text:
The Independent JPEG Group's JPEG software
==========================================

README for release 6b of 27-Mar-1998
====================================

This distribution contains the sixth public release of the Independent JPEG
Group's free JPEG software.  You are welcome to redistribute this software and
to use it for any purpose, subject to the conditions under LEGAL ISSUES, below.

Serious users of this software (particularly those incorporating it into
larger programs) should contact IJG at jpeg-info@uunet.uu.net to be added to
our electronic mailing list.  Mailing list members are notified of updates
and have a chance to participate in technical discussions, etc.

This software is the work of Tom Lane, Philip Gladstone, Jim Boucher,
Lee Crocker, Julian Minguillon, Luis Ortiz, George Phillips, Davide Rossi,
Guido Vollbeding, Ge' Weijers, and other members of the Independent JPEG
Group.

IJG is not affiliated with the official ISO JPEG standards committee.

DOCUMENTATION ROADMAP
=====================

This file contains the following sections:

OVERVIEW            General description of JPEG and the IJG software.
LEGAL ISSUES        Copyright, lack of warranty, terms of distribution.
REFERENCES          Where to learn more about JPEG.
ARCHIVE LOCATIONS   Where to find newer versions of this software.
RELATED SOFTWARE    Other stuff you should get.
FILE FORMAT WARS    Software *not* to get.
TO DO               Plans for future IJG releases.

Other documentation files in the distribution are:

User documentation:
  install.doc       How to configure and install the IJG software.
  usage.doc         Usage instructions for cjpeg, djpeg, jpegtran,
                    rdjpgcom, and wrjpgcom.
  *.1               Unix-style man pages for programs (same info as usage.doc).
  wizard.doc        Advanced usage instructions for JPEG wizards only.
  change.log        Version-to-version change highlights.
Programmer and internal documentation:
  libjpeg.doc       How to use the JPEG library in your own programs.
  example.c         Sample code for calling the JPEG library.
  structure.doc     Overview of the JPEG library's internal structure.
  filelist.doc      Road map of IJG files.
  coderules.doc     Coding style rules --- please read if you contribute code.

Please read at least the files install.doc and usage.doc.  Useful information
can also be found in the JPEG FAQ (Frequently Asked Questions) article.  See
ARCHIVE LOCATIONS below to find out where to obtain the FAQ article.

If you want to understand how the JPEG code works, we suggest reading one or
more of the REFERENCES, then looking at the documentation files (in roughly
the order listed) before diving into the code.

OVERVIEW
========

This package contains C software to implement JPEG image compression and
decompression.  JPEG (pronounced "jay-peg") is a standardized compression
method for full-color and gray-scale images.  JPEG is intended for compressing
"real-world" scenes; line drawings, cartoons and other non-realistic images
are not its strong suit.  JPEG is lossy, meaning that the output image is not
exactly identical to the input image.  Hence you must not use JPEG if you
have to have identical output bits.  However, on typical photographic images,
very good compression levels can be obtained with no visible change, and
remarkably high compression levels are possible if you can tolerate a
low-quality image.  For more details, see the references, or just experiment
with various compression settings.

This software implements JPEG baseline, extended-sequential, and progressive
compression processes.  Provision is made for supporting all variants of these
processes, although some uncommon parameter settings aren't implemented yet.
For legal reasons, we are not distributing code for the arithmetic-coding
variants of JPEG; see LEGAL ISSUES.  We have made no provision for supporting
the hierarchical or lossless processes defined in the standard.

We provide a set of library routines for reading and writing JPEG image files,
plus two sample applications "cjpeg" and "djpeg", which use the library to
perform conversion between JPEG and some other popular image file formats.
The library is intended to be reused in other applications.

In order to support file conversion and viewing software, we have included
considerable functionality beyond the bare JPEG coding/decoding capability;
for example, the color quantization modules are not strictly part of JPEG
decoding, but they are essential for output to colormapped file formats or
colormapped displays.  These extra functions can be compiled out of the
library if not required for a particular application.  We have also included
"jpegtran", a utility for lossless transcoding between different JPEG
processes, and "rdjpgcom" and "wrjpgcom", two simple applications for
inserting and extracting textual comments in JFIF files.

The emphasis in designing this software has been on achieving portability and
flexibility, while also making it fast enough to be useful.  In particular,
the software is not intended to be read as a tutorial on JPEG.  (See the
REFERENCES section for introductory material.)  Rather, it is intended to
be reliable, portable, industrial-strength code.  We do not claim to have
achieved that goal in every aspect of the software, but we strive for it.

We welcome the use of this software as a component of commercial products.
No royalty is required, but we do ask for an acknowledgement in product
documentation, as described under LEGAL ISSUES.

LEGAL ISSUES
============

In plain English:

1. We don't promise that this software works.  (But if you find any bugs,
   please let us know!)
2. You can use this software for whatever you want.  You don't have to pay us.
3. You may not pretend that you wrote this software.  If you use it in a
   program, you must acknowledge somewhere in your documentation that
   you've used the IJG code.

In legalese:

The authors make NO WARRANTY or representation, either express or implied,
with respect to this software, its quality, accuracy, merchantability, or
fitness for a particular purpose.  This software is provided "AS IS", and you,
its user, assume the entire risk as to its quality and accuracy.

This software is copyright (C) 1991-1998, Thomas G. Lane.
All Rights Reserved except as specified below.

Permission is hereby granted to use, copy, modify, and distribute this
software (or portions thereof) for any purpose, without fee, subject to these
conditions:
(1) If any part of the source code for this software is distributed, then this
README file must be included, with this copyright and no-warranty notice
unaltered; and any additions, deletions, or changes to the original files
must be clearly indicated in accompanying documentation.
(2) If only executable code is distributed, then the accompanying
documentation must state that "this software is based in part on the work of
the Independent JPEG Group".
(3) Permission for use of this software is granted only if the user accepts
full responsibility for any undesirable consequences; the authors accept
NO LIABILITY for damages of any kind.

These conditions apply to any software derived from or based on the IJG code,
not just to the unmodified library.  If you use our work, you ought to
acknowledge us.

Permission is NOT granted for the use of any IJG author's name or company name
in advertising or publicity relating to this software or products derived from
it.  This software may be referred to only as "the Independent JPEG Group's
software".

We specifically permit and encourage the use of this software as the basis of
commercial products, provided that all warranty or liability claims are
assumed by the product vendor.

ansi2knr.c is included in this distribution by permission of L. Peter Deutsch,
sole proprietor of its copyright holder, Aladdin Enterprises of Menlo Park, CA.
ansi2knr.c is NOT covered by the above copyright and conditions, but instead
by the usual distribution terms of the Free Software Foundation; principally,
that you must include source code if you redistribute it.  (See the file
ansi2knr.c for full details.)  However, since ansi2knr.c is not needed as part
of any program generated from the IJG code, this does not limit you more than
the foregoing paragraphs do.

The Unix configuration script "configure" was produced with GNU Autoconf.
It is copyright by the Free Software Foundation but is freely distributable.
The same holds for its supporting scripts (config.guess, config.sub,
ltconfig, ltmain.sh).  Another support script, install-sh, is copyright
by M.I.T. but is also freely distributable.

It appears that the arithmetic coding option of the JPEG spec is covered by
patents owned by IBM, AT&T, and Mitsubishi.  Hence arithmetic coding cannot
legally be used without obtaining one or more licenses.  For this reason,
support for arithmetic coding has been removed from the free JPEG software.
(Since arithmetic coding provides only a marginal gain over the unpatented
Huffman mode, it is unlikely that very many implementations will support it.)
So far as we are aware, there are no patent restrictions on the remaining
code.

The IJG distribution formerly included code to read and write GIF files.
To avoid entanglement with the Unisys LZW patent, GIF reading support has
been removed altogether, and the GIF writer has been simplified to produce
"uncompressed GIFs".  This technique does not use the LZW algorithm; the
resulting GIF files are larger than usual, but are readable by all standard
GIF decoders.

We are required to state that
    "The Graphics Interchange Format(c) is the Copyright property of
    CompuServe Incorporated.  GIF(sm) is a Service Mark property of
    CompuServe Incorporated."

REFERENCES
==========

We highly recommend reading one or more of these references before trying to
understand the innards of the JPEG software.

The best short technical introduction to the JPEG compression algorithm is
	Wallace, Gregory K.  "The JPEG Still Picture Compression Standard",
	Communications of the ACM, April 1991 (vol. 34 no. 4), pp. 30-44.
(Adjacent articles in that issue discuss MPEG motion picture compression,
applications of JPEG, and related topics.)  If you don't have the CACM issue
handy, a PostScript file containing a revised version of Wallace's article is
available at ftp://ftp.uu.net/graphics/jpeg/wallace.ps.gz.  The file (actually
a preprint for an article that appeared in IEEE Trans. Consumer Electronics)
omits the sample images that appeared in CACM, but it includes corrections
and some added material.  Note: the Wallace article is copyright ACM and IEEE,
and it may not be used for commercial purposes.

A somewhat less technical, more leisurely introduction to JPEG can be found in
"The Data Compression Book" by Mark Nelson and Jean-loup Gailly, published by
M&T Books (New York), 2nd ed. 1996, ISBN 1-55851-434-1.  This book provides
good explanations and example C code for a multitude of compression methods
including JPEG.  It is an excellent source if you are comfortable reading C
code but don't know much about data compression in general.  The book's JPEG
sample code is far from industrial-strength, but when you are ready to look
at a full implementation, you've got one here...

The best full description of JPEG is the textbook "JPEG Still Image Data
Compression Standard" by William B. Pennebaker and Joan L. Mitchell, published
by Van Nostrand Reinhold, 1993, ISBN 0-442-01272-1.  Price US$59.95, 638 pp.
The book includes the complete text of the ISO JPEG standards (DIS 10918-1
and draft DIS 10918-2).  This is by far the most complete exposition of JPEG
in existence, and we highly recommend it.

The JPEG standard itself is not available electronically; you must order a
paper copy through ISO or ITU.  (Unless you feel a need to own a certified
official copy, we recommend buying the Pennebaker and Mitchell book instead;
it's much cheaper and includes a great deal of useful explanatory material.)
In the USA, copies of the standard may be ordered from ANSI Sales at (212)
642-4900, or from Global Engineering Documents at (800) 854-7179.  (ANSI
doesn't take credit card orders, but Global does.)  It's not cheap: as of
1992, ANSI was charging $95 for Part 1 and $47 for Part 2, plus 7%
shipping/handling.  The standard is divided into two parts, Part 1 being the
actual specification, while Part 2 covers compliance testing methods.  Part 1
is titled "Digital Compression and Coding of Continuous-tone Still Images,
Part 1: Requirements and guidelines" and has document numbers ISO/IEC IS
10918-1, ITU-T T.81.  Part 2 is titled "Digital Compression and Coding of
Continuous-tone Still Images, Part 2: Compliance testing" and has document
numbers ISO/IEC IS 10918-2, ITU-T T.83.

Some extensions to the original JPEG standard are defined in JPEG Part 3,
a newer ISO standard numbered ISO/IEC IS 10918-3 and ITU-T T.84.  IJG
currently does not support any Part 3 extensions.

The JPEG standard does not specify all details of an interchangeable file
format.  For the omitted details we follow the "JFIF" conventions, revision
1.02.  A copy of the JFIF spec is available from:
	Literature Department
	C-Cube Microsystems, Inc.
	1778 McCarthy Blvd.
	Milpitas, CA 95035
	phone (408) 944-6300,  fax (408) 944-6314
A PostScript version of this document is available by FTP at
ftp://ftp.uu.net/graphics/jpeg/jfif.ps.gz.  There is also a plain text
version at ftp://ftp.uu.net/graphics/jpeg/jfif.txt.gz, but it is missing
the figures.

The TIFF 6.0 file format specification can be obtained by FTP from
ftp://ftp.sgi.com/graphics/tiff/TIFF6.ps.gz.  The JPEG incorporation scheme
found in the TIFF 6.0 spec of 3-June-92 has a number of serious problems.
IJG does not recommend use of the TIFF 6.0 design (TIFF Compression tag 6).
Instead, we recommend the JPEG design proposed by TIFF Technical Note #2
(Compression tag 7).  Copies of this Note can be obtained from ftp.sgi.com or
from ftp://ftp.uu.net/graphics/jpeg/.  It is expected that the next revision
of the TIFF spec will replace the 6.0 JPEG design with the Note's design.
Although IJG's own code does not support TIFF/JPEG, the free libtiff library
uses our library to implement TIFF/JPEG per the Note.  libtiff is available
from ftp://ftp.sgi.com/graphics/tiff/.

ARCHIVE LOCATIONS
=================

The "official" archive site for this software is ftp.uu.net (Internet
address 192.48.96.9).  The most recent released version can always be found
there in directory graphics/jpeg.  This particular version will be archived
as ftp://ftp.uu.net/graphics/jpeg/jpegsrc.v6b.tar.gz.  If you don't have
direct Internet access, UUNET's archives are also available via UUCP; contact
help@uunet.uu.net for information on retrieving files that way.

Numerous Internet sites maintain copies of the UUNET files.  However, only
ftp.uu.net is guaranteed to have the latest official version.

You can also obtain this software in DOS-compatible "zip" archive format from
the SimTel archives (ftp://ftp.simtel.net/pub/simtelnet/msdos/graphics/), or
on CompuServe in the Graphics Support forum (GO CIS:GRAPHSUP), library 12
"JPEG Tools".  Again, these versions may sometimes lag behind the ftp.uu.net
release.

The JPEG FAQ (Frequently Asked Questions) article is a useful source of
general information about JPEG.  It is updated constantly and therefore is
not included in this distribution.  The FAQ is posted every two weeks to
Usenet newsgroups comp.graphics.misc, news.answers, and other groups.
It is available on the World Wide Web at http://www.faqs.org/faqs/jpeg-faq/
and other news.answers archive sites, including the official news.answers
archive at rtfm.mit.edu: ftp://rtfm.mit.edu/pub/usenet/news.answers/jpeg-faq/.
If you don't have Web or FTP access, send e-mail to mail-server@rtfm.mit.edu
with body
	send usenet/news.answers/jpeg-faq/part1
	send usenet/news.answers/jpeg-faq/part2

RELATED SOFTWARE
================

Numerous viewing and image manipulation programs now support JPEG.  (Quite a
few of them use this library to do so.)  The JPEG FAQ described above lists
some of the more popular free and shareware viewers, and tells where to
obtain them on Internet.

If you are on a Unix machine, we highly recommend Jef Poskanzer's free
PBMPLUS software, which provides many useful operations on PPM-format image
files.  In particular, it can convert PPM images to and from a wide range of
other formats, thus making cjpeg/djpeg considerably more useful.  The latest
version is distributed by the NetPBM group, and is available from numerous
sites, notably ftp://wuarchive.wustl.edu/graphics/graphics/packages/NetPBM/.
Unfortunately PBMPLUS/NETPBM is not nearly as portable as the IJG software is;
you are likely to have difficulty making it work on any non-Unix machine.

A different free JPEG implementation, written by the PVRG group at Stanford,
is available from ftp://havefun.stanford.edu/pub/jpeg/.  This program
is designed for research and experimentation rather than production use;
it is slower, harder to use, and less portable than the IJG code, but it
is easier to read and modify.  Also, the PVRG code supports lossless JPEG,
which we do not.  (On the other hand, it doesn't do progressive JPEG.)

FILE FORMAT WARS
================

Some JPEG programs produce files that are not compatible with our library.
The root of the problem is that the ISO JPEG committee failed to specify a
concrete file format.  Some vendors "filled in the blanks" on their own,
creating proprietary formats that no one else could read.  (For example, none
of the early commercial JPEG implementations for the Macintosh were able to
exchange compressed files.)

The file format we have adopted is called JFIF (see REFERENCES).  This format
has been agreed to by a number of major commercial JPEG vendors, and it has
become the de facto standard.  JFIF is a minimal or "low end" representation.
We recommend the use of TIFF/JPEG (TIFF revision 6.0 as modified by TIFF
Technical Note #2) for "high end" applications that need to record a lot of
additional data about an image.  TIFF/JPEG is fairly new and not yet widely
supported, unfortunately.

The upcoming JPEG Part 3 standard defines a file format called SPIFF.
SPIFF is interoperable with JFIF, in the sense that most JFIF decoders should
be able to read the most common variant of SPIFF.  SPIFF has some technical
advantages over JFIF, but its major claim to fame is simply that it is an
official standard rather than an informal one.  At this point it is unclear
whether SPIFF will supersede JFIF or whether JFIF will remain the de-facto
standard.  IJG intends to support SPIFF once the standard is frozen, but we
have not decided whether it should become our default output format or not.
(In any case, our decoder will remain capable of reading JFIF indefinitely.)

Various proprietary file formats incorporating JPEG compression also exist.
We have little or no sympathy for the existence of these formats.  Indeed,
one of the original reasons for developing this free software was to help
force convergence on common, open format standards for JPEG files.  Don't
use a proprietary file format!

TO DO
=====

The major thrust for v7 will probably be improvement of visual quality.
The current method for scaling the quantization tables is known not to be
very good at low Q values.  We also intend to investigate block boundary
smoothing, "poor man's variable quantization", and other means of improving
quality-vs-file-size performance without sacrificing compatibility.

In future versions, we are considering supporting some of the upcoming JPEG
Part 3 extensions --- principally, variable quantization and the SPIFF file
format.

As always, speeding things up is of great interest.

Please send bug reports, offers of help, etc. to jpeg-info@uunet.uu.net.


text:
/*
 * jcmaster.c
 *
 * Copyright (C) 1991-1997, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains master control logic for the JPEG compressor.
 * These routines are concerned with parameter validation, initial setup,
 * and inter-pass control (determining the number of passes and the work
 * to be done in each pass).
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"

/* Private state */

typedef enum {
	main_pass,		/* input data, also do first output step */
	huff_opt_pass,		/* Huffman code optimization pass */
	output_pass		/* data output pass */
} c_pass_type;

typedef struct {
  struct jpeg_comp_master pub;	/* public fields */

  c_pass_type pass_type;	/* the type of the current pass */

  int pass_number;		/* # of passes completed */
  int total_passes;		/* total # of passes needed */

  int scan_number;		/* current index in scan_info[] */
} my_comp_master;

typedef my_comp_master * my_master_ptr;

/*
 * Support routines that do various essential calculations.
 */

LOCAL(void)
initial_setup (j_compress_ptr cinfo)
/* Do computations that are needed before master selection phase */
{
  int ci;
  jpeg_component_info *compptr;
  long samplesperrow;
  JDIMENSION jd_samplesperrow;

  /* Sanity check on image dimensions */
  if (cinfo->image_height <= 0 || cinfo->image_width <= 0
      || cinfo->num_components <= 0 || cinfo->input_components <= 0)
    ERREXIT(cinfo, JERR_EMPTY_IMAGE);

  /* Make sure image isn't bigger than I can handle */
  if ((long) cinfo->image_height > (long) JPEG_MAX_DIMENSION ||
      (long) cinfo->image_width > (long) JPEG_MAX_DIMENSION)
    ERREXIT1(cinfo, JERR_IMAGE_TOO_BIG, (unsigned int) JPEG_MAX_DIMENSION);

  /* Width of an input scanline must be representable as JDIMENSION. */
  samplesperrow = (long) cinfo->image_width * (long) cinfo->input_components;
  jd_samplesperrow = (JDIMENSION) samplesperrow;
  if ((long) jd_samplesperrow != samplesperrow)
    ERREXIT(cinfo, JERR_WIDTH_OVERFLOW);

  /* For now, precision must match compiled-in value... */
  if (cinfo->data_precision != BITS_IN_JSAMPLE)
    ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);

  /* Check that number of components won't exceed internal array sizes */
  if (cinfo->num_components > MAX_COMPONENTS)
    ERREXIT2(cinfo, JERR_COMPONENT_COUNT, cinfo->num_components,
	     MAX_COMPONENTS);

  /* Compute maximum sampling factors; check factor validity */
  cinfo->max_h_samp_factor = 1;
  cinfo->max_v_samp_factor = 1;
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
       ci++, compptr++) {
    if (compptr->h_samp_factor<=0 || compptr->h_samp_factor>MAX_SAMP_FACTOR ||
	compptr->v_samp_factor<=0 || compptr->v_samp_factor>MAX_SAMP_FACTOR)
      ERREXIT(cinfo, JERR_BAD_SAMPLING);
    cinfo->max_h_samp_factor = MAX(cinfo->max_h_samp_factor,
				   compptr->h_samp_factor);
    cinfo->max_v_samp_factor = MAX(cinfo->max_v_samp_factor,
				   compptr->v_samp_factor);
  }

  /* Compute dimensions of components */
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
       ci++, compptr++) {
    /* Fill in the correct component_index value; don't rely on application */
    compptr->component_index = ci;
    /* For compression, we never do DCT scaling. */
    compptr->DCT_scaled_size = DCTSIZE;
    /* Size in DCT blocks */
    compptr->width_in_blocks = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_width * (long) compptr->h_samp_factor,
		    (long) (cinfo->max_h_samp_factor * DCTSIZE));
    compptr->height_in_blocks = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_height * (long) compptr->v_samp_factor,
		    (long) (cinfo->max_v_samp_factor * DCTSIZE));
    /* Size in samples */
    compptr->downsampled_width = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_width * (long) compptr->h_samp_factor,
		    (long) cinfo->max_h_samp_factor);
    compptr->downsampled_height = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_height * (long) compptr->v_samp_factor,
		    (long) cinfo->max_v_samp_factor);
    /* Mark component needed (this flag isn't actually used for compression) */
    compptr->component_needed = TRUE;
  }

  /* Compute number of fully interleaved MCU rows (number of times that
   * main controller will call coefficient controller).
   */
  cinfo->total_iMCU_rows = (JDIMENSION)
    jdiv_round_up((long) cinfo->image_height,
		  (long) (cinfo->max_v_samp_factor*DCTSIZE));
}

#ifdef C_MULTISCAN_FILES_SUPPORTED

LOCAL(void)
validate_script (j_compress_ptr cinfo)
/* Verify that the scan script in cinfo->scan_info[] is valid; also
 * determine whether it uses progressive JPEG, and set cinfo->progressive_mode.
 */
{
  const jpeg_scan_info * scanptr;
  int scanno, ncomps, ci, coefi, thisi;
  int Ss, Se, Ah, Al;
  boolean component_sent[MAX_COMPONENTS];
#ifdef C_PROGRESSIVE_SUPPORTED
  int * last_bitpos_ptr;
  int last_bitpos[MAX_COMPONENTS][DCTSIZE2];
  /* -1 until that coefficient has been seen; then last Al for it */
#endif

  if (cinfo->num_scans <= 0)
    ERREXIT1(cinfo, JERR_BAD_SCAN_SCRIPT, 0);

  /* For sequential JPEG, all scans must have Ss=0, Se=DCTSIZE2-1;
   * for progressive JPEG, no scan can have this.
   */
  scanptr = cinfo->scan_info;
  if (scanptr->Ss != 0 || scanptr->Se != DCTSIZE2-1) {
#ifdef C_PROGRESSIVE_SUPPORTED
    cinfo->progressive_mode = TRUE;
    last_bitpos_ptr = & last_bitpos[0][0];
    for (ci = 0; ci < cinfo->num_components; ci++)
      for (coefi = 0; coefi < DCTSIZE2; coefi++)
	*last_bitpos_ptr++ = -1;
#else
    ERREXIT(cinfo, JERR_NOT_COMPILED);
#endif
  } else {
    cinfo->progressive_mode = FALSE;
    for (ci = 0; ci < cinfo->num_components; ci++)
      component_sent[ci] = FALSE;
  }

  for (scanno = 1; scanno <= cinfo->num_scans; scanptr++, scanno++) {
    /* Validate component indexes */
    ncomps = scanptr->comps_in_scan;
    if (ncomps <= 0 || ncomps > MAX_COMPS_IN_SCAN)
      ERREXIT2(cinfo, JERR_COMPONENT_COUNT, ncomps, MAX_COMPS_IN_SCAN);
    for (ci = 0; ci < ncomps; ci++) {
      thisi = scanptr->component_index[ci];
      if (thisi < 0 || thisi >= cinfo->num_components)
	ERREXIT1(cinfo, JERR_BAD_SCAN_SCRIPT, scanno);
      /* Components must appear in SOF order within each scan */
      if (ci > 0 && thisi <= scanptr->component_index[ci-1])
	ERREXIT1(cinfo, JERR_BAD_SCAN_SCRIPT, scanno);
    }
    /* Validate progression parameters */
    Ss = scanptr->Ss;
    Se = scanptr->Se;
    Ah = scanptr->Ah;
    Al = scanptr->Al;
    if (cinfo->progressive_mode) {
#ifdef C_PROGRESSIVE_SUPPORTED
      /* The JPEG spec simply gives the ranges 0..13 for Ah and Al, but that
       * seems wrong: the upper bound ought to depend on data precision.
       * Perhaps they really meant 0..N+1 for N-bit precision.
       * Here we allow 0..10 for 8-bit data; Al larger than 10 results in
       * out-of-range reconstructed DC values during the first DC scan,
       * which might cause problems for some decoders.
       */
#if BITS_IN_JSAMPLE == 8
#define MAX_AH_AL 10
#else
#define MAX_AH_AL 13
#endif
      if (Ss < 0 || Ss >= DCTSIZE2 || Se < Ss || Se >= DCTSIZE2 ||
	  Ah < 0 || Ah > MAX_AH_AL || Al < 0 || Al > MAX_AH_AL)
	ERREXIT1(cinfo, JERR_BAD_PROG_SCRIPT, scanno);
      if (Ss == 0) {
	if (Se != 0)		/* DC and AC together not OK */
	  ERREXIT1(cinfo, JERR_BAD_PROG_SCRIPT, scanno);
      } else {
	if (ncomps != 1)	/* AC scans must be for only one component */
	  ERREXIT1(cinfo, JERR_BAD_PROG_SCRIPT, scanno);
      }
      for (ci = 0; ci < ncomps; ci++) {
	last_bitpos_ptr = & last_bitpos[scanptr->component_index[ci]][0];
	if (Ss != 0 && last_bitpos_ptr[0] < 0) /* AC without prior DC scan */
	  ERREXIT1(cinfo, JERR_BAD_PROG_SCRIPT, scanno);
	for (coefi = Ss; coefi <= Se; coefi++) {
	  if (last_bitpos_ptr[coefi] < 0) {
	    /* first scan of this coefficient */
	    if (Ah != 0)
	      ERREXIT1(cinfo, JERR_BAD_PROG_SCRIPT, scanno);
	  } else {
	    /* not first scan */
	    if (Ah != last_bitpos_ptr[coefi] || Al != Ah-1)
	      ERREXIT1(cinfo, JERR_BAD_PROG_SCRIPT, scanno);
	  }
	  last_bitpos_ptr[coefi] = Al;
	}
      }
#endif
    } else {
      /* For sequential JPEG, all progression parameters must be these: */
      if (Ss != 0 || Se != DCTSIZE2-1 || Ah != 0 || Al != 0)
	ERREXIT1(cinfo, JERR_BAD_PROG_SCRIPT, scanno);
      /* Make sure components are not sent twice */
      for (ci = 0; ci < ncomps; ci++) {
	thisi = scanptr->component_index[ci];
	if (component_sent[thisi])
	  ERREXIT1(cinfo, JERR_BAD_SCAN_SCRIPT, scanno);
	component_sent[thisi] = TRUE;
      }
    }
  }

  /* Now verify that everything got sent. */
  if (cinfo->progressive_mode) {
#ifdef C_PROGRESSIVE_SUPPORTED
    /* For progressive mode, we only check that at least some DC data
     * got sent for each component; the spec does not require that all bits
     * of all coefficients be transmitted.  Would it be wiser to enforce
     * transmission of all coefficient bits??
     */
    for (ci = 0; ci < cinfo->num_components; ci++) {
      if (last_bitpos[ci][0] < 0)
	ERREXIT(cinfo, JERR_MISSING_DATA);
    }
#endif
  } else {
    for (ci = 0; ci < cinfo->num_components; ci++) {
      if (! component_sent[ci])
	ERREXIT(cinfo, JERR_MISSING_DATA);
    }
  }
}

#endif /* C_MULTISCAN_FILES_SUPPORTED */

LOCAL(void)
select_scan_parameters (j_compress_ptr cinfo)
/* Set up the scan parameters for the current scan */
{
  int ci;

#ifdef C_MULTISCAN_FILES_SUPPORTED
  if (cinfo->scan_info != NULL) {
    /* Prepare for current scan --- the script is already validated */
    my_master_ptr master = (my_master_ptr) cinfo->master;
    const jpeg_scan_info * scanptr = cinfo->scan_info + master->scan_number;

    cinfo->comps_in_scan = scanptr->comps_in_scan;
    for (ci = 0; ci < scanptr->comps_in_scan; ci++) {
      cinfo->cur_comp_info[ci] =
	&cinfo->comp_info[scanptr->component_index[ci]];
    }
    cinfo->Ss = scanptr->Ss;
    cinfo->Se = scanptr->Se;
    cinfo->Ah = scanptr->Ah;
    cinfo->Al = scanptr->Al;
  }
  else
#endif
  {
    /* Prepare for single sequential-JPEG scan containing all components */
    if (cinfo->num_components > MAX_COMPS_IN_SCAN)
      ERREXIT2(cinfo, JERR_COMPONENT_COUNT, cinfo->num_components,
	       MAX_COMPS_IN_SCAN);
    cinfo->comps_in_scan = cinfo->num_components;
    for (ci = 0; ci < cinfo->num_components; ci++) {
      cinfo->cur_comp_info[ci] = &cinfo->comp_info[ci];
    }
    cinfo->Ss = 0;
    cinfo->Se = DCTSIZE2-1;
    cinfo->Ah = 0;
    cinfo->Al = 0;
  }
}

LOCAL(void)
per_scan_setup (j_compress_ptr cinfo)
/* Do computations that are needed before processing a JPEG scan */
/* cinfo->comps_in_scan and cinfo->cur_comp_info[] are already set */
{
  int ci, mcublks, tmp;
  jpeg_component_info *compptr;

  if (cinfo->comps_in_scan == 1) {

    /* Noninterleaved (single-component) scan */
    compptr = cinfo->cur_comp_info[0];

    /* Overall image size in MCUs */
    cinfo->MCUs_per_row = compptr->width_in_blocks;
    cinfo->MCU_rows_in_scan = compptr->height_in_blocks;

    /* For noninterleaved scan, always one block per MCU */
    compptr->MCU_width = 1;
    compptr->MCU_height = 1;
    compptr->MCU_blocks = 1;
    compptr->MCU_sample_width = DCTSIZE;
    compptr->last_col_width = 1;
    /* For noninterleaved scans, it is convenient to define last_row_height
     * as the number of block rows present in the last iMCU row.
     */
    tmp = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
    if (tmp == 0) tmp = compptr->v_samp_factor;
    compptr->last_row_height = tmp;

    /* Prepare array describing MCU composition */
    cinfo->blocks_in_MCU = 1;
    cinfo->MCU_membership[0] = 0;

  } else {

    /* Interleaved (multi-component) scan */
    if (cinfo->comps_in_scan <= 0 || cinfo->comps_in_scan > MAX_COMPS_IN_SCAN)
      ERREXIT2(cinfo, JERR_COMPONENT_COUNT, cinfo->comps_in_scan,
	       MAX_COMPS_IN_SCAN);

    /* Overall image size in MCUs */
    cinfo->MCUs_per_row = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_width,
		    (long) (cinfo->max_h_samp_factor*DCTSIZE));
    cinfo->MCU_rows_in_scan = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_height,
		    (long) (cinfo->max_v_samp_factor*DCTSIZE));

    cinfo->blocks_in_MCU = 0;

    for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
      compptr = cinfo->cur_comp_info[ci];
      /* Sampling factors give # of blocks of component in each MCU */
      compptr->MCU_width = compptr->h_samp_factor;
      compptr->MCU_height = compptr->v_samp_factor;
      compptr->MCU_blocks = compptr->MCU_width * compptr->MCU_height;
      compptr->MCU_sample_width = compptr->MCU_width * DCTSIZE;
      /* Figure number of non-dummy blocks in last MCU column & row */
      tmp = (int) (compptr->width_in_blocks % compptr->MCU_width);
      if (tmp == 0) tmp = compptr->MCU_width;
      compptr->last_col_width = tmp;
      tmp = (int) (compptr->height_in_blocks % compptr->MCU_height);
      if (tmp == 0) tmp = compptr->MCU_height;
      compptr->last_row_height = tmp;
      /* Prepare array describing MCU composition */
      mcublks = compptr->MCU_blocks;
      if (cinfo->blocks_in_MCU + mcublks > C_MAX_BLOCKS_IN_MCU)
	ERREXIT(cinfo, JERR_BAD_MCU_SIZE);
      while (mcublks-- > 0) {
	cinfo->MCU_membership[cinfo->blocks_in_MCU++] = ci;
      }
    }

  }

  /* Convert restart specified in rows to actual MCU count. */
  /* Note that count must fit in 16 bits, so we provide limiting. */
  if (cinfo->restart_in_rows > 0) {
    long nominal = (long) cinfo->restart_in_rows * (long) cinfo->MCUs_per_row;
    cinfo->restart_interval = (unsigned int) MIN(nominal, 65535L);
  }
}

/*
 * Per-pass setup.
 * This is called at the beginning of each pass.  We determine which modules
 * will be active during this pass and give them appropriate start_pass calls.
 * We also set is_last_pass to indicate whether any more passes will be
 * required.
 */

METHODDEF(void)
prepare_for_pass (j_compress_ptr cinfo)
{
  my_master_ptr master = (my_master_ptr) cinfo->master;

  switch (master->pass_type) {
  case main_pass:
    /* Initial pass: will collect input data, and do either Huffman
     * optimization or data output for the first scan.
     */
    select_scan_parameters(cinfo);
    per_scan_setup(cinfo);
    if (! cinfo->raw_data_in) {
      (*cinfo->cconvert->start_pass) (cinfo);
      (*cinfo->downsample->start_pass) (cinfo);
      (*cinfo->prep->start_pass) (cinfo, JBUF_PASS_THRU);
    }
    (*cinfo->fdct->start_pass) (cinfo);
    (*cinfo->entropy->start_pass) (cinfo, cinfo->optimize_coding);
    (*cinfo->coef->start_pass) (cinfo,
				(master->total_passes > 1 ?
				 JBUF_SAVE_AND_PASS : JBUF_PASS_THRU));
    (*cinfo->main->start_pass) (cinfo, JBUF_PASS_THRU);
    if (cinfo->optimize_coding) {
      /* No immediate data output; postpone writing frame/scan headers */
      master->pub.call_pass_startup = FALSE;
    } else {
      /* Will write frame/scan headers at first jpeg_write_scanlines call */
      master->pub.call_pass_startup = TRUE;
    }
    break;
#ifdef ENTROPY_OPT_SUPPORTED
  case huff_opt_pass:
    /* Do Huffman optimization for a scan after the first one. */
    select_scan_parameters(cinfo);
    per_scan_setup(cinfo);
    if (cinfo->Ss != 0 || cinfo->Ah == 0 || cinfo->arith_code) {
      (*cinfo->entropy->start_pass) (cinfo, TRUE);
      (*cinfo->coef->start_pass) (cinfo, JBUF_CRANK_DEST);
      master->pub.call_pass_startup = FALSE;
      break;
    }
    /* Special case: Huffman DC refinement scans need no Huffman table
     * and therefore we can skip the optimization pass for them.
     */
    master->pass_type = output_pass;
    master->pass_number++;
    /*FALLTHROUGH*/
#endif
  case output_pass:
    /* Do a data-output pass. */
    /* We need not repeat per-scan setup if prior optimization pass did it. */
    if (! cinfo->optimize_coding) {
      select_scan_parameters(cinfo);
      per_scan_setup(cinfo);
    }
    (*cinfo->entropy->start_pass) (cinfo, FALSE);
    (*cinfo->coef->start_pass) (cinfo, JBUF_CRANK_DEST);
    /* We emit frame/scan headers now */
    if (master->scan_number == 0)
      (*cinfo->marker->write_frame_header) (cinfo);
    (*cinfo->marker->write_scan_header) (cinfo);
    master->pub.call_pass_startup = FALSE;
    break;
  default:
    ERREXIT(cinfo, JERR_NOT_COMPILED);
  }

  master->pub.is_last_pass = (master->pass_number == master->total_passes-1);

  /* Set up progress monitor's pass info if present */
  if (cinfo->progress != NULL) {
    cinfo->progress->completed_passes = master->pass_number;
    cinfo->progress->total_passes = master->total_passes;
  }
}

/*
 * Special start-of-pass hook.
 * This is called by jpeg_write_scanlines if call_pass_startup is TRUE.
 * In single-pass processing, we need this hook because we don't want to
 * write frame/scan headers during jpeg_start_compress; we want to let the
 * application write COM markers etc. between jpeg_start_compress and the
 * jpeg_write_scanlines loop.
 * In multi-pass processing, this routine is not used.
 */

METHODDEF(void)
pass_startup (j_compress_ptr cinfo)
{
  cinfo->master->call_pass_startup = FALSE; /* reset flag so call only once */

  (*cinfo->marker->write_frame_header) (cinfo);
  (*cinfo->marker->write_scan_header) (cinfo);
}

/*
 * Finish up at end of pass.
 */

METHODDEF(void)
finish_pass_master (j_compress_ptr cinfo)
{
  my_master_ptr master = (my_master_ptr) cinfo->master;

  /* The entropy coder always needs an end-of-pass call,
   * either to analyze statistics or to flush its output buffer.
   */
  (*cinfo->entropy->finish_pass) (cinfo);

  /* Update state for next pass */
  switch (master->pass_type) {
  case main_pass:
    /* next pass is either output of scan 0 (after optimization)
     * or output of scan 1 (if no optimization).
     */
    master->pass_type = output_pass;
    if (! cinfo->optimize_coding)
      master->scan_number++;
    break;
  case huff_opt_pass:
    /* next pass is always output of current scan */
    master->pass_type = output_pass;
    break;
  case output_pass:
    /* next pass is either optimization or output of next scan */
    if (cinfo->optimize_coding)
      master->pass_type = huff_opt_pass;
    master->scan_number++;
    break;
  }

  master->pass_number++;
}

/*
 * Initialize master compression control.
 */

GLOBAL(void)
jinit_c_master_control (j_compress_ptr cinfo, boolean transcode_only)
{
  my_master_ptr master;

  master = (my_master_ptr)
      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
				  SIZEOF(my_comp_master));
  cinfo->master = (struct jpeg_comp_master *) master;
  master->pub.prepare_for_pass = prepare_for_pass;
  master->pub.pass_startup = pass_startup;
  master->pub.finish_pass = finish_pass_master;
  master->pub.is_last_pass = FALSE;

  /* Validate parameters, determine derived values */
  initial_setup(cinfo);

  if (cinfo->scan_info != NULL) {
#ifdef C_MULTISCAN_FILES_SUPPORTED
    validate_script(cinfo);
#else
    ERREXIT(cinfo, JERR_NOT_COMPILED);
#endif
  } else {
    cinfo->progressive_mode = FALSE;
    cinfo->num_scans = 1;
  }

  if (cinfo->progressive_mode)	/*  TEMPORARY HACK ??? */
    cinfo->optimize_coding = TRUE; /* assume default tables no good for progressive mode */

  /* Initialize my private state */
  if (transcode_only) {
    /* no main pass in transcoding */
    if (cinfo->optimize_coding)
      master->pass_type = huff_opt_pass;
    else
      master->pass_type = output_pass;
  } else {
    /* for normal compression, first pass is always this type: */
    master->pass_type = main_pass;
  }
  master->scan_number = 0;
  master->pass_number = 0;
  if (cinfo->optimize_coding)
    master->total_passes = cinfo->num_scans * 2;
  else
    master->total_passes = cinfo->num_scans;
}

repo_name: fedden/RenderMan

mime_type: text/x-c++


text:
/*
 * jdsample.c
 *
 * Copyright (C) 1991-1996, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains upsampling routines.
 *
 * Upsampling input data is counted in "row groups".  A row group
 * is defined to be (v_samp_factor * DCT_scaled_size / min_DCT_scaled_size)
 * sample rows of each component.  Upsampling will normally produce
 * max_v_samp_factor pixel rows from each row group (but this could vary
 * if the upsampler is applying a scale factor of its own).
 *
 * An excellent reference for image resampling is
 *   Digital Image Warping, George Wolberg, 1990.
 *   Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"

/* Pointer to routine to upsample a single component */
typedef JMETHOD(void, upsample1_ptr,
		(j_decompress_ptr cinfo, jpeg_component_info * compptr,
		 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr));

/* Private subobject */

typedef struct {
  struct jpeg_upsampler pub;	/* public fields */

  /* Color conversion buffer.  When using separate upsampling and color
   * conversion steps, this buffer holds one upsampled row group until it
   * has been color converted and output.
   * Note: we do not allocate any storage for component(s) which are full-size,
   * ie do not need rescaling.  The corresponding entry of color_buf[] is
   * simply set to point to the input data array, thereby avoiding copying.
   */
  JSAMPARRAY color_buf[MAX_COMPONENTS];

  /* Per-component upsampling method pointers */
  upsample1_ptr methods[MAX_COMPONENTS];

  int next_row_out;		/* counts rows emitted from color_buf */
  JDIMENSION rows_to_go;	/* counts rows remaining in image */

  /* Height of an input row group for each component. */
  int rowgroup_height[MAX_COMPONENTS];

  /* These arrays save pixel expansion factors so that int_expand need not
   * recompute them each time.  They are unused for other upsampling methods.
   */
  UINT8 h_expand[MAX_COMPONENTS];
  UINT8 v_expand[MAX_COMPONENTS];
} my_upsampler2;

typedef my_upsampler2 * my_upsample_ptr2;

/*
 * Initialize for an upsampling pass.
 */

METHODDEF(void)
start_pass_upsample (j_decompress_ptr cinfo)
{
  my_upsample_ptr2 upsample = (my_upsample_ptr2) cinfo->upsample;

  /* Mark the conversion buffer empty */
  upsample->next_row_out = cinfo->max_v_samp_factor;
  /* Initialize total-height counter for detecting bottom of image */
  upsample->rows_to_go = cinfo->output_height;
}

/*
 * Control routine to do upsampling (and color conversion).
 *
 * In this version we upsample each component independently.
 * We upsample one row group into the conversion buffer, then apply
 * color conversion a row at a time.
 */

METHODDEF(void)
sep_upsample (j_decompress_ptr cinfo,
	      JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
	      JDIMENSION,
	      JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
	      JDIMENSION out_rows_avail)
{
  my_upsample_ptr2 upsample = (my_upsample_ptr2) cinfo->upsample;
  int ci;
  jpeg_component_info * compptr;
  JDIMENSION num_rows;

  /* Fill the conversion buffer, if it's empty */
  if (upsample->next_row_out >= cinfo->max_v_samp_factor) {
    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
	 ci++, compptr++) {
      /* Invoke per-component upsample method.  Notice we pass a POINTER
       * to color_buf[ci], so that fullsize_upsample can change it.
       */
      (*upsample->methods[ci]) (cinfo, compptr,
	input_buf[ci] + (*in_row_group_ctr * upsample->rowgroup_height[ci]),
	upsample->color_buf + ci);
    }
    upsample->next_row_out = 0;
  }

  /* Color-convert and emit rows */

  /* How many we have in the buffer: */
  num_rows = (JDIMENSION) (cinfo->max_v_samp_factor - upsample->next_row_out);
  /* Not more than the distance to the end of the image.  Need this test
   * in case the image height is not a multiple of max_v_samp_factor:
   */
  if (num_rows > upsample->rows_to_go)
    num_rows = upsample->rows_to_go;
  /* And not more than what the client can accept: */
  out_rows_avail -= *out_row_ctr;
  if (num_rows > out_rows_avail)
    num_rows = out_rows_avail;

  (*cinfo->cconvert->color_convert) (cinfo, upsample->color_buf,
				     (JDIMENSION) upsample->next_row_out,
				     output_buf + *out_row_ctr,
				     (int) num_rows);

  /* Adjust counts */
  *out_row_ctr += num_rows;
  upsample->rows_to_go -= num_rows;
  upsample->next_row_out += num_rows;
  /* When the buffer is emptied, declare this input row group consumed */
  if (upsample->next_row_out >= cinfo->max_v_samp_factor)
    (*in_row_group_ctr)++;
}

/*
 * These are the routines invoked by sep_upsample to upsample pixel values
 * of a single component.  One row group is processed per call.
 */

/*
 * For full-size components, we just make color_buf[ci] point at the
 * input buffer, and thus avoid copying any data.  Note that this is
 * safe only because sep_upsample doesn't declare the input row group
 * "consumed" until we are done color converting and emitting it.
 */

METHODDEF(void)
fullsize_upsample (j_decompress_ptr, jpeg_component_info *,
		   JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
{
  *output_data_ptr = input_data;
}

/*
 * This is a no-op version used for "uninteresting" components.
 * These components will not be referenced by color conversion.
 */

METHODDEF(void)
noop_upsample (j_decompress_ptr, jpeg_component_info *,
	       JSAMPARRAY, JSAMPARRAY * output_data_ptr)
{
  *output_data_ptr = NULL;	/* safety check */
}

/*
 * This version handles any integral sampling ratios.
 * This is not used for typical JPEG files, so it need not be fast.
 * Nor, for that matter, is it particularly accurate: the algorithm is
 * simple replication of the input pixel onto the corresponding output
 * pixels.  The hi-falutin sampling literature refers to this as a
 * "box filter".  A box filter tends to introduce visible artifacts,
 * so if you are actually going to use 3:1 or 4:1 sampling ratios
 * you would be well advised to improve this code.
 */

METHODDEF(void)
int_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
	      JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
{
  my_upsample_ptr2 upsample = (my_upsample_ptr2) cinfo->upsample;
  JSAMPARRAY output_data = *output_data_ptr;
  JSAMPROW inptr, outptr;
  JSAMPLE invalue;
  int h;
  JSAMPROW outend;
  int h_expand, v_expand;
  int inrow, outrow;

  h_expand = upsample->h_expand[compptr->component_index];
  v_expand = upsample->v_expand[compptr->component_index];

  inrow = outrow = 0;
  while (outrow < cinfo->max_v_samp_factor) {
    /* Generate one output row with proper horizontal expansion */
    inptr = input_data[inrow];
    outptr = output_data[outrow];
    outend = outptr + cinfo->output_width;
    while (outptr < outend) {
      invalue = *inptr++;	/* don't need GETJSAMPLE() here */
      for (h = h_expand; h > 0; h--) {
	*outptr++ = invalue;
      }
    }
    /* Generate any additional output rows by duplicating the first one */
    if (v_expand > 1) {
      jcopy_sample_rows(output_data, outrow, output_data, outrow+1,
			v_expand-1, cinfo->output_width);
    }
    inrow++;
    outrow += v_expand;
  }
}

/*
 * Fast processing for the common case of 2:1 horizontal and 1:1 vertical.
 * It's still a box filter.
 */

METHODDEF(void)
h2v1_upsample (j_decompress_ptr cinfo, jpeg_component_info *,
	       JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
{
  JSAMPARRAY output_data = *output_data_ptr;
  JSAMPROW inptr, outptr;
  JSAMPLE invalue;
  JSAMPROW outend;
  int inrow;

  for (inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++) {
    inptr = input_data[inrow];
    outptr = output_data[inrow];
    outend = outptr + cinfo->output_width;
    while (outptr < outend) {
      invalue = *inptr++;	/* don't need GETJSAMPLE() here */
      *outptr++ = invalue;
      *outptr++ = invalue;
    }
  }
}

/*
 * Fast processing for the common case of 2:1 horizontal and 2:1 vertical.
 * It's still a box filter.
 */

METHODDEF(void)
h2v2_upsample (j_decompress_ptr cinfo, jpeg_component_info *,
	       JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
{
  JSAMPARRAY output_data = *output_data_ptr;
  JSAMPROW inptr, outptr;
  JSAMPLE invalue;
  JSAMPROW outend;
  int inrow, outrow;

  inrow = outrow = 0;
  while (outrow < cinfo->max_v_samp_factor) {
    inptr = input_data[inrow];
    outptr = output_data[outrow];
    outend = outptr + cinfo->output_width;
    while (outptr < outend) {
      invalue = *inptr++;	/* don't need GETJSAMPLE() here */
      *outptr++ = invalue;
      *outptr++ = invalue;
    }
    jcopy_sample_rows(output_data, outrow, output_data, outrow+1,
		      1, cinfo->output_width);
    inrow++;
    outrow += 2;
  }
}

/*
 * Fancy processing for the common case of 2:1 horizontal and 1:1 vertical.
 *
 * The upsampling algorithm is linear interpolation between pixel centers,
 * also known as a "triangle filter".  This is a good compromise between
 * speed and visual quality.  The centers of the output pixels are 1/4 and 3/4
 * of the way between input pixel centers.
 *
 * A note about the "bias" calculations: when rounding fractional values to
 * integer, we do not want to always round 0.5 up to the next integer.
 * If we did that, we'd introduce a noticeable bias towards larger values.
 * Instead, this code is arranged so that 0.5 will be rounded up or down at
 * alternate pixel locations (a simple ordered dither pattern).
 */

METHODDEF(void)
h2v1_fancy_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
		     JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
{
  JSAMPARRAY output_data = *output_data_ptr;
  JSAMPROW inptr, outptr;
  int invalue;
  JDIMENSION colctr;
  int inrow;

  for (inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++) {
    inptr = input_data[inrow];
    outptr = output_data[inrow];
    /* Special case for first column */
    invalue = GETJSAMPLE(*inptr++);
    *outptr++ = (JSAMPLE) invalue;
    *outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(*inptr) + 2) >> 2);

    for (colctr = compptr->downsampled_width - 2; colctr > 0; colctr--) {
      /* General case: 3/4 * nearer pixel + 1/4 * further pixel */
      invalue = GETJSAMPLE(*inptr++) * 3;
      *outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(inptr[-2]) + 1) >> 2);
      *outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(*inptr) + 2) >> 2);
    }

    /* Special case for last column */
    invalue = GETJSAMPLE(*inptr);
    *outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(inptr[-1]) + 1) >> 2);
    *outptr++ = (JSAMPLE) invalue;
  }
}

/*
 * Fancy processing for the common case of 2:1 horizontal and 2:1 vertical.
 * Again a triangle filter; see comments for h2v1 case, above.
 *
 * It is OK for us to reference the adjacent input rows because we demanded
 * context from the main buffer controller (see initialization code).
 */

METHODDEF(void)
h2v2_fancy_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
		     JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
{
  JSAMPARRAY output_data = *output_data_ptr;
  JSAMPROW inptr0, inptr1, outptr;
#if BITS_IN_JSAMPLE == 8
  int thiscolsum, lastcolsum, nextcolsum;
#else
  INT32 thiscolsum, lastcolsum, nextcolsum;
#endif
  JDIMENSION colctr;
  int inrow, outrow, v;

  inrow = outrow = 0;
  while (outrow < cinfo->max_v_samp_factor) {
    for (v = 0; v < 2; v++) {
      /* inptr0 points to nearest input row, inptr1 points to next nearest */
      inptr0 = input_data[inrow];
      if (v == 0)		/* next nearest is row above */
	inptr1 = input_data[inrow-1];
      else			/* next nearest is row below */
	inptr1 = input_data[inrow+1];
      outptr = output_data[outrow++];

      /* Special case for first column */
      thiscolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
      nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
      *outptr++ = (JSAMPLE) ((thiscolsum * 4 + 8) >> 4);
      *outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 7) >> 4);
      lastcolsum = thiscolsum; thiscolsum = nextcolsum;

      for (colctr = compptr->downsampled_width - 2; colctr > 0; colctr--) {
	/* General case: 3/4 * nearer pixel + 1/4 * further pixel in each */
	/* dimension, thus 9/16, 3/16, 3/16, 1/16 overall */
	nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
	*outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4);
	*outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 7) >> 4);
	lastcolsum = thiscolsum; thiscolsum = nextcolsum;
      }

      /* Special case for last column */
      *outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4);
      *outptr++ = (JSAMPLE) ((thiscolsum * 4 + 7) >> 4);
    }
    inrow++;
  }
}

/*
 * Module initialization routine for upsampling.
 */

GLOBAL(void)
jinit_upsampler (j_decompress_ptr cinfo)
{
  my_upsample_ptr2 upsample;
  int ci;
  jpeg_component_info * compptr;
  boolean need_buffer, do_fancy;
  int h_in_group, v_in_group, h_out_group, v_out_group;

  upsample = (my_upsample_ptr2)
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
				SIZEOF(my_upsampler2));
  cinfo->upsample = (struct jpeg_upsampler *) upsample;
  upsample->pub.start_pass = start_pass_upsample;
  upsample->pub.upsample = sep_upsample;
  upsample->pub.need_context_rows = FALSE; /* until we find out differently */

  if (cinfo->CCIR601_sampling)	/* this isn't supported */
    ERREXIT(cinfo, JERR_CCIR601_NOTIMPL);

  /* jdmainct.c doesn't support context rows when min_DCT_scaled_size = 1,
   * so don't ask for it.
   */
  do_fancy = cinfo->do_fancy_upsampling && cinfo->min_DCT_scaled_size > 1;

  /* Verify we can handle the sampling factors, select per-component methods,
   * and create storage as needed.
   */
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
       ci++, compptr++) {
    /* Compute size of an "input group" after IDCT scaling.  This many samples
     * are to be converted to max_h_samp_factor * max_v_samp_factor pixels.
     */
    h_in_group = (compptr->h_samp_factor * compptr->DCT_scaled_size) /
		 cinfo->min_DCT_scaled_size;
    v_in_group = (compptr->v_samp_factor * compptr->DCT_scaled_size) /
		 cinfo->min_DCT_scaled_size;
    h_out_group = cinfo->max_h_samp_factor;
    v_out_group = cinfo->max_v_samp_factor;
    upsample->rowgroup_height[ci] = v_in_group; /* save for use later */
    need_buffer = TRUE;
    if (! compptr->component_needed) {
      /* Don't bother to upsample an uninteresting component. */
      upsample->methods[ci] = noop_upsample;
      need_buffer = FALSE;
    } else if (h_in_group == h_out_group && v_in_group == v_out_group) {
      /* Fullsize components can be processed without any work. */
      upsample->methods[ci] = fullsize_upsample;
      need_buffer = FALSE;
    } else if (h_in_group * 2 == h_out_group &&
	       v_in_group == v_out_group) {
      /* Special cases for 2h1v upsampling */
      if (do_fancy && compptr->downsampled_width > 2)
	upsample->methods[ci] = h2v1_fancy_upsample;
      else
	upsample->methods[ci] = h2v1_upsample;
    } else if (h_in_group * 2 == h_out_group &&
	       v_in_group * 2 == v_out_group) {
      /* Special cases for 2h2v upsampling */
      if (do_fancy && compptr->downsampled_width > 2) {
	upsample->methods[ci] = h2v2_fancy_upsample;
	upsample->pub.need_context_rows = TRUE;
      } else
	upsample->methods[ci] = h2v2_upsample;
    } else if ((h_out_group % h_in_group) == 0 &&
	       (v_out_group % v_in_group) == 0) {
      /* Generic integral-factors upsampling method */
      upsample->methods[ci] = int_upsample;
      upsample->h_expand[ci] = (UINT8) (h_out_group / h_in_group);
      upsample->v_expand[ci] = (UINT8) (v_out_group / v_in_group);
    } else
      ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL);
    if (need_buffer) {
      upsample->color_buf[ci] = (*cinfo->mem->alloc_sarray)
	((j_common_ptr) cinfo, JPOOL_IMAGE,
	 (JDIMENSION) jround_up((long) cinfo->output_width,
				(long) cinfo->max_h_samp_factor),
	 (JDIMENSION) cinfo->max_v_samp_factor);
    }
  }
}


text:
/*
 * jidctfst.c
 *
 * Copyright (C) 1994-1998, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains a fast, not so accurate integer implementation of the
 * inverse DCT (Discrete Cosine Transform).  In the IJG code, this routine
 * must also perform dequantization of the input coefficients.
 *
 * A 2-D IDCT can be done by 1-D IDCT on each column followed by 1-D IDCT
 * on each row (or vice versa, but it's more convenient to emit a row at
 * a time).  Direct algorithms are also available, but they are much more
 * complex and seem not to be any faster when reduced to code.
 *
 * This implementation is based on Arai, Agui, and Nakajima's algorithm for
 * scaled DCT.  Their original paper (Trans. IEICE E-71(11):1095) is in
 * Japanese, but the algorithm is described in the Pennebaker & Mitchell
 * JPEG textbook (see REFERENCES section in file README).  The following code
 * is based directly on figure 4-8 in P&M.
 * While an 8-point DCT cannot be done in less than 11 multiplies, it is
 * possible to arrange the computation so that many of the multiplies are
 * simple scalings of the final outputs.  These multiplies can then be
 * folded into the multiplications or divisions by the JPEG quantization
 * table entries.  The AA&N method leaves only 5 multiplies and 29 adds
 * to be done in the DCT itself.
 * The primary disadvantage of this method is that with fixed-point math,
 * accuracy is lost due to imprecise representation of the scaled
 * quantization values.  The smaller the quantization table entry, the less
 * precise the scaled value, so this implementation does worse with high-
 * quality-setting files than with low-quality ones.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
#include "jdct.h"		/* Private declarations for DCT subsystem */

#ifdef DCT_IFAST_SUPPORTED

/*
 * This module is specialized to the case DCTSIZE = 8.
 */

#if DCTSIZE != 8
  Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
#endif

/* Scaling decisions are generally the same as in the LL&M algorithm;
 * see jidctint.c for more details.  However, we choose to descale
 * (right shift) multiplication products as soon as they are formed,
 * rather than carrying additional fractional bits into subsequent additions.
 * This compromises accuracy slightly, but it lets us save a few shifts.
 * More importantly, 16-bit arithmetic is then adequate (for 8-bit samples)
 * everywhere except in the multiplications proper; this saves a good deal
 * of work on 16-bit-int machines.
 *
 * The dequantized coefficients are not integers because the AA&N scaling
 * factors have been incorporated.  We represent them scaled up by PASS1_BITS,
 * so that the first and second IDCT rounds have the same input scaling.
 * For 8-bit JSAMPLEs, we choose IFAST_SCALE_BITS = PASS1_BITS so as to
 * avoid a descaling shift; this compromises accuracy rather drastically
 * for small quantization table entries, but it saves a lot of shifts.
 * For 12-bit JSAMPLEs, there's no hope of using 16x16 multiplies anyway,
 * so we use a much larger scaling factor to preserve accuracy.
 *
 * A final compromise is to represent the multiplicative constants to only
 * 8 fractional bits, rather than 13.  This saves some shifting work on some
 * machines, and may also reduce the cost of multiplication (since there
 * are fewer one-bits in the constants).
 */

#if BITS_IN_JSAMPLE == 8
#define CONST_BITS  8
#define PASS1_BITS  2
#else
#define CONST_BITS  8
#define PASS1_BITS  1		/* lose a little precision to avoid overflow */
#endif

/* Some C compilers fail to reduce "FIX(constant)" at compile time, thus
 * causing a lot of useless floating-point operations at run time.
 * To get around this we use the following pre-calculated constants.
 * If you change CONST_BITS you may want to add appropriate values.
 * (With a reasonable C compiler, you can just rely on the FIX() macro...)
 */

#if CONST_BITS == 8
#define FIX_1_082392200  ((INT32)  277)		/* FIX(1.082392200) */
#define FIX_1_414213562  ((INT32)  362)		/* FIX(1.414213562) */
#define FIX_1_847759065  ((INT32)  473)		/* FIX(1.847759065) */
#define FIX_2_613125930  ((INT32)  669)		/* FIX(2.613125930) */
#else
#define FIX_1_082392200  FIX(1.082392200)
#define FIX_1_414213562  FIX(1.414213562)
#define FIX_1_847759065  FIX(1.847759065)
#define FIX_2_613125930  FIX(2.613125930)
#endif

/* We can gain a little more speed, with a further compromise in accuracy,
 * by omitting the addition in a descaling shift.  This yields an incorrectly
 * rounded result half the time...
 */

#ifndef USE_ACCURATE_ROUNDING
#undef DESCALE
#define DESCALE(x,n)  RIGHT_SHIFT(x, n)
#endif

/* Multiply a DCTELEM variable by an INT32 constant, and immediately
 * descale to yield a DCTELEM result.
 */

#define MULTIPLY(var,const)  ((DCTELEM) DESCALE((var) * (const), CONST_BITS))

/* Dequantize a coefficient by multiplying it by the multiplier-table
 * entry; produce a DCTELEM result.  For 8-bit data a 16x16->16
 * multiplication will do.  For 12-bit data, the multiplier table is
 * declared INT32, so a 32-bit multiply will be used.
 */

#if BITS_IN_JSAMPLE == 8
#define DEQUANTIZE(coef,quantval)  (((IFAST_MULT_TYPE) (coef)) * (quantval))
#else
#define DEQUANTIZE(coef,quantval)  \
	DESCALE((coef)*(quantval), IFAST_SCALE_BITS-PASS1_BITS)
#endif

/* Like DESCALE, but applies to a DCTELEM and produces an int.
 * We assume that int right shift is unsigned if INT32 right shift is.
 */

#ifdef RIGHT_SHIFT_IS_UNSIGNED
#define ISHIFT_TEMPS	DCTELEM ishift_temp;
#if BITS_IN_JSAMPLE == 8
#define DCTELEMBITS  16		/* DCTELEM may be 16 or 32 bits */
#else
#define DCTELEMBITS  32		/* DCTELEM must be 32 bits */
#endif
#define IRIGHT_SHIFT(x,shft)  \
    ((ishift_temp = (x)) < 0 ? \
     (ishift_temp >> (shft)) | ((~((DCTELEM) 0)) << (DCTELEMBITS-(shft))) : \
     (ishift_temp >> (shft)))
#else
#define ISHIFT_TEMPS
#define IRIGHT_SHIFT(x,shft)	((x) >> (shft))
#endif

#ifdef USE_ACCURATE_ROUNDING
#define IDESCALE(x,n)  ((int) IRIGHT_SHIFT((x) + (1 << ((n)-1)), n))
#else
#define IDESCALE(x,n)  ((int) IRIGHT_SHIFT(x, n))
#endif

/*
 * Perform dequantization and inverse DCT on one block of coefficients.
 */

GLOBAL(void)
jpeg_idct_ifast (j_decompress_ptr cinfo, jpeg_component_info * compptr,
		 JCOEFPTR coef_block,
		 JSAMPARRAY output_buf, JDIMENSION output_col)
{
  DCTELEM tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
  DCTELEM tmp10, tmp11, tmp12, tmp13;
  DCTELEM z5, z10, z11, z12, z13;
  JCOEFPTR inptr;
  IFAST_MULT_TYPE * quantptr;
  int * wsptr;
  JSAMPROW outptr;
  JSAMPLE *range_limit = IDCT_range_limit(cinfo);
  int ctr;
  int workspace[DCTSIZE2];	/* buffers data between passes */
  SHIFT_TEMPS			/* for DESCALE */
  ISHIFT_TEMPS			/* for IDESCALE */

  /* Pass 1: process columns from input, store into work array. */

  inptr = coef_block;
  quantptr = (IFAST_MULT_TYPE *) compptr->dct_table;
  wsptr = workspace;
  for (ctr = DCTSIZE; ctr > 0; ctr--) {
    /* Due to quantization, we will usually find that many of the input
     * coefficients are zero, especially the AC terms.  We can exploit this
     * by short-circuiting the IDCT calculation for any column in which all
     * the AC terms are zero.  In that case each output is equal to the
     * DC coefficient (with scale factor as needed).
     * With typical images and quantization tables, half or more of the
     * column DCT calculations can be simplified this way.
     */

    if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*2] == 0 &&
	inptr[DCTSIZE*3] == 0 && inptr[DCTSIZE*4] == 0 &&
	inptr[DCTSIZE*5] == 0 && inptr[DCTSIZE*6] == 0 &&
	inptr[DCTSIZE*7] == 0) {
      /* AC terms all zero */
      int dcval = (int) DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);

      wsptr[DCTSIZE*0] = dcval;
      wsptr[DCTSIZE*1] = dcval;
      wsptr[DCTSIZE*2] = dcval;
      wsptr[DCTSIZE*3] = dcval;
      wsptr[DCTSIZE*4] = dcval;
      wsptr[DCTSIZE*5] = dcval;
      wsptr[DCTSIZE*6] = dcval;
      wsptr[DCTSIZE*7] = dcval;

      inptr++;			/* advance pointers to next column */
      quantptr++;
      wsptr++;
      continue;
    }

    /* Even part */

    tmp0 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
    tmp1 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2]);
    tmp2 = DEQUANTIZE(inptr[DCTSIZE*4], quantptr[DCTSIZE*4]);
    tmp3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6]);

    tmp10 = tmp0 + tmp2;	/* phase 3 */
    tmp11 = tmp0 - tmp2;

    tmp13 = tmp1 + tmp3;	/* phases 5-3 */
    tmp12 = MULTIPLY(tmp1 - tmp3, FIX_1_414213562) - tmp13; /* 2*c4 */

    tmp0 = tmp10 + tmp13;	/* phase 2 */
    tmp3 = tmp10 - tmp13;
    tmp1 = tmp11 + tmp12;
    tmp2 = tmp11 - tmp12;

    /* Odd part */

    tmp4 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]);
    tmp5 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]);
    tmp6 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]);
    tmp7 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]);

    z13 = tmp6 + tmp5;		/* phase 6 */
    z10 = tmp6 - tmp5;
    z11 = tmp4 + tmp7;
    z12 = tmp4 - tmp7;

    tmp7 = z11 + z13;		/* phase 5 */
    tmp11 = MULTIPLY(z11 - z13, FIX_1_414213562); /* 2*c4 */

    z5 = MULTIPLY(z10 + z12, FIX_1_847759065); /* 2*c2 */
    tmp10 = MULTIPLY(z12, FIX_1_082392200) - z5; /* 2*(c2-c6) */
    tmp12 = MULTIPLY(z10, - FIX_2_613125930) + z5; /* -2*(c2+c6) */

    tmp6 = tmp12 - tmp7;	/* phase 2 */
    tmp5 = tmp11 - tmp6;
    tmp4 = tmp10 + tmp5;

    wsptr[DCTSIZE*0] = (int) (tmp0 + tmp7);
    wsptr[DCTSIZE*7] = (int) (tmp0 - tmp7);
    wsptr[DCTSIZE*1] = (int) (tmp1 + tmp6);
    wsptr[DCTSIZE*6] = (int) (tmp1 - tmp6);
    wsptr[DCTSIZE*2] = (int) (tmp2 + tmp5);
    wsptr[DCTSIZE*5] = (int) (tmp2 - tmp5);
    wsptr[DCTSIZE*4] = (int) (tmp3 + tmp4);
    wsptr[DCTSIZE*3] = (int) (tmp3 - tmp4);

    inptr++;			/* advance pointers to next column */
    quantptr++;
    wsptr++;
  }

  /* Pass 2: process rows from work array, store into output array. */
  /* Note that we must descale the results by a factor of 8 == 2**3, */
  /* and also undo the PASS1_BITS scaling. */

  wsptr = workspace;
  for (ctr = 0; ctr < DCTSIZE; ctr++) {
    outptr = output_buf[ctr] + output_col;
    /* Rows of zeroes can be exploited in the same way as we did with columns.
     * However, the column calculation has created many nonzero AC terms, so
     * the simplification applies less often (typically 5% to 10% of the time).
     * On machines with very fast multiplication, it's possible that the
     * test takes more time than it's worth.  In that case this section
     * may be commented out.
     */

#ifndef NO_ZERO_ROW_TEST
    if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 && wsptr[4] == 0 &&
	wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) {
      /* AC terms all zero */
      JSAMPLE dcval = range_limit[IDESCALE(wsptr[0], PASS1_BITS+3)
				  & RANGE_MASK];

      outptr[0] = dcval;
      outptr[1] = dcval;
      outptr[2] = dcval;
      outptr[3] = dcval;
      outptr[4] = dcval;
      outptr[5] = dcval;
      outptr[6] = dcval;
      outptr[7] = dcval;

      wsptr += DCTSIZE;		/* advance pointer to next row */
      continue;
    }
#endif

    /* Even part */

    tmp10 = ((DCTELEM) wsptr[0] + (DCTELEM) wsptr[4]);
    tmp11 = ((DCTELEM) wsptr[0] - (DCTELEM) wsptr[4]);

    tmp13 = ((DCTELEM) wsptr[2] + (DCTELEM) wsptr[6]);
    tmp12 = MULTIPLY((DCTELEM) wsptr[2] - (DCTELEM) wsptr[6], FIX_1_414213562)
	    - tmp13;

    tmp0 = tmp10 + tmp13;
    tmp3 = tmp10 - tmp13;
    tmp1 = tmp11 + tmp12;
    tmp2 = tmp11 - tmp12;

    /* Odd part */

    z13 = (DCTELEM) wsptr[5] + (DCTELEM) wsptr[3];
    z10 = (DCTELEM) wsptr[5] - (DCTELEM) wsptr[3];
    z11 = (DCTELEM) wsptr[1] + (DCTELEM) wsptr[7];
    z12 = (DCTELEM) wsptr[1] - (DCTELEM) wsptr[7];

    tmp7 = z11 + z13;		/* phase 5 */
    tmp11 = MULTIPLY(z11 - z13, FIX_1_414213562); /* 2*c4 */

    z5 = MULTIPLY(z10 + z12, FIX_1_847759065); /* 2*c2 */
    tmp10 = MULTIPLY(z12, FIX_1_082392200) - z5; /* 2*(c2-c6) */
    tmp12 = MULTIPLY(z10, - FIX_2_613125930) + z5; /* -2*(c2+c6) */

    tmp6 = tmp12 - tmp7;	/* phase 2 */
    tmp5 = tmp11 - tmp6;
    tmp4 = tmp10 + tmp5;

    /* Final output stage: scale down by a factor of 8 and range-limit */

    outptr[0] = range_limit[IDESCALE(tmp0 + tmp7, PASS1_BITS+3)
			    & RANGE_MASK];
    outptr[7] = range_limit[IDESCALE(tmp0 - tmp7, PASS1_BITS+3)
			    & RANGE_MASK];
    outptr[1] = range_limit[IDESCALE(tmp1 + tmp6, PASS1_BITS+3)
			    & RANGE_MASK];
    outptr[6] = range_limit[IDESCALE(tmp1 - tmp6, PASS1_BITS+3)
			    & RANGE_MASK];
    outptr[2] = range_limit[IDESCALE(tmp2 + tmp5, PASS1_BITS+3)
			    & RANGE_MASK];
    outptr[5] = range_limit[IDESCALE(tmp2 - tmp5, PASS1_BITS+3)
			    & RANGE_MASK];
    outptr[4] = range_limit[IDESCALE(tmp3 + tmp4, PASS1_BITS+3)
			    & RANGE_MASK];
    outptr[3] = range_limit[IDESCALE(tmp3 - tmp4, PASS1_BITS+3)
			    & RANGE_MASK];

    wsptr += DCTSIZE;		/* advance pointer to next row */
  }
}

#endif /* DCT_IFAST_SUPPORTED */


text:
/*
 * jcmainct.c
 *
 * Copyright (C) 1994-1996, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains the main buffer controller for compression.
 * The main buffer lies between the pre-processor and the JPEG
 * compressor proper; it holds downsampled data in the JPEG colorspace.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"

/* Note: currently, there is no operating mode in which a full-image buffer
 * is needed at this step.  If there were, that mode could not be used with
 * "raw data" input, since this module is bypassed in that case.  However,
 * we've left the code here for possible use in special applications.
 */
#undef FULL_MAIN_BUFFER_SUPPORTED

/* Private buffer controller object */

typedef struct {
  struct jpeg_c_main_controller pub; /* public fields */

  JDIMENSION cur_iMCU_row;	/* number of current iMCU row */
  JDIMENSION rowgroup_ctr;	/* counts row groups received in iMCU row */
  boolean suspended;		/* remember if we suspended output */
  J_BUF_MODE pass_mode;		/* current operating mode */

  /* If using just a strip buffer, this points to the entire set of buffers
   * (we allocate one for each component).  In the full-image case, this
   * points to the currently accessible strips of the virtual arrays.
   */
  JSAMPARRAY buffer[MAX_COMPONENTS];

#ifdef FULL_MAIN_BUFFER_SUPPORTED
  /* If using full-image storage, this array holds pointers to virtual-array
   * control blocks for each component.  Unused if not full-image storage.
   */
  jvirt_sarray_ptr whole_image[MAX_COMPONENTS];
#endif
} my_main_controller;

typedef my_main_controller * my_main_ptr;

/* Forward declarations */
METHODDEF(void) process_data_simple_main
	JPP((j_compress_ptr cinfo, JSAMPARRAY input_buf,
	     JDIMENSION *in_row_ctr, JDIMENSION in_rows_avail));
#ifdef FULL_MAIN_BUFFER_SUPPORTED
METHODDEF(void) process_data_buffer_main
	JPP((j_compress_ptr cinfo, JSAMPARRAY input_buf,
	     JDIMENSION *in_row_ctr, JDIMENSION in_rows_avail));
#endif

/*
 * Initialize for a processing pass.
 */

METHODDEF(void)
start_pass_main (j_compress_ptr cinfo, J_BUF_MODE pass_mode)
{
  my_main_ptr main_ = (my_main_ptr) cinfo->main;

  /* Do nothing in raw-data mode. */
  if (cinfo->raw_data_in)
    return;

  main_->cur_iMCU_row = 0;	/* initialize counters */
  main_->rowgroup_ctr = 0;
  main_->suspended = FALSE;
  main_->pass_mode = pass_mode;	/* save mode for use by process_data */

  switch (pass_mode) {
  case JBUF_PASS_THRU:
#ifdef FULL_MAIN_BUFFER_SUPPORTED
    if (main_->whole_image[0] != NULL)
      ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
#endif
    main_->pub.process_data = process_data_simple_main;
    break;
#ifdef FULL_MAIN_BUFFER_SUPPORTED
  case JBUF_SAVE_SOURCE:
  case JBUF_CRANK_DEST:
  case JBUF_SAVE_AND_PASS:
    if (main_->whole_image[0] == NULL)
      ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
    main_->pub.process_data = process_data_buffer_main;
    break;
#endif
  default:
    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
    break;
  }
}

/*
 * Process some data.
 * This routine handles the simple pass-through mode,
 * where we have only a strip buffer.
 */

METHODDEF(void)
process_data_simple_main (j_compress_ptr cinfo,
			  JSAMPARRAY input_buf, JDIMENSION *in_row_ctr,
			  JDIMENSION in_rows_avail)
{
  my_main_ptr main_ = (my_main_ptr) cinfo->main;

  while (main_->cur_iMCU_row < cinfo->total_iMCU_rows) {
    /* Read input data if we haven't filled the main buffer yet */
    if (main_->rowgroup_ctr < DCTSIZE)
      (*cinfo->prep->pre_process_data) (cinfo,
					input_buf, in_row_ctr, in_rows_avail,
					main_->buffer, &main_->rowgroup_ctr,
					(JDIMENSION) DCTSIZE);

    /* If we don't have a full iMCU row buffered, return to application for
     * more data.  Note that preprocessor will always pad to fill the iMCU row
     * at the bottom of the image.
     */
    if (main_->rowgroup_ctr != DCTSIZE)
      return;

    /* Send the completed row to the compressor */
    if (! (*cinfo->coef->compress_data) (cinfo, main_->buffer)) {
      /* If compressor did not consume the whole row, then we must need to
       * suspend processing and return to the application.  In this situation
       * we pretend we didn't yet consume the last input row; otherwise, if
       * it happened to be the last row of the image, the application would
       * think we were done.
       */
      if (! main_->suspended) {
	(*in_row_ctr)--;
	main_->suspended = TRUE;
      }
      return;
    }
    /* We did finish the row.  Undo our little suspension hack if a previous
     * call suspended; then mark the main buffer empty.
     */
    if (main_->suspended) {
      (*in_row_ctr)++;
      main_->suspended = FALSE;
    }
    main_->rowgroup_ctr = 0;
    main_->cur_iMCU_row++;
  }
}

#ifdef FULL_MAIN_BUFFER_SUPPORTED

/*
 * Process some data.
 * This routine handles all of the modes that use a full-size buffer.
 */

METHODDEF(void)
process_data_buffer_main (j_compress_ptr cinfo,
			  JSAMPARRAY input_buf, JDIMENSION *in_row_ctr,
			  JDIMENSION in_rows_avail)
{
  my_main_ptr main = (my_main_ptr) cinfo->main;
  int ci;
  jpeg_component_info *compptr;
  boolean writing = (main->pass_mode != JBUF_CRANK_DEST);

  while (main->cur_iMCU_row < cinfo->total_iMCU_rows) {
    /* Realign the virtual buffers if at the start of an iMCU row. */
    if (main->rowgroup_ctr == 0) {
      for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
	   ci++, compptr++) {
	main->buffer[ci] = (*cinfo->mem->access_virt_sarray)
	  ((j_common_ptr) cinfo, main->whole_image[ci],
	   main->cur_iMCU_row * (compptr->v_samp_factor * DCTSIZE),
	   (JDIMENSION) (compptr->v_samp_factor * DCTSIZE), writing);
      }
      /* In a read pass, pretend we just read some source data. */
      if (! writing) {
	*in_row_ctr += cinfo->max_v_samp_factor * DCTSIZE;
	main->rowgroup_ctr = DCTSIZE;
      }
    }

    /* If a write pass, read input data until the current iMCU row is full. */
    /* Note: preprocessor will pad if necessary to fill the last iMCU row. */
    if (writing) {
      (*cinfo->prep->pre_process_data) (cinfo,
					input_buf, in_row_ctr, in_rows_avail,
					main->buffer, &main->rowgroup_ctr,
					(JDIMENSION) DCTSIZE);
      /* Return to application if we need more data to fill the iMCU row. */
      if (main->rowgroup_ctr < DCTSIZE)
	return;
    }

    /* Emit data, unless this is a sink-only pass. */
    if (main->pass_mode != JBUF_SAVE_SOURCE) {
      if (! (*cinfo->coef->compress_data) (cinfo, main->buffer)) {
	/* If compressor did not consume the whole row, then we must need to
	 * suspend processing and return to the application.  In this situation
	 * we pretend we didn't yet consume the last input row; otherwise, if
	 * it happened to be the last row of the image, the application would
	 * think we were done.
	 */
	if (! main->suspended) {
	  (*in_row_ctr)--;
	  main->suspended = TRUE;
	}
	return;
      }
      /* We did finish the row.  Undo our little suspension hack if a previous
       * call suspended; then mark the main buffer empty.
       */
      if (main->suspended) {
	(*in_row_ctr)++;
	main->suspended = FALSE;
      }
    }

    /* If get here, we are done with this iMCU row.  Mark buffer empty. */
    main->rowgroup_ctr = 0;
    main->cur_iMCU_row++;
  }
}

#endif /* FULL_MAIN_BUFFER_SUPPORTED */

/*
 * Initialize main buffer controller.
 */

GLOBAL(void)
jinit_c_main_controller (j_compress_ptr cinfo, boolean need_full_buffer)
{
  my_main_ptr main_;
  int ci;
  jpeg_component_info *compptr;

  main_ = (my_main_ptr)
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
				SIZEOF(my_main_controller));
  cinfo->main = (struct jpeg_c_main_controller *) main_;
  main_->pub.start_pass = start_pass_main;

  /* We don't need to create a buffer in raw-data mode. */
  if (cinfo->raw_data_in)
    return;

  /* Create the buffer.  It holds downsampled data, so each component
   * may be of a different size.
   */
  if (need_full_buffer) {
#ifdef FULL_MAIN_BUFFER_SUPPORTED
    /* Allocate a full-image virtual array for each component */
    /* Note we pad the bottom to a multiple of the iMCU height */
    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
	 ci++, compptr++) {
      main->whole_image[ci] = (*cinfo->mem->request_virt_sarray)
	((j_common_ptr) cinfo, JPOOL_IMAGE, FALSE,
	 compptr->width_in_blocks * DCTSIZE,
	 (JDIMENSION) jround_up((long) compptr->height_in_blocks,
				(long) compptr->v_samp_factor) * DCTSIZE,
	 (JDIMENSION) (compptr->v_samp_factor * DCTSIZE));
    }
#else
    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
#endif
  } else {
#ifdef FULL_MAIN_BUFFER_SUPPORTED
    main_->whole_image[0] = NULL; /* flag for no virtual arrays */
#endif
    /* Allocate a strip buffer for each component */
    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
	 ci++, compptr++) {
      main_->buffer[ci] = (*cinfo->mem->alloc_sarray)
	((j_common_ptr) cinfo, JPOOL_IMAGE,
	 compptr->width_in_blocks * DCTSIZE,
	 (JDIMENSION) (compptr->v_samp_factor * DCTSIZE));
    }
  }
}


text:
/*
 * jversion.h
 *
 * Copyright (C) 1991-1998, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains software version identification.
 */

#define JVERSION	"6b  27-Mar-1998"

#define JCOPYRIGHT	"Copyright (C) 1998, Thomas G. Lane"


text:
/*
 * jidctint.c
 *
 * Copyright (C) 1991-1998, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains a slow-but-accurate integer implementation of the
 * inverse DCT (Discrete Cosine Transform).  In the IJG code, this routine
 * must also perform dequantization of the input coefficients.
 *
 * A 2-D IDCT can be done by 1-D IDCT on each column followed by 1-D IDCT
 * on each row (or vice versa, but it's more convenient to emit a row at
 * a time).  Direct algorithms are also available, but they are much more
 * complex and seem not to be any faster when reduced to code.
 *
 * This implementation is based on an algorithm described in
 *   C. Loeffler, A. Ligtenberg and G. Moschytz, "Practical Fast 1-D DCT
 *   Algorithms with 11 Multiplications", Proc. Int'l. Conf. on Acoustics,
 *   Speech, and Signal Processing 1989 (ICASSP '89), pp. 988-991.
 * The primary algorithm described there uses 11 multiplies and 29 adds.
 * We use their alternate method with 12 multiplies and 32 adds.
 * The advantage of this method is that no data path contains more than one
 * multiplication; this allows a very simple and accurate implementation in
 * scaled fixed-point arithmetic, with a minimal number of shifts.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
#include "jdct.h"		/* Private declarations for DCT subsystem */

#ifdef DCT_ISLOW_SUPPORTED

/*
 * This module is specialized to the case DCTSIZE = 8.
 */

#if DCTSIZE != 8
  Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
#endif

/*
 * The poop on this scaling stuff is as follows:
 *
 * Each 1-D IDCT step produces outputs which are a factor of sqrt(N)
 * larger than the true IDCT outputs.  The final outputs are therefore
 * a factor of N larger than desired; since N=8 this can be cured by
 * a simple right shift at the end of the algorithm.  The advantage of
 * this arrangement is that we save two multiplications per 1-D IDCT,
 * because the y0 and y4 inputs need not be divided by sqrt(N).
 *
 * We have to do addition and subtraction of the integer inputs, which
 * is no problem, and multiplication by fractional constants, which is
 * a problem to do in integer arithmetic.  We multiply all the constants
 * by CONST_SCALE and convert them to integer constants (thus retaining
 * CONST_BITS bits of precision in the constants).  After doing a
 * multiplication we have to divide the product by CONST_SCALE, with proper
 * rounding, to produce the correct output.  This division can be done
 * cheaply as a right shift of CONST_BITS bits.  We postpone shifting
 * as long as possible so that partial sums can be added together with
 * full fractional precision.
 *
 * The outputs of the first pass are scaled up by PASS1_BITS bits so that
 * they are represented to better-than-integral precision.  These outputs
 * require BITS_IN_JSAMPLE + PASS1_BITS + 3 bits; this fits in a 16-bit word
 * with the recommended scaling.  (To scale up 12-bit sample data further, an
 * intermediate INT32 array would be needed.)
 *
 * To avoid overflow of the 32-bit intermediate results in pass 2, we must
 * have BITS_IN_JSAMPLE + CONST_BITS + PASS1_BITS <= 26.  Error analysis
 * shows that the values given below are the most effective.
 */

#if BITS_IN_JSAMPLE == 8
#define CONST_BITS  13
#define PASS1_BITS  2
#else
#define CONST_BITS  13
#define PASS1_BITS  1		/* lose a little precision to avoid overflow */
#endif

/* Some C compilers fail to reduce "FIX(constant)" at compile time, thus
 * causing a lot of useless floating-point operations at run time.
 * To get around this we use the following pre-calculated constants.
 * If you change CONST_BITS you may want to add appropriate values.
 * (With a reasonable C compiler, you can just rely on the FIX() macro...)
 */

#if CONST_BITS == 13
#define FIX_0_298631336  ((INT32)  2446)	/* FIX(0.298631336) */
#define FIX_0_390180644  ((INT32)  3196)	/* FIX(0.390180644) */
#define FIX_0_541196100  ((INT32)  4433)	/* FIX(0.541196100) */
#define FIX_0_765366865  ((INT32)  6270)	/* FIX(0.765366865) */
#define FIX_0_899976223  ((INT32)  7373)	/* FIX(0.899976223) */
#define FIX_1_175875602  ((INT32)  9633)	/* FIX(1.175875602) */
#define FIX_1_501321110  ((INT32)  12299)	/* FIX(1.501321110) */
#define FIX_1_847759065  ((INT32)  15137)	/* FIX(1.847759065) */
#define FIX_1_961570560  ((INT32)  16069)	/* FIX(1.961570560) */
#define FIX_2_053119869  ((INT32)  16819)	/* FIX(2.053119869) */
#define FIX_2_562915447  ((INT32)  20995)	/* FIX(2.562915447) */
#define FIX_3_072711026  ((INT32)  25172)	/* FIX(3.072711026) */
#else
#define FIX_0_298631336  FIX(0.298631336)
#define FIX_0_390180644  FIX(0.390180644)
#define FIX_0_541196100  FIX(0.541196100)
#define FIX_0_765366865  FIX(0.765366865)
#define FIX_0_899976223  FIX(0.899976223)
#define FIX_1_175875602  FIX(1.175875602)
#define FIX_1_501321110  FIX(1.501321110)
#define FIX_1_847759065  FIX(1.847759065)
#define FIX_1_961570560  FIX(1.961570560)
#define FIX_2_053119869  FIX(2.053119869)
#define FIX_2_562915447  FIX(2.562915447)
#define FIX_3_072711026  FIX(3.072711026)
#endif

/* Multiply an INT32 variable by an INT32 constant to yield an INT32 result.
 * For 8-bit samples with the recommended scaling, all the variable
 * and constant values involved are no more than 16 bits wide, so a
 * 16x16->32 bit multiply can be used instead of a full 32x32 multiply.
 * For 12-bit samples, a full 32-bit multiplication will be needed.
 */

#if BITS_IN_JSAMPLE == 8
#define MULTIPLY(var,const)  MULTIPLY16C16(var,const)
#else
#define MULTIPLY(var,const)  ((var) * (const))
#endif

/* Dequantize a coefficient by multiplying it by the multiplier-table
 * entry; produce an int result.  In this module, both inputs and result
 * are 16 bits or less, so either int or short multiply will work.
 */

#define DEQUANTIZE(coef,quantval)  (((ISLOW_MULT_TYPE) (coef)) * (quantval))

/*
 * Perform dequantization and inverse DCT on one block of coefficients.
 */

GLOBAL(void)
jpeg_idct_islow (j_decompress_ptr cinfo, jpeg_component_info * compptr,
		 JCOEFPTR coef_block,
		 JSAMPARRAY output_buf, JDIMENSION output_col)
{
  INT32 tmp0, tmp1, tmp2, tmp3;
  INT32 tmp10, tmp11, tmp12, tmp13;
  INT32 z1, z2, z3, z4, z5;
  JCOEFPTR inptr;
  ISLOW_MULT_TYPE * quantptr;
  int * wsptr;
  JSAMPROW outptr;
  JSAMPLE *range_limit = IDCT_range_limit(cinfo);
  int ctr;
  int workspace[DCTSIZE2];	/* buffers data between passes */
  SHIFT_TEMPS

  /* Pass 1: process columns from input, store into work array. */
  /* Note results are scaled up by sqrt(8) compared to a true IDCT; */
  /* furthermore, we scale the results by 2**PASS1_BITS. */

  inptr = coef_block;
  quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
  wsptr = workspace;
  for (ctr = DCTSIZE; ctr > 0; ctr--) {
    /* Due to quantization, we will usually find that many of the input
     * coefficients are zero, especially the AC terms.  We can exploit this
     * by short-circuiting the IDCT calculation for any column in which all
     * the AC terms are zero.  In that case each output is equal to the
     * DC coefficient (with scale factor as needed).
     * With typical images and quantization tables, half or more of the
     * column DCT calculations can be simplified this way.
     */

    if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*2] == 0 &&
	inptr[DCTSIZE*3] == 0 && inptr[DCTSIZE*4] == 0 &&
	inptr[DCTSIZE*5] == 0 && inptr[DCTSIZE*6] == 0 &&
	inptr[DCTSIZE*7] == 0) {
      /* AC terms all zero */
      int dcval = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]) << PASS1_BITS;

      wsptr[DCTSIZE*0] = dcval;
      wsptr[DCTSIZE*1] = dcval;
      wsptr[DCTSIZE*2] = dcval;
      wsptr[DCTSIZE*3] = dcval;
      wsptr[DCTSIZE*4] = dcval;
      wsptr[DCTSIZE*5] = dcval;
      wsptr[DCTSIZE*6] = dcval;
      wsptr[DCTSIZE*7] = dcval;

      inptr++;			/* advance pointers to next column */
      quantptr++;
      wsptr++;
      continue;
    }

    /* Even part: reverse the even part of the forward DCT. */
    /* The rotator is sqrt(2)*c(-6). */

    z2 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2]);
    z3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6]);

    z1 = MULTIPLY(z2 + z3, FIX_0_541196100);
    tmp2 = z1 + MULTIPLY(z3, - FIX_1_847759065);
    tmp3 = z1 + MULTIPLY(z2, FIX_0_765366865);

    z2 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
    z3 = DEQUANTIZE(inptr[DCTSIZE*4], quantptr[DCTSIZE*4]);

    tmp0 = (z2 + z3) << CONST_BITS;
    tmp1 = (z2 - z3) << CONST_BITS;

    tmp10 = tmp0 + tmp3;
    tmp13 = tmp0 - tmp3;
    tmp11 = tmp1 + tmp2;
    tmp12 = tmp1 - tmp2;

    /* Odd part per figure 8; the matrix is unitary and hence its
     * transpose is its inverse.  i0..i3 are y7,y5,y3,y1 respectively.
     */

    tmp0 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]);
    tmp1 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]);
    tmp2 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]);
    tmp3 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]);

    z1 = tmp0 + tmp3;
    z2 = tmp1 + tmp2;
    z3 = tmp0 + tmp2;
    z4 = tmp1 + tmp3;
    z5 = MULTIPLY(z3 + z4, FIX_1_175875602); /* sqrt(2) * c3 */

    tmp0 = MULTIPLY(tmp0, FIX_0_298631336); /* sqrt(2) * (-c1+c3+c5-c7) */
    tmp1 = MULTIPLY(tmp1, FIX_2_053119869); /* sqrt(2) * ( c1+c3-c5+c7) */
    tmp2 = MULTIPLY(tmp2, FIX_3_072711026); /* sqrt(2) * ( c1+c3+c5-c7) */
    tmp3 = MULTIPLY(tmp3, FIX_1_501321110); /* sqrt(2) * ( c1+c3-c5-c7) */
    z1 = MULTIPLY(z1, - FIX_0_899976223); /* sqrt(2) * (c7-c3) */
    z2 = MULTIPLY(z2, - FIX_2_562915447); /* sqrt(2) * (-c1-c3) */
    z3 = MULTIPLY(z3, - FIX_1_961570560); /* sqrt(2) * (-c3-c5) */
    z4 = MULTIPLY(z4, - FIX_0_390180644); /* sqrt(2) * (c5-c3) */

    z3 += z5;
    z4 += z5;

    tmp0 += z1 + z3;
    tmp1 += z2 + z4;
    tmp2 += z2 + z3;
    tmp3 += z1 + z4;

    /* Final output stage: inputs are tmp10..tmp13, tmp0..tmp3 */

    wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp3, CONST_BITS-PASS1_BITS);
    wsptr[DCTSIZE*7] = (int) DESCALE(tmp10 - tmp3, CONST_BITS-PASS1_BITS);
    wsptr[DCTSIZE*1] = (int) DESCALE(tmp11 + tmp2, CONST_BITS-PASS1_BITS);
    wsptr[DCTSIZE*6] = (int) DESCALE(tmp11 - tmp2, CONST_BITS-PASS1_BITS);
    wsptr[DCTSIZE*2] = (int) DESCALE(tmp12 + tmp1, CONST_BITS-PASS1_BITS);
    wsptr[DCTSIZE*5] = (int) DESCALE(tmp12 - tmp1, CONST_BITS-PASS1_BITS);
    wsptr[DCTSIZE*3] = (int) DESCALE(tmp13 + tmp0, CONST_BITS-PASS1_BITS);
    wsptr[DCTSIZE*4] = (int) DESCALE(tmp13 - tmp0, CONST_BITS-PASS1_BITS);

    inptr++;			/* advance pointers to next column */
    quantptr++;
    wsptr++;
  }

  /* Pass 2: process rows from work array, store into output array. */
  /* Note that we must descale the results by a factor of 8 == 2**3, */
  /* and also undo the PASS1_BITS scaling. */

  wsptr = workspace;
  for (ctr = 0; ctr < DCTSIZE; ctr++) {
    outptr = output_buf[ctr] + output_col;
    /* Rows of zeroes can be exploited in the same way as we did with columns.
     * However, the column calculation has created many nonzero AC terms, so
     * the simplification applies less often (typically 5% to 10% of the time).
     * On machines with very fast multiplication, it's possible that the
     * test takes more time than it's worth.  In that case this section
     * may be commented out.
     */

#ifndef NO_ZERO_ROW_TEST
    if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 && wsptr[4] == 0 &&
	wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) {
      /* AC terms all zero */
      JSAMPLE dcval = range_limit[(int) DESCALE((INT32) wsptr[0], PASS1_BITS+3)
				  & RANGE_MASK];

      outptr[0] = dcval;
      outptr[1] = dcval;
      outptr[2] = dcval;
      outptr[3] = dcval;
      outptr[4] = dcval;
      outptr[5] = dcval;
      outptr[6] = dcval;
      outptr[7] = dcval;

      wsptr += DCTSIZE;		/* advance pointer to next row */
      continue;
    }
#endif

    /* Even part: reverse the even part of the forward DCT. */
    /* The rotator is sqrt(2)*c(-6). */

    z2 = (INT32) wsptr[2];
    z3 = (INT32) wsptr[6];

    z1 = MULTIPLY(z2 + z3, FIX_0_541196100);
    tmp2 = z1 + MULTIPLY(z3, - FIX_1_847759065);
    tmp3 = z1 + MULTIPLY(z2, FIX_0_765366865);

    tmp0 = ((INT32) wsptr[0] + (INT32) wsptr[4]) << CONST_BITS;
    tmp1 = ((INT32) wsptr[0] - (INT32) wsptr[4]) << CONST_BITS;

    tmp10 = tmp0 + tmp3;
    tmp13 = tmp0 - tmp3;
    tmp11 = tmp1 + tmp2;
    tmp12 = tmp1 - tmp2;

    /* Odd part per figure 8; the matrix is unitary and hence its
     * transpose is its inverse.  i0..i3 are y7,y5,y3,y1 respectively.
     */

    tmp0 = (INT32) wsptr[7];
    tmp1 = (INT32) wsptr[5];
    tmp2 = (INT32) wsptr[3];
    tmp3 = (INT32) wsptr[1];

    z1 = tmp0 + tmp3;
    z2 = tmp1 + tmp2;
    z3 = tmp0 + tmp2;
    z4 = tmp1 + tmp3;
    z5 = MULTIPLY(z3 + z4, FIX_1_175875602); /* sqrt(2) * c3 */

    tmp0 = MULTIPLY(tmp0, FIX_0_298631336); /* sqrt(2) * (-c1+c3+c5-c7) */
    tmp1 = MULTIPLY(tmp1, FIX_2_053119869); /* sqrt(2) * ( c1+c3-c5+c7) */
    tmp2 = MULTIPLY(tmp2, FIX_3_072711026); /* sqrt(2) * ( c1+c3+c5-c7) */
    tmp3 = MULTIPLY(tmp3, FIX_1_501321110); /* sqrt(2) * ( c1+c3-c5-c7) */
    z1 = MULTIPLY(z1, - FIX_0_899976223); /* sqrt(2) * (c7-c3) */
    z2 = MULTIPLY(z2, - FIX_2_562915447); /* sqrt(2) * (-c1-c3) */
    z3 = MULTIPLY(z3, - FIX_1_961570560); /* sqrt(2) * (-c3-c5) */
    z4 = MULTIPLY(z4, - FIX_0_390180644); /* sqrt(2) * (c5-c3) */

    z3 += z5;
    z4 += z5;

    tmp0 += z1 + z3;
    tmp1 += z2 + z4;
    tmp2 += z2 + z3;
    tmp3 += z1 + z4;

    /* Final output stage: inputs are tmp10..tmp13, tmp0..tmp3 */

    outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp3,
					  CONST_BITS+PASS1_BITS+3)
			    & RANGE_MASK];
    outptr[7] = range_limit[(int) DESCALE(tmp10 - tmp3,
					  CONST_BITS+PASS1_BITS+3)
			    & RANGE_MASK];
    outptr[1] = range_limit[(int) DESCALE(tmp11 + tmp2,
					  CONST_BITS+PASS1_BITS+3)
			    & RANGE_MASK];
    outptr[6] = range_limit[(int) DESCALE(tmp11 - tmp2,
					  CONST_BITS+PASS1_BITS+3)
			    & RANGE_MASK];
    outptr[2] = range_limit[(int) DESCALE(tmp12 + tmp1,
					  CONST_BITS+PASS1_BITS+3)
			    & RANGE_MASK];
    outptr[5] = range_limit[(int) DESCALE(tmp12 - tmp1,
					  CONST_BITS+PASS1_BITS+3)
			    & RANGE_MASK];
    outptr[3] = range_limit[(int) DESCALE(tmp13 + tmp0,
					  CONST_BITS+PASS1_BITS+3)
			    & RANGE_MASK];
    outptr[4] = range_limit[(int) DESCALE(tmp13 - tmp0,
					  CONST_BITS+PASS1_BITS+3)
			    & RANGE_MASK];

    wsptr += DCTSIZE;		/* advance pointer to next row */
  }
}

#endif /* DCT_ISLOW_SUPPORTED */