fill_bits(img__zbuf *z) {
  do {
    if (z->code_buffer >= (1U << z->num_bits)) {
      z->zbuffer = z->zbuffer_end; /* treat this as EOF so we fail. */
      return;
    }
    z->code_buffer |= (unsigned int)img__zget8(z) << z->num_bits;
    z->num_bits += 8;
  } while (z->num_bits <= 24);
}

img_inline static unsigned int
img__zreceive(img__zbuf *z, int n) {
  unsigned int k;
  if (z->num_bits < n) img__fill_bits(z);
  k = z->code_buffer & ((1 << n) - 1);
  z->code_buffer >>= n;
  z->num_bits -= n;
  return k;
}

static int
img__zhuffman_decode_slowpath(img__zbuf *a, img__zhuffman *z) {
  int b, s, k;
  // not resolved by fast table, so compute it the slow way
  // use jpeg approach, which requires MSbits at top
  k = img__bit_reverse(a->code_buffer, 16);
  for (s = IMG__ZFAST_BITS + 1;; ++s)
    if (k < z->maxcode[s]) break;
  if (s >= 16) return -1;  // invalid code!
  // code size is s, so:
  b = (k >> (16 - s)) - z->firstcode[s] + z->firstsymbol[s];
  if ((size_t)b >= sizeof(z->size)) return -1;  // some data was corrupt somewhere!
  if (z->size[b] != s)
    return -1;  // was originally an assert, but report failure instead.
  a->code_buffer >>= s;
  a->num_bits -= s;
  return z->value[b];
}

img_inline static int
img__zhuffman_decode(img__zbuf *a, img__zhuffman *z) {
  int b, s;
  if (a->num_bits < 16) {
    if (img__zeof(a)) {
      return -1; /* report error for unexpected end of data. */
    }
    img__fill_bits(a);
  }
  b = z->fast[a->code_buffer & IMG__ZFAST_MASK];
  if (b) {
    s = b >> 9;
    a->code_buffer >>= s;
    a->num_bits -= s;
    return b & 511;
  }
  return img__zhuffman_decode_slowpath(a, z);
}

static int
img__zexpand(img__zbuf *z, char *zout, int n)  // need to make room for n bytes
{
  char *q;
  unsigned int cur, limit, old_limit;
  z->zout = zout;
  if (!z->z_expandable) return img__err("output buffer limit", "Corrupt PNG");
  cur = (unsigned int)(z->zout - z->zout_start);
  limit = old_limit = (unsigned)(z->zout_end - z->zout_start);
  if (UINT_MAX - cur < (unsigned)n)
    return img__err("outofmem", "Out of memory");
  while (cur + n > limit) {
    if (limit > UINT_MAX / 2) return img__err("outofmem", "Out of memory");
    limit *= 2;
  }
  q = (char *)IMG_REALLOC_SIZED(z->zout_start, old_limit, limit);
  IMG_NOTUSED(old_limit);
  if (q == NULL) return img__err("outofmem", "Out of memory");
  z->zout_start = q;
  z->zout = q + cur;
  z->zout_end = q + limit;
  return 1;
}

static const int img__zlength_base[31] = {
    3,  4,  5,  6,  7,  8,  9,  10,  11,  13,  15,  17,  19,  23, 27, 31,
    35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0,  0};

static const int img__zlength_extra[31] = {0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1,
                                           1, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4,
                                           4, 4, 5, 5, 5, 5, 0, 0, 0};

static const int img__zdist_base[32] = {
    1,    2,    3,    4,    5,    7,     9,     13,    17,  25,   33,
    49,   65,   97,   129,  193,  257,   385,   513,   769, 1025, 1537,
    2049, 3073, 4097, 6145, 8193, 12289, 16385, 24577, 0,   0};

static const int img__zdist_extra[32] = {0, 0, 0,  0,  1,  1,  2,  2,  3,  3,
                                         4, 4, 5,  5,  6,  6,  7,  7,  8,  8,
                                         9, 9, 10, 10, 11, 11, 12, 12, 13, 13};

static int
img__parse_huffman_block(img__zbuf *a) {
  char *zout = a->zout;
  for (;;) {
    int z = img__zhuffman_decode(a, &a->z_length);
    if (z < 256) {
      if (z < 0)
        return img__err("bad huffman code",
                        "Corrupt PNG");  // error in huffman codes
      if (zout >= a->zout_end) {
        if (!img__zexpand(a, zout, 1)) return 0;
        zout = a->zout;
      }
      *zout++ = (char)z;
    } else {
      img_uc *p;
      int len, dist;
      if (z == 256) {
        a->zout = zout;
        return 1;
      }
      z -= 257;
      len = img__zlength_base[z];
      if (img__zlength_extra[z]) len += img__zreceive(a, img__zlength_extra[z]);
      z = img__zhuffman_decode(a, &a->z_distance);
      if (z < 0) return img__err("bad huffman code", "Corrupt PNG");
      dist = img__zdist_base[z];
      if (img__zdist_extra[z]) dist += img__zreceive(a, img__zdist_extra[z]);
      if (zout - a->zout_start < dist)
        return img__err("bad dist", "Corrupt PNG");
      if (zout + len > a->zout_end) {
        if (!img__zexpand(a, zout, len)) return 0;
        zout = a->zout;
      }
      p = (img_uc *)(zout - dist);
      if (dist == 1) {  // run of one byte; common in images.
        img_uc v = *p;
        if (len) {
          do *zout++ = v;
          while (--len);
        }
      } else {
        if (len) {
          do *zout++ = *p++;
          while (--len);
        }
      }
    }
  }
}

static int
img__compute_huffman_codes(img__zbuf *a) {
  static const img_uc length_dezigzag[19] = {16, 17, 18, 0, 8,  7, 9,  6, 10, 5,
                                             11, 4,  12, 3, 13, 2, 14, 1, 15};
  img__zhuffman z_codelength;
  img_uc lencodes[286 + 32 + 137];  // padding for maximum single op
  img_uc codelength_sizes[19];
  int i, n;

  int hlit = img__zreceive(a, 5) + 257;
  int hdist = img__zreceive(a, 5) + 1;
  int hclen = img__zreceive(a, 4) + 4;
  int ntot = hlit + hdist;

  memset(codelength_sizes, 0, sizeof(codelength_sizes));
  for (i = 0; i < hclen; ++i) {
    int s = img__zreceive(a, 3);
    codelength_sizes[length_dezigzag[i]] = (img_uc)s;
  }
  if (!img__zbuild_huffman(&z_codelength, codelength_sizes, 19)) return 0;

  n = 0;
  while (n < ntot) {
    int c = img__zhuffman_decode(a, &z_codelength);
    if (c < 0 || c >= 19) return img__err("bad codelengths", "Corrupt PNG");
    if (c < 16)
      lencodes[n++] = (img_uc)c;
    else {
      img_uc fill = 0;
      if (c == 16) {
        c = img__zreceive(a, 2) + 3;
        if (n == 0) return img__err("bad codelengths", "Corrupt PNG");
        fill = lencodes[n - 1];
      } else if (c == 17) {
        c = img__zreceive(a, 3) + 3;
      } else if (c == 18) {
        c = img__zreceive(a, 7) + 11;
      } else {
        return img__err("bad codelengths", "Corrupt PNG");
      }
      if (ntot - n < c) return img__err("bad codelengths", "Corrupt PNG");
      memset(lencodes + n, fill, c);
      n += c;
    }
  }
  if (n != ntot) return img__err("bad codelengths", "Corrupt PNG");
  if (!img__zbuild_huffman(&a->z_length, lencodes, hlit)) return 0;
  if (!img__zbuild_huffman(&a->z_distance, lencodes + hlit, hdist)) return 0;
  return 1;
}

static int
img__parse_uncompressed_block(img__zbuf *a) {
  img_uc header[4];
  int len, nlen, k;
  if (a->num_bits & 7) img__zreceive(a, a->num_bits & 7);  // discard
  // drain the bit-packed data into header
  k = 0;
  while (a->num_bits > 0) {
    header[k++] =
        (img_uc)(a->code_buffer & 255);  // suppress MSVC run-time check
    a->code_buffer >>= 8;
    a->num_bits -= 8;
  }
  if (a->num_bits < 0) return img__err("zlib corrupt", "Corrupt PNG");
  // now fill header the normal way
  while (k < 4) header[k++] = img__zget8(a);
  len = header[1] * 256 + header[0];
  nlen = header[3] * 256 + header[2];
  if (nlen != (len ^ 0xffff)) return img__err("zlib corrupt", "Corrupt PNG");
  if (a->zbuffer + len > a->zbuffer_end)
    return img__err("read past buffer", "Corrupt PNG");
  if (a->zout + len > a->zout_end)
    if (!img__zexpand(a, a->zout, len)) return 0;
  memcpy(a->zout, a->zbuffer, len);
  a->zbuffer += len;
  a->zout += len;
  return 1;
}

static int
img__parse_zlib_header(img__zbuf *a) {
  int cmf = img__zget8(a);
  int cm = cmf & 15;
  /* int cinfo = cmf >> 4; */
  int flg = img__zget8(a);
  if (img__zeof(a))
    return img__err("bad zlib header", "Corrupt PNG");  // zlib spec
  if ((cmf * 256 + flg) % 31 != 0)
    return img__err("bad zlib header", "Corrupt PNG");  // zlib spec
  if (flg & 32)
    return img__err("no preset dict",
                    "Corrupt PNG");  // preset dictionary not allowed in png
  if (cm != 8)
    return img__err("bad compression",
                    "Corrupt PNG");  // DEFLATE required for png
  // window = 1 << (8 + cinfo)... but who cares, we fully buffer output
  return 1;
}

static const img_uc img__zdefault_length[288] = {
    8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
    8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
    8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
    8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
    8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
    8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
    9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
    9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
    9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
    9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
    9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 7, 7, 7, 7, 7, 7, 7, 7,
    7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8};
static const img_uc img__zdefault_distance[32] = {
    5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5,
    5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5};
/*
Init algorithm:
{
   int i;   // use <= to match clearly with spec
   for (i=0; i <= 143; ++i)     img__zdefault_length[i]   = 8;
   for (   ; i <= 255; ++i)     img__zdefault_length[i]   = 9;
   for (   ; i <= 279; ++i)     img__zdefault_length[i]   = 7;
   for (   ; i <= 287; ++i)     img__zdefault_length[i]   = 8;

   for (i=0; i <=  31; ++i)     img__zdefault_distance[i] = 5;
}
*/

static int
img__parse_zlib(img__zbuf *a, int parse_header) {
  int final, type;
  if (parse_header)
    if (!img__parse_zlib_header(a)) return 0;
  a->num_bits = 0;
  a->code_buffer = 0;
  do {
    final = img__zreceive(a, 1);
    type = img__zreceive(a, 2);
    if (type == 0) {
      if (!img__parse_uncompressed_block(a)) return 0;
    } else if (type == 3) {
      return 0;
    } else {
      if (type == 1) {
        // use fixed code lengths
        if (!img__zbuild_huffman(&a->z_length, img__zdefault_length, 288))
          return 0;
        if (!img__zbuild_huffman(&a->z_distance, img__zdefault_distance, 32))
          return 0;
      } else {
        if (!img__compute_huffman_codes(a)) return 0;
      }
      if (!img__parse_huffman_block(a)) return 0;
    }
  } while (!final);
  return 1;
}

static int
img__do_zlib(img__zbuf *a, char *obuf, int olen, int exp, int parse_header) {
  a->zout_start = obuf;
  a->zout = obuf;
  a->zout_end = obuf + olen;
  a->z_expandable = exp;

  return img__parse_zlib(a, parse_header);
}

static char *
img_zlib_decode_malloc_guesssize(const char *buffer, int len, int initial_size,
                                 int *outlen) {
  img__zbuf a;
  char *p = (char *)img__malloc(initial_size);
  if (p == NULL) return NULL;
  a.zbuffer = (img_uc *)buffer;
  a.zbuffer_end = (img_uc *)buffer + len;
  if (img__do_zlib(&a, p, initial_size, 1, 1)) {
    if (outlen) *outlen = (int)(a.zout - a.zout_start);
    return a.zout_start;
  } else {
    IMG_FREE(a.zout_start);
    return NULL;
  }
}

static char *
img_zlib_decode_malloc(char const *buffer, int len, int *outlen) {
  return img_zlib_decode_malloc_guesssize(buffer, len, 16384, outlen);
}

static char *
img_zlib_decode_malloc_guesssize_headerflag(const char *buffer, int len,
                                            int initial_size, int *outlen,
                                            int parse_header) {
  img__zbuf a;
  char *p = (char *)img__malloc(initial_size);
  if (p == NULL) return NULL;
  a.zbuffer = (img_uc *)buffer;
  a.zbuffer_end = (img_uc *)buffer + len;
  if (img__do_zlib(&a, p, initial_size, 1, parse_header)) {
    if (outlen) *outlen = (int)(a.zout - a.zout_start);
    return a.zout_start;
  } else {
    IMG_FREE(a.zout_start);
    return NULL;
  }
}

static int
img_zlib_decode_buffer(char *obuffer, int olen, char const *ibuffer, int ilen) {
  img__zbuf a;
  a.zbuffer = (img_uc *)ibuffer;
  a.zbuffer_end = (img_uc *)ibuffer + ilen;
  if (img__do_zlib(&a, obuffer, olen, 0, 1))
    return (int)(a.zout - a.zout_start);
  else
    return -1;
}

static char *
img_zlib_decode_noheader_malloc(char const *buffer, int len, int *outlen) {
  img__zbuf a;
  char *p = (char *)img__malloc(16384);
  if (p == NULL) return NULL;
  a.zbuffer = (img_uc *)buffer;
  a.zbuffer_end = (img_uc *)buffer + len;
  if (img__do_zlib(&a, p, 16384, 1, 0)) {
    if (outlen) *outlen = (int)(a.zout - a.zout_start);
    return a.zout_start;
  } else {
    IMG_FREE(a.zout_start);
    return NULL;
  }
}

static int
img_zlib_decode_noheader_buffer(char *obuffer, int olen, const char *ibuffer,
                                int ilen) {
  img__zbuf a;
  a.zbuffer = (img_uc *)ibuffer;
  a.zbuffer_end = (img_uc *)ibuffer + ilen;
  if (img__do_zlib(&a, obuffer, olen, 0, 0))
    return (int)(a.zout - a.zout_start);
  else
    return -1;
}
#endif

// public domain "baseline" PNG decoder   v0.10  Sean Barrett 2006-11-18
//    simple implementation
//      - only 8-bit samples
//      - no CRC checking
//      - allocates lots of intermediate memory
//        - avoids problem of streaming data between subsystems
//        - avoids explicit window management
//    performance
//      - uses stb_zlib, a PD zlib implementation with fast huffman decoding

#ifndef IMG_NO_PNG
typedef struct {
  img__uint32 length;
  img__uint32 type;
} img__pngchunk;

static img__pngchunk
img__get_chunk_header(img__context *s) {
  img__pngchunk c;
  c.length = img__get32be(s);
  c.type = img__get32be(s);
  return c;
}

static int
img__check_png_header(img__context *s) {
  static const img_uc png_sig[8] = {137, 80, 78, 71, 13, 10, 26, 10};
  int i;
  for (i = 0; i < 8; ++i)
    if (img__get8(s) != png_sig[i]) return img__err("bad png sig", "Not a PNG");
  return 1;
}

typedef struct {
  img__context *s;
  img_uc *idata, *expanded, *out;
  int depth;
} img__png;

enum {
  IMG__F_none = 0,
  IMG__F_sub = 1,
  IMG__F_up = 2,
  IMG__F_avg = 3,
  IMG__F_paeth = 4,
  // synthetic filters used for first scanline to avoid needing a dummy row of
  // 0s
  IMG__F_avg_first,
  IMG__F_paeth_first
};

static img_uc first_row_filter[5] = {IMG__F_none, IMG__F_sub, IMG__F_none,
                                     IMG__F_avg_first, IMG__F_paeth_first};

static int
img__paeth(int a, int b, int c) {
  int p = a + b - c;
  int pa = abs(p - a);
  int pb = abs(p - b);
  int pc = abs(p - c);
  if (pa <= pb && pa <= pc) return a;
  if (pb <= pc) return b;
  return c;
}

static const img_uc img__depth_scale_table[9] = {0, 0xff, 0x55, 0,   0x11,
                                                 0, 0,    0,    0x01};

// create the png data from post-deflated data
static int
img__create_png_image_raw(img__png *a, img_uc *raw, img__uint32 raw_len,
                          int out_n, img__uint32 x, img__uint32 y, int depth,
                          int color) {
  int bytes = (depth == 16 ? 2 : 1);
  img__context *s = a->s;
  img__uint32 i, j, stride = x * out_n * bytes;
  img__uint32 img_len, img_width_bytes;
  int k;
  int img_n = s->img_n;  // copy it into a local for later

  int output_bytes = out_n * bytes;
  int filter_bytes = img_n * bytes;
  int width = x;

  IMG_ASSERT(out_n == s->img_n || out_n == s->img_n + 1);
  a->out = (img_uc *)img__malloc_mad3(
      x, y, output_bytes, 0);  // extra bytes to write off the end into
  if (!a->out) return img__err("outofmem", "Out of memory");

  if (!img__mad3sizes_valid(img_n, x, depth, 7))
    return img__err("too large", "Corrupt PNG");
  img_width_bytes = (((img_n * x * depth) + 7) >> 3);
  img_len = (img_width_bytes + 1) * y;

  // we used to check for exact match between raw_len and img_len on
  // non-interlaced PNGs, but issue #276 reported a PNG in the wild that had
  // extra data at the end (all zeros), so just check for raw_len < img_len
  // always.
  if (raw_len < img_len) return img__err("not enough pixels", "Corrupt PNG");

  for (j = 0; j < y; ++j) {
    img_uc *cur = a->out + stride * j;
    img_uc *prior;
    int filter = *raw++;

    if (filter > 4) return img__err("invalid filter", "Corrupt PNG");

    if (depth < 8) {
      if (img_width_bytes > x) return img__err("invalid width", "Corrupt PNG");
      cur +=
          x * out_n - img_width_bytes;  // store output to the rightmost img_len
                                        // bytes, so we can decode in place
      filter_bytes = 1;
      width = img_width_bytes;
    }
    prior = cur - stride;  // bugfix: need to compute this after 'cur +='
                           // computation above

    // if first row, use special filter that doesn't sample previous row
    if (j == 0) filter = first_row_filter[filter];

    // handle first byte explicitly
    for (k = 0; k < filter_bytes; ++k) {
      switch (filter) {
        case IMG__F_none:
          cur[k] = raw[k];
          break;
        case IMG__F_sub:
          cur[k] = raw[k];
          break;
        case IMG__F_up:
          cur[k] = IMG__BYTECAST(raw[k] + prior[k]);
          break;
        case IMG__F_avg:
          cur[k] = IMG__BYTECAST(raw[k] + (prior[k] >> 1));
          break;
        case IMG__F_paeth:
          cur[k] = IMG__BYTECAST(raw[k] + img__paeth(0, prior[k], 0));
          break;
        case IMG__F_avg_first:
          cur[k] = raw[k];
          break;
        case IMG__F_paeth_first:
          cur[k] = raw[k];
          break;
      }
    }

    if (depth == 8) {
      if (img_n != out_n) cur[img_n] = 255;  // first pixel
      raw += img_n;
      cur += out_n;
      prior += out_n;
    } else if (depth == 16) {
      if (img_n != out_n) {
        cur[filter_bytes] = 255;      // first pixel top byte
        cur[filter_bytes + 1] = 255;  // first pixel bottom byte
      }
      raw += filter_bytes;
      cur += output_bytes;
      prior += output_bytes;
    } else {
      raw += 1;
      cur += 1;
      prior += 1;
    }

    // this is a little gross, so that we don't switch per-pixel or
    // per-component
    if (depth < 8 || img_n == out_n) {
      int nk = (width - 1) * filter_bytes;
#define IMG__CASE(f) \
  case f:            \
    for (k = 0; k < nk; ++k)
      switch (filter) {
        // "none" filter turns into a memcpy here; make that explicit.
        case IMG__F_none:
          memcpy(cur, raw, nk);
          break;
          IMG__CASE(IMG__F_sub) {
            cur[k] = IMG__BYTECAST(raw[k] + cur[k - filter_bytes]);
          }
          break;
          IMG__CASE(IMG__F_up) { cur[k] = IMG__BYTECAST(raw[k] + prior[k]); }
          break;
          IMG__CASE(IMG__F_avg) {
            cur[k] = IMG__BYTECAST(raw[k] +
                                   ((prior[k] + cur[k - filter_bytes]) >> 1));
          }
          break;
          IMG__CASE(IMG__F_paeth) {
            cur[k] = IMG__BYTECAST(raw[k] +
                                   img__paeth(cur[k - filter_bytes], prior[k],
                                              prior[k - filter_bytes]));
          }
          break;
          IMG__CASE(IMG__F_avg_first) {
            cur[k] = IMG__BYTECAST(raw[k] + (cur[k - filter_bytes] >> 1));
          }
          break;
          IMG__CASE(IMG__F_paeth_first) {
            cur[k] =
                IMG__BYTECAST(raw[k] + img__paeth(cur[k - filter_bytes], 0, 0));
          }
          break;
      }
#undef IMG__CASE
      raw += nk;
    } else {
      IMG_ASSERT(img_n + 1 == out_n);
#define IMG__CASE(f)                                                           \
  case f:                                                                      \
    for (i = x - 1; i >= 1; --i, cur[filter_bytes] = 255, raw += filter_bytes, \
        cur += output_bytes, prior += output_bytes)                            \
      for (k = 0; k < filter_bytes; ++k)
      switch (filter) {
        IMG__CASE(IMG__F_none) { cur[k] = raw[k]; }
        break;
        IMG__CASE(IMG__F_sub) {
          cur[k] = IMG__BYTECAST(raw[k] + cur[k - output_bytes]);
        }
        break;
        IMG__CASE(IMG__F_up) { cur[k] = IMG__BYTECAST(raw[k] + prior[k]); }
        break;
        IMG__CASE(IMG__F_avg) {
          cur[k] =
              IMG__BYTECAST(raw[k] + ((prior[k] + cur[k - output_bytes]) >> 1));
        }
        break;
        IMG__CASE(IMG__F_paeth) {
          cur[k] =
              IMG__BYTECAST(raw[k] + img__paeth(cur[k - output_bytes], prior[k],
                                                prior[k - output_bytes]));
        }
        break;
        IMG__CASE(IMG__F_avg_first) {
          cur[k] = IMG__BYTECAST(raw[k] + (cur[k - output_bytes] >> 1));
        }
        break;
        IMG__CASE(IMG__F_paeth_first) {
          cur[k] =
              IMG__BYTECAST(raw[k] + img__paeth(cur[k - output_bytes], 0, 0));
        }
        break;
      }
#undef IMG__CASE

      // the loop above sets the high byte of the pixels' alpha, but for
      // 16 bit png files we also need the low byte set. we'll do that here.
      if (depth == 16) {
        cur = a->out + stride * j;  // start at the beginning of the row again
        for (i = 0; i < x; ++i, cur += output_bytes) {
          cur[filter_bytes + 1] = 255;
        }
      }
    }
  }

  // we make a separate pass to expand bits to pixels; for performance,
  // this could run two scanlines behind the above code, so it won't
  // intefere with filtering but will still be in the cache.
  if (depth < 8) {
    for (j = 0; j < y; ++j) {
      img_uc *cur = a->out + stride * j;
      img_uc *in = a->out + stride * j + x * out_n - img_width_bytes;
      // unpack 1/2/4-bit into a 8-bit buffer. allows us to keep the common
      // 8-bit path optimal at minimal cost for 1/2/4-bit png guarante byte
      // alignment, if width is not multiple of 8/4/2 we'll decode dummy
      // trailing data that will be skipped in the later loop
      img_uc scale = (color == 0)
                         ? img__depth_scale_table[depth]
                         : 1;  // scale grayscale values to 0..255 range

      // note that the final byte might overshoot and write more data than
      // desired. we can allocate enough data that this never writes out of
      // memory, but it could also overwrite the next scanline. can it overwrite
      // non-empty data on the next scanline? yes, consider 1-pixel-wide
      // scanlines with 1-bit-per-pixel. so we need to explicitly clamp the
      // final ones

      if (depth == 4) {
        for (k = x * img_n; k >= 2; k -= 2, ++in) {
          *cur++ = scale * ((*in >> 4));
          *cur++ = scale * ((*in) & 0x0f);
        }
        if (k > 0) *cur++ = scale * ((*in >> 4));
      } else if (depth == 2) {
        for (k = x * img_n; k >= 4; k -= 4, ++in) {
          *cur++ = scale * ((*in >> 6));
          *cur++ = scale * ((*in >> 4) & 0x03);
          *cur++ = scale * ((*in >> 2) & 0x03);
          *cur++ = scale * ((*in) & 0x03);
        }
        if (k > 0) *cur++ = scale * ((*in >> 6));
        if (k > 1) *cur++ = scale * ((*in >> 4) & 0x03);
        if (k > 2) *cur++ = scale * ((*in >> 2) & 0x03);
      } else if (depth == 1) {
        for (k = x * img_n; k >= 8; k -= 8, ++in) {
          *cur++ = scale * ((*in >> 7));
          *cur++ = scale * ((*in >> 6) & 0x01);
          *cur++ = scale * ((*in >> 5) & 0x01);
          *cur++ = scale * ((*in >> 4) & 0x01);
          *cur++ = scale * ((*in >> 3) & 0x01);
          *cur++ = scale * ((*in >> 2) & 0x01);
          *cur++ = scale * ((*in >> 1) & 0x01);
          *cur++ = scale * ((*in) & 0x01);
        }
        if (k > 0) *cur++ = scale * ((*in >> 7));
        if (k > 1) *cur++ = scale * ((*in >> 6) & 0x01);
        if (k > 2) *cur++ = scale * ((*in >> 5) & 0x01);
        if (k > 3) *cur++ = scale * ((*in >> 4) & 0x01);
        if (k > 4) *cur++ = scale * ((*in >> 3) & 0x01);
        if (k > 5) *cur++ = scale * ((*in >> 2) & 0x01);
        if (k > 6) *cur++ = scale * ((*in >> 1) & 0x01);
      }
      if (img_n != out_n) {
        int q;
        // insert alpha = 255
        cur = a->out + stride * j;
        if (img_n == 1) {
          for (q = x - 1; q >= 0; --q) {
            cur[q * 2 + 1] = 255;
            cur[q * 2 + 0] = cur[q];
          }
        } else {
          IMG_ASSERT(img_n == 3);
          for (q = x - 1; q >= 0; --q) {
            cur[q * 4 + 3] = 255;
            cur[q * 4 + 2] = cur[q * 3 + 2];
            cur[q * 4 + 1] = cur[q * 3 + 1];
            cur[q * 4 + 0] = cur[q * 3 + 0];
          }
        }
      }
    }
  } else if (depth == 16) {
    // force the image data from big-endian to platform-native.
    // this is done in a separate pass due to the decoding relying
    // on the data being untouched, but could probably be done
    // per-line during decode if care is taken.
    img_uc *cur = a->out;
    img__uint16 *cur16 = (img__uint16 *)cur;

    for (i = 0; i < x * y * out_n; ++i, cur16++, cur += 2) {
      *cur16 = (unsigned short)((cur[0] << 8) | cur[1]);
    }
  }

  return 1;
}

static int
img__create_png_image(img__png *a, img_uc *image_data,
                      img__uint32 image_data_len, int out_n, int depth,
                      int color, int interlaced) {
  int bytes = (depth == 16 ? 2 : 1);
  int out_bytes = out_n * bytes;
  img_uc *final;
  int p;
  if (!interlaced)
    return img__create_png_image_raw(a, image_data, image_data_len, out_n,
                                     a->s->img_x, a->s->img_y, depth, color);

  // de-interlacing
  final = (img_uc *)img__malloc_mad3(a->s->img_x, a->s->img_y, out_bytes, 0);
  for (p = 0; p < 7; ++p) {
    int xorig[] = {0, 4, 0, 2, 0, 1, 0};
    int yorig[] = {0, 0, 4, 0, 2, 0, 1};
    int xspc[] = {8, 8, 4, 4, 2, 2, 1};
    int yspc[] = {8, 8, 8, 4, 4, 2, 2};
    int i, j, x, y;
    // pass1_x[4] = 0, pass1_x[5] = 1, pass1_x[12] = 1
    x = (a->s->img_x - xorig[p] + xspc[p] - 1) / xspc[p];
    y = (a->s->img_y - yorig[p] + yspc[p] - 1) / yspc[p];
    if (x && y) {
      img__uint32 img_len = ((((a->s->img_n * x * depth) + 7) >> 3) + 1) * y;
      if (!img__create_png_image_raw(a, image_data, image_data_len, out_n, x, y,
                                     depth, color)) {
        IMG_FREE(final);
        return 0;
      }
      for (j = 0; j < y; ++j) {
        for (i = 0; i < x; ++i) {
          int out_y = j * yspc[p] + yorig[p];
          int out_x = i * xspc[p] + xorig[p];
          memcpy(final + out_y * a->s->img_x * out_bytes + out_x * out_bytes,
                 a->out + (j * x + i) * out_bytes, out_bytes);
        }
      }
      IMG_FREE(a->out);
      image_data += img_len;
      image_data_len -= img_len;
    }
  }
  a->out = final;

  return 1;
}

static int
img__compute_transparency(img__png *z, img_uc tc[3], int out_n) {
  img__context *s = z->s;
  img__uint32 i, pixel_count = s->img_x * s->img_y;
  img_uc *p = z->out;

  // compute color-based transparency, assuming we've
  // already got 255 as the alpha value in the output
  IMG_ASSERT(out_n == 2 || out_n == 4);

  if (out_n == 2) {
    for (i = 0; i < pixel_count; ++i) {
      p[1] = (p[0] == tc[0] ? 0 : 255);
      p += 2;
    }
  } else {
    for (i = 0; i < pixel_count; ++i) {
      if (p[0] == tc[0] && p[1] == tc[1] && p[2] == tc[2]) p[3] = 0;
      p += 4;
    }
  }
  return 1;
}

static int
img__compute_transparency16(img__png *z, img__uint16 tc[3], int out_n) {
  img__context *s = z->s;
  img__uint32 i, pixel_count = s->img_x * s->img_y;
  img__uint16 *p = (img__uint16 *)z->out;

  // compute color-based transparency, assuming we've
  // already got 65535 as the alpha value in the output
  IMG_ASSERT(out_n == 2 || out_n == 4);

  if (out_n == 2) {
    for (i = 0; i < pixel_count; ++i) {
      p[1] = (p[0] == tc[0] ? 0 : 65535);
      p += 2;
    }
  } else {
    for (i = 0; i < pixel_count; ++i) {
      if (p[0] == tc[0] && p[1] == tc[1] && p[2] == tc[2]) p[3] = 0;
      p += 4;
    }
  }
  return 1;
}

static int
img__expand_png_palette(img__png *a, img_uc *palette, int len, int pal_img_n) {
  img__uint32 i, pixel_count = a->s->img_x * a->s->img_y;
  img_uc *p, *temp_out, *orig = a->out;

  p = (img_uc *)img__malloc_mad2(pixel_count, pal_img_n, 0);
  if (p == NULL) return img__err("outofmem", "Out of memory");

  // between here and free(out) below, exitting would leak
  temp_out = p;

  if (pal_img_n == 3) {
    for (i = 0; i < pixel_count; ++i) {
      int n = orig[i] * 4;
      p[0] = palette[n];
      p[1] = palette[n + 1];
      p[2] = palette[n + 2];
      p += 3;
    }
  } else {
    for (i = 0; i < pixel_count; ++i) {
      int n = orig[i] * 4;
      p[0] = palette[n];
      p[1] = palette[n + 1];
      p[2] = palette[n + 2];
      p[3] = palette[n + 3];
      p += 4;
    }
  }
  IMG_FREE(a->out);
  a->out = temp_out;

  IMG_NOTUSED(len);

  return 1;
}

static int img__unpremultiply_on_load = 0;
static int img__de_iphone_flag = 0;

static void
img_set_unpremultiply_on_load(int flag_true_if_should_unpremultiply) {
  img__unpremultiply_on_load = flag_true_if_should_unpremultiply;
}

static void
img_convert_iphone_png_to_rgb(int flag_true_if_should_convert) {
  img__de_iphone_flag = flag_true_if_should_convert;
}

static void
img__de_iphone(img__png *z) {
  img__context *s = z->s;
  img__uint32 i, pixel_count = s->img_x * s->img_y;
  img_uc *p = z->out;

  if (s->img_out_n == 3) {  // convert bgr to rgb
    for (i = 0; i < pixel_count; ++i) {
      img_uc t = p[0];
      p[0] = p[2];
      p[2] = t;
      p += 3;
    }
  } else {
    IMG_ASSERT(s->img_out_n == 4);
    if (img__unpremultiply_on_load) {
      // convert bgr to rgb and unpremultiply
      for (i = 0; i < pixel_count; ++i) {
        img_uc a = p[3];
        img_uc t = p[0];
        if (a) {
          img_uc half = a / 2;
          p[0] = (p[2] * 255 + half) / a;
          p[1] = (p[1] * 255 + half) / a;
          p[2] = (t * 255 + half) / a;
        } else {
          p[0] = p[2];
          p[2] = t;
        }
        p += 4;
      }
    } else {
      // convert bgr to rgb
      for (i = 0; i < pixel_count; ++i) {
        img_uc t = p[0];
        p[0] = p[2];
        p[2] = t;
        p += 4;
      }
    }
  }
}

#define IMG__PNG_TYPE(a, b, c, d)                                         \
  (((unsigned)(a) << 24) + ((unsigned)(b) << 16) + ((unsigned)(c) << 8) + \
   (unsigned)(d))

static int
img__parse_png_file(img__png *z, int scan, int req_comp) {
  img_uc palette[1024], pal_img_n = 0;
  img_uc has_trans = 0, tc[3] = {0};
  img__uint16 tc16[3];
  img__uint32 ioff = 0, idata_limit = 0, i, pal_len = 0;
  int first = 1, k, interlace = 0, color = 0, is_iphone = 0;
  img__context *s = z->s;

  z->expanded = NULL;
  z->idata = NULL;
  z->out = NULL;

  if (!img__check_png_header(s)) return 0;

  if (scan == IMG__SCAN_type) return 1;

  for (;;) {
    img__pngchunk c = img__get_chunk_header(s);
    switch (c.type) {
      case IMG__PNG_TYPE('C', 'g', 'B', 'I'):
        is_iphone = 1;
        img__skip(s, c.length);
        break;
      case IMG__PNG_TYPE('I', 'H', 'D', 'R'): {
        int comp, filter;
        if (!first) return img__err("multiple IHDR", "Corrupt PNG");
        first = 0;
        if (c.length != 13) return img__err("bad IHDR len", "Corrupt PNG");
        s->img_x = img__get32be(s);
        s->img_y = img__get32be(s);
        if (s->img_y > IMG_MAX_DIMENSIONS)
          return img__err("too large", "Very large image (corrupt?)");
        if (s->img_x > IMG_MAX_DIMENSIONS)
          return img__err("too large", "Very large image (corrupt?)");
        z->depth = img__get8(s);
        if (z->depth != 1 && z->depth != 2 && z->depth != 4 && z->depth != 8 &&
            z->depth != 16)
          return img__err("1/2/4/8/16-bit only",
                          "PNG not supported: 1/2/4/8/16-bit only");
        color = img__get8(s);
        if (color > 6) return img__err("bad ctype", "Corrupt PNG");
        if (color == 3 && z->depth == 16)
          return img__err("bad ctype", "Corrupt PNG");
        if (color == 3)
          pal_img_n = 3;
        else if (color & 1)
          return img__err("bad ctype", "Corrupt PNG");
        comp = img__get8(s);
        if (comp) return img__err("bad comp method", "Corrupt PNG");
        filter = img__get8(s);
        if (filter) return img__err("bad filter method", "Corrupt PNG");
        interlace = img__get8(s);
        if (interlace > 1)
          return img__err("bad interlace method", "Corrupt PNG");
        if (!s->img_x || !s->img_y)
          return img__err("0-pixel image", "Corrupt PNG");
        if (!pal_img_n) {
          s->img_n = (color & 2 ? 3 : 1) + (color & 4 ? 1 : 0);
          if ((1 << 30) / s->img_x / s->img_n < s->img_y)
            return img__err("too large", "Image too large to decode");
          if (scan == IMG__SCAN_header) return 1;
        } else {
          // if paletted, then pal_n is our final components, and
          // img_n is # components to decompress/filter.
          s->img_n = 1;
          if ((1 << 30) / s->img_x / 4 < s->img_y)
            return img__err("too large", "Corrupt PNG");
          // if SCAN_header, have to scan to see if we have a tRNS
        }
        break;
      }

      case IMG__PNG_TYPE('P', 'L', 'T', 'E'): {
        if (first) return img__err("first not IHDR", "Corrupt PNG");
        if (c.length > 256 * 3) return img__err("invalid PLTE", "Corrupt PNG");
        pal_len = c.length / 3;
        if (pal_len * 3 != c.length)
          return img__err("invalid PLTE", "Corrupt PNG");
        for (i = 0; i < pal_len; ++i) {
          palette[i * 4 + 0] = img__get8(s);
          palette[i * 4 + 1] = img__get8(s);
          palette[i * 4 + 2] = img__get8(s);
          palette[i * 4 + 3] = 255;
        }
        break;
      }

      case IMG__PNG_TYPE('t', 'R', 'N', 'S'): {
        if (first) return img__err("first not IHDR", "Corrupt PNG");
        if (z->idata) return img__err("tRNS after IDAT", "Corrupt PNG");
        if (pal_img_n) {
          if (scan == IMG__SCAN_header) {
            s->img_n = 4;
            return 1;
          }
          if (pal_len == 0) return img__err("tRNS before PLTE", "Corrupt PNG");
          if (c.length > pal_len)
            return img__err("bad tRNS len", "Corrupt PNG");
          pal_img_n = 4;
          for (i = 0; i < c.length; ++i) palette[i * 4 + 3] = img__get8(s);
        } else {
          if (!(s->img_n & 1))
            return img__err("tRNS with alpha", "Corrupt PNG");
          if (c.length != (img__uint32)s->img_n * 2)
            return img__err("bad tRNS len", "Corrupt PNG");
          has_trans = 1;
          if (z->depth == 16) {
            for (k = 0; k < s->img_n; ++k)
              tc16[k] = (img__uint16)img__get16be(s);  // copy the values as-is
          } else {
            for (k = 0; k < s->img_n; ++k)
              tc[k] = (img_uc)(img__get16be(s) & 255) *
                      img__depth_scale_table[z->depth];  // non 8-bit images
                                                         // will be larger
          }
        }
        break;
      }

      case IMG__PNG_TYPE('I', 'D', 'A', 'T'): {
        if (first) return img__err("first not IHDR", "Corrupt PNG");
        if (pal_img_n && !pal_len) return img__err("no PLTE", "Corrupt PNG");
        if (scan == IMG__SCAN_header) {
          s->img_n = pal_img_n;
          return 1;
        }
        if ((int)(ioff + c.length) < (int)ioff) return 0;
        if (ioff + c.length > idata_limit) {
          img__uint32 idata_limit_old = idata_limit;
          img_uc *p;
          if (idata_limit == 0) idata_limit = c.length > 4096 ? c.length : 4096;
          while (ioff + c.length > idata_limit) idata_limit *= 2;
          IMG_NOTUSED(idata_limit_old);
          p = (img_uc *)IMG_REALLOC_SIZED(z->idata, idata_limit_old,
                                          idata_limit);
          if (p == NULL) return img__err("outofmem", "Out of memory");
          z->idata = p;
        }
        if (!img__getn(s, z->idata + ioff, c.length))
          return img__err("outofdata", "Corrupt PNG");
        ioff += c.length;
        break;
      }

      case IMG__PNG_TYPE('I', 'E', 'N', 'D'): {
        img__uint32 raw_len, bpl;
        if (first) return img__err("first not IHDR", "Corrupt PNG");
        if (scan != IMG__SCAN_load) return 1;
        if (z->idata == NULL) return img__err("no IDAT", "Corrupt PNG");
        // initial guess for decoded data size to avoid unnecessary reallocs
        bpl = (s->img_x * z->depth + 7) / 8;  // bytes per line, per component
        raw_len = bpl * s->img_y * s->img_n /* pixels */ +
                  s->img_y /* filter mode per row */;
        z->expanded = (img_uc *)img_zlib_decode_malloc_guesssize_headerflag(
            (char *)z->idata, ioff, raw_len, (int *)&raw_len, !is_iphone);
        if (z->expanded == NULL) return 0;  // zlib should set error
        IMG_FREE(z->idata);
        z->idata = NULL;
        if ((req_comp == s->img_n + 1 && req_comp != 3 && !pal_img_n) ||
            has_trans)
          s->img_out_n = s->img_n + 1;
        else
          s->img_out_n = s->img_n;
        if (!img__create_png_image(z, z->expanded, raw_len, s->img_out_n,
                                   z->depth, color, interlace))
          return 0;
        if (has_trans) {
          if (z->depth == 16) {
            if (!img__compute_transparency16(z, tc16, s->img_out_n)) return 0;
          } else {
            if (!img__compute_transparency(z, tc, s->img_out_n)) return 0;
          }
        }
        if (is_iphone && img__de_iphone_flag && s->img_out_n > 2)
          img__de_iphone(z);
        if (pal_img_n) {
          // pal_img_n == 3 or 4
          s->img_n = pal_img_n;  // record the actual colors we had
          s->img_out_n = pal_img_n;
          if (req_comp >= 3) s->img_out_n = req_comp;
          if (!img__expand_png_palette(z, palette, pal_len, s->img_out_n))
            return 0;
        } else if (has_trans) {
          // non-paletted image with tRNS -> source image has (constant) alpha
          ++s->img_n;
        }
        IMG_FREE(z->expanded);
        z->expanded = NULL;
        // end of PNG chunk, read and skip CRC
        img__get32be(s);
        return 1;
      }

      default:
        // if critical, fail
        if (first) return img__err("first not IHDR", "Corrupt PNG");
        if ((c.type & (1 << 29)) == 0) {
#ifndef IMG_NO_FAILURE_STRINGS
          // not threadsafe
          static char invalid_chunk[] = "XXXX PNG chunk not known";
          invalid_chunk[0] = IMG__BYTECAST(c.type >> 24);
          invalid_chunk[1] = IMG__BYTECAST(c.type >> 16);
          invalid_chunk[2] = IMG__BYTECAST(c.type >> 8);
          invalid_chunk[3] = IMG__BYTECAST(c.type >> 0);
#endif
          return img__err(invalid_chunk,
                          "PNG not supported: unknown PNG chunk type");
        }
        img__skip(s, c.length);
        break;
    }
    // end of PNG chunk, read and skip CRC
    img__get32be(s);
  }
}

static void *
img__do_png(img__png *p, int *x, int *y, int *n, int req_comp,
            img__result_info *ri) {
  void *result = NULL;
  if (req_comp < 0 || req_comp > 4)
    return img__errpuc("bad req_comp", "Internal error");
  if (img__parse_png_file(p, IMG__SCAN_load, req_comp)) {
    if (p->depth <= 8)
      ri->bits_per_channel = 8;
    else if (p->depth == 16)
      ri->bits_per_channel = 16;
    else
      return img__errpuc("bad bits_per_channel",
                         "PNG not supported: unsupported color depth");
    result = p->out;
    p->out = NULL;
    if (req_comp && req_comp != p->s->img_out_n) {
      if (ri->bits_per_channel == 8)
        result = img__convert_format((unsigned char *)result, p->s->img_out_n,
                                     req_comp, p->s->img_x, p->s->img_y);
      else
        result = img__convert_format16((img__uint16 *)result, p->s->img_out_n,
                                       req_comp, p->s->img_x, p->s->img_y);
      p->s->img_out_n = req_comp;
      if (result == NULL) return result;
    }
    *x = p->s->img_x;
    *y = p->s->img_y;
    if (n) *n = p->s->img_n;
  }
  IMG_FREE(p->out);
  p->out = NULL;
  IMG_FREE(p->expanded);
  p->expanded = NULL;
  IMG_FREE(p->idata);
  p->idata = NULL;

  return result;
}

static void *
img__png_load(img__context *s, int *x, int *y, int *comp, int req_comp,
              img__result_info *ri) {
  img__png p;
  p.s = s;
  return img__do_png(&p, x, y, comp, req_comp, ri);
}

static int
img__png_test(img__context *s) {
  int r;
  r = img__check_png_header(s);
  img__rewind(s);
  return r;
}

static int
img__png_info_raw(img__png *p, int *x, int *y, int *comp) {
  if (!img__parse_png_file(p, IMG__SCAN_header, 0)) {
    img__rewind(p->s);
    return 0;
  }
  if (x) *x = p->s->img_x;
  if (y) *y = p->s->img_y;
  if (comp) *comp = p->s->img_n;
  return 1;
}

static int
img__png_info(img__context *s, int *x, int *y, int *comp) {
  img__png p;
  p.s = s;
  return img__png_info_raw(&p, x, y, comp);
}

static int
img__png_is16(img__context *s) {
  img__png p;
  p.s = s;
  if (!img__png_info_raw(&p, NULL, NULL, NULL)) return 0;
  if (p.depth != 16) {
    img__rewind(p.s);
    return 0;
  }
  return 1;
}
#endif

// Microsoft/Windows BMP image

#ifndef IMG_NO_BMP
static int
img__bmp_test_raw(img__context *s) {
  int r;
  int sz;
  if (img__get8(s) != 'B') return 0;
  if (img__get8(s) != 'M') return 0;
  img__get32le(s);  // discard filesize
  img__get16le(s);  // discard reserved
  img__get16le(s);  // discard reserved
  img__get32le(s);  // discard data offset
  sz = img__get32le(s);
  r = (sz == 12 || sz == 40 || sz == 56 || sz == 108 || sz == 124);
  return r;
}

static int
img__bmp_test(img__context *s) {
  int r = img__bmp_test_raw(s);
  img__rewind(s);
  return r;
}

// returns 0..31 for the highest set bit
static int
img__high_bit(unsigned int z) {
  int n = 0;
  if (z == 0) return -1;
  if (z >= 0x10000) {
    n += 16;
    z >>= 16;
  }
  if (z >= 0x00100) {
    n += 8;
    z >>= 8;
  }
  if (z >= 0x00010) {
    n += 4;
    z >>= 4;
  }
  if (z >= 0x00004) {
    n += 2;
    z >>= 2;
  }
  if (z >= 0x00002) {
    n += 1; /* >>=  1;*/
  }
  return n;
}

static int
img__bitcount(unsigned int a) {
  a = (a & 0x55555555) + ((a >> 1) & 0x55555555);  // max 2
  a = (a & 0x33333333) + ((a >> 2) & 0x33333333);  // max 4
  a = (a + (a >> 4)) & 0x0f0f0f0f;                 // max 8 per 4, now 8 bits
  a = (a + (a >> 8));                              // max 16 per 8 bits
  a = (a + (a >> 16));                             // max 32 per 8 bits
  return a & 0xff;
}

// extract an arbitrarily-aligned N-bit value (N=bits)
// from v, and then make it 8-bits long and fractionally
// extend it to full full range.
static int
img__shiftsigned(unsigned int v, int shift, int bits) {
  static unsigned int mul_table[9] = {
      0,
      0xff /*0b11111111*/,
      0x55 /*0b01010101*/,
      0x49 /*0b01001001*/,
      0x11 /*0b00010001*/,
      0x21 /*0b00100001*/,
      0x41 /*0b01000001*/,
      0x81 /*0b10000001*/,
      0x01 /*0b00000001*/,
  };
  static unsigned int shift_table[9] = {
      0, 0, 0, 1, 0, 2, 4, 6, 0,
  };
  if (shift < 0)
    v <<= -shift;
  else
    v >>= shift;
  IMG_ASSERT(v < 256);
  v >>= (8 - bits);
  IMG_ASSERT(bits >= 0 && bits <= 8);
  return (int)((unsigned)v * mul_table[bits]) >> shift_table[bits];
}

typedef struct {
  int bpp, offset, hsz;
  unsigned int mr, mg, mb, ma, all_a;
  int extra_read;
} img__bmp_data;

static void *
img__bmp_parse_header(img__context *s, img__bmp_data *info) {
  int hsz;
  if (img__get8(s) != 'B' || img__get8(s) != 'M')
    return img__errpuc("not BMP", "Corrupt BMP");
  img__get32le(s);  // discard filesize
  img__get16le(s);  // discard reserved
  img__get16le(s);  // discard reserved
  info->offset = img__get32le(s);
  info->hsz = hsz = img__get32le(s);
  info->mr = info->mg = info->mb = info->ma = 0;
  info->extra_read = 14;

  if (info->offset < 0) return img__errpuc("bad BMP", "bad BMP");

  if (hsz != 12 && hsz != 40 && hsz != 56 && hsz != 108 && hsz != 124)
    return img__errpuc("unknown BMP", "BMP type not supported: unknown");
  if (hsz == 12) {
    s->img_x = img__get16le(s);
    s->img_y = img__get16le(s);
  } else {
    s->img_x = img__get32le(s);
    s->img_y = img__get32le(s);
  }
  if (img__get16le(s) != 1) return img__errpuc("bad BMP", "bad BMP");
  info->bpp = img__get16le(s);
  if (hsz != 12) {
    int compress = img__get32le(s);
    if (compress == 1 || compress == 2)
      return img__errpuc("BMP RLE", "BMP type not supported: RLE");
    img__get32le(s);  // discard sizeof
    img__get32le(s);  // discard hres
    img__get32le(s);  // discard vres
    img__get32le(s);  // discard colorsused
    img__get32le(s);  // discard max important
    if (hsz == 40 || hsz == 56) {
      if (hsz == 56) {
        img__get32le(s);
        img__get32le(s);
        img__get32le(s);
        img__get32le(s);
      }
      if (info->bpp == 16 || info->bpp == 32) {
        if (compress == 0) {
          if (info->bpp == 32) {
            info->mr = 0xffu << 16;
            info->mg = 0xffu << 8;
            info->mb = 0xffu << 0;
            info->ma = 0xffu << 24;
            info->all_a = 0;  // if all_a is 0 at end, then we loaded alpha
                              // channel but it was all 0
          } else {
            info->mr = 31u << 10;
            info->mg = 31u << 5;
            info->mb = 31u << 0;
          }
        } else if (compress == 3) {
          info->mr = img__get32le(s);
          info->mg = img__get32le(s);
          info->mb = img__get32le(s);
          info->extra_read += 12;
          // not documented, but generated by photoshop and handled by mspaint
          if (info->mr == info->mg && info->mg == info->mb) {
            // ?!?!?
            return img__errpuc("bad BMP", "bad BMP");
          }
        } else
          return img__errpuc("bad BMP", "bad BMP");
      }
    } else {
      int i;
      if (hsz != 108 && hsz != 124) return img__errpuc("bad BMP", "bad BMP");
      info->mr = img__get32le(s);
      info->mg = img__get32le(s);
      info->mb = img__get32le(s);
      info->ma = img__get32le(s);
      img__get32le(s);  // discard color space
      for (i = 0; i < 12; ++i)
        img__get32le(s);  // discard color space parameters
      if (hsz == 124) {
        img__get32le(s);  // discard rendering intent
        img__get32le(s);  // discard offset of profile data
        img__get32le(s);  // discard size of profile data
        img__get32le(s);  // discard reserved
      }
    }
  }
  return (void *)1;
}

static void *
img__bmp_load(img__context *s, int *x, int *y, int *comp, int req_comp,
              img__result_info *ri) {
  img_uc *out;
  unsigned int mr = 0, mg = 0, mb = 0, ma = 0, all_a;
  img_uc pal[256][4];
  int psize = 0, i, j, width;
  int flip_vertically, pad, target;
  img__bmp_data info;
  IMG_NOTUSED(ri);

  info.all_a = 255;
  if (img__bmp_parse_header(s, &info) == NULL)
    return NULL;  // error code already set

  flip_vertically = ((int)s->img_y) > 0;
  s->img_y = abs((int)s->img_y);

  if (s->img_y > IMG_MAX_DIMENSIONS)
    return img__errpuc("too large", "Very large image (corrupt?)");
  if (s->img_x > IMG_MAX_DIMENSIONS)
    return img__errpuc("too large", "Very large image (corrupt?)");

  mr = info.mr;
  mg = info.mg;
  mb = info.mb;
  ma = info.ma;
  all_a = info.all_a;

  if (info.hsz == 12) {
    if (info.bpp < 24) psize = (info.offset - info.extra_read - 24) / 3;
  } else {
    if (info.bpp < 16) psize = (info.offset - info.extra_read - info.hsz) >> 2;
  }
  if (psize == 0) {
    IMG_ASSERT(info.offset ==
               s->callback_already_read +
                   (int)(s->img_buffer - s->img_buffer_original));
    if (info.offset !=
        s->callback_already_read + (s->img_buffer - s->buffer_start)) {
      return img__errpuc("bad offset", "Corrupt BMP");
    }
  }

  if (info.bpp == 24 && ma == 0xff000000)
    s->img_n = 3;
  else
    s->img_n = ma ? 4 : 3;
  if (req_comp && req_comp >= 3)  // we can directly decode 3 or 4
    target = req_comp;
  else
    target = s->img_n;  // if they want monochrome, we'll post-convert

  // sanity-check size
  if (!img__mad3sizes_valid(target, s->img_x, s->img_y, 0))
    return img__errpuc("too large", "Corrupt BMP");

  out = (img_uc *)img__malloc_mad3(target, s->img_x, s->img_y, 0);
  if (!out) return img__errpuc("outofmem", "Out of memory");
  if (info.bpp < 16) {
    int z = 0;
    if (psize == 0 || psize > 256) {
      IMG_FREE(out);
      return img__errpuc("invalid", "Corrupt BMP");
    }
    for (i = 0; i < psize; ++i) {
      pal[i][2] = img__get8(s);
      pal[i][1] = img__get8(s);
      pal[i][0] = img__get8(s);
      if (info.hsz != 12) img__get8(s);
      pal[i][3] = 255;
    }
    img__skip(s, info.offset - info.extra_read - info.hsz -
                     psize * (info.hsz == 12 ? 3 : 4));
    if (info.bpp == 1)
      width = (s->img_x + 7) >> 3;
    else if (info.bpp == 4)
      width = (s->img_x + 1) >> 1;
    else if (info.bpp == 8)
      width = s->img_x;
    else {
      IMG_FREE(out);
      return img__errpuc("bad bpp", "Corrupt BMP");
    }
    pad = (-width) & 3;
    if (info.bpp == 1) {
      for (j = 0; j < (int)s->img_y; ++j) {
        int bit_offset = 7, v = img__get8(s);
        for (i = 0; i < (int)s->img_x; ++i) {
          int color = (v >> bit_offset) & 0x1;
          out[z++] = pal[color][0];
          out[z++] = pal[color][1];
          out[z++] = pal[color][2];
          if (target == 4) out[z++] = 255;
          if (i + 1 == (int)s->img_x) break;
          if ((--bit_offset) < 0) {
            bit_offset = 7;
            v = img__get8(s);
          }
        }
        img__skip(s, pad);
      }
    } else {
      for (j = 0; j < (int)s->img_y; ++j) {
        for (i = 0; i < (int)s->img_x; i += 2) {
          int v = img__get8(s), v2 = 0;
          if (info.bpp == 4) {
            v2 = v & 15;
            v >>= 4;
          }
          out[z++] = pal[v][0];
          out[z++] = pal[v][1];
          out[z++] = pal[v][2];
          if (target == 4) out[z++] = 255;
          if (i + 1 == (int)s->img_x) break;
          v = (info.bpp == 8) ? img__get8(s) : v2;
          out[z++] = pal[v][0];
          out[z++] = pal[v][1];
          out[z++] = pal[v][2];
          if (target == 4) out[z++] = 255;
        }
        img__skip(s, pad);
      }
    }
  } else {
    int rshift = 0, gshift = 0, bshift = 0, ashift = 0, rcount = 0, gcount = 0,
        bcount = 0, acount = 0;
    int z = 0;
    int easy = 0;
    img__skip(s, info.offset - info.extra_read - info.hsz);
    if (info.bpp == 24)
      width = 3 * s->img_x;
    else if (info.bpp == 16)
      width = 2 * s->img_x;
    else /* bpp = 32 and pad = 0 */
      width = 0;
    pad = (-width) & 3;
    if (info.bpp == 24) {
      easy = 1;
    } else if (info.bpp == 32) {
      if (mb == 0xff && mg == 0xff00 && mr == 0x00ff0000 && ma == 0xff000000)
        easy = 2;
    }
    if (!easy) {
      if (!mr || !mg || !mb) {
        IMG_FREE(out);
        return img__errpuc("bad masks", "Corrupt BMP");
      }
      // right shift amt to put high bit in position #7
      rshift = img__high_bit(mr) - 7;
      rcount = img__bitcount(mr);
      gshift = img__high_bit(mg) - 7;
      gcount = img__bitcount(mg);
      bshift = img__high_bit(mb) - 7;
      bcount = img__bitcount(mb);
      ashift = img__high_bit(ma) - 7;
      acount = img__bitcount(ma);
      if (rcount > 8 || gcount > 8 || bcount > 8 || acount > 8) {
        IMG_FREE(out);
        return img__errpuc("bad masks", "Corrupt BMP");
      }
    }
    for (j = 0; j < (int)s->img_y; ++j) {
      if (easy) {
        for (i = 0; i < (int)s->img_x; ++i) {
          unsigned char a;
          out[z + 2] = img__get8(s);
          out[z + 1] = img__get8(s);
          out[z + 0] = img__get8(s);
          z += 3;
          a = (easy == 2 ? img__get8(s) : 255);
          all_a |= a;
          if (target == 4) out[z++] = a;
        }
      } else {
        int bpp = info.bpp;
        for (i = 0; i < (int)s->img_x; ++i) {
          img__uint32 v =
              (bpp == 16 ? (img__uint32)img__get16le(s) : img__get32le(s));
          unsigned int a;
          out[z++] = IMG__BYTECAST(img__shiftsigned(v & mr, rshift, rcount));
          out[z++] = IMG__BYTECAST(img__shiftsigned(v & mg, gshift, gcount));
          out[z++] = IMG__BYTECAST(img__shiftsigned(v & mb, bshift, bcount));
          a = (ma ? img__shiftsigned(v & ma, ashift, acount) : 255);
          all_a |= a;
          if (target == 4) out[z++] = IMG__BYTECAST(a);
        }
      }
      img__skip(s, pad);
    }
  }

  // if alpha channel is all 0s, replace with all 255s
  if (target == 4 && all_a == 0)
    for (i = 4 * s->img_x * s->img_y - 1; i >= 0; i -= 4) out[i] = 255;

  if (flip_vertically) {
    img_uc t;
    for (j = 0; j < (int)s->img_y >> 1; ++j) {
      img_uc *p1 = out + j * s->img_x * target;
      img_uc *p2 = out + (s->img_y - 1 - j) * s->img_x * target;
      for (i = 0; i < (int)s->img_x * target; ++i) {
        t = p1[i];
        p1[i] = p2[i];
        p2[i] = t;
      }
    }
  }

  if (req_comp && req_comp != target) {
    out = img__convert_format(out, target, req_comp, s->img_x, s->img_y);
    if (out == NULL) return out;  // img__convert_format frees input on failure
  }

  *x = s->img_x;
  *y = s->img_y;
  if (comp) *comp = s->img_n;
  return out;
}
#endif

// Targa Truevision - TGA
// by Jonathan Dummer
#ifndef IMG_NO_TGA
// returns IMG_rgb or whatever, 0 on error
static int
img__tga_get_comp(int bits_per_pixel, int is_grey, int *is_rgb16) {
  // only RGB or RGBA (incl. 16bit) or grey allowed
  if (is_rgb16) *is_rgb16 = 0;
  switch (bits_per_pixel) {
    case 8:
      return IMG_grey;
    case 16:
      if (is_grey) return IMG_grey_alpha;
      // fallthrough
    case 15:
      if (is_rgb16) *is_rgb16 = 1;
      return IMG_rgb;
    case 24:  // fallthrough
    case 32:
      return bits_per_pixel / 8;
    default:
      return 0;
  }
}

static int
img__tga_info(img__context *s, int *x, int *y, int *comp) {
  int tga_w, tga_h, tga_comp, tga_image_type, tga_bits_per_pixel,
      tga_colormap_bpp;
  int sz, tga_colormap_type;
  img__get8(s);                      // discard Offset
  tga_colormap_type = img__get8(s);  // colormap type
  if (tga_colormap_type > 1) {
    img__rewind(s);
    return 0;  // only RGB or indexed allowed
  }
  tga_image_type = img__get8(s);  // image type
  if (tga_colormap_type == 1) {   // colormapped (paletted) image
    if (tga_image_type != 1 && tga_image_type != 9) {
      img__rewind(s);
      return 0;
    }
    img__skip(s,
              4);  // skip index of first colormap entry and number of entries
    sz = img__get8(s);  //   check bits per palette color entry
    if ((sz != 8) && (sz != 15) && (sz != 16) && (sz != 24) && (sz != 32)) {
      img__rewind(s);
      return 0;
    }
    img__skip(s, 4);  // skip image x and y origin
    tga_colormap_bpp = sz;
  } else {  // "normal" image w/o colormap - only RGB or grey allowed, +/- RLE
    if ((tga_image_type != 2) && (tga_image_type != 3) &&
        (tga_image_type != 10) && (tga_image_type != 11)) {
      img__rewind(s);
      return 0;  // only RGB or grey allowed, +/- RLE
    }
    img__skip(s, 9);  // skip colormap specification and image x/y origin
    tga_colormap_bpp = 0;
  }
  tga_w = img__get16le(s);
  if (tga_w < 1) {
    img__rewind(s);
    return 0;  // test width
  }
  tga_h = img__get16le(s);
  if (tga_h < 1) {
    img__rewind(s);
    return 0;  // test height
  }
  tga_bits_per_pixel = img__get8(s);  // bits per pixel
  img__get8(s);                       // ignore alpha bits
  if (tga_colormap_bpp != 0) {
    if ((tga_bits_per_pixel != 8) && (tga_bits_per_pixel != 16)) {
      // when using a colormap, tga_bits_per_pixel is the size of the indexes
      // I don't think anything but 8 or 16bit indexes makes sense
      img__rewind(s);
      return 0;
    }
    tga_comp = img__tga_get_comp(tga_colormap_bpp, 0, NULL);
  } else {
    tga_comp = img__tga_get_comp(
        tga_bits_per_pixel, (tga_image_type == 3) || (tga_image_type == 11),
        NULL);
  }
  if (!tga_comp) {
    img__rewind(s);
    return 0;
  }
  if (x) *x = tga_w;
  if (y) *y = tga_h;
  if (comp) *comp = tga_comp;
  return 1;  // seems to have passed everything
}

static int
img__tga_test(img__context *s) {
  int ret = 0;
  int sz, tga_color_type;
  img__get8(s);                           //   discard Offset
  tga_color_type = img__get8(s);          //   color type
  if (tga_color_type > 1) goto errorEnd;  //   only RGB or indexed allowed
  sz = img__get8(s);                      //   image type
  if (tga_color_type == 1) {              // colormapped (paletted) image
    if (sz != 1 && sz != 9)
      goto errorEnd;  // colortype 1 demands image type 1 or 9
    img__skip(s,
              4);  // skip index of first colormap entry and number of entries
    sz = img__get8(s);  //   check bits per palette color entry
    if ((sz != 8) && (sz != 15) && (sz != 16) && (sz != 24) && (sz != 32))
      goto errorEnd;
    img__skip(s, 4);  // skip image x and y origin
  } else {            // "normal" image w/o colormap
    if ((sz != 2) && (sz != 3) && (sz != 10) && (sz != 11))
      goto errorEnd;  // only RGB or grey allowed, +/- RLE
    img__skip(s, 9);  // skip colormap specification and image x/y origin
  }
  if (img__get16le(s) < 1) goto errorEnd;  //   test width
  if (img__get16le(s) < 1) goto errorEnd;  //   test height
  sz = img__get8(s);                       //   bits per pixel
  if ((tga_color_type == 1) && (sz != 8) && (sz != 16))
    goto errorEnd;  // for colormapped images, bpp is size of an index
  if ((sz != 8) && (sz != 15) && (sz != 16) && (sz != 24) && (sz != 32))
    goto errorEnd;

  ret = 1;  // if we got this far, everything's good and we can return 1 instead
            // of 0

errorEnd:
  img__rewind(s);
  return ret;
}

// read 16bit value and convert to 24bit RGB
static void
img__tga_read_rgb16(img__context *s, img_uc *out) {
  img__uint16 px = (img__uint16)img__get16le(s);
  img__uint16 fiveBitMask = 31;
  // we have 3 channels with 5bits each
  int r = (px >> 10) & fiveBitMask;
  int g = (px >> 5) & fiveBitMask;
  int b = px & fiveBitMask;
  // Note that this saves the data in RGB(A) order, so it doesn't need to be
  // swapped later
  out[0] = (img_uc)((r * 255) / 31);
  out[1] = (img_uc)((g * 255) / 31);
  out[2] = (img_uc)((b * 255) / 31);

  // some people claim that the most significant bit might be used for alpha
  // (possibly if an alpha-bit is set in the "image descriptor byte")
  // but that only made 16bit test images completely translucent..
  // so let's treat all 15 and 16bit TGAs as RGB with no alpha.
}

static void *
img__tga_load(img__context *s, int *x, int *y, int *comp, int req_comp,
              img__result_info *ri) {
  //   read in the TGA header stuff
  int tga_offset = img__get8(s);
  int tga_indexed = img__get8(s);
  int tga_image_type = img__get8(s);
  int tga_is_RLE = 0;
  int tga_palette_start = img__get16le(s);
  int tga_palette_len = img__get16le(s);
  int tga_palette_bits = img__get8(s);
  int tga_x_origin = img__get16le(s);
  int tga_y_origin = img__get16le(s);
  int tga_width = img__get16le(s);
  int tga_height = img__get16le(s);
  int tga_bits_per_pixel = img__get8(s);
  int tga_comp, tga_rgb16 = 0;
  int tga_inverted = img__get8(s);
  // int tga_alpha_bits = tga_inverted & 15; // the 4 lowest bits - unused
  // (useless?)
  //   image data
  unsigned char *tga_data;
  unsigned char *tga_palette = NULL;
  int i, j;
  unsigned char raw_data[4] = {0};
  int RLE_count = 0;
  int RLE_repeating = 0;
  int read_next_pixel = 1;
  IMG_NOTUSED(ri);
  IMG_NOTUSED(tga_x_origin);  // @TODO
  IMG_NOTUSED(tga_y_origin);  // @TODO

  if (tga_height > IMG_MAX_DIMENSIONS)
    return img__errpuc("too large", "Very large image (corrupt?)");
  if (tga_width > IMG_MAX_DIMENSIONS)
    return img__errpuc("too large", "Very large image (corrupt?)");

  //   do a tiny bit of precessing
  if (tga_image_type >= 8) {
    tga_image_type -= 8;
    tga_is_RLE = 1;
  }
  tga_inverted = 1 - ((tga_inverted >> 5) & 1);

  //   If I'm paletted, then I'll use the number of bits from the palette
  if (tga_indexed)
    tga_comp = img__tga_get_comp(tga_palette_bits, 0, &tga_rgb16);
  else
    tga_comp = img__tga_get_comp(tga_bits_per_pixel, (tga_image_type == 3),
                                 &tga_rgb16);

  if (!tga_comp)  // shouldn't really happen, img__tga_test() should have
                  // ensured basic consistency
    return img__errpuc("bad format", "Can't find out TGA pixelformat");

  //   tga info
  *x = tga_width;
  *y = tga_height;
  if (comp) *comp = tga_comp;

  if (!img__mad3sizes_valid(tga_width, tga_height, tga_comp, 0))
    return img__errpuc("too large", "Corrupt TGA");

  tga_data =
      (unsigned char *)img__malloc_mad3(tga_width, tga_height, tga_comp, 0);
  if (!tga_data) return img__errpuc("outofmem", "Out of memory");

  // skip to the data's starting position (offset usually = 0)
  img__skip(s, tga_offset);

  if (!tga_indexed && !tga_is_RLE && !tga_rgb16) {
    for (i = 0; i < tga_height; ++i) {
      int row = tga_inverted ? tga_height - i - 1 : i;
      img_uc *tga_row = tga_data + row * tga_width * tga_comp;
      img__getn(s, tga_row, tga_width * tga_comp);
    }
  } else {
    //   do I need to load a palette?
    if (tga_indexed) {
      if (tga_palette_len == 0) { /* you have to have at least one entry! */
        IMG_FREE(tga_data);
        return img__errpuc("bad palette", "Corrupt TGA");
      }

      //   any data to skip? (offset usually = 0)
      img__skip(s, tga_palette_start);
      //   load the palette
      tga_palette =
          (unsigned char *)img__malloc_mad2(tga_palette_len, tga_comp, 0);
      if (!tga_palette) {
        IMG_FREE(tga_data);
        return img__errpuc("outofmem", "Out of memory");
      }
      if (tga_rgb16) {
        img_uc *pal_entry = tga_palette;
        IMG_ASSERT(tga_comp == IMG_rgb);
        for (i = 0; i < tga_palette_len; ++i) {
          img__tga_read_rgb16(s, pal_entry);
          pal_entry += tga_comp;
        }
      } else if (!img__getn(s, tga_palette, tga_palette_len * tga_comp)) {
        IMG_FREE(tga_data);
        IMG_FREE(tga_palette);
        return img__errpuc("bad palette", "Corrupt TGA");
      }
    }
    //   load the data
    for (i = 0; i < tga_width * tga_height; ++i) {
      //   if I'm in RLE mode, do I need to get a RLE img__pngchunk?
      if (tga_is_RLE) {
        if (RLE_count == 0) {
          //   yep, get the next byte as a RLE command
          int RLE_cmd = img__get8(s);
          RLE_count = 1 + (RLE_cmd & 127);
          RLE_repeating = RLE_cmd >> 7;
          read_next_pixel = 1;
        } else if (!RLE_repeating) {
          read_next_pixel = 1;
        }
      } else {
        read_next_pixel = 1;
      }
      //   OK, if I need to read a pixel, do it now
      if (read_next_pixel) {
        //   load however much data we did have
        if (tga_indexed) {
          // read in index, then perform the lookup
          int pal_idx =
              (tga_bits_per_pixel == 8) ? img__get8(s) : img__get16le(s);
          if (pal_idx >= tga_palette_len) {
            // invalid index
            pal_idx = 0;
          }
          pal_idx *= tga_comp;
          for (j = 0; j < tga_comp; ++j) {
            raw_data[j] = tga_palette[pal_idx + j];
          }
        } else if (tga_rgb16) {
          IMG_ASSERT(tga_comp == IMG_rgb);
          img__tga_read_rgb16(s, raw_data);
        } else {
          //   read in the data raw
          for (j = 0; j < tga_comp; ++j) {
            raw_data[j] = img__get8(s);
          }
        }
        //   clear the reading flag for the next pixel
        read_next_pixel = 0;
      }  // end of reading a pixel

      // copy data
      for (j = 0; j < tga_comp; ++j) tga_data[i * tga_comp + j] = raw_data[j];

      //   in case we're in RLE mode, keep counting down
      --RLE_count;
    }
    //   do I need to invert the image?
    if (tga_inverted) {
      for (j = 0; j * 2 < tga_height; ++j) {
        int index1 = j * tga_width * tga_comp;
        int index2 = (tga_height - 1 - j) * tga_width * tga_comp;
        for (i = tga_width * tga_comp; i > 0; --i) {
          unsigned char temp = tga_data[index1];
          tga_data[index1] = tga_data[index2];
          tga_data[index2] = temp;
          ++index1;
          ++index2;
        }
      }
    }
    //   clear my palette, if I had one
    if (tga_palette != NULL) {
      IMG_FREE(tga_palette);
    }
  }

  // swap RGB - if the source data was RGB16, it already is in the right order
  if (tga_comp >= 3 && !tga_rgb16) {
    unsigned char *tga_pixel = tga_data;
    for (i = 0; i < tga_width * tga_height; ++i) {
      unsigned char temp = tga_pixel[0];
      tga_pixel[0] = tga_pixel[2];
      tga_pixel[2] = temp;
      tga_pixel += tga_comp;
    }
  }

  // convert to target component count
  if (req_comp && req_comp != tga_comp)
    tga_data = img__convert_format(tga_data, tga_comp, req_comp, tga_width,
                                   tga_height);

  //   the things I do to get rid of an error message, and yet keep
  //   Microsoft's C compilers happy... [8^(
  tga_palette_start = tga_palette_len = tga_palette_bits = tga_x_origin =
      tga_y_origin = 0;
  IMG_NOTUSED(tga_palette_start);
  //   OK, done
  return tga_data;
}
#endif

// *************************************************************************************************
// Photoshop PSD loader -- PD by Thatcher Ulrich, integration by Nicolas Schulz,
// tweaked by STB

#ifndef IMG_NO_PSD
static int
img__psd_test(img__context *s) {
  int r = (img__get32be(s) == 0x38425053);
  img__rewind(s);
  return r;
}

static int
img__psd_decode_rle(img__context *s, img_uc *p, int pixelCount) {
  int count, nleft, len;

  count = 0;
  while ((nleft = pixelCount - count) > 0) {
    len = img__get8(s);
    if (len == 128) {
      // No-op.
    } else if (len < 128) {
      // Copy next len+1 bytes literally.
      len++;
      if (len > nleft) return 0;  // corrupt data
      count += len;
      while (len) {
        *p = img__get8(s);
        p += 4;
        len--;
      }
    } else if (len > 128) {
      img_uc val;
      // Next -len+1 bytes in the dest are replicated from next source byte.
      // (Interpret len as a negative 8-bit int.)
      len = 257 - len;
      if (len > nleft) return 0;  // corrupt data
      val = img__get8(s);
      count += len;
      while (len) {
        *p = val;
        p += 4;
        len--;
      }
    }
  }

  return 1;
}

static void *
img__psd_load(img__context *s, int *x, int *y, int *comp, int req_comp,
              img__result_info *ri, int bpc) {
  int pixelCount;
  int channelCount, compression;
  int channel, i;
  int bitdepth;
  int w, h;
  img_uc *out;
  IMG_NOTUSED(ri);

  // Check identifier
  if (img__get32be(s) != 0x38425053)  // "8BPS"
    return img__errpuc("not PSD", "Corrupt PSD image");

  // Check file type version.
  if (img__get16be(s) != 1)
    return img__errpuc("wrong version", "Unsupported version of PSD image");

  // Skip 6 reserved bytes.
  img__skip(s, 6);

  // Read the number of channels (R, G, B, A, etc).
  channelCount = img__get16be(s);
  if (channelCount < 0 || channelCount > 16)
    return img__errpuc("wrong channel count",
                       "Unsupported number of channels in PSD image");

  // Read the rows and columns of the image.
  h = img__get32be(s);
  w = img__get32be(s);

  if (h > IMG_MAX_DIMENSIONS)
    return img__errpuc("too large", "Very large image (corrupt?)");
  if (w > IMG_MAX_DIMENSIONS)
    return img__errpuc("too large", "Very large image (corrupt?)");

  // Make sure the depth is 8 bits.
  bitdepth = img__get16be(s);
  if (bitdepth != 8 && bitdepth != 16)
    return img__errpuc("unsupported bit depth",
                       "PSD bit depth is not 8 or 16 bit");

  // Make sure the color mode is RGB.
  // Valid options are:
  //   0: Bitmap
  //   1: Grayscale
  //   2: Indexed color
  //   3: RGB color
  //   4: CMYK color
  //   7: Multichannel
  //   8: Duotone
  //   9: Lab color
  if (img__get16be(s) != 3)
    return img__errpuc("wrong color format", "PSD is not in RGB color format");

  // Skip the Mode Data.  (It's the palette for indexed color; other info for
  // other modes.)
  img__skip(s, img__get32be(s));

  // Skip the image resources.  (resolution, pen tool paths, etc)
  img__skip(s, img__get32be(s));

  // Skip the reserved data.
  img__skip(s, img__get32be(s));

  // Find out if the data is compressed.
  // Known values:
  //   0: no compression
  //   1: RLE compressed
  compression = img__get16be(s);
  if (compression > 1)
    return img__errpuc("bad compression",
                       "PSD has an unknown compression format");

  // Check size
  if (!img__mad3sizes_valid(4, w, h, 0))
    return img__errpuc("too large", "Corrupt PSD");

  // Create the destination image.

  if (!compression && bitdepth == 16 && bpc == 16) {
    out = (img_uc *)img__malloc_mad3(8, w, h, 0);
    ri->bits_per_channel = 16;
  } else
    out = (img_uc *)img__malloc(4 * w * h);

  if (!out) return img__errpuc("outofmem", "Out of memory");
  pixelCount = w * h;

  // Initialize the data to zero.
  // memset( out, 0, pixelCount * 4 );

  // Finally, the image data.
  if (compression) {
    // RLE as used by .PSD and .TIFF
    // Loop until you get the number of unpacked bytes you are expecting:
    //     Read the next source byte into n.
    //     If n is between 0 and 127 inclusive, copy the next n+1 bytes
    //     literally. Else if n is between -127 and -1 inclusive, copy the next
    //     byte -n+1 times. Else if n is 128, noop.
    // Endloop

    // The RLE-compressed data is preceded by a 2-byte data count for each row
    // in the data, which we're going to just skip.
    img__skip(s, h * channelCount * 2);

    // Read the RLE data by channel.
    for (channel = 0; channel < 4; channel++) {
      img_uc *p;

      p = out + channel;
      if (channel >= channelCount) {
        // Fill this channel with default data.
        for (i = 0; i < pixelCount; i++, p += 4) *p = (channel == 3 ? 255 : 0);
      } else {
        // Read the RLE data.
        if (!img__psd_decode_rle(s, p, pixelCount)) {
          IMG_FREE(out);
          return img__errpuc("corrupt", "bad RLE data");
        }
      }
    }

  } else {
    // We're at the raw image data.  It's each channel in order (Red, Green,
    // Blue, Alpha, ...) where each channel consists of an 8-bit (or 16-bit)
    // value for each pixel in the image.

    // Read the data by channel.
    for (channel = 0; channel < 4; channel++) {
      if (channel >= channelCount) {
        // Fill this channel with default data.
        if (bitdepth == 16 && bpc == 16) {
          img__uint16 *q = ((img__uint16 *)out) + channel;
          img__uint16 val = channel == 3 ? 65535 : 0;
          for (i = 0; i < pixelCount; i++, q += 4) *q = val;
        } else {
          img_uc *p = out + channel;
          img_uc val = channel == 3 ? 255 : 0;
          for (i = 0; i < pixelCount; i++, p += 4) *p = val;
        }
      } else {
        if (ri->bits_per_channel == 16) {  // output bpc
          img__uint16 *q = ((img__uint16 *)out) + channel;
          for (i = 0; i < pixelCount; i++, q += 4)
            *q = (img__uint16)img__get16be(s);
        } else {
          img_uc *p = out + channel;
          if (bitdepth == 16) {  // input bpc
            for (i = 0; i < pixelCount; i++, p += 4)
              *p = (img_uc)(img__get16be(s) >> 8);
          } else {
            for (i = 0; i < pixelCount; i++, p += 4) *p = img__get8(s);
          }
        }
      }
    }
  }

  // remove weird white matte from PSD
  if (channelCount >= 4) {
    if (ri->bits_per_channel == 16) {
      for (i = 0; i < w * h; ++i) {
        img__uint16 *pixel = (img__uint16 *)out + 4 * i;
        if (pixel[3] != 0 && pixel[3] != 65535) {
          float a = pixel[3] / 65535.0f;
          float ra = 1.0f / a;
          float inv_a = 65535.0f * (1 - ra);
          pixel[0] = (img__uint16)(pixel[0] * ra + inv_a);
          pixel[1] = (img__uint16)(pixel[1] * ra + inv_a);
          pixel[2] = (img__uint16)(pixel[2] * ra + inv_a);
        }
      }
    } else {
      for (i = 0; i < w * h; ++i) {
        unsigned char *pixel = out + 4 * i;
        if (pixel[3] != 0 && pixel[3] != 255) {
          float a = pixel[3] / 255.0f;
          float ra = 1.0f / a;
          float inv_a = 255.0f * (1 - ra);
          pixel[0] = (unsigned char)(pixel[0] * ra + inv_a);
          pixel[1] = (unsigned char)(pixel[1] * ra + inv_a);
          pixel[2] = (unsigned char)(pixel[2] * ra + inv_a);
        }
      }
    }
  }

  // convert to desired output format
  if (req_comp && req_comp != 4) {
    if (ri->bits_per_channel == 16)
      out = (img_uc *)img__convert_format16((img__uint16 *)out, 4, req_comp, w,
                                            h);
    else
      out = img__convert_format(out, 4, req_comp, w, h);
    if (out == NULL) return out;  // img__convert_format frees input on failure
  }

  if (comp) *comp = 4;
  *y = h;
  *x = w;

  return out;
}
#endif

// *************************************************************************************************
// Softimage PIC loader
// by Tom Seddon
//
// See http://softimage.wiki.softimage.com/index.php/INFO:_PIC_file_format
// See http://ozviz.wasp.uwa.edu.au/~pbourke/dataformats/softimagepic/

#ifndef IMG_NO_PIC
static int
img__pic_is4(img__context *s, const char *str) {
  int i;
  for (i = 0; i < 4; ++i)
    if (img__get8(s) != (img_uc)str[i]) return 0;

  return 1;
}

static int
img__pic_test_core(img__context *s) {
  int i;

  if (!img__pic_is4(s, "\x53\x80\xF6\x34")) return 0;

  for (i = 0; i < 84; ++i) img__get8(s);

  if (!img__pic_is4(s, "PICT")) return 0;

  return 1;
}

typedef struct {
  img_uc size, type, channel;
} img__pic_packet;

static img_uc *
img__readval(img__context *s, int channel, img_uc *dest) {
  int mask = 0x80, i;

  for (i = 0; i < 4; ++i, mask >>= 1) {
    if (channel & mask) {
      if (img__at_eof(s)) return img__errpuc("bad file", "PIC file too short");
      dest[i] = img__get8(s);
    }
  }

  return dest;
}

static void
img__copyval(int channel, img_uc *dest, const img_uc *src) {
  int mask = 0x80, i;

  for (i = 0; i < 4; ++i, mask >>= 1)
    if (channel & mask) dest[i] = src[i];
}

static img_uc *
img__pic_load_core(img__context *s, int width, int height, int *comp,
                   img_uc *result) {
  int act_comp = 0, num_packets = 0, y, chained;
  img__pic_packet packets[10];

  // this will (should...) cater for even some bizarre stuff like having data
  // for the same channel in multiple packets.
  do {
    img__pic_packet *packet;

    if (num_packets == sizeof(packets) / sizeof(packets[0]))
      return img__errpuc("bad format", "too many packets");

    packet = &packets[num_packets++];

    chained = img__get8(s);
    packet->size = img__get8(s);
    packet->type = img__get8(s);
    packet->channel = img__get8(s);

    act_comp |= packet->channel;

    if (img__at_eof(s))
      return img__errpuc("bad file", "file too short (reading packets)");
    if (packet->size != 8)
      return img__errpuc("bad format", "packet isn't 8bpp");
  } while (chained);

  *comp = (act_comp & 0x10 ? 4 : 3);  // has alpha channel?

  for (y = 0; y < height; ++y) {
    int packet_idx;

    for (packet_idx = 0; packet_idx < num_packets; ++packet_idx) {
      img__pic_packet *packet = &packets[packet_idx];
      img_uc *dest = result + y * width * 4;

      switch (packet->type) {
        default:
          return img__errpuc("bad format", "packet has bad compression type");

        case 0: {  // uncompressed
          int x;

          for (x = 0; x < width; ++x, dest += 4)
            if (!img__readval(s, packet->channel, dest)) return 0;
          break;
        }

        case 1:  // Pure RLE
        {
          int left = width, i;

          while (left > 0) {
            img_uc count, value[4];

            count = img__get8(s);
            if (img__at_eof(s))
              return img__errpuc("bad file",
                                 "file too short (pure read count)");

            if (count > left) count = (img_uc)left;

            if (!img__readval(s, packet->channel, value)) return 0;

            for (i = 0; i < count; ++i, dest += 4)
              img__copyval(packet->channel, dest, value);
            left -= count;
          }
        } break;

        case 2: {  // Mixed RLE
          int left = width;
          while (left > 0) {
            int count = img__get8(s), i;
            if (img__at_eof(s))
              return img__errpuc("bad file",
                                 "file too short (mixed read count)");

            if (count >= 128) {  // Repeated
              img_uc value[4];

              if (count == 128)
                count = img__get16be(s);
              else
                count -= 127;
              if (count > left)
                return img__errpuc("bad file", "scanline overrun");

              if (!img__readval(s, packet->channel, value)) return 0;

              for (i = 0; i < count; ++i, dest += 4)
                img__copyval(packet->channel, dest, value);
            } else {  // Raw
              ++count;
              if (count > left)
                return img__errpuc("bad file", "scanline overrun");

              for (i = 0; i < count; ++i, dest += 4)
                if (!img__readval(s, packet->channel, dest)) return 0;
            }
            left -= count;
          }
          break;
        }
      }
    }
  }

  return result;
}

static void *
img__pic_load(img__context *s, int *px, int *py, int *comp, int req_comp,
              img__result_info *ri) {
  img_uc *result;
  int i, x, y, internal_comp;
  IMG_NOTUSED(ri);

  if (!comp) comp = &internal_comp;

  for (i = 0; i < 92; ++i) img__get8(s);

  x = img__get16be(s);
  y = img__get16be(s);

  if (y > IMG_MAX_DIMENSIONS)
    return img__errpuc("too large", "Very large image (corrupt?)");
  if (x > IMG_MAX_DIMENSIONS)
    return img__errpuc("too large", "Very large image (corrupt?)");

  if (img__at_eof(s))
    return img__errpuc("bad file", "file too short (pic header)");
  if (!img__mad3sizes_valid(x, y, 4, 0))
    return img__errpuc("too large", "PIC image too large to decode");

  img__get32be(s);  // skip `ratio'
  img__get16be(s);  // skip `fields'
  img__get16be(s);  // skip `pad'

  // intermediate buffer is RGBA
  result = (img_uc *)img__malloc_mad3(x, y, 4, 0);
  memset(result, 0xff, x * y * 4);

  if (!img__pic_load_core(s, x, y, comp, result)) {
    IMG_FREE(result);
    result = 0;
  }
  *px = x;
  *py = y;
  if (req_comp == 0) req_comp = *comp;
  result = img__convert_format(result, 4, req_comp, x, y);

  return result;
}

static int
img__pic_test(img__context *s) {
  int r = img__pic_test_core(s);
  img__rewind(s);
  return r;
}
#endif

// *************************************************************************************************
// GIF loader -- public domain by Jean-Marc Lienher -- simplified/shrunk by stb

#ifndef IMG_NO_GIF
typedef struct {
  img__int16 prefix;
  img_uc first;
  img_uc suffix;
} img__gif_lzw;

typedef struct {
  int w, h;
  img_uc *out;         // output buffer (always 4 components)
  img_uc *background;  // The current "background" as far as a gif is concerned
  img_uc *history;
  int flags, bgindex, ratio, transparent, eflags;
  img_uc pal[256][4];
  img_uc lpal[256][4];
  img__gif_lzw codes[8192];
  img_uc *color_table;
  int parse, step;
  int lflags;
  int start_x, start_y;
  int max_x, max_y;
  int cur_x, cur_y;
  int line_size;
  int delay;
} img__gif;

static int
img__gif_test_raw(img__context *s) {
  int sz;
  if (img__get8(s) != 'G' || img__get8(s) != 'I' || img__get8(s) != 'F' ||
      img__get8(s) != '8')
    return 0;
  sz = img__get8(s);
  if (sz != '9' && sz != '7') return 0;
  if (img__get8(s) != 'a') return 0;
  return 1;
}

static int
img__gif_test(img__context *s) {
  int r = img__gif_test_raw(s);
  img__rewind(s);
  return r;
}

static void
img__gif_parse_colortable(img__context *s, img_uc pal[256][4], int num_entries,
                          int transp) {
  int i;
  for (i = 0; i < num_entries; ++i) {
    pal[i][2] = img__get8(s);
    pal[i][1] = img__get8(s);
    pal[i][0] = img__get8(s);
    pal[i][3] = transp == i ? 0 : 255;
  }
}

static int
img__gif_header(img__context *s, img__gif *g, int *comp, int is_info) {
  img_uc version;
  if (img__get8(s) != 'G' || img__get8(s) != 'I' || img__get8(s) != 'F' ||
      img__get8(s) != '8')
    return img__err("not GIF", "Corrupt GIF");

  version = img__get8(s);
  if (version != '7' && version != '9')
    return img__err("not GIF", "Corrupt GIF");
  if (img__get8(s) != 'a') return img__err("not GIF", "Corrupt GIF");

  img__g_failure_reason = "";
  g->w = img__get16le(s);
  g->h = img__get16le(s);
  g->flags = img__get8(s);
  g->bgindex = img__get8(s);
  g->ratio = img__get8(s);
  g->transparent = -1;

  if (g->w > IMG_MAX_DIMENSIONS)
    return img__err("too large", "Very large image (corrupt?)");
  if (g->h > IMG_MAX_DIMENSIONS)
    return img__err("too large", "Very large image (corrupt?)");

  if (comp != 0)
    *comp = 4;  // can't actually tell whether it's 3 or 4 until we parse the
                // comments

  if (is_info) return 1;

  if (g->flags & 0x80)
    img__gif_parse_colortable(s, g->pal, 2 << (g->flags & 7), -1);

  return 1;
}

static int
img__gif_info_raw(img__context *s, int *x, int *y, int *comp) {
  img__gif *g = (img__gif *)img__malloc(sizeof(img__gif));
  if (!img__gif_header(s, g, comp, 1)) {
    IMG_FREE(g);
    img__rewind(s);
    return 0;
  }
  if (x) *x = g->w;
  if (y) *y = g->h;
  IMG_FREE(g);
  return 1;
}

static void
img__out_gif_code(img__gif *g, img__uint16 code) {
  img_uc *p, *c;
  int idx;

  // recurse to decode the prefixes, since the linked-list is backwards,
  // and working backwards through an interleaved image would be nasty
  if (g->codes[code].prefix >= 0) img__out_gif_code(g, g->codes[code].prefix);

  if (g->cur_y >= g->max_y) return;

  idx = g->cur_x + g->cur_y;
  p = &g->out[idx];
  g->history[idx / 4] = 1;

  c = &g->color_table[g->codes[code].suffix * 4];
  if (c[3] > 128) {  // don't render transparent pixels;
    p[0] = c[2];
    p[1] = c[1];
    p[2] = c[0];
    p[3] = c[3];
  }
  g->cur_x += 4;

  if (g->cur_x >= g->max_x) {
    g->cur_x = g->start_x;
    g->cur_y += g->step;

    while (g->cur_y >= g->max_y && g->parse > 0) {
      g->step = (1 << g->parse) * g->line_size;
      g->cur_y = g->start_y + (g->step >> 1);
      --g->parse;
    }
  }
}

static img_uc *
img__process_gif_raster(img__context *s, img__gif *g) {
  img_uc lzw_cs;
  img__int32 len, init_code;
  img__uint32 first;
  img__int32 codesize, codemask, avail, oldcode, bits, valid_bits, clear;
  img__gif_lzw *p;

  lzw_cs = img__get8(s);
  if (lzw_cs > 12) return NULL;
  clear = 1 << lzw_cs;
  first = 1;
  codesize = lzw_cs + 1;
  codemask = (1 << codesize) - 1;
  bits = 0;
  valid_bits = 0;
  for (init_code = 0; init_code < clear; init_code++) {
    g->codes[init_code].prefix = -1;
    g->codes[init_code].first = (img_uc)init_code;
    g->codes[init_code].suffix = (img_uc)init_code;
  }

  // support no starting clear code
  avail = clear + 2;
  oldcode = -1;

  len = 0;
  for (;;) {
    if (valid_bits < codesize) {
      if (len == 0) {
        len = img__get8(s);  // start new block
        if (len == 0) return g->out;
      }
      --len;
      bits |= (img__int32)img__get8(s) << valid_bits;
      valid_bits += 8;
    } else {
      img__int32 code = bits & codemask;
      bits >>= codesize;
      valid_bits -= codesize;
      // @OPTIMIZE: is there some way we can accelerate the non-clear path?
      if (code == clear) {  // clear code
        codesize = lzw_cs + 1;
        codemask = (1 << codesize) - 1;
        avail = clear + 2;
        oldcode = -1;
        first = 0;
      } else if (code == clear + 1) {  // end of stream code
        img__skip(s, len);
        while ((len = img__get8(s)) > 0) img__skip(s, len);
        return g->out;
      } else if (code <= avail) {
        if (first) {
          return img__errpuc("no clear code", "Corrupt GIF");
        }

        if (oldcode >= 0) {
          p = &g->codes[avail++];
          if (avail > 8192) {
            return img__errpuc("too many codes", "Corrupt GIF");
          }

          p->prefix = (img__int16)oldcode;
          p->first = g->codes[oldcode].first;
          p->suffix = (code == avail) ? p->first : g->codes[code].first;
        } else if (code == avail)
          return img__errpuc("illegal code in raster", "Corrupt GIF");

        img__out_gif_code(g, (img__uint16)code);

        if ((avail & codemask) == 0 && avail <= 0x0FFF) {
          codesize++;
          codemask = (1 << codesize) - 1;
        }

        oldcode = code;
      } else {
        return img__errpuc("illegal code in raster", "Corrupt GIF");
      }
    }
  }
}

// this function is designed to support animated gifs, although stb_image
// doesn't support it two back is the image from two frames ago, used for a very
// specific disposal format
static img_uc *
img__gif_load_next(img__context *s, img__gif *g, int *comp, int req_comp,
                   img_uc *two_back) {
  int dispose;
  int first_frame;
  int pi;
  int pcount;
  IMG_NOTUSED(req_comp);

  // on first frame, any non-written pixels get the background colour
  // (non-transparent)
  first_frame = 0;
  if (g->out == 0) {
    if (!img__gif_header(s, g, comp, 0))
      return 0;  // img__g_failure_reason set by img__gif_header
    if (!img__mad3sizes_valid(4, g->w, g->h, 0))
      return img__errpuc("too large", "GIF image is too large");
    pcount = g->w * g->h;
    g->out = (img_uc *)img__malloc(4 * pcount);
    g->background = (img_uc *)img__malloc(4 * pcount);
    g->history = (img_uc *)img__malloc(pcount);
    if (!g->out || !g->background || !g->history)
      return img__errpuc("outofmem", "Out of memory");

    // image is treated as "transparent" at the start - ie, nothing overwrites
    // the current background; background colour is only used for pixels that
    // are not rendered first frame, after that "background" color refers to the
    // color that was there the previous frame.
    memset(g->out, 0x00, 4 * pcount);
    memset(g->background, 0x00,
           4 * pcount);  // state of the background (starts transparent)
    memset(g->history, 0x00,
           pcount);  // pixels that were affected previous frame
    first_frame = 1;
  } else {
    // second frame - how do we dispose of the previous one?
    dispose = (g->eflags & 0x1C) >> 2;
    pcount = g->w * g->h;

    if ((dispose == 3) && (two_back == 0)) {
      dispose = 2;  // if I don't have an image to revert back to, default to
                    // the old background
    }

    if (dispose == 3) {  // use previous graphic
      for (pi = 0; pi < pcount; ++pi) {
        if (g->history[pi]) {
          memcpy(&g->out[pi * 4], &two_back[pi * 4], 4);
        }
      }
    } else if (dispose == 2) {
      // restore what was changed last frame to background before that frame;
      for (pi = 0; pi < pcount; ++pi) {
        if (g->history[pi]) {
          memcpy(&g->out[pi * 4], &g->background[pi * 4], 4);
        }
      }
    } else {
      // This is a non-disposal case eithe way, so just
      // leave the pixels as is, and they will become the new background
      // 1: do not dispose
      // 0:  not specified.
    }

    // background is what out is after the undoing of the previou frame;
    memcpy(g->background, g->out, 4 * g->w * g->h);
  }

  // clear my history;
  memset(g->history, 0x00,
         g->w * g->h);  // pixels that were affected previous frame

  for (;;) {
    int tag = img__get8(s);
    switch (tag) {
      case 0x2C: /* Image Descriptor */
      {
        img__int32 x, y, w, h;
        img_uc *o;

        x = img__get16le(s);
        y = img__get16le(s);
        w = img__get16le(s);
        h = img__get16le(s);
        if (((x + w) > (g->w)) || ((y + h) > (g->h)))
          return img__errpuc("bad Image Descriptor", "Corrupt GIF");

        g->line_size = g->w * 4;
        g->start_x = x * 4;
        g->start_y = y * g->line_size;
        g->max_x = g->start_x + w * 4;
        g->max_y = g->start_y + h * g->line_size;
        g->cur_x = g->start_x;
        g->cur_y = g->start_y;

        // if the width of the specified rectangle is 0, that means
        // we may not see *any* pixels or the image is malformed;
        // to make sure this is caught, move the current y down to
        // max_y (which is what out_gif_code checks).
        if (w == 0) g->cur_y = g->max_y;

        g->lflags = img__get8(s);

        if (g->lflags & 0x40) {
          g->step = 8 * g->line_size;  // first interlaced spacing
          g->parse = 3;
        } else {
          g->step = g->line_size;
          g->parse = 0;
        }

        if (g->lflags & 0x80) {
          img__gif_parse_colortable(s, g->lpal, 2 << (g->lflags & 7),
                                    g->eflags & 0x01 ? g->transparent : -1);
          g->color_table = (img_uc *)g->lpal;
        } else if (g->flags & 0x80) {
          g->color_table = (img_uc *)g->pal;
        } else
          return img__errpuc("missing color table", "Corrupt GIF");

        o = img__process_gif_raster(s, g);
        if (!o) return NULL;

        // if this was the first frame,
        pcount = g->w * g->h;
        if (first_frame && (g->bgindex > 0)) {
          // if first frame, any pixel not drawn to gets the background color
          for (pi = 0; pi < pcount; ++pi) {
            if (g->history[pi] == 0) {
              g->pal[g->bgindex][3] =
                  255;  // just in case it was made transparent, undo that; It
                        // will be reset next frame if need be;
              memcpy(&g->out[pi * 4], &g->pal[g->bgindex], 4);
            }
          }
        }

        return o;
      }

      case 0x21:  // Comment Extension.
      {
        int len;
        int ext = img__get8(s);
        if (ext == 0xF9) {  // Graphic Control Extension.
          len = img__get8(s);
          if (len == 4) {
            g->eflags = img__get8(s);
            g->delay =
                10 *
                img__get16le(
                    s);  // delay - 1/100th of a second, saving as 1/1000ths.

            // unset old transparent
            if (g->transparent >= 0) {
              g->pal[g->transparent][3] = 255;
            }
            if (g->eflags & 0x01) {
              g->transparent = img__get8(s);
              if (g->transparent >= 0) {
                g->pal[g->transparent][3] = 0;
              }
            } else {
              // don't need transparent
              img__skip(s, 1);
              g->transparent = -1;
            }
          } else {
            img__skip(s, len);
            break;
          }
        }
        while ((len = img__get8(s)) != 0) {
          img__skip(s, len);
        }
        break;
      }

      case 0x3B:             // gif stream termination code
        return (img_uc *)s;  // using '1' causes warning on some compilers

      default:
        return img__errpuc("unknown code", "Corrupt GIF");
    }
  }
}

static void *
img__load_gif_main(img__context *s, int **delays, int *x, int *y, int *z,
                   int *comp, int req_comp) {
  if (img__gif_test(s)) {
    int layers = 0;
    img_uc *u = 0;
    img_uc *out = 0;
    img_uc *two_back = 0;
    img__gif g;
    int stride;
    int out_size = 0;
    int delays_size = 0;
    memset(&g, 0, sizeof(g));
    if (delays) {
      *delays = 0;
    }

    do {
      u = img__gif_load_next(s, &g, comp, req_comp, two_back);
      if (u == (img_uc *)s) u = 0;  // end of animated gif marker

      if (u) {
        *x = g.w;
        *y = g.h;
        ++layers;
        stride = g.w * g.h * 4;

        if (out) {
          void *tmp =
              (img_uc *)IMG_REALLOC_SIZED(out, out_size, layers * stride);
          if (NULL == tmp) {
            IMG_FREE(g.out);
            IMG_FREE(g.history);
            IMG_FREE(g.background);
            return img__errpuc("outofmem", "Out of memory");
          } else {
            out = (img_uc *)tmp;
            out_size = layers * stride;
          }

          if (delays) {
            *delays = (int *)IMG_REALLOC_SIZED(*delays, delays_size,
                                               sizeof(int) * layers);
            delays_size = layers * sizeof(int);
          }
        } else {
          out = (img_uc *)img__malloc(layers * stride);
          out_size = layers * stride;
          if (delays) {
            *delays = (int *)img__malloc(layers * sizeof(int));
            delays_size = layers * sizeof(int);
          }
        }
        memcpy(out + ((layers - 1) * stride), u, stride);
        if (layers >= 2) {
          two_back = out - 2 * stride;
        }

        if (delays) {
          (*delays)[layers - 1U] = g.delay;
        }
      }
    } while (u != 0);

    // free temp buffer;
    IMG_FREE(g.out);
    IMG_FREE(g.history);
    IMG_FREE(g.background);

    // do the final conversion after loading everything;
    if (req_comp && req_comp != 4)
      out = img__convert_format(out, 4, req_comp, layers * g.w, g.h);

    *z = layers;
    return out;
  } else {
    return img__errpuc("not GIF", "Image was not as a gif type.");
  }
}

static void *
img__gif_load(img__context *s, int *x, int *y, int *comp, int req_comp,
              img__result_info *ri) {
  img_uc *u = 0;
  img__gif g;
  memset(&g, 0, sizeof(g));
  IMG_NOTUSED(ri);

  u = img__gif_load_next(s, &g, comp, req_comp, 0);
  if (u == (img_uc *)s) u = 0;  // end of animated gif marker
  if (u) {
    *x = g.w;
    *y = g.h;

    // moved conversion to after successful load so that the same
    // can be done for multiple frames.
    if (req_comp && req_comp != 4)
      u = img__convert_format(u, 4, req_comp, g.w, g.h);
  } else if (g.out) {
    // if there was an error and we allocated an image buffer, free it!
    IMG_FREE(g.out);
  }

  // free buffers needed for multiple frame loading;
  IMG_FREE(g.history);
  IMG_FREE(g.background);

  return u;
}

static int
img__gif_info(img__context *s, int *x, int *y, int *comp) {
  return img__gif_info_raw(s, x, y, comp);
}
#endif

// *************************************************************************************************
// Radiance RGBE HDR loader
// originally by Nicolas Schulz
#ifndef IMG_NO_HDR
static int
img__hdr_test_core(img__context *s, const char *signature) {
  int i;
  for (i = 0; signature[i]; ++i)
    if (img__get8(s) != signature[i]) return 0;
  img__rewind(s);
  return 1;
}

static int
img__hdr_test(img__context *s) {
  int r = img__hdr_test_core(s, "#?RADIANCE\n");
  img__rewind(s);
  if (!r) {
    r = img__hdr_test_core(s, "#?RGBE\n");
    img__rewind(s);
  }
  return r;
}

#define IMG__HDR_BUFLEN 1024
static char *
img__hdr_gettoken(img__context *z, char *buffer) {
  int len = 0;
  char c = '\0';

  c = (char)img__get8(z);

  while (!img__at_eof(z) && c != '\n') {
    buffer[len++] = c;
    if (len == IMG__HDR_BUFLEN - 1) {
      // flush to end of line
      while (!img__at_eof(z) && img__get8(z) != '\n')
        ;
      break;
    }
    c = (char)img__get8(z);
  }

  buffer[len] = 0;
  return buffer;
}

static void
img__hdr_convert(float *output, img_uc *input, int req_comp) {
  if (input[3] != 0) {
    float f1;
    // Exponent
    f1 = (float)ldexp(1.0f, input[3] - (int)(128 + 8));
    if (req_comp <= 2)
      output[0] = (input[0] + input[1] + input[2]) * f1 / 3;
    else {
      output[0] = input[0] * f1;
      output[1] = input[1] * f1;
      output[2] = input[2] * f1;
    }
    if (req_comp == 2) output[1] = 1;
    if (req_comp == 4) output[3] = 1;
  } else {
    switch (req_comp) {
      case 4:
        output[3] = 1; /* fallthrough */
      case 3:
        output[0] = output[1] = output[2] = 0;
        break;
      case 2:
        output[1] = 1; /* fallthrough */
      case 1:
        output[0] = 0;
        break;
    }
  }
}

static float *
img__hdr_load(img__context *s, int *x, int *y, int *comp, int req_comp,
              img__result_info *ri) {
  char buffer[IMG__HDR_BUFLEN];
  char *token;
  int valid = 0;
  int width, height;
  img_uc *scanline;
  float *hdr_data;
  int len;
  unsigned char count, value;
  int i, j, k, c1, c2, z;
  const char *headerToken;
  IMG_NOTUSED(ri);

  // Check identifier
  headerToken = img__hdr_gettoken(s, buffer);
  if (strcmp(headerToken, "#?RADIANCE") != 0 &&
      strcmp(headerToken, "#?RGBE") != 0)
    return img__errpf("not HDR", "Corrupt HDR image");

  // Parse header
  for (;;) {
    token = img__hdr_gettoken(s, buffer);
    if (token[0] == 0) break;
    if (strcmp(token, "FORMAT=32-bit_rle_rgbe") == 0) valid = 1;
  }

  if (!valid) return img__errpf("unsupported format", "Unsupported HDR format");

  // Parse width and height
  // can't use sscanf() if we're not using stdio!
  token = img__hdr_gettoken(s, buffer);
  if (strncmp(token, "-Y ", 3))
    return img__errpf("unsupported data layout", "Unsupported HDR format");
  token += 3;
  height = (int)strtol(token, &token, 10);
  while (*token == ' ') ++token;
  if (strncmp(token, "+X ", 3))
    return img__errpf("unsupported data layout", "Unsupported HDR format");
  token += 3;
  width = (int)strtol(token, NULL, 10);

  if (height > IMG_MAX_DIMENSIONS)
    return img__errpf("too large", "Very large image (corrupt?)");
  if (width > IMG_MAX_DIMENSIONS)
    return img__errpf("too large", "Very large image (corrupt?)");

  *x = width;
  *y = height;

  if (comp) *comp = 3;
  if (req_comp == 0) req_comp = 3;

  if (!img__mad4sizes_valid(width, height, req_comp, sizeof(float), 0))
    return img__errpf("too large", "HDR image is too large");

  // Read data
  hdr_data =
      (float *)img__malloc_mad4(width, height, req_comp, sizeof(float), 0);
  if (!hdr_data) return img__errpf("outofmem", "Out of memory");

  // Load image data
  // image data is stored as some number of sca
  if (width < 8 || width >= 32768) {
    // Read flat data
    for (j = 0; j < height; ++j) {
      for (i = 0; i < width; ++i) {
        img_uc rgbe[4];
      main_decode_loop:
        img__getn(s, rgbe, 4);
        img__hdr_convert(hdr_data + j * width * req_comp + i * req_comp, rgbe,
                         req_comp);
      }
    }
  } else {
    // Read RLE-encoded data
    scanline = NULL;

    for (j = 0; j < height; ++j) {
      c1 = img__get8(s);
      c2 = img__get8(s);
      len = img__get8(s);
      if (c1 != 2 || c2 != 2 || (len & 0x80)) {
        // not run-length encoded, so we have to actually use THIS data as a
        // decoded pixel (note this can't be a valid pixel--one of RGB must be
        // >= 128)
        img_uc rgbe[4];
        rgbe[0] = (img_uc)c1;
        rgbe[1] = (img_uc)c2;
        rgbe[2] = (img_uc)len;
        rgbe[3] = (img_uc)img__get8(s);
        img__hdr_convert(hdr_data, rgbe, req_comp);
        i = 1;
        j = 0;
        IMG_FREE(scanline);
        goto main_decode_loop;  // yes, this makes no sense
      }
      len <<= 8;
      len |= img__get8(s);
      if (len != width) {
        IMG_FREE(hdr_data);
        IMG_FREE(scanline);
        return img__errpf("invalid decoded scanline length", "corrupt HDR");
      }
      if (scanline == NULL) {
        scanline = (img_uc *)img__malloc_mad2(width, 4, 0);
        if (!scanline) {
          IMG_FREE(hdr_data);
          return img__errpf("outofmem", "Out of memory");
        }
      }

      for (k = 0; k < 4; ++k) {
        int nleft;
        i = 0;
        while ((nleft = width - i) > 0) {
          count = img__get8(s);
          if (count > 128) {
            // Run
            value = img__get8(s);
            count -= 128;
            if (count > nleft) {
              IMG_FREE(hdr_data);
              IMG_FREE(scanline);
              return img__errpf("corrupt", "bad RLE data in HDR");
            }
            for (z = 0; z < count; ++z) scanline[i++ * 4 + k] = value;
          } else {
            // Dump
            if (count > nleft) {
              IMG_FREE(hdr_data);
              IMG_FREE(scanline);
              return img__errpf("corrupt", "bad RLE data in HDR");
            }
            for (z = 0; z < count; ++z) scanline[i++ * 4 + k] = img__get8(s);
          }
        }
      }
      for (i = 0; i < width; ++i)
        img__hdr_convert(hdr_data + (j * width + i) * req_comp,
                         scanline + i * 4, req_comp);
    }
    if (scanline) IMG_FREE(scanline);
  }

  return hdr_data;
}

static int
img__hdr_info(img__context *s, int *x, int *y, int *comp) {
  char buffer[IMG__HDR_BUFLEN];
  char *token;
  int valid = 0;
  int dummy;

  if (!x) x = &dummy;
  if (!y) y = &dummy;
  if (!comp) comp = &dummy;

  if (img__hdr_test(s) == 0) {
    img__rewind(s);
    return 0;
  }

  for (;;) {
    token = img__hdr_gettoken(s, buffer);
    if (token[0] == 0) break;
    if (strcmp(token, "FORMAT=32-bit_rle_rgbe") == 0) valid = 1;
  }

  if (!valid) {
    img__rewind(s);
    return 0;
  }
  token = img__hdr_gettoken(s, buffer);
  if (strncmp(token, "-Y ", 3)) {
    img__rewind(s);
    return 0;
  }
  token += 3;
  *y = (int)strtol(token, &token, 10);
  while (*token == ' ') ++token;
  if (strncmp(token, "+X ", 3)) {
    img__rewind(s);
    return 0;
  }
  token += 3;
  *x = (int)strtol(token, NULL, 10);
  *comp = 3;
  return 1;
}
#endif  // IMG_NO_HDR

#ifndef IMG_NO_BMP
static int
img__bmp_info(img__context *s, int *x, int *y, int *comp) {
  void *p;
  img__bmp_data info;

  info.all_a = 255;
  p = img__bmp_parse_header(s, &info);
  img__rewind(s);
  if (p == NULL) return 0;
  if (x) *x = s->img_x;
  if (y) *y = s->img_y;
  if (comp) {
    if (info.bpp == 24 && info.ma == 0xff000000)
      *comp = 3;
    else
      *comp = info.ma ? 4 : 3;
  }
  return 1;
}
#endif

#ifndef IMG_NO_PSD
static int
img__psd_info(img__context *s, int *x, int *y, int *comp) {
  int channelCount, dummy, depth;
  if (!x) x = &dummy;
  if (!y) y = &dummy;
  if (!comp) comp = &dummy;
  if (img__get32be(s) != 0x38425053) {
    img__rewind(s);
    return 0;
  }
  if (img__get16be(s) != 1) {
    img__rewind(s);
    return 0;
  }
  img__skip(s, 6);
  channelCount = img__get16be(s);
  if (channelCount < 0 || channelCount > 16) {
    img__rewind(s);
    return 0;
  }
  *y = img__get32be(s);
  *x = img__get32be(s);
  depth = img__get16be(s);
  if (depth != 8 && depth != 16) {
    img__rewind(s);
    return 0;
  }
  if (img__get16be(s) != 3) {
    img__rewind(s);
    return 0;
  }
  *comp = 4;
  return 1;
}

static int
img__psd_is16(img__context *s) {
  int channelCount, depth;
  if (img__get32be(s) != 0x38425053) {
    img__rewind(s);
    return 0;
  }
  if (img__get16be(s) != 1) {
    img__rewind(s);
    return 0;
  }
  img__skip(s, 6);
  channelCount = img__get16be(s);
  if (channelCount < 0 || channelCount > 16) {
    img__rewind(s);
    return 0;
  }
  (void)img__get32be(s);
  (void)img__get32be(s);
  depth = img__get16be(s);
  if (depth != 16) {
    img__rewind(s);
    return 0;
  }
  return 1;
}
#endif

#ifndef IMG_NO_PIC
static int
img__pic_info(img__context *s, int *x, int *y, int *comp) {
  int act_comp = 0, num_packets = 0, chained, dummy;
  img__pic_packet packets[10];

  if (!x) x = &dummy;
  if (!y) y = &dummy;
  if (!comp) comp = &dummy;

  if (!img__pic_is4(s, "\x53\x80\xF6\x34")) {
    img__rewind(s);
    return 0;
  }

  img__skip(s, 88);

  *x = img__get16be(s);
  *y = img__get16be(s);
  if (img__at_eof(s)) {
    img__rewind(s);
    return 0;
  }
  if ((*x) != 0 && (1 << 28) / (*x) < (*y)) {
    img__rewind(s);
    return 0;
  }

  img__skip(s, 8);

  do {
    img__pic_packet *packet;

    if (num_packets == sizeof(packets) / sizeof(packets[0])) return 0;

    packet = &packets[num_packets++];
    chained = img__get8(s);
    packet->size = img__get8(s);
    packet->type = img__get8(s);
    packet->channel = img__get8(s);
    act_comp |= packet->channel;

    if (img__at_eof(s)) {
      img__rewind(s);
      return 0;
    }
    if (packet->size != 8) {
      img__rewind(s);
      return 0;
    }
  } while (chained);

  *comp = (act_comp & 0x10 ? 4 : 3);

  return 1;
}
#endif

// *************************************************************************************************
// Portable Gray Map and Portable Pixel Map loader
// by Ken Miller
//
// PGM: http://netpbm.sourceforge.net/doc/pgm.html
// PPM: http://netpbm.sourceforge.net/doc/ppm.html
//
// Known limitations:
//    Does not support comments in the header section
//    Does not support ASCII image data (formats P2 and P3)
//    Does not support 16-bit-per-channel

#ifndef IMG_NO_PNM

static int
img__pnm_test(img__context *s) {
  char p, t;
  p = (char)img__get8(s);
  t = (char)img__get8(s);
  if (p != 'P' || (t != '5' && t != '6')) {
    img__rewind(s);
    return 0;
  }
  return 1;
}

static void *
img__pnm_load(img__context *s, int *x, int *y, int *comp, int req_comp,
              img__result_info *ri) {
  img_uc *out;
  IMG_NOTUSED(ri);

  if (!img__pnm_info(s, (int *)&s->img_x, (int *)&s->img_y, (int *)&s->img_n))
    return 0;

  if (s->img_y > IMG_MAX_DIMENSIONS)
    return img__errpuc("too large", "Very large image (corrupt?)");
  if (s->img_x > IMG_MAX_DIMENSIONS)
    return img__errpuc("too large", "Very large image (corrupt?)");

  *x = s->img_x;
  *y = s->img_y;
  if (comp) *comp = s->img_n;

  if (!img__mad3sizes_valid(s->img_n, s->img_x, s->img_y, 0))
    return img__errpuc("too large", "PNM too large");

  out = (img_uc *)img__malloc_mad3(s->img_n, s->img_x, s->img_y, 0);
  if (!out) return img__errpuc("outofmem", "Out of memory");
  img__getn(s, out, s->img_n * s->img_x * s->img_y);

  if (req_comp && req_comp != s->img_n) {
    out = img__convert_format(out, s->img_n, req_comp, s->img_x, s->img_y);
    if (out == NULL) return out;  // img__convert_format frees input on failure
  }
  return out;
}

static int
img__pnm_isspace(char c) {
  return c == ' ' || c == '\t' || c == '\n' || c == '\v' || c == '\f' ||
         c == '\r';
}

static void
img__pnm_skip_whitespace(img__context *s, char *c) {
  for (;;) {
    while (!img__at_eof(s) && img__pnm_isspace(*c)) *c = (char)img__get8(s);

    if (img__at_eof(s) || *c != '#') break;

    while (!img__at_eof(s) && *c != '\n' && *c != '\r') *c = (char)img__get8(s);
  }
}

static int
img__pnm_isdigit(char c) {
  return c >= '0' && c <= '9';
}

static int
img__pnm_getinteger(img__context *s, char *c) {
  int value = 0;

  while (!img__at_eof(s) && img__pnm_isdigit(*c)) {
    value = value * 10 + (*c - '0');
    *c = (char)img__get8(s);
  }

  return value;
}

static int
img__pnm_info(img__context *s, int *x, int *y, int *comp) {
  int maxv, dummy;
  char c, p, t;

  if (!x) x = &dummy;
  if (!y) y = &dummy;
  if (!comp) comp = &dummy;

  img__rewind(s);

  // Get identifier
  p = (char)img__get8(s);
  t = (char)img__get8(s);
  if (p != 'P' || (t != '5' && t != '6')) {
    img__rewind(s);
    return 0;
  }

  *comp =
      (t == '6') ? 3 : 1;  // '5' is 1-component .pgm; '6' is 3-component .ppm

  c = (char)img__get8(s);
  img__pnm_skip_whitespace(s, &c);

  *x = img__pnm_getinteger(s, &c);  // read width
  img__pnm_skip_whitespace(s, &c);

  *y = img__pnm_getinteger(s, &c);  // read height
  img__pnm_skip_whitespace(s, &c);

  maxv = img__pnm_getinteger(s, &c);  // read max value

  if (maxv > 255)
    return img__err("max value > 255", "PPM image not 8-bit");
  else
    return 1;
}
#endif

static int
img__info_main(img__context *s, int *x, int *y, int *comp) {
#ifndef IMG_NO_JPEG
  if (img__jpeg_info(s, x, y, comp)) return 1;
#endif

#ifndef IMG_NO_PNG
  if (img__png_info(s, x, y, comp)) return 1;
#endif

#ifndef IMG_NO_GIF
  if (img__gif_info(s, x, y, comp)) return 1;
#endif

#ifndef IMG_NO_BMP
  if (img__bmp_info(s, x, y, comp)) return 1;
#endif

#ifndef IMG_NO_PSD
  if (img__psd_info(s, x, y, comp)) return 1;
#endif

#ifndef IMG_NO_PIC
  if (img__pic_info(s, x, y, comp)) return 1;
#endif

#ifndef IMG_NO_PNM
  if (img__pnm_info(s, x, y, comp)) return 1;
#endif

#ifndef IMG_NO_HDR
  if (img__hdr_info(s, x, y, comp)) return 1;
#endif

// test tga last because it's a crappy test!
#ifndef IMG_NO_TGA
  if (img__tga_info(s, x, y, comp)) return 1;
#endif
  return img__err("unknown image type",
                  "Image not of any known type, or corrupt");
}

static int
img__is_16_main(img__context *s) {
#ifndef IMG_NO_PNG
  if (img__png_is16(s)) return 1;
#endif

#ifndef IMG_NO_PSD
  if (img__psd_is16(s)) return 1;
#endif

  return 0;
}

#ifndef IMG_NO_STDIO
static int
img_info(char const *filename, int *x, int *y, int *comp) {
  FILE *f = img__fopen(filename, "rb");
  int result;
  if (!f) return img__err("can't fopen", "Unable to open file");
  result = img_info_from_file(f, x, y, comp);
  fclose(f);
  return result;
}

static int
img_info_from_file(FILE *f, int *x, int *y, int *comp) {
  int r;
  img__context s;
  long pos = ftell(f);
  img__start_file(&s, f);
  r = img__info_main(&s, x, y, comp);
  fseek(f, pos, SEEK_SET);
  return r;
}

static int
img_is_16_bit(char const *filename) {
  FILE *f = img__fopen(filename, "rb");
  int result;
  if (!f) return img__err("can't fopen", "Unable to open file");
  result = img_is_16_bit_from_file(f);
  fclose(f);
  return result;
}

static int
img_is_16_bit_from_file(FILE *f) {
  int r;
  img__context s;
  long pos = ftell(f);
  img__start_file(&s, f);
  r = img__is_16_main(&s);
  fseek(f, pos, SEEK_SET);
  return r;
}
#endif  // !IMG_NO_STDIO

static int
img_info_from_memory(img_uc const *buffer, int len, int *x, int *y, int *comp) {
  img__context s;
  img__start_mem(&s, buffer, len);
  return img__info_main(&s, x, y, comp);
}

static int
img_info_from_callbacks(img_io_callbacks const *c, void *user, int *x, int *y,
                        int *comp) {
  img__context s;
  img__start_callbacks(&s, (img_io_callbacks *)c, user);
  return img__info_main(&s, x, y, comp);
}

static int
img_is_16_bit_from_memory(img_uc const *buffer, int len) {
  img__context s;
  img__start_mem(&s, buffer, len);
  return img__is_16_main(&s);
}

static int
img_is_16_bit_from_callbacks(img_io_callbacks const *c, void *user) {
  img__context s;
  img__start_callbacks(&s, (img_io_callbacks *)c, user);
  return img__is_16_main(&s);
}

#if defined(__GNUC__) || defined(__clang__)
#pragma GCC diagnostic pop
#endif