nuclear@14: The Independent JPEG Group's JPEG software nuclear@14: ========================================== nuclear@14: nuclear@14: README for release 8c of 16-Jan-2011 nuclear@14: ==================================== nuclear@14: nuclear@14: This distribution contains the eighth public release of the Independent JPEG nuclear@14: Group's free JPEG software. You are welcome to redistribute this software and nuclear@14: to use it for any purpose, subject to the conditions under LEGAL ISSUES, below. nuclear@14: nuclear@14: This software is the work of Tom Lane, Guido Vollbeding, Philip Gladstone, nuclear@14: Bill Allombert, Jim Boucher, Lee Crocker, Bob Friesenhahn, Ben Jackson, nuclear@14: Julian Minguillon, Luis Ortiz, George Phillips, Davide Rossi, Ge' Weijers, nuclear@14: and other members of the Independent JPEG Group. nuclear@14: nuclear@14: IJG is not affiliated with the official ISO JPEG standards committee. nuclear@14: nuclear@14: nuclear@14: DOCUMENTATION ROADMAP nuclear@14: ===================== nuclear@14: nuclear@14: This file contains the following sections: nuclear@14: nuclear@14: OVERVIEW General description of JPEG and the IJG software. nuclear@14: LEGAL ISSUES Copyright, lack of warranty, terms of distribution. nuclear@14: REFERENCES Where to learn more about JPEG. nuclear@14: ARCHIVE LOCATIONS Where to find newer versions of this software. nuclear@14: ACKNOWLEDGMENTS Special thanks. nuclear@14: FILE FORMAT WARS Software *not* to get. nuclear@14: TO DO Plans for future IJG releases. nuclear@14: nuclear@14: Other documentation files in the distribution are: nuclear@14: nuclear@14: User documentation: nuclear@14: install.txt How to configure and install the IJG software. nuclear@14: usage.txt Usage instructions for cjpeg, djpeg, jpegtran, nuclear@14: rdjpgcom, and wrjpgcom. nuclear@14: *.1 Unix-style man pages for programs (same info as usage.txt). nuclear@14: wizard.txt Advanced usage instructions for JPEG wizards only. nuclear@14: change.log Version-to-version change highlights. nuclear@14: Programmer and internal documentation: nuclear@14: libjpeg.txt How to use the JPEG library in your own programs. nuclear@14: example.c Sample code for calling the JPEG library. nuclear@14: structure.txt Overview of the JPEG library's internal structure. nuclear@14: filelist.txt Road map of IJG files. nuclear@14: coderules.txt Coding style rules --- please read if you contribute code. nuclear@14: nuclear@14: Please read at least the files install.txt and usage.txt. Some information nuclear@14: can also be found in the JPEG FAQ (Frequently Asked Questions) article. See nuclear@14: ARCHIVE LOCATIONS below to find out where to obtain the FAQ article. nuclear@14: nuclear@14: If you want to understand how the JPEG code works, we suggest reading one or nuclear@14: more of the REFERENCES, then looking at the documentation files (in roughly nuclear@14: the order listed) before diving into the code. nuclear@14: nuclear@14: nuclear@14: OVERVIEW nuclear@14: ======== nuclear@14: nuclear@14: This package contains C software to implement JPEG image encoding, decoding, nuclear@14: and transcoding. JPEG (pronounced "jay-peg") is a standardized compression nuclear@14: method for full-color and gray-scale images. nuclear@14: nuclear@14: This software implements JPEG baseline, extended-sequential, and progressive nuclear@14: compression processes. Provision is made for supporting all variants of these nuclear@14: processes, although some uncommon parameter settings aren't implemented yet. nuclear@14: We have made no provision for supporting the hierarchical or lossless nuclear@14: processes defined in the standard. nuclear@14: nuclear@14: We provide a set of library routines for reading and writing JPEG image files, nuclear@14: plus two sample applications "cjpeg" and "djpeg", which use the library to nuclear@14: perform conversion between JPEG and some other popular image file formats. nuclear@14: The library is intended to be reused in other applications. nuclear@14: nuclear@14: In order to support file conversion and viewing software, we have included nuclear@14: considerable functionality beyond the bare JPEG coding/decoding capability; nuclear@14: for example, the color quantization modules are not strictly part of JPEG nuclear@14: decoding, but they are essential for output to colormapped file formats or nuclear@14: colormapped displays. These extra functions can be compiled out of the nuclear@14: library if not required for a particular application. nuclear@14: nuclear@14: We have also included "jpegtran", a utility for lossless transcoding between nuclear@14: different JPEG processes, and "rdjpgcom" and "wrjpgcom", two simple nuclear@14: applications for inserting and extracting textual comments in JFIF files. nuclear@14: nuclear@14: The emphasis in designing this software has been on achieving portability and nuclear@14: flexibility, while also making it fast enough to be useful. In particular, nuclear@14: the software is not intended to be read as a tutorial on JPEG. (See the nuclear@14: REFERENCES section for introductory material.) Rather, it is intended to nuclear@14: be reliable, portable, industrial-strength code. We do not claim to have nuclear@14: achieved that goal in every aspect of the software, but we strive for it. nuclear@14: nuclear@14: We welcome the use of this software as a component of commercial products. nuclear@14: No royalty is required, but we do ask for an acknowledgement in product nuclear@14: documentation, as described under LEGAL ISSUES. nuclear@14: nuclear@14: nuclear@14: LEGAL ISSUES nuclear@14: ============ nuclear@14: nuclear@14: In plain English: nuclear@14: nuclear@14: 1. We don't promise that this software works. (But if you find any bugs, nuclear@14: please let us know!) nuclear@14: 2. You can use this software for whatever you want. You don't have to pay us. nuclear@14: 3. You may not pretend that you wrote this software. If you use it in a nuclear@14: program, you must acknowledge somewhere in your documentation that nuclear@14: you've used the IJG code. nuclear@14: nuclear@14: In legalese: nuclear@14: nuclear@14: The authors make NO WARRANTY or representation, either express or implied, nuclear@14: with respect to this software, its quality, accuracy, merchantability, or nuclear@14: fitness for a particular purpose. This software is provided "AS IS", and you, nuclear@14: its user, assume the entire risk as to its quality and accuracy. nuclear@14: nuclear@14: This software is copyright (C) 1991-2011, Thomas G. Lane, Guido Vollbeding. nuclear@14: All Rights Reserved except as specified below. nuclear@14: nuclear@14: Permission is hereby granted to use, copy, modify, and distribute this nuclear@14: software (or portions thereof) for any purpose, without fee, subject to these nuclear@14: conditions: nuclear@14: (1) If any part of the source code for this software is distributed, then this nuclear@14: README file must be included, with this copyright and no-warranty notice nuclear@14: unaltered; and any additions, deletions, or changes to the original files nuclear@14: must be clearly indicated in accompanying documentation. nuclear@14: (2) If only executable code is distributed, then the accompanying nuclear@14: documentation must state that "this software is based in part on the work of nuclear@14: the Independent JPEG Group". nuclear@14: (3) Permission for use of this software is granted only if the user accepts nuclear@14: full responsibility for any undesirable consequences; the authors accept nuclear@14: NO LIABILITY for damages of any kind. nuclear@14: nuclear@14: These conditions apply to any software derived from or based on the IJG code, nuclear@14: not just to the unmodified library. If you use our work, you ought to nuclear@14: acknowledge us. nuclear@14: nuclear@14: Permission is NOT granted for the use of any IJG author's name or company name nuclear@14: in advertising or publicity relating to this software or products derived from nuclear@14: it. This software may be referred to only as "the Independent JPEG Group's nuclear@14: software". nuclear@14: nuclear@14: We specifically permit and encourage the use of this software as the basis of nuclear@14: commercial products, provided that all warranty or liability claims are nuclear@14: assumed by the product vendor. nuclear@14: nuclear@14: nuclear@14: ansi2knr.c is included in this distribution by permission of L. Peter Deutsch, nuclear@14: sole proprietor of its copyright holder, Aladdin Enterprises of Menlo Park, CA. nuclear@14: ansi2knr.c is NOT covered by the above copyright and conditions, but instead nuclear@14: by the usual distribution terms of the Free Software Foundation; principally, nuclear@14: that you must include source code if you redistribute it. (See the file nuclear@14: ansi2knr.c for full details.) However, since ansi2knr.c is not needed as part nuclear@14: of any program generated from the IJG code, this does not limit you more than nuclear@14: the foregoing paragraphs do. nuclear@14: nuclear@14: The Unix configuration script "configure" was produced with GNU Autoconf. nuclear@14: It is copyright by the Free Software Foundation but is freely distributable. nuclear@14: The same holds for its supporting scripts (config.guess, config.sub, nuclear@14: ltmain.sh). Another support script, install-sh, is copyright by X Consortium nuclear@14: but is also freely distributable. nuclear@14: nuclear@14: The IJG distribution formerly included code to read and write GIF files. nuclear@14: To avoid entanglement with the Unisys LZW patent, GIF reading support has nuclear@14: been removed altogether, and the GIF writer has been simplified to produce nuclear@14: "uncompressed GIFs". This technique does not use the LZW algorithm; the nuclear@14: resulting GIF files are larger than usual, but are readable by all standard nuclear@14: GIF decoders. nuclear@14: nuclear@14: We are required to state that nuclear@14: "The Graphics Interchange Format(c) is the Copyright property of nuclear@14: CompuServe Incorporated. GIF(sm) is a Service Mark property of nuclear@14: CompuServe Incorporated." nuclear@14: nuclear@14: nuclear@14: REFERENCES nuclear@14: ========== nuclear@14: nuclear@14: We recommend reading one or more of these references before trying to nuclear@14: understand the innards of the JPEG software. nuclear@14: nuclear@14: The best short technical introduction to the JPEG compression algorithm is nuclear@14: Wallace, Gregory K. "The JPEG Still Picture Compression Standard", nuclear@14: Communications of the ACM, April 1991 (vol. 34 no. 4), pp. 30-44. nuclear@14: (Adjacent articles in that issue discuss MPEG motion picture compression, nuclear@14: applications of JPEG, and related topics.) If you don't have the CACM issue nuclear@14: handy, a PostScript file containing a revised version of Wallace's article is nuclear@14: available at http://www.ijg.org/files/wallace.ps.gz. The file (actually nuclear@14: a preprint for an article that appeared in IEEE Trans. Consumer Electronics) nuclear@14: omits the sample images that appeared in CACM, but it includes corrections nuclear@14: and some added material. Note: the Wallace article is copyright ACM and IEEE, nuclear@14: and it may not be used for commercial purposes. nuclear@14: nuclear@14: A somewhat less technical, more leisurely introduction to JPEG can be found in nuclear@14: "The Data Compression Book" by Mark Nelson and Jean-loup Gailly, published by nuclear@14: M&T Books (New York), 2nd ed. 1996, ISBN 1-55851-434-1. This book provides nuclear@14: good explanations and example C code for a multitude of compression methods nuclear@14: including JPEG. It is an excellent source if you are comfortable reading C nuclear@14: code but don't know much about data compression in general. The book's JPEG nuclear@14: sample code is far from industrial-strength, but when you are ready to look nuclear@14: at a full implementation, you've got one here... nuclear@14: nuclear@14: The best currently available description of JPEG is the textbook "JPEG Still nuclear@14: Image Data Compression Standard" by William B. Pennebaker and Joan L. nuclear@14: Mitchell, published by Van Nostrand Reinhold, 1993, ISBN 0-442-01272-1. nuclear@14: Price US$59.95, 638 pp. The book includes the complete text of the ISO JPEG nuclear@14: standards (DIS 10918-1 and draft DIS 10918-2). nuclear@14: Although this is by far the most detailed and comprehensive exposition of nuclear@14: JPEG publicly available, we point out that it is still missing an explanation nuclear@14: of the most essential properties and algorithms of the underlying DCT nuclear@14: technology. nuclear@14: If you think that you know about DCT-based JPEG after reading this book, nuclear@14: then you are in delusion. The real fundamentals and corresponding potential nuclear@14: of DCT-based JPEG are not publicly known so far, and that is the reason for nuclear@14: all the mistaken developments taking place in the image coding domain. nuclear@14: nuclear@14: The original JPEG standard is divided into two parts, Part 1 being the actual nuclear@14: specification, while Part 2 covers compliance testing methods. Part 1 is nuclear@14: titled "Digital Compression and Coding of Continuous-tone Still Images, nuclear@14: Part 1: Requirements and guidelines" and has document numbers ISO/IEC IS nuclear@14: 10918-1, ITU-T T.81. Part 2 is titled "Digital Compression and Coding of nuclear@14: Continuous-tone Still Images, Part 2: Compliance testing" and has document nuclear@14: numbers ISO/IEC IS 10918-2, ITU-T T.83. nuclear@14: IJG JPEG 8 introduces an implementation of the JPEG SmartScale extension nuclear@14: which is specified in a contributed document at ITU and ISO with title "ITU-T nuclear@14: JPEG-Plus Proposal for Extending ITU-T T.81 for Advanced Image Coding", April nuclear@14: 2006, Geneva, Switzerland. The latest version of the document is Revision 3. nuclear@14: nuclear@14: The JPEG standard does not specify all details of an interchangeable file nuclear@14: format. For the omitted details we follow the "JFIF" conventions, revision nuclear@14: 1.02. JFIF 1.02 has been adopted as an Ecma International Technical Report nuclear@14: and thus received a formal publication status. It is available as a free nuclear@14: download in PDF format from nuclear@14: http://www.ecma-international.org/publications/techreports/E-TR-098.htm. nuclear@14: A PostScript version of the JFIF document is available at nuclear@14: http://www.ijg.org/files/jfif.ps.gz. There is also a plain text version at nuclear@14: http://www.ijg.org/files/jfif.txt.gz, but it is missing the figures. nuclear@14: nuclear@14: The TIFF 6.0 file format specification can be obtained by FTP from nuclear@14: ftp://ftp.sgi.com/graphics/tiff/TIFF6.ps.gz. The JPEG incorporation scheme nuclear@14: found in the TIFF 6.0 spec of 3-June-92 has a number of serious problems. nuclear@14: IJG does not recommend use of the TIFF 6.0 design (TIFF Compression tag 6). nuclear@14: Instead, we recommend the JPEG design proposed by TIFF Technical Note #2 nuclear@14: (Compression tag 7). Copies of this Note can be obtained from nuclear@14: http://www.ijg.org/files/. It is expected that the next revision nuclear@14: of the TIFF spec will replace the 6.0 JPEG design with the Note's design. nuclear@14: Although IJG's own code does not support TIFF/JPEG, the free libtiff library nuclear@14: uses our library to implement TIFF/JPEG per the Note. nuclear@14: nuclear@14: nuclear@14: ARCHIVE LOCATIONS nuclear@14: ================= nuclear@14: nuclear@14: The "official" archive site for this software is www.ijg.org. nuclear@14: The most recent released version can always be found there in nuclear@14: directory "files". This particular version will be archived as nuclear@14: http://www.ijg.org/files/jpegsrc.v8c.tar.gz, and in Windows-compatible nuclear@14: "zip" archive format as http://www.ijg.org/files/jpegsr8c.zip. nuclear@14: nuclear@14: The JPEG FAQ (Frequently Asked Questions) article is a source of some nuclear@14: general information about JPEG. nuclear@14: It is available on the World Wide Web at http://www.faqs.org/faqs/jpeg-faq/ nuclear@14: and other news.answers archive sites, including the official news.answers nuclear@14: archive at rtfm.mit.edu: ftp://rtfm.mit.edu/pub/usenet/news.answers/jpeg-faq/. nuclear@14: If you don't have Web or FTP access, send e-mail to mail-server@rtfm.mit.edu nuclear@14: with body nuclear@14: send usenet/news.answers/jpeg-faq/part1 nuclear@14: send usenet/news.answers/jpeg-faq/part2 nuclear@14: nuclear@14: nuclear@14: ACKNOWLEDGMENTS nuclear@14: =============== nuclear@14: nuclear@14: Thank to Juergen Bruder for providing me with a copy of the common DCT nuclear@14: algorithm article, only to find out that I had come to the same result nuclear@14: in a more direct and comprehensible way with a more generative approach. nuclear@14: nuclear@14: Thank to Istvan Sebestyen and Joan L. Mitchell for inviting me to the nuclear@14: ITU JPEG (Study Group 16) meeting in Geneva, Switzerland. nuclear@14: nuclear@14: Thank to Thomas Wiegand and Gary Sullivan for inviting me to the nuclear@14: Joint Video Team (MPEG & ITU) meeting in Geneva, Switzerland. nuclear@14: nuclear@14: Thank to John Korejwa and Massimo Ballerini for inviting me to nuclear@14: fruitful consultations in Boston, MA and Milan, Italy. nuclear@14: nuclear@14: Thank to Hendrik Elstner, Roland Fassauer, Simone Zuck, Guenther nuclear@14: Maier-Gerber, Walter Stoeber, Fred Schmitz, and Norbert Braunagel nuclear@14: for corresponding business development. nuclear@14: nuclear@14: Thank to Nico Zschach and Dirk Stelling of the technical support team nuclear@14: at the Digital Images company in Halle for providing me with extra nuclear@14: equipment for configuration tests. nuclear@14: nuclear@14: Thank to Richard F. Lyon (then of Foveon Inc.) for fruitful nuclear@14: communication about JPEG configuration in Sigma Photo Pro software. nuclear@14: nuclear@14: Thank to Andrew Finkenstadt for hosting the ijg.org site. nuclear@14: nuclear@14: Last but not least special thank to Thomas G. Lane for the original nuclear@14: design and development of this singular software package. nuclear@14: nuclear@14: nuclear@14: FILE FORMAT WARS nuclear@14: ================ nuclear@14: nuclear@14: The ISO JPEG standards committee actually promotes different formats like nuclear@14: "JPEG 2000" or "JPEG XR" which are incompatible with original DCT-based nuclear@14: JPEG and which are based on faulty technologies. IJG therefore does not nuclear@14: and will not support such momentary mistakes (see REFERENCES). nuclear@14: We have little or no sympathy for the promotion of these formats. Indeed, nuclear@14: one of the original reasons for developing this free software was to help nuclear@14: force convergence on common, interoperable format standards for JPEG files. nuclear@14: Don't use an incompatible file format! nuclear@14: (In any case, our decoder will remain capable of reading existing JPEG nuclear@14: image files indefinitely.) nuclear@14: nuclear@14: nuclear@14: TO DO nuclear@14: ===== nuclear@14: nuclear@14: Version 8 is the first release of a new generation JPEG standard nuclear@14: to overcome the limitations of the original JPEG specification. nuclear@14: More features are being prepared for coming releases... nuclear@14: nuclear@14: Please send bug reports, offers of help, etc. to jpeg-info@uc.ag.