| The Independent JPEG Group's JPEG software |
| ========================================== |
| |
| README for release 9a of 19-Jan-2014 |
| ==================================== |
| |
| 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, |
| 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. |
| 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 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. |
| |
| |
| 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) 1991-2014, 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. |
| |
| The IJG distribution formerly included code to read and write GIF files. |
| To avoid entanglement with the Unisys LZW patent (now expired), 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." |
| |
| |
| 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 PostScript file containing a revised version of Wallace's article is |
| available at http://www.ijg.org/files/wallace.ps.gz. 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, 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 |
| http://www.ecma-international.org/publications/techreports/E-TR-098.htm. |
| A PostScript version of the JFIF document is available at |
| http://www.ijg.org/files/jfif.ps.gz. There is also a plain text version at |
| http://www.ijg.org/files/jfif.txt.gz, but it is missing the figures. |
| |
| 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 |
| http://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 as |
| http://www.ijg.org/files/jpegsrc.v9a.tar.gz, and in Windows-compatible |
| "zip" archive format as http://www.ijg.org/files/jpegsr9a.zip. |
| |
| 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. |
| |
| Last but not least special thank to Thomas G. Lane for the original |
| design and development of this singular software package. |
| |
| |
| 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@jpegclub.org. |