Name: image/library/libjpeg
        Summary: jpeg - The Independent JPEG Groups JPEG software
      Publisher: solaris
        Version: 9.6
  Build Release: 11.4
         Branch: 11.4.90.0.0.212.0
 Packaging Date: Wed Dec 17 20:27:21 2025
           Size: 2.05 MB
Compressed Size: 956.50 kB
           FMRI: pkg://solaris/image/library/libjpeg@9.6,11.4-11.4.90.0.0.212.0:20251217T202721Z

License:
## Files:
README

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

README for release 9f of 14-Jan-2024
====================================

This distribution contains the ninth 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.

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

IJG is not affiliated with the ISO/IEC JTC1/SC29/WG1 standards committee
(previously known as JPEG, together with ITU-T SG16).


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.
ACKNOWLEDGMENTS     Special thanks.
FILE FORMAT WARS    Software *not* to get.
TO DO               Plans for future IJG releases.

Other documentation files in the distribution are:

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

Please read at least the files install.txt and usage.txt.  Some 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 encoding, decoding,
and transcoding.  JPEG (pronounced "jay-peg") is a standardized compression
method for full-color and grayscale images.

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.
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) 1991-2024, Thomas G. Lane, Guido Vollbeding.
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.


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,
ltmain.sh).  Another support script, install-sh, is copyright by X Consortium
but is also freely distributable.


REFERENCES
==========

We 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 PDF file containing a revised version of Wallace's article is
available at https://www.ijg.org/files/Wallace.JPEG.pdf.  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 currently available 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).
Although this is by far the most detailed and comprehensive exposition of
JPEG publicly available, we point out that it is still missing an explanation
of the most essential properties and algorithms of the underlying DCT
technology.
If you think that you know about DCT-based JPEG after reading this book,
then you are in delusion.  The real fundamentals and corresponding potential
of DCT-based JPEG are not publicly known so far, and that is the reason for
all the mistaken developments taking place in the image coding domain.

The original JPEG 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.
IJG JPEG 8 introduced an implementation of the JPEG SmartScale extension
which is specified in two documents:  A contributed document at ITU and ISO
with title "ITU-T JPEG-Plus Proposal for Extending ITU-T T.81 for Advanced
Image Coding", April 2006, Geneva, Switzerland.  The latest version of this
document is Revision 3.  And a contributed document ISO/IEC JTC1/SC29/WG1 N
5799 with title "Evolution of JPEG", June/July 2011, Berlin, Germany.
IJG JPEG 9 introduces a reversible color transform for improved lossless
compression which is described in a contributed document ISO/IEC JTC1/SC29/
WG1 N 6080 with title "JPEG 9 Lossless Coding", June/July 2012, Paris, France.

The JPEG standard does not specify all details of an interchangeable file
format.  For the omitted details we follow the "JFIF" conventions, version 2.
JFIF version 1 has been adopted as Recommendation ITU-T T.871 (05/2011) :
Information technology - Digital compression and coding of continuous-tone
still images: JPEG File Interchange Format (JFIF).  It is available as a
free download in PDF file format from https://www.itu.int/rec/T-REC-T.871.
A PDF file of the older JFIF document is available at
https://www.w3.org/Graphics/JPEG/jfif3.pdf.

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
https://www.ijg.org/files/.  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.


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

The "official" archive site for this software is www.ijg.org.
The most recent released version can always be found there in
directory "files".  This particular version will be archived
in Windows-compatible "zip" archive format as
https://www.ijg.org/files/jpegsr9f.zip, and
in Unix-compatible "tar.gz" archive format as
https://www.ijg.org/files/jpegsrc.v9f.tar.gz.

The JPEG FAQ (Frequently Asked Questions) article is a source of some
general information about JPEG.
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


ACKNOWLEDGMENTS
===============

Thank to Juergen Bruder for providing me with a copy of the common DCT
algorithm article, only to find out that I had come to the same result
in a more direct and comprehensible way with a more generative approach.

Thank to Istvan Sebestyen and Joan L. Mitchell for inviting me to the
ITU JPEG (Study Group 16) meeting in Geneva, Switzerland.

Thank to Thomas Wiegand and Gary Sullivan for inviting me to the
Joint Video Team (MPEG & ITU) meeting in Geneva, Switzerland.

Thank to Thomas Richter and Daniel Lee for inviting me to the
ISO/IEC JTC1/SC29/WG1 (previously known as JPEG, together with ITU-T SG16)
meeting in Berlin, Germany.

Thank to John Korejwa and Massimo Ballerini for inviting me to
fruitful consultations in Boston, MA and Milan, Italy.

Thank to Hendrik Elstner, Roland Fassauer, Simone Zuck, Guenther
Maier-Gerber, Walter Stoeber, Fred Schmitz, and Norbert Braunagel
for corresponding business development.

Thank to Nico Zschach and Dirk Stelling of the technical support team
at the Digital Images company in Halle for providing me with extra
equipment for configuration tests.

Thank to Richard F. Lyon (then of Foveon Inc.) for fruitful
communication about JPEG configuration in Sigma Photo Pro software.

Thank to Andrew Finkenstadt for hosting the ijg.org site.

Thank to Thomas G. Lane for the original design and development
of this singular software package.

Thank to Lars Goehler, Andreas Heinecke, Sebastian Fuss,
Yvonne Roebert, Andrej Werner, Ulf-Dietrich Braumann,
and Nina Ssymank for support and public relations.


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

The ISO/IEC JTC1/SC29/WG1 standards committee (previously known as JPEG,
together with ITU-T SG16) currently promotes different formats containing
the name "JPEG" which is misleading because these formats are incompatible
with original DCT-based JPEG and are based on faulty technologies.
IJG therefore does not and will not support such momentary mistakes
(see REFERENCES).
There exist also distributions under the name "OpenJPEG" promoting such
kind of formats which is misleading because they don't support original
JPEG images.
We have no sympathy for the promotion of inferior formats.  Indeed, one of
the original reasons for developing this free software was to help force
convergence on common, interoperable format standards for JPEG files.
Don't use an incompatible file format!
(In any case, our decoder will remain capable of reading existing JPEG
image files indefinitely.)

The ISO committee pretends to be "responsible for the popular JPEG" in their
public reports which is not true because they don't respond to actual
requirements for the maintenance of the original JPEG specification.
Furthermore, the ISO committee pretends to "ensure interoperability" with
their standards which is not true because their "standards" support only
application-specific and proprietary use cases and contain mathematically
incorrect code.

There are currently different distributions in circulation containing the
name "libjpeg" which is misleading because they don't have the features and
are incompatible with formats supported by actual IJG libjpeg distributions.
One of those fakes is released by members of the ISO committee and just uses
the name of libjpeg for misdirection of people, similar to the abuse of the
name JPEG as described above, while having nothing in common with actual IJG
libjpeg distributions and containing mathematically incorrect code.
The other one claims to be a "derivative" or "fork" of the original libjpeg,
but violates the license conditions as described under LEGAL ISSUES above
and violates basic C programming properties.
We have no sympathy for the release of misleading, incorrect and illegal
distributions derived from obsolete code bases.
Don't use an obsolete code base!

According to the UCC (Uniform Commercial Code) law, IJG has the lawful and
legal right to foreclose on certain standardization bodies and other
institutions or corporations that knowingly perform substantial and
systematic deceptive acts and practices, fraud, theft, and damaging of the
value of the people of this planet without their knowing, willing and
intentional consent.
The titles, ownership, and rights of these institutions and all their assets
are now duly secured and held in trust for the free people of this planet.
People of the planet, on every country, may have a financial interest in
the assets of these former principals, agents, and beneficiaries of the
foreclosed institutions and corporations.
IJG asserts what is: that each man, woman, and child has unalienable value
and rights granted and deposited in them by the Creator and not any one of
the people is subordinate to any artificial principality, corporate fiction
or the special interest of another without their appropriate knowing,
willing and intentional consent made by contract or accommodation agreement.
IJG expresses that which already was.
The people have already determined and demanded that public administration
entities, national governments, and their supporting judicial systems must
be fully transparent, accountable, and liable.
IJG has secured the value for all concerned free people of the planet.

A partial list of foreclosed institutions and corporations ("Hall of Shame")
is currently prepared and will be published later.


TO DO
=====

Version 9 is the second release of a new generation JPEG standard
to overcome the limitations of the original JPEG specification,
and is the first true source reference JPEG codec.
More features are being prepared for coming releases...

Please send bug reports, offers of help, etc. to jpeg-info@ijg.org.


## Files:
cderror.h

cderror.h

Copyright (C) 1994-1997, Thomas G. Lane.
Modified 2009-2020 by Guido Vollbeding.
This file is part of the Independent JPEG Group's software.
For conditions of distribution and use, see the accompanying README file.

This file defines the error and message codes for the cjpeg/djpeg
applications.  These strings are not needed as part of the JPEG library
proper.
Edit this file to add new codes, or to translate the message strings to
some other language.


## Files:
cdjpeg.c

cdjpeg.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 common support routines used by the IJG application
programs (cjpeg, djpeg, jpegtran).


## Files:
cdjpeg.h

cdjpeg.h

Copyright (C) 1994-1997, Thomas G. Lane.
Modified 2019 by Guido Vollbeding.
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 common declarations for the sample applications
cjpeg and djpeg.  It is NOT used by the core JPEG library.


## Files:
cjpeg.c

 cjpeg.c

 Copyright (C) 1991-1998, Thomas G. Lane.
 Modified 2003-2013 by Guido Vollbeding.
 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 command-line user interface for the JPEG compressor.
 It should work on any system with Unix- or MS-DOS-style command lines.

 Two different command line styles are permitted, depending on the
 compile-time switch TWO_FILE_COMMANDLINE:
	cjpeg [options]  inputfile outputfile
	cjpeg [options]  [inputfile]
 In the second style, output is always to standard output, which you'd
 normally redirect to a file or pipe to some other program.  Input is
 either from a named file or from standard input (typically redirected).
 The second style is convenient on Unix but is unhelpful on systems that
 don't support pipes.  Also, you MUST use the first style if your system
 doesn't do binary I/O to stdin/stdout.
 To simplify script writing, the "-outfile" switch is provided.  The syntax
	cjpeg [options]  -outfile outputfile  inputfile
 works regardless of which command line style is used.


## Files:
cjpegalt.c

alternate cjpeg.c

Copyright (C) 1991-1998, Thomas G. Lane.
Modified 2009-2023 by Guido Vollbeding.
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 an alternate user interface for the JPEG compressor.
One or more input files are named on the command line, and output file
names are created by substituting ".jpg" for the input file's extension.


## Files:
ckconfig.c

ckconfig.c

Copyright (C) 1991-1994, 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.


## Files:
djpeg.c

 djpeg.c

 Copyright (C) 1991-1997, Thomas G. Lane.
 Modified 2009-2019 by Guido Vollbeding.
 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 command-line user interface for the JPEG decompressor.
 It should work on any system with Unix- or MS-DOS-style command lines.

 Two different command line styles are permitted, depending on the
 compile-time switch TWO_FILE_COMMANDLINE:
	djpeg [options]  inputfile outputfile
	djpeg [options]  [inputfile]
 In the second style, output is always to standard output, which you'd
 normally redirect to a file or pipe to some other program.  Input is
 either from a named file or from standard input (typically redirected).
 The second style is convenient on Unix but is unhelpful on systems that
 don't support pipes.  Also, you MUST use the first style if your system
 doesn't do binary I/O to stdin/stdout.
 To simplify script writing, the "-outfile" switch is provided.  The syntax
	djpeg [options]  -outfile outputfile  inputfile
 works regardless of which command line style is used.


## Files:
djpegalt.c

alternate djpeg.c

Copyright (C) 1991-1997, Thomas G. Lane.
Modified 2009-2023 by Guido Vollbeding.
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 an alternate user interface for the JPEG decompressor.
One or more input files are named on the command line, and output file
names are created by substituting an appropriate extension.


## Files:
jcapimin.c

jcapimin.c

Copyright (C) 1994-1998, Thomas G. Lane.
Modified 2003-2010 by Guido Vollbeding.
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 application interface code for the compression half
of the JPEG library.  These are the "minimum" API routines that may be
needed in either the normal full-compression case or the transcoding-only
case.

Most of the routines intended to be called directly by an application
are in this file or in jcapistd.c.  But also see jcparam.c for
parameter-setup helper routines, jcomapi.c for routines shared by
compression and decompression, and jctrans.c for the transcoding case.


## Files:
jcapistd.c

jcapistd.c

Copyright (C) 1994-1996, Thomas G. Lane.
Modified 2013 by Guido Vollbeding.
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 application interface code for the compression half
of the JPEG library.  These are the "standard" API routines that are
used in the normal full-compression case.  They are not used by a
transcoding-only application.  Note that if an application links in
jpeg_start_compress, it will end up linking in the entire compressor.
We thus must separate this file from jcapimin.c to avoid linking the
whole compression library into a transcoder.


## Files:
jccoefct.c

jccoefct.c

Copyright (C) 1994-1997, Thomas G. Lane.
Modified 2003-2022 by Guido Vollbeding.
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 coefficient buffer controller for compression.
This controller is the top level of the JPEG compressor proper.
The coefficient buffer lies between forward-DCT and entropy encoding steps.


## Files:
jccolor.c

jccolor.c

Copyright (C) 1991-1996, Thomas G. Lane.
Modified 2011-2023 by Guido Vollbeding.
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 input colorspace conversion routines.


## Files:
jcdctmgr.c

jcdctmgr.c

Copyright (C) 1994-1996, Thomas G. Lane.
Modified 2003-2020 by Guido Vollbeding.
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 forward-DCT management logic.
This code selects a particular DCT implementation to be used,
and it performs related housekeeping chores including coefficient
quantization.


## Files:
jchuff.c

jchuff.c

Copyright (C) 1991-1997, Thomas G. Lane.
Modified 2006-2023 by Guido Vollbeding.
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 Huffman entropy encoding routines.
Both sequential and progressive modes are supported in this single module.

Much of the complexity here has to do with supporting output suspension.
If the data destination module demands suspension, we want to be able to
back up to the start of the current MCU.  To do this, we copy state
variables into local working storage, and update them back to the
permanent JPEG objects only upon successful completion of an MCU.

We do not support output suspension for the progressive JPEG mode, since
the library currently does not allow multiple-scan files to be written
with output suspension.


## Files:
jcinit.c

jcinit.c

Copyright (C) 1991-1997, Thomas G. Lane.
Modified 2003-2017 by Guido Vollbeding.
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 initialization logic for the JPEG compressor.
This routine is in charge of selecting the modules to be executed and
making an initialization call to each one.

Logically, this code belongs in jcmaster.c.  It's split out because
linking this routine implies linking the entire compression library.
For a transcoding-only application, we want to be able to use jcmaster.c
without linking in the whole library.


## Files:
jcmainct.c

jcmainct.c

Copyright (C) 1994-1996, Thomas G. Lane.
Modified 2003-2012 by Guido Vollbeding.
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.


## Files:
jcmarker.c

jcmarker.c

Copyright (C) 1991-1998, Thomas G. Lane.
Modified 2003-2019 by Guido Vollbeding.
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 routines to write JPEG datastream markers.


## Files:
jcmaster.c

jcmaster.c

Copyright (C) 1991-1997, Thomas G. Lane.
Modified 2003-2020 by Guido Vollbeding.
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).


## Files:
jcomapi.c

jcomapi.c

Copyright (C) 1994-1997, Thomas G. Lane.
Modified 2019 by Guido Vollbeding.
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 application interface routines that are used for both
compression and decompression.


## Files:
jcparam.c

jcparam.c

Copyright (C) 1991-1998, Thomas G. Lane.
Modified 2003-2022 by Guido Vollbeding.
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 optional default-setting code for the JPEG compressor.
Applications do not have to use this file, but those that don't use it
must know a lot more about the innards of the JPEG code.


## Files:
jcprepct.c

jcprepct.c

Copyright (C) 1994-1996, Thomas G. Lane.
Modified 2003-2020 by Guido Vollbeding.
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 compression preprocessing controller.
This controller manages the color conversion, downsampling,
and edge expansion steps.

Most of the complexity here is associated with buffering input rows
as required by the downsampler.  See the comments at the head of
jcsample.c for the downsampler's needs.


## Files:
jcsample.c

jcsample.c

Copyright (C) 1991-1996, Thomas G. Lane.
Modified 2003-2020 by Guido Vollbeding.
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 downsampling routines.

Downsampling input data is counted in "row groups".  A row group
is defined to be max_v_samp_factor pixel rows of each component,
from which the downsampler produces v_samp_factor sample rows.
A single row group is processed in each call to the downsampler module.

The downsampler is responsible for edge-expansion of its output data
to fill an integral number of DCT blocks horizontally.  The source buffer
may be modified if it is helpful for this purpose (the source buffer is
allocated wide enough to correspond to the desired output width).
The caller (the prep controller) is responsible for vertical padding.

The downsampler may request "context rows" by setting need_context_rows
during startup.  In this case, the input arrays will contain at least
one row group's worth of pixels above and below the passed-in data;
the caller will create dummy rows at image top and bottom by replicating
the first or last real pixel row.

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.

The downsampling algorithm used here is a simple average of the source
pixels covered by the output pixel.  The hi-falutin sampling literature
refers to this as a "box filter".  In general the characteristics of a box
filter are not very good, but for the specific cases we normally use (1:1
and 2:1 ratios) the box is equivalent to a "triangle filter" which is not
nearly so bad.  If you intend to use other sampling ratios, you'd be well
advised to improve this code.

A simple input-smoothing capability is provided.  This is mainly intended
for cleaning up color-dithered GIF input files (if you find it inadequate,
we suggest using an external filtering program such as pnmconvol).  When
enabled, each input pixel P is replaced by a weighted sum of itself and its
eight neighbors.  P's weight is 1-8*SF and each neighbor's weight is SF,
where SF = (smoothing_factor / 1024).
Currently, smoothing is only supported for 2h2v sampling factors.


## Files:
jctrans.c

jctrans.c

Copyright (C) 1995-1998, Thomas G. Lane.
Modified 2000-2020 by Guido Vollbeding.
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 library routines for transcoding compression,
that is, writing raw DCT coefficient arrays to an output JPEG file.
The routines in jcapimin.c will also be needed by a transcoder.


## Files:
jdapimin.c

jdapimin.c

Copyright (C) 1994-1998, Thomas G. Lane.
Modified 2009-2020 by Guido Vollbeding.
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 application interface code for the decompression half
of the JPEG library.  These are the "minimum" API routines that may be
needed in either the normal full-decompression case or the
transcoding-only case.

Most of the routines intended to be called directly by an application
are in this file or in jdapistd.c.  But also see jcomapi.c for routines
shared by compression and decompression, and jdtrans.c for the transcoding
case.


## Files:
jdapistd.c

jdapistd.c

Copyright (C) 1994-1996, Thomas G. Lane.
Modified 2002-2013 by Guido Vollbeding.
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 application interface code for the decompression half
of the JPEG library.  These are the "standard" API routines that are
used in the normal full-decompression case.  They are not used by a
transcoding-only application.  Note that if an application links in
jpeg_start_decompress, it will end up linking in the entire decompressor.
We thus must separate this file from jdapimin.c to avoid linking the
whole decompression library into a transcoder.


## Files:
jdatadst.c

jdatadst.c

Copyright (C) 1994-1996, Thomas G. Lane.
Modified 2009-2022 by Guido Vollbeding.
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 compression data destination routines for the case of
emitting JPEG data to memory or to a file (or any stdio stream).
While these routines are sufficient for most applications,
some will want to use a different destination manager.
IMPORTANT: we assume that fwrite() will correctly transcribe an array of
JOCTETs into 8-bit-wide elements on external storage.  If char is wider
than 8 bits on your machine, you may need to do some tweaking.


## Files:
jdatasrc.c

jdatasrc.c

Copyright (C) 1994-1996, Thomas G. Lane.
Modified 2009-2022 by Guido Vollbeding.
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 decompression data source routines for the case of
reading JPEG data from memory or from a file (or any stdio stream).
While these routines are sufficient for most applications,
some will want to use a different source manager.
IMPORTANT: we assume that fread() will correctly transcribe an array of
JOCTETs from 8-bit-wide elements on external storage.  If char is wider
than 8 bits on your machine, you may need to do some tweaking.


## Files:
jdcoefct.c

jdcoefct.c

Copyright (C) 1994-1997, Thomas G. Lane.
Modified 2002-2020 by Guido Vollbeding.
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 coefficient buffer controller for decompression.
This controller is the top level of the JPEG decompressor proper.
The coefficient buffer lies between entropy decoding and inverse-DCT steps.

In buffered-image mode, this controller is the interface between
input-oriented processing and output-oriented processing.
Also, the input side (only) is used when reading a file for transcoding.


## Files:
jdcolor.c

jdcolor.c

Copyright (C) 1991-1997, Thomas G. Lane.
Modified 2011-2023 by Guido Vollbeding.
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 output colorspace conversion routines.


## Files:
jdct.h

jdct.h

Copyright (C) 1994-1996, Thomas G. Lane.
Modified 2002-2023 by Guido Vollbeding.
This file is part of the Independent JPEG Group's software.
For conditions of distribution and use, see the accompanying README file.

This include file contains common declarations for the forward and
inverse DCT modules.  These declarations are private to the DCT managers
(jcdctmgr.c, jddctmgr.c) and the individual DCT algorithms.
The individual DCT algorithms are kept in separate files to ease
machine-dependent tuning (e.g., assembly coding).


## Files:
jddctmgr.c

jddctmgr.c

Copyright (C) 1994-1996, Thomas G. Lane.
Modified 2002-2013 by Guido Vollbeding.
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 inverse-DCT management logic.
This code selects a particular IDCT implementation to be used,
and it performs related housekeeping chores.  No code in this file
is executed per IDCT step, only during output pass setup.

Note that the IDCT routines are responsible for performing coefficient
dequantization as well as the IDCT proper.  This module sets up the
dequantization multiplier table needed by the IDCT routine.


## Files:
jdhuff.c

jdhuff.c

Copyright (C) 1991-1997, Thomas G. Lane.
Modified 2006-2020 by Guido Vollbeding.
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 Huffman entropy decoding routines.
Both sequential and progressive modes are supported in this single module.

Much of the complexity here has to do with supporting input suspension.
If the data source module demands suspension, we want to be able to back
up to the start of the current MCU.  To do this, we copy state variables
into local working storage, and update them back to the permanent
storage only upon successful completion of an MCU.


## Files:
jdinput.c

jdinput.c

Copyright (C) 1991-1997, Thomas G. Lane.
Modified 2002-2020 by Guido Vollbeding.
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 input control logic for the JPEG decompressor.
These routines are concerned with controlling the decompressor's input
processing (marker reading and coefficient decoding).  The actual input
reading is done in jdmarker.c, jdhuff.c, and jdarith.c.


## Files:
jdmainct.c

jdmainct.c

Copyright (C) 1994-1996, Thomas G. Lane.
Modified 2002-2020 by Guido Vollbeding.
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 decompression.
The main buffer lies between the JPEG decompressor proper and the
post-processor; it holds downsampled data in the JPEG colorspace.

Note that this code is bypassed in raw-data mode, since the application
supplies the equivalent of the main buffer in that case.


## Files:
jdmarker.c

jdmarker.c

Copyright (C) 1991-1998, Thomas G. Lane.
Modified 2009-2019 by Guido Vollbeding.
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 routines to decode JPEG datastream markers.
Most of the complexity arises from our desire to support input
suspension: if not all of the data for a marker is available,
we must exit back to the application.  On resumption, we reprocess
the marker.


## Files:
jdmaster.c

jdmaster.c

Copyright (C) 1991-1997, Thomas G. Lane.
Modified 2002-2020 by Guido Vollbeding.
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 decompressor.
These routines are concerned with selecting the modules to be executed
and with determining the number of passes and the work to be done in each
pass.


## Files:
jdmerge.c

 jdmerge.c

 Copyright (C) 1994-1996, Thomas G. Lane.
 Modified 2013-2022 by Guido Vollbeding.
 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 code for merged upsampling/color conversion.

 This file combines functions from jdsample.c and jdcolor.c;
 read those files first to understand what's going on.

 When the chroma components are to be upsampled by simple replication
 (ie, box filtering), we can save some work in color conversion by
 calculating all the output pixels corresponding to a pair of chroma
 samples at one time.  In the conversion equations
	R = Y           + K1 * Cr
	G = Y + K2 * Cb + K3 * Cr
	B = Y + K4 * Cb
 only the Y term varies among the group of pixels corresponding to a pair
 of chroma samples, so the rest of the terms can be calculated just once.
 At typical sampling ratios, this eliminates half or three-quarters
 of the multiplications needed for color conversion.

 This file currently provides implementations for the following cases:
	YCC => RGB color conversion only (YCbCr or BG_YCC).
	Sampling ratios of 2h1v or 2h2v.
	No scaling needed at upsample time.
	Corner-aligned (non-CCIR601) sampling alignment.
 Other special cases could be added, but in most applications these
 are the only common cases.  (For uncommon cases we fall back on
 the more general code in jdsample.c and jdcolor.c.)


## Files:
jdpostct.c

jdpostct.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 decompression postprocessing controller.
This controller manages the upsampling, color conversion, and color
quantization/reduction steps; specifically, it controls the buffering
between upsample/color conversion and color quantization/reduction.

If no color quantization/reduction is required, then this module has no
work to do, and it just hands off to the upsample/color conversion code.
An integrated upsample/convert/quantize process would replace this module
entirely.


## Files:
jdsample.c

jdsample.c

Copyright (C) 1991-1996, Thomas G. Lane.
Modified 2002-2020 by Guido Vollbeding.
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_v_scaled_size / min_DCT_v_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.


## Files:
jdtrans.c

jdtrans.c

Copyright (C) 1995-1997, Thomas G. Lane.
Modified 2000-2009 by Guido Vollbeding.
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 library routines for transcoding decompression,
that is, reading raw DCT coefficient arrays from an input JPEG file.
The routines in jdapimin.c will also be needed by a transcoder.


## Files:
jerror.c

jerror.c

Copyright (C) 1991-1998, Thomas G. Lane.
Modified 2012-2015 by Guido Vollbeding.
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 simple error-reporting and trace-message routines.
These are suitable for Unix-like systems and others where writing to
stderr is the right thing to do.  Many applications will want to replace
some or all of these routines.

If you define USE_WINDOWS_MESSAGEBOX in jconfig.h or in the makefile,
you get a Windows-specific hack to display error messages in a dialog box.
It ain't much, but it beats dropping error messages into the bit bucket,
which is what happens to output to stderr under most Windows C compilers.

These routines are used by both the compression and decompression code.


## Files:
jerror.h

jerror.h

Copyright (C) 1994-1997, Thomas G. Lane.
Modified 1997-2018 by Guido Vollbeding.
This file is part of the Independent JPEG Group's software.
For conditions of distribution and use, see the accompanying README file.

This file defines the error and message codes for the JPEG library.
Edit this file to add new codes, or to translate the message strings to
some other language.
A set of error-reporting macros are defined too.  Some applications using
the JPEG library may wish to include this file to get the error codes
and/or the macros.


## Files:
jfdctflt.c

jfdctflt.c

Copyright (C) 1994-1996, Thomas G. Lane.
Modified 2003-2017 by Guido Vollbeding.
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 floating-point implementation of the
forward DCT (Discrete Cosine Transform).

This implementation should be more accurate than either of the integer
DCT implementations.  However, it may not give the same results on all
machines because of differences in roundoff behavior.  Speed will depend
on the hardware's floating point capacity.

A 2-D DCT can be done by 1-D DCT on each row followed by 1-D DCT
on each column.  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 a fixed-point
implementation, accuracy is lost due to imprecise representation of the
scaled quantization values.  However, that problem does not arise if
we use floating point arithmetic.


## Files:
jfdctfst.c

jfdctfst.c

Copyright (C) 1994-1996, Thomas G. Lane.
Modified 2003-2017 by Guido Vollbeding.
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
forward DCT (Discrete Cosine Transform).

A 2-D DCT can be done by 1-D DCT on each row followed by 1-D DCT
on each column.  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.


## Files:
jfdctint.c

jfdctint.c

Copyright (C) 1991-1996, Thomas G. Lane.
Modification developed 2003-2018 by Guido Vollbeding.
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
forward DCT (Discrete Cosine Transform).

A 2-D DCT can be done by 1-D DCT on each row followed by 1-D DCT
on each column.  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.

We also provide FDCT routines with various input sample block sizes for
direct resolution reduction or enlargement and for direct resolving the
common 2x1 and 1x2 subsampling cases without additional resampling: NxN
(N=1...16), 2NxN, and Nx2N (N=1...8) pixels for one 8x8 output DCT block.

For N<8 we fill the remaining block coefficients with zero.
For N>8 we apply a partial N-point FDCT on the input samples, computing
just the lower 8 frequency coefficients and discarding the rest.

We must scale the output coefficients of the N-point FDCT appropriately
to the standard 8-point FDCT level by 8/N per 1-D pass.  This scaling
is folded into the constant multipliers (pass 2) and/or final/initial
shifting.

CAUTION: We rely on the FIX() macro except for the N=1,2,4,8 cases
since there would be too many additional constants to pre-calculate.


## Files:
jidctflt.c

jidctflt.c

Copyright (C) 1994-1998, Thomas G. Lane.
Modified 2010-2017 by Guido Vollbeding.
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 floating-point implementation of the
inverse DCT (Discrete Cosine Transform).  In the IJG code, this routine
must also perform dequantization of the input coefficients.

This implementation should be more accurate than either of the integer
IDCT implementations.  However, it may not give the same results on all
machines because of differences in roundoff behavior.  Speed will depend
on the hardware's floating point capacity.

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 a fixed-point
implementation, accuracy is lost due to imprecise representation of the
scaled quantization values.  However, that problem does not arise if
we use floating point arithmetic.


## Files:
jidctfst.c

jidctfst.c

Copyright (C) 1994-1998, Thomas G. Lane.
Modified 2015-2017 by Guido Vollbeding.
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.


## Files:
jidctint.c

jidctint.c

Copyright (C) 1991-1998, Thomas G. Lane.
Modification developed 2002-2018 by Guido Vollbeding.
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.

We also provide IDCT routines with various output sample block sizes for
direct resolution reduction or enlargement and for direct resolving the
common 2x1 and 1x2 subsampling cases without additional resampling: NxN
(N=1...16), 2NxN, and Nx2N (N=1...8) pixels for one 8x8 input DCT block.

For N<8 we simply take the corresponding low-frequency coefficients of
the 8x8 input DCT block and apply an NxN point IDCT on the sub-block
to yield the downscaled outputs.
This can be seen as direct low-pass downsampling from the DCT domain
point of view rather than the usual spatial domain point of view,
yielding significant computational savings and results at least
as good as common bilinear (averaging) spatial downsampling.

For N>8 we apply a partial NxN IDCT on the 8 input coefficients as
lower frequencies and higher frequencies assumed to be zero.
It turns out that the computational effort is similar to the 8x8 IDCT
regarding the output size.
Furthermore, the scaling and descaling is the same for all IDCT sizes.

CAUTION: We rely on the FIX() macro except for the N=1,2,4,8 cases
since there would be too many additional constants to pre-calculate.


## Files:
jinclude.h

jinclude.h

Copyright (C) 1991-1994, Thomas G. Lane.
Modified 2017-2022 by Guido Vollbeding.
This file is part of the Independent JPEG Group's software.
For conditions of distribution and use, see the accompanying README file.

This file exists to provide a single place to fix any problems with
including the wrong system include files.  (Common problems are taken
care of by the standard jconfig symbols, but on really weird systems
you may have to edit this file.)

NOTE: this file is NOT intended to be included by applications using
the JPEG library.  Most applications need only include jpeglib.h.


## Files:
jmemansi.c

jmemansi.c

Copyright (C) 1992-1996, 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 provides a simple generic implementation of the system-
dependent portion of the JPEG memory manager.  This implementation
assumes that you have the ANSI-standard library routine tmpfile().
Also, the problem of determining the amount of memory available
is shoved onto the user.


## Files:
jmemdos.c

jmemdos.c

Copyright (C) 1992-1997, 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 provides an MS-DOS-compatible implementation of the system-
dependent portion of the JPEG memory manager.  Temporary data can be
stored in extended or expanded memory as well as in regular DOS files.

If you use this file, you must be sure that NEED_FAR_POINTERS is defined
if you compile in a small-data memory model; it should NOT be defined if
you use a large-data memory model.  This file is not recommended if you
are using a flat-memory-space 386 environment such as DJGCC or Watcom C.
Also, this code will NOT work if struct fields are aligned on greater than
2-byte boundaries.

Based on code contributed by Ge' Weijers.


## Files:
jmemmac.c

jmemmac.c

Copyright (C) 1992-1997, 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.

jmemmac.c provides an Apple Macintosh implementation of the system-
dependent portion of the JPEG memory manager.

If you use jmemmac.c, then you must define USE_MAC_MEMMGR in the
JPEG_INTERNALS part of jconfig.h.

jmemmac.c uses the Macintosh toolbox routines NewPtr and DisposePtr
instead of malloc and free.  It accurately determines the amount of
memory available by using CompactMem.  Notice that if left to its
own devices, this code can chew up all available space in the
application's zone, with the exception of the rather small "slop"
factor computed in jpeg_mem_available().  The application can ensure
that more space is left over by reducing max_memory_to_use.

Large images are swapped to disk using temporary files and System 7.0+'s
temporary folder functionality.

Note that jmemmac.c depends on two features of MacOS that were first
introduced in System 7: FindFolder and the FSSpec-based calls.
If your application uses jmemmac.c and is run under System 6 or earlier,
and the jpeg library decides it needs a temporary file, it will abort,
printing error messages about requiring System 7.  (If no temporary files
are created, it will run fine.)

If you want to use jmemmac.c in an application that might be used with
System 6 or earlier, then you should remove dependencies on FindFolder
and the FSSpec calls.  You will need to replace FindFolder with some
other mechanism for finding a place to put temporary files, and you
should replace the FSSpec calls with their HFS equivalents:

    FSpDelete     ->  HDelete
    FSpGetFInfo   ->  HGetFInfo
    FSpCreate     ->  HCreate
    FSpOpenDF     ->  HOpen      *** Note: not HOpenDF ***
    FSMakeFSSpec  ->  (fill in spec by hand.)

(Use HOpen instead of HOpenDF.  HOpen is just a glue-interface to PBHOpen,
which is on all HFS macs.  HOpenDF is a System 7 addition which avoids the
ages-old problem of names starting with a period.)

Contributed by Sam Bushell (jsam@iagu.on.net) and
Dan Gildor (gyld@in-touch.com).


## Files:
jmemmgr.c

jmemmgr.c

Copyright (C) 1991-1997, Thomas G. Lane.
Modified 2011-2019 by Guido Vollbeding.
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 JPEG system-independent memory management
routines.  This code is usable across a wide variety of machines; most
of the system dependencies have been isolated in a separate file.
The major functions provided here are:
  * pool-based allocation and freeing of memory;
  * policy decisions about how to divide available memory among the
    virtual arrays;
  * control logic for swapping virtual arrays between main memory and
    backing storage.
The separate system-dependent file provides the actual backing-storage
access code, and it contains the policy decision about how much total
main memory to use.
This file is system-dependent in the sense that some of its functions
are unnecessary in some systems.  For example, if there is enough virtual
memory so that backing storage will never be used, much of the virtual
array control logic could be removed.  (Of course, if you have that much
memory then you shouldn't care about a little bit of unused code...)


## Files:
jmemname.c

jmemname.c

Copyright (C) 1992-1997, 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 provides a generic implementation of the system-dependent
portion of the JPEG memory manager.  This implementation assumes that
you must explicitly construct a name for each temp file.
Also, the problem of determining the amount of memory available
is shoved onto the user.


## Files:
jmemnobs.c

jmemnobs.c

Copyright (C) 1992-1996, Thomas G. Lane.
Modified 2019 by Guido Vollbeding.
This file is part of the Independent JPEG Group's software.
For conditions of distribution and use, see the accompanying README file.

This file provides a really simple implementation of the system-
dependent portion of the JPEG memory manager.  This implementation
assumes that no backing-store files are needed: all required space
can be obtained from malloc().
This is very portable in the sense that it'll compile on almost anything,
but you'd better have lots of main memory (or virtual memory) if you want
to process big images.
Note that the max_memory_to_use option is respected by this implementation.


## Files:
jmemsys.h

jmemsys.h

Copyright (C) 1992-1997, 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 include file defines the interface between the system-independent
and system-dependent portions of the JPEG memory manager.  No other
modules need include it.  (The system-independent portion is jmemmgr.c;
there are several different versions of the system-dependent portion.)

This file works as-is for the system-dependent memory managers supplied
in the IJG distribution.  You may need to modify it if you write a
custom memory manager.  If system-dependent changes are needed in
this file, the best method is to #ifdef them based on a configuration
symbol supplied in jconfig.h, as we have done with USE_MSDOS_MEMMGR
and USE_MAC_MEMMGR.


## Files:
jmorecfg.h

jmorecfg.h

Copyright (C) 1991-1997, Thomas G. Lane.
Modified 1997-2022 by Guido Vollbeding.
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 additional configuration options that customize the
JPEG software for special applications or support machine-dependent
optimizations.  Most users will not need to touch this file.


## Files:
jpegint.h

jpegint.h

Copyright (C) 1991-1997, Thomas G. Lane.
Modified 1997-2020 by Guido Vollbeding.
This file is part of the Independent JPEG Group's software.
For conditions of distribution and use, see the accompanying README file.

This file provides common declarations for the various JPEG modules.
These declarations are considered internal to the JPEG library; most
applications using the library shouldn't need to include this file.


## Files:
jpeglib.h

jpeglib.h

Copyright (C) 1991-1998, Thomas G. Lane.
Modified 2002-2022 by Guido Vollbeding.
This file is part of the Independent JPEG Group's software.
For conditions of distribution and use, see the accompanying README file.

This file defines the application interface for the JPEG library.
Most applications using the library need only include this file,
and perhaps jerror.h if they want to know the exact error codes.


## Files:
jpegtran.c

jpegtran.c

Copyright (C) 1995-2019, Thomas G. Lane, Guido Vollbeding.
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 command-line user interface for JPEG transcoding.
It is very similar to cjpeg.c, and partly to djpeg.c, but provides
lossless transcoding between different JPEG file formats.  It also
provides some lossless and sort-of-lossless transformations of JPEG data.


## Files:
jquant1.c

jquant1.c

Copyright (C) 1991-1996, Thomas G. Lane.
Modified 2011-2020 by Guido Vollbeding.
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 1-pass color quantization (color mapping) routines.
These routines provide mapping to a fixed color map using equally spaced
color values.  Optional Floyd-Steinberg or ordered dithering is available.


## Files:
jquant2.c

jquant2.c

Copyright (C) 1991-1996, Thomas G. Lane.
Modified 2011-2020 by Guido Vollbeding.
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 2-pass color quantization (color mapping) routines.
These routines provide selection of a custom color map for an image,
followed by mapping of the image to that color map, with optional
Floyd-Steinberg dithering.
It is also possible to use just the second pass to map to an arbitrary
externally-given color map.

Note: ordered dithering is not supported, since there isn't any fast
way to compute intercolor distances; it's unclear that ordered dither's
fundamental assumptions even hold with an irregularly spaced color map.


## Files:
jutils.c

jutils.c

Copyright (C) 1991-1996, Thomas G. Lane.
Modified 2009-2020 by Guido Vollbeding.
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 tables and miscellaneous utility routines needed
for both compression and decompression.
Note we prefix all global names with "j" to minimize conflicts with
a surrounding application.


## Files:
jversion.h

jversion.h

Copyright (C) 1991-2024, Thomas G. Lane, Guido Vollbeding.
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.


## Files:
ltmain.sh

Copyright (C) 1996-2019, 2021-2022 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.


## Files:
ltmain.sh

GNU Libtool is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

As a special exception to the GNU General Public License,
if you distribute this file as part of a program or library that
is built using GNU Libtool, you may include this file under the
same distribution terms that you use for the rest of that program.

GNU Libtool is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.


## Files:
ltmain.sh

This is free software.  There is NO warranty; not even for
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Copyright (C) 2004-2019, 2021 Bootstrap Authors

This file is dual licensed under the terms of the MIT license
<https://opensource.org/license/MIT>, and GPL version 2 or later
<http://www.gnu.org/licenses/gpl-2.0.html>.  You must apply one of
these licenses when using or redistributing this software or any of
the files within it.  See the URLs above, or the file `LICENSE`
included in the Bootstrap distribution for the full license texts.


## Files:
ltmain.sh

This is free software.  There is NO warranty; not even for
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Copyright (C) 2010-2019, 2021 Bootstrap Authors

This file is dual licensed under the terms of the MIT license
<https://opensource.org/license/MIT>, and GPL version 2 or later
<http://www.gnu.org/licenses/gpl-2.0.html>.  You must apply one of
these licenses when using or redistributing this software or any of
the files within it.  See the URLs above, or the file `LICENSE`
included in the Bootstrap distribution for the full license texts.


## Files:
ltmain.sh

This file is a library for parsing options in your shell scripts along
with assorted other useful supporting features that you can make use
of too.

For the simplest scripts you might need only:

  #!/bin/sh
  . relative/path/to/funclib.sh
  . relative/path/to/options-parser
  scriptversion=1.0
  func_options ${1+"$@"}
  eval set dummy "$func_options_result"; shift
  ...rest of your script...

In order for the '--version' option to work, you will need to have a
suitably formatted comment like the one at the top of this file
starting with '# Written by ' and ending with '# Copyright'.

For '-h' and '--help' to work, you will also need a one line
description of your script's purpose in a comment directly above the
'# Written by ' line, like the one at the top of this file.

The default options also support '--debug', which will turn on shell
execution tracing (see the comment above debug_cmd below for another
use), and '--verbose' and the func_verbose function to allow your script
to display verbose messages only when your user has specified
'--verbose'.

After sourcing this file, you can plug in processing for additional
options by amending the variables from the 'Configuration' section
below, and following the instructions in the 'Option parsing'
section further down.


## Files:
ltmain.sh

func_version
------------
Echo version message to standard output and exit.
The version message is extracted from the calling file's header
comments, with leading '# ' stripped:
  1. First display the progname and version
  2. Followed by the header comment line matching  /^# Written by /
  3. Then a blank line followed by the first following line matching
     /^# Copyright /
  4. Immediately followed by any lines between the previous matches,
     except lines preceding the intervening completely blank line.
For example, see the header comments of this file.


## Files:
rdbmp.c

rdbmp.c

Copyright (C) 1994-1996, Thomas G. Lane.
Modified 2009-2019 by Guido Vollbeding.
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 routines to read input images in Microsoft "BMP"
format (MS Windows 3.x, OS/2 1.x, and OS/2 2.x flavors).
Currently, only 8-, 24-, and 32-bit images are supported, not 1-bit or
4-bit (feeding such low-depth images into JPEG would be silly anyway).
Also, we don't support RLE-compressed files.

These routines may need modification for non-Unix environments or
specialized applications.  As they stand, they assume input from
an ordinary stdio stream.  They further assume that reading begins
at the start of the file; start_input may need work if the
user interface has already read some data (e.g., to determine that
the file is indeed BMP format).

This code contributed by James Arthur Boucher.


## Files:
rdcolmap.c

rdcolmap.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 implements djpeg's "-map file" switch.  It reads a source image
and constructs a colormap to be supplied to the JPEG decompressor.

Currently, these file formats are supported for the map file:
  GIF: the contents of the GIF's global colormap are used.
  PPM (either text or raw flavor): the entire file is read and
     each unique pixel value is entered in the map.
Note that reading a large PPM file will be horrendously slow.
Typically, a PPM-format map file should contain just one pixel
of each desired color.  Such a file can be extracted from an
ordinary image PPM file with ppmtomap(1).

Rescaling a PPM that has a maxval unequal to MAXJSAMPLE is not
currently implemented.


## Files:
rdcolmap.c
rdppm.c

  Portions of this code are based on the PBMPLUS library, which is:
*
* Copyright (C) 1988 by Jef Poskanzer.
*
* Permission to use, copy, modify, and distribute this software and its
* documentation for any purpose and without fee is hereby granted, provided
* that the above copyright notice appear in all copies and that both that
* copyright notice and this permission notice appear in supporting
* documentation.  This software is provided "as is" without express or
* implied warranty.


## Files:
rdgif.c

rdgif.c

Copyright (C) 1991-1996, Thomas G. Lane.
Modified 2019-2020 by Guido Vollbeding.
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 routines to read input images in GIF format.

These routines may need modification for non-Unix environments or
specialized applications.  As they stand, they assume input from
an ordinary stdio stream.  They further assume that reading begins
at the start of the file; start_input may need work if the
user interface has already read some data (e.g., to determine that
the file is indeed GIF format).


## Files:
rdgif.c

This code is loosely based on giftoppm from the PBMPLUS distribution
of Feb. 1991.  That file contains the following copyright notice:
+-------------------------------------------------------------------+
| Copyright 1990, David Koblas.                                     |
|   Permission to use, copy, modify, and distribute this software   |
|   and its documentation for any purpose and without fee is hereby |
|   granted, provided that the above copyright notice appear in all |
|   copies and that both that copyright notice and this permission  |
|   notice appear in supporting documentation.  This software is    |
|   provided "as is" without express or implied warranty.           |
+-------------------------------------------------------------------+


## Files:
rdjpgcom.c

rdjpgcom.c

Copyright (C) 1994-1997, Thomas G. Lane.
Modified 2009 by Bill Allombert, Guido Vollbeding.
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 very simple stand-alone application that displays
the text in COM (comment) markers in a JFIF file.
This may be useful as an example of the minimum logic needed to parse
JPEG markers.


## Files:
rdppm.c

rdppm.c

Copyright (C) 1991-1997, Thomas G. Lane.
Modified 2009-2020 by Bill Allombert, Guido Vollbeding.
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 routines to read input images in PPM/PGM format.
The extended 2-byte-per-sample raw PPM/PGM formats are supported.
The PBMPLUS library is NOT required to compile this software
(but it is highly useful as a set of PPM image manipulation programs).

These routines may need modification for non-Unix environments or
specialized applications.  As they stand, they assume input from
an ordinary stdio stream.  They further assume that reading begins
at the start of the file; start_input may need work if the
user interface has already read some data (e.g., to determine that
the file is indeed PPM format).


## Files:
rdrle.c

rdrle.c

Copyright (C) 1991-1996, Thomas G. Lane.
Modified 2019 by Guido Vollbeding.
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 routines to read input images in Utah RLE format.
The Utah Raster Toolkit library is required (version 3.1 or later).

These routines may need modification for non-Unix environments or
specialized applications.  As they stand, they assume input from
an ordinary stdio stream.  They further assume that reading begins
at the start of the file; start_input may need work if the
user interface has already read some data (e.g., to determine that
the file is indeed RLE format).

Based on code contributed by Mike Lijewski,
with updates from Robert Hutchinson.


## Files:
rdswitch.c

 rdswitch.c

 Copyright (C) 1991-1996, Thomas G. Lane.
 Modified 2003-2020 by Guido Vollbeding.
 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 routines to process some of cjpeg's more complicated
 command-line switches.  Switches processed here are:
	-qtables file		Read quantization tables from text file
	-scans file		Read scan script from text file
	-quality N[,N,...]	Set quality ratings
	-qslots N[,N,...]	Set component quantization table selectors
	-sample HxV[,HxV,...]	Set component sampling factors


## Files:
rdtarga.c

rdtarga.c

Copyright (C) 1991-1996, Thomas G. Lane.
Modified 2017-2019 by Guido Vollbeding.
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 routines to read input images in Targa format.

These routines may need modification for non-Unix environments or
specialized applications.  As they stand, they assume input from
an ordinary stdio stream.  They further assume that reading begins
at the start of the file; start_input may need work if the
user interface has already read some data (e.g., to determine that
the file is indeed Targa format).

Based on code contributed by Lee Daniel Crocker.


## Files:
transupp.c

transupp.c

Copyright (C) 1997-2023, Thomas G. Lane, Guido Vollbeding.
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 image transformation routines and other utility code
used by the jpegtran sample application.  These are NOT part of the core
JPEG library.  But we keep these routines separate from jpegtran.c to
ease the task of maintaining jpegtran-like programs that have other user
interfaces.


## Files:
transupp.h

transupp.h

Copyright (C) 1997-2019, Thomas G. Lane, Guido Vollbeding.
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 declarations for image transformation routines and
other utility code used by the jpegtran sample application.  These are
NOT part of the core JPEG library.  But we keep these routines separate
from jpegtran.c to ease the task of maintaining jpegtran-like programs
that have other user interfaces.

NOTE: all the routines declared here have very specific requirements
about when they are to be executed during the reading and writing of the
source and destination files.  See the comments in transupp.c, or see
jpegtran.c for an example of correct usage.


## Files:
wrbmp.c

wrbmp.c

Copyright (C) 1994-1996, Thomas G. Lane.
Modified 2017-2019 by Guido Vollbeding.
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 routines to write output images in Microsoft "BMP"
format (MS Windows 3.x and OS/2 1.x flavors).
Either 8-bit colormapped or 24-bit full-color format can be written.
No compression is supported.

These routines may need modification for non-Unix environments or
specialized applications.  As they stand, they assume output to
an ordinary stdio stream.

This code contributed by James Arthur Boucher.


## Files:
wrgif.c

wrgif.c

Copyright (C) 1991-1996, Thomas G. Lane.
Modified 2015-2019 by Guido Vollbeding.
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 routines to write output images in GIF format.

These routines may need modification for non-Unix environments or
specialized applications.  As they stand, they assume output to
an ordinary stdio stream.


## Files:
wrgif.c

This code is loosely based on ppmtogif from the PBMPLUS distribution
of Feb. 1991.  That file contains the following copyright notice:
   Based on GIFENCODE by David Rowley <mgardi@watdscu.waterloo.edu>.
   Lempel-Ziv compression based on "compress" by Spencer W. Thomas et al.
   Copyright (C) 1989 by Jef Poskanzer.
   Permission to use, copy, modify, and distribute this software and its
   documentation for any purpose and without fee is hereby granted, provided
   that the above copyright notice appear in all copies and that both that
   copyright notice and this permission notice appear in supporting
   documentation.  This software is provided "as is" without express or
   implied warranty.


## Files:
wrjpgcom.c

wrjpgcom.c

Copyright (C) 1994-1997, Thomas G. Lane.
Modified 2015-2017 by Guido Vollbeding.
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 very simple stand-alone application that inserts
user-supplied text as a COM (comment) marker in a JFIF file.
This may be useful as an example of the minimum logic needed to parse
JPEG markers.


## Files:
wrppm.c

wrppm.c

Copyright (C) 1991-1996, Thomas G. Lane.
Modified 2009-2020 by Guido Vollbeding.
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 routines to write output images in PPM/PGM format.
The extended 2-byte-per-sample raw PPM/PGM formats are supported.
The PBMPLUS library is NOT required to compile this software
(but it is highly useful as a set of PPM image manipulation programs).

These routines may need modification for non-Unix environments or
specialized applications.  As they stand, they assume output to
an ordinary stdio stream.


## Files:
wrrle.c

wrrle.c

Copyright (C) 1991-1996, Thomas G. Lane.
Modified 2017-2019 by Guido Vollbeding.
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 routines to write output images in RLE format.
The Utah Raster Toolkit library is required (version 3.1 or later).

These routines may need modification for non-Unix environments or
specialized applications.  As they stand, they assume output to
an ordinary stdio stream.

Based on code contributed by Mike Lijewski,
with updates from Robert Hutchinson.


## Files:
wrtarga.c

wrtarga.c

Copyright (C) 1991-1996, Thomas G. Lane.
Modified 2015-2019 by Guido Vollbeding.
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 routines to write output images in Targa format.

These routines may need modification for non-Unix environments or
specialized applications.  As they stand, they assume output to
an ordinary stdio stream.

Based on code contributed by Lee Daniel Crocker.