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