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+The Independent JPEG Group's JPEG software
+README for release 8c of 16-Jan-2011
+This distribution contains the eighth 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,
+Julian Minguillon, Luis Ortiz, George Phillips, Davide Rossi, Ge' Weijers,
+and other members of the Independent JPEG Group.
+IJG is not affiliated with the official ISO JPEG standards committee.
+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.
+ 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.
+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 gray-scale 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.
+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) 1991-2011, 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
+(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
+We specifically permit and encourage the use of this software as the basis of
+commercial products, provided that all warranty or liability claims are
+assumed by the product vendor.
+ansi2knr.c is included in this distribution by permission of L. Peter Deutsch,
+sole proprietor of its copyright holder, Aladdin Enterprises of Menlo Park, CA.
+ansi2knr.c is NOT covered by the above copyright and conditions, but instead
+by the usual distribution terms of the Free Software Foundation; principally,
+that you must include source code if you redistribute it. (See the file
+ansi2knr.c for full details.) However, since ansi2knr.c is not needed as part
+of any program generated from the IJG code, this does not limit you more than
+the foregoing paragraphs do.
+The Unix configuration script "configure" was produced with GNU Autoconf.
+It is copyright by the Free Software Foundation but is freely distributable.
+The same holds for its supporting scripts (config.guess, config.sub, Another support script, install-sh, is copyright by X Consortium
+but is also freely distributable.
+The IJG distribution formerly included code to read and write GIF files.
+To avoid entanglement with the Unisys LZW patent, GIF reading support has
+been removed altogether, and the GIF writer has been simplified to produce
+"uncompressed GIFs". This technique does not use the LZW algorithm; the
+resulting GIF files are larger than usual, but are readable by all standard
+GIF decoders.
+We are required to state that
+ "The Graphics Interchange Format(c) is the Copyright property of
+ CompuServe Incorporated. GIF(sm) is a Service Mark property of
+ CompuServe Incorporated."
+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 PostScript file containing a revised version of Wallace's article is
+available at 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
+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 introduces an implementation of the JPEG SmartScale extension
+which is specified in 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 the document is Revision 3.
+The JPEG standard does not specify all details of an interchangeable file
+format. For the omitted details we follow the "JFIF" conventions, revision
+1.02. JFIF 1.02 has been adopted as an Ecma International Technical Report
+and thus received a formal publication status. It is available as a free
+download in PDF format from
+A PostScript version of the JFIF document is available at
+ There is also a plain text version at
+, but it is missing the figures.
+The TIFF 6.0 file format specification can be obtained by FTP from
+ 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
+ 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.
+The "official" archive site for this software is
+The most recent released version can always be found there in
+directory "files". This particular version will be archived as
+, and in Windows-compatible
+"zip" archive format as
+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
+and other news.answers archive sites, including the official news.answers
+archive at
+If you don't have Web or FTP access, send e-mail to
+with body
+ send usenet/news.answers/jpeg-faq/part1
+ send usenet/news.answers/jpeg-faq/part2
+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 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 site.
+Last but not least special thank to Thomas G. Lane for the original
+design and development of this singular software package.
+The ISO JPEG standards committee actually promotes different formats like
+"JPEG 2000" or "JPEG XR" which are incompatible with original DCT-based
+JPEG and which are based on faulty technologies. IJG therefore does not
+and will not support such momentary mistakes (see REFERENCES).
+We have little or no sympathy for the promotion of these 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.)
+Version 8 is the first release of a new generation JPEG standard
+to overcome the limitations of the original JPEG specification.
+More features are being prepared for coming releases...
+Please send bug reports, offers of help, etc. to