Dec 072017
The Independent JPEG Group's JPEG software. Full C source code.
File JPSRC2.ZIP from The Programmer’s Corner in
Category C Source Code
The Independent JPEG Group’s JPEG software. Full C source code.
File Name File Size Zip Size Zip Type
ANSI2KNR.C 16738 6296 deflated
ARCHITEC 62702 19837 deflated
CHANGELO 1143 642 deflated
CJPEG.1 3895 1827 deflated
CODINGRU 4047 1938 deflated
CONFIG.C 13711 3922 deflated
DJPEG.1 2937 1334 deflated
EGETOPT.C 7512 2840 deflated
JBSMOOTH.C 3398 1446 deflated
JCARITH.C 1197 619 deflated
JCCOLOR.C 5835 1558 deflated
JCDEFLTS.C 14251 4404 deflated
JCEXPAND.C 2016 863 deflated
JCHUFF.C 20179 5679 deflated
JCMAIN.C 10716 3784 deflated
JCMASTER.C 4148 1484 deflated
JCMCU.C 6010 2192 deflated
JCONFIG.H 11159 3977 deflated
JCPIPE.C 26908 5548 deflated
JCSAMPLE.C 3890 1263 deflated
JDARITH.C 1180 611 deflated
JDCOLOR.C 5579 1626 deflated
JDDEFLTS.C 4340 1749 deflated
JDHUFF.C 8219 2822 deflated
JDMAIN.C 9336 3274 deflated
JDMASTER.C 5729 1910 deflated
JDMCU.C 3775 1329 deflated
JDPIPE.C 48760 9014 deflated
JDSAMPLE.C 3786 1217 deflated
JERROR.C 2131 964 deflated
JFWDDCT.C 7353 2654 deflated
JINCLUDE.H 3674 1550 deflated
JPEGDATA.H 36358 8961 deflated
JQUANT1.C 13479 3913 deflated
JQUANT2.C 3545 1281 deflated
JRDGIF.C 20522 6278 deflated
JRDJFIF.C 18823 5352 deflated
JRDPPM.C 9285 2630 deflated
JRDRLE.C 11761 3289 deflated
JRDTARGA.C 14339 4259 deflated
JREVDCT.C 7480 2660 deflated
JUTILS.C 3063 1183 deflated
JVERSION.H 366 236 deflated
JVIRTMEM.C 19975 5177 deflated
JWRGIF.C 14676 4894 deflated
JWRJFIF.C 12074 3659 deflated
JWRPPM.C 4534 1427 deflated
JWRRLE.C 6933 2559 deflated
JWRTARGA.C 6199 1962 deflated
MAKCJPEG.CF 252 135 deflated
MAKCJPEG.LNK 315 140 deflated
MAKCJPEG.LST 224 112 deflated
MAKDJPEG.CF 276 145 deflated
MAKDJPEG.LNK 345 149 deflated
MAKDJPEG.LST 248 121 deflated
MAKEFILE.ANS 5906 1897 deflated
MAKEFILE.MAN 5346 1613 deflated
MAKEFILE.MC5 5631 1704 deflated
MAKEFILE.MC6 5375 1607 deflated
MAKEFILE.PWC 5190 1559 deflated
MAKEFILE.SAS 5772 1824 deflated
MAKEFILE.TC 4968 1383 deflated
MAKEFILE.UNI 6497 2051 deflated
MAKLJPEG.CF 415 168 deflated
README 16239 6651 deflated
SETUP 11666 4757 deflated
TESTIMG.JPG 4383 4223 deflated
TESTIMG.PPM 46890 41341 deflated
TESTORIG.JPG 4380 4220 deflated
USAGE 7669 3239 deflated

Download File JPSRC2.ZIP Here

Contents of the README file

The Independent JPEG Group's JPEG software

README for release 2 of 13-Dec-91

This distribution contains the second 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.

For installation instructions, see file SETUP; for usage instructions, see
file USAGE (or the cjpeg.1 and djpeg.1 manual pages).

This software is still undergoing revision. Updated versions may be obtained
by FTP or UUCP to and other archive sites; see ARCHIVE LOCATIONS
below for details.

If you intend to become a serious user of this software, please contact
[email protected] to be added to our electronic mailing list. Then
you'll be notified of updates and have a chance to participate in discussions,

This software is the work of Tom Lane, Philip Gladstone, Luis Ortiz,
Lee Crocker, and other members of the Independent JPEG Group.


The CompuServe distribution has a few differences from the standard Usenet
distribution to accommodate common microcomputer file formats. First, the
filenames have been truncated to eight characters plus a three-character
extension. This affects the following files:

changelog --> changelo
architecture --> architec
codingrules --> codingru
makefile.ansi --> makefile.ans
makefile.unix --> makefile.uni
makefile.manx -->

Second, all text files not specific to non-MSDOS environments have CR/LF
line terminations instead of LF only.


useful for anything, nor to be compatible with subsequent releases, nor to be
an accurate implementation of the JPEG standard. (See LEGAL ISSUES for even
more disclaimers.)

Please report any problems with this software to [email protected]


This distribution contains 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
"real-world" scenes; cartoons and other non-realistic images are not its
strong suit. JPEG is lossy, meaning that the output image is not necessarily
identical to the input image. Hence you should not use JPEG if you have to
have identical output bits. However, on typical images of real-world scenes,
very good compression levels can be obtained with no visible change, and
amazingly high compression levels can be obtained if you can tolerate a
low-quality image. For more details, see the references, or just experiment
with various compression settings.

The software implements JPEG baseline and extended-sequential 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 process; see
LEGAL ISSUES. At present we have made no provision for supporting the
progressive or lossless processes defined in the standard.

The present software is still largely in the prototype stage. It does not
support all possible variants of the JPEG standard, and some functions have
rather slow and/or crude implementations. However, it is useful already.

The emphasis in designing this software has been on achieving portability and
flexibility, while also making it fast enough to be useful. We have not yet
undertaken serious performance measurement or tuning; we intend to do so in
the future.

This software can be used on several levels:

* As canned software for JPEG compression and decompression. Just edit the
Makefile and configuration files as needed (see file SETUP), compile and go.
Members of the independent JPEG group will improve the out-of-the-box
functionality and speed as time goes on.

* As the basis for other JPEG programs. For example, you could incorporate
the decompressor into a general image viewing package by replacing the
output module with write-to-screen functions. For an implementation on
specific hardware, you might want to replace some of the inner loops with
assembly code. For a non-command-line-driven system, you might want a
different user interface. (Members of the group will be producing Macintosh
and Amiga versions with more appropriate user interfaces, for example.)

* As a toolkit for experimentation with JPEG and JPEG-like algorithms. Most
of the individual decisions you might want to mess with are packaged up into
separate modules. For example, the details of color-space conversion and
subsampling techniques are each localized in one compressor and one
decompressor module. You'd probably also want to extend the user interface
to give you more detailed control over the JPEG compression parameters.

In particular, we welcome the use of this software as the basis for commercial
products; no royalty is required.


The "official" archive site for this software is (Internet
address or The most recent released version can
always be found there in directory graphics/jpeg. This particular version
will be archived as jpegsrc.v2.tar.Z. If you are on the Internet, you can
retrieve files from UUNET by anonymous FTP. If you don't have FTP access,
UUNET's archives are also available via UUCP; contact [email protected]
for information on retrieving files that way.

Various other Internet sites maintain copies of the UUNET file, which may or
may not be up-to-date. In Europe, try (; look in
directory pub/graphics/programs/jpeg).

You can also obtain this software from CompuServe, in the GRAPHSUPPORT forum
(GO PICS), library 10; this version will be file

If you are not reasonably handy at configuring and installing portable C
programs, you may have some difficulty installing this package. You may
prefer to obtain a pre-built executable version. A collection of pre-built
executables for various machines is currently available for anonymous FTP at ( --- this number is due to change soon);
look under /pub/JPEG. The administrators of this system ask that FTP traffic
be limited to non-prime hours. For more information on this archive, please
contact Steve Davis ([email protected]). This collection is not maintained by
the Independent JPEG Group, and programs in it may not be the latest version.


You will probably want Jef Poskanzer's PBMPLUS image 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. You can FTP
this free software from (contrib/pbmplus*.tar.Z) or (pbmplus*.tar.Z). Unfortunately PBMPLUS is not nearly as
portable as the JPEG software is; you are likely to have difficulty making it
work on any non-Unix machine.

If you are using X Windows you might want to use the xv or xloadimage viewers
to save yourself the trouble of converting PPM to some other format. Both of
these can be found in the contrib directory at
There will soon be a new release of xv that incorporates our software and thus
can read and write JPEG files directly. (NOTE: since xv internally reduces
all images to 8 bits/pixel, a JPEG file written by xv will not be very high
quality. Caveat user.)


Handmade Software's shareware PC program GIF2JPG produces files that are
totally incompatible with our programs. They use a proprietary format that is
an amalgam of GIF and JPEG representations. However, you can force GIF2JPG
to produce compatible files with its -j switch, and their decompression
program JPG2GIF can read our files (at least ones produced with our default
option settings).

Unfortunately, most commercial JPEG implementations are also incompatible as
of this writing, especially programs released before summer 1991. The root of
the problem is that the ISO JPEG committee failed to specify a concrete file
format. Many 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 we expect
that it will become the de facto standard. JFIF is a minimal representation;
work is also going forward to incorporate JPEG compression into the TIFF
standard, for use in "high end" applications that need to record a lot of
additional data about an image. We intend to support JPEG-in-TIFF in the
future. We hope that these two formats will be sufficient and that other,
incompatible JPEG file formats will not proliferate.

Indeed, part of the reason for developing and releasing this free software is
to help force rapid convergence to de facto standards for JPEG file formats.


The best and most readily available introduction to the JPEG compression
algorithm is Wallace's article in the April '91 CACM:
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.) We highly recommend reading that
article before trying to understand the innards of any JPEG software.

For more detail about the JPEG standard you pretty much have to go to the
draft standard (which is not nearly as intelligible as Wallace's article).
The standard is not now available electronically; you must order a paper copy
through ISO. In the US, copies may be ordered from ANSI Sales at (212)
642-4900. The standard is divided into two parts: Part 1 is the actual
specification, and Part 2 covers compliance testing methods. The current
"committee draft" version of Part 1 is titled "Digital Compression and Coding
of Continuous-tone Still Images, Part 1: Requirements and guidelines" and has
document number ISO/IEC CD 10918-1. (The alternate number SC2 N2215 should
also be mentioned when ordering.) This draft is expected to be superseded by
the Draft International Standard version around the end of November 1991.
Ordering info will be the same as above, but replace "CD" with "DIS" in the
document number (alternate number not yet known). The committee draft of
Part 2 is expected to be available around the end of December 1991. It will
be titled "Digital Compression and Coding of Continuous-tone Still Images,
Part 2: Compliance testing" and will have document number ISO/IEC CD 10918-2
(alternate number not yet known).

The JPEG standard does not specify all details of an interchangeable file
format. For the omitted details we follow the "JFIF" conventions, revision
1.01. A copy of the JFIF spec is available from:
Literature Department
C-Cube Microsystems, Inc.
399A West Trimble Road
San Jose, CA 95131
(408) 944-6300
Requests can also be e-mailed to [email protected] The same source can
supply copies of the draft JPEG-in-TIFF specs.

If you want to understand this implementation, start by reading the
"architecture" documentation file. Please read "codingrules" if you want to
contribute any code.


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, 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
(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.

Permission is NOT granted for the use of any author's name or author's 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 product generated from the JPEG code, this does not limit you more than
the foregoing paragraphs do.

It appears that the arithmetic coding option of the JPEG spec is covered by
patents owned by IBM and AT&T, as well as a pending Japanese patent of
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
people will choose to use it. If you do obtain the necessary licenses,
contact [email protected] for a copy of our arithmetic coding modules.)
So far as we are aware, there are no patent restrictions on the remaining

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."


Many of the modules need fleshing out to provide more complete
implementations, or to provide faster paths for common cases. The greatest
needs are for (a) decent color quantization, and (b) a memory manager
implementation that can work in limited memory by swapping "big" images to
temporary files. I (Tom Lane) am going to work on color quantization next.
Volunteers to write a PC memory manager, or to work on any other modules, are

We'd appreciate it if people would compile and check out the code on as wide a
variety of systems as possible, and report any portability problems
encountered (with solutions, if possible). Checks of file compatibility with
other JPEG implementations would also be of interest. Finally, we would
appreciate code profiles showing where the most time is spent, especially on
unusual systems.

Please send bug reports, offers of help, etc. to [email protected]
From CompuServe, use the address ">internet:[email protected]".

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