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diff --git a/gs/jpeg/README b/gs/jpeg/README deleted file mode 100644 index fa69a18c6..000000000 --- a/gs/jpeg/README +++ /dev/null @@ -1,383 +0,0 @@ -The Independent JPEG Group's JPEG software -========================================== - -README for release 6a of 7-Feb-96 -================================= - -This distribution contains the sixth 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. - -Serious users of this software (particularly those incorporating it into -larger programs) should contact IJG at jpeg-info@uunet.uu.net to be added to -our electronic mailing list. Mailing list members are notified of updates -and have a chance to participate in technical discussions, etc. - -This software is the work of Tom Lane, Philip Gladstone, Luis Ortiz, Jim -Boucher, Lee Crocker, Julian Minguillon, 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. - - -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. -RELATED SOFTWARE Other stuff you should get. -FILE FORMAT WARS Software *not* to get. -TO DO Plans for future IJG releases. - -Other documentation files in the distribution are: - -User documentation: - install.doc How to configure and install the IJG software. - usage.doc Usage instructions for cjpeg, djpeg, jpegtran, - rdjpgcom, and wrjpgcom. - *.1 Unix-style man pages for programs (same info as usage.doc). - wizard.doc Advanced usage instructions for JPEG wizards only. - change.log Version-to-version change highlights. -Programmer and internal documentation: - libjpeg.doc How to use the JPEG library in your own programs. - example.c Sample code for calling the JPEG library. - structure.doc Overview of the JPEG library's internal structure. - filelist.doc Road map of IJG files. - coderules.doc Coding style rules --- please read if you contribute code. - -Please read at least the files install.doc and usage.doc. Useful 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 compression and -decompression. JPEG (pronounced "jay-peg") is a standardized compression -method for full-color and gray-scale images. JPEG is intended for compressing -"real-world" scenes; line drawings, cartoons and other non-realistic images -are not its strong suit. JPEG is lossy, meaning that the output image is not -exactly identical to the input image. Hence you must not use JPEG if you -have to have identical output bits. However, on typical photographic images, -very good compression levels can be obtained with no visible change, and -remarkably high compression levels are possible if you can tolerate a -low-quality image. For more details, see the references, or just experiment -with various compression settings. - -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. -For legal reasons, we are not distributing code for the arithmetic-coding -variants of JPEG; see LEGAL ISSUES. 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) 1991-1996, 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 -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. - - -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 configuration script "configure" was produced with GNU Autoconf. It -is copyright by the Free Software Foundation but is freely distributable. - -It appears that the arithmetic coding option of the JPEG spec is covered by -patents owned by IBM, AT&T, and 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 implementations will support it.) -So far as we are aware, there are no patent restrictions on the remaining -code. - -WARNING: Unisys has begun to enforce their patent on LZW compression against -GIF encoders and decoders. You will need a license from Unisys to use the -included rdgif.c or wrgif.c files in a commercial or shareware application. -At this time, Unisys is not enforcing their patent against freeware, so -distribution of this package remains legal. However, we intend to remove -GIF support from the IJG package as soon as a suitable replacement format -becomes reasonably popular. - -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 highly 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 ftp.uu.net, graphics/jpeg/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, published by M&T Books (Redwood -City, CA), 1991, ISBN 1-55851-216-0. 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 full 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). This is by far the most complete exposition of JPEG -in existence, and we highly recommend it. - -The JPEG standard itself is not available electronically; you must order a -paper copy through ISO or ITU. (Unless you feel a need to own a certified -official copy, we recommend buying the Pennebaker and Mitchell book instead; -it's much cheaper and includes a great deal of useful explanatory material.) -In the USA, copies of the standard may be ordered from ANSI Sales at (212) -642-4900, or from Global Engineering Documents at (800) 854-7179. (ANSI -doesn't take credit card orders, but Global does.) It's not cheap: as of -1992, ANSI was charging $95 for Part 1 and $47 for Part 2, plus 7% -shipping/handling. The 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. - -Extensions to the original JPEG standard are defined in JPEG Part 3, a new ISO -document. Part 3 is undergoing ISO balloting and is expected to be approved -by the end of 1995; it will have document numbers ISO/IEC IS 10918-3, ITU-T -T.84. IJG currently does not support any Part 3 extensions. - -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. A copy of the JFIF spec is available from: - Literature Department - C-Cube Microsystems, Inc. - 1778 McCarthy Blvd. - Milpitas, CA 95035 - phone (408) 944-6300, fax (408) 944-6314 -A PostScript version of this document is available at ftp.uu.net, file -graphics/jpeg/jfif.ps.gz. It can also be obtained by e-mail from the C-Cube -mail server, netlib@c3.pla.ca.us. Send the message "send jfif_ps from jpeg" -to the server to obtain the JFIF document; send the message "help" if you have -trouble. - -The TIFF 6.0 file format specification can be obtained by FTP from sgi.com -(192.48.153.1), file graphics/tiff/TIFF6.ps.Z; or you can order a printed -copy from Aldus Corp. at (206) 628-6593. 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 sgi.com or -from ftp.uu.net:/graphics/jpeg/. 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. libtiff is available -from sgi.com:/graphics/tiff/. - - -ARCHIVE LOCATIONS -================= - -The "official" archive site for this software is ftp.uu.net (Internet -address 192.48.96.9). The most recent released version can always be found -there in directory graphics/jpeg. This particular version will be archived -as graphics/jpeg/jpegsrc.v6a.tar.gz. If you are on the Internet, you -can retrieve files from ftp.uu.net by standard anonymous FTP. If you don't -have FTP access, UUNET's archives are also available via UUCP; contact -help@uunet.uu.net for information on retrieving files that way. - -Numerous Internet sites maintain copies of the UUNET files. However, only -ftp.uu.net is guaranteed to have the latest official version. - -You can also obtain this software in DOS-compatible "zip" archive format from -the SimTel archives (ftp.coast.net:/SimTel/msdos/graphics/), or on CompuServe -in the Graphics Support forum (GO CIS:GRAPHSUP), library 12 "JPEG Tools". -Again, these versions may sometimes lag behind the ftp.uu.net release. - -The JPEG FAQ (Frequently Asked Questions) article is a useful source of -general information about JPEG. It is updated constantly and therefore is -not included in this distribution. The FAQ is posted every two weeks to -Usenet newsgroups comp.graphics.misc, news.answers, and other groups. -You can always obtain the latest version from the news.answers archive at -rtfm.mit.edu. By FTP, fetch /pub/usenet/news.answers/jpeg-faq/part1 and -.../part2. If you don't have FTP, 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 - - -RELATED SOFTWARE -================ - -Numerous viewing and image manipulation programs now support JPEG. (Quite a -few of them use this library to do so.) The JPEG FAQ described above lists -some of the more popular free and shareware viewers, and tells where to -obtain them on Internet. - -If you are on a Unix machine, we highly recommend Jef Poskanzer's free -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 obtain this package by FTP from ftp.x.org -(contrib/pbmplus*.tar.Z) or ftp.ee.lbl.gov (pbmplus*.tar.Z). There is also -a newer update of this package called NETPBM, available from -wuarchive.wustl.edu under directory /graphics/graphics/packages/NetPBM/. -Unfortunately PBMPLUS/NETPBM is not nearly as portable as the IJG software -is; you are likely to have difficulty making it work on any non-Unix machine. - -A different free JPEG implementation, written by the PVRG group at Stanford, -is available from havefun.stanford.edu in directory pub/jpeg. This program -is designed for research and experimentation rather than production use; -it is slower, harder to use, and less portable than the IJG code, but it -is easier to read and modify. Also, the PVRG code supports lossless JPEG, -which we do not. - - -FILE FORMAT WARS -================ - -Some JPEG programs produce files that are not compatible with our library. -The root of the problem is that the ISO JPEG committee failed to specify a -concrete file format. Some 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 it has -become the de facto standard. JFIF is a minimal or "low end" representation. -We recommend the use of TIFF/JPEG (TIFF revision 6.0 as modified by TIFF -Technical Note #2) for "high end" applications that need to record a lot of -additional data about an image. TIFF/JPEG is fairly new and not yet widely -supported, unfortunately. - -The upcoming JPEG Part 3 standard defines a file format called SPIFF. -SPIFF is interoperable with JFIF, in the sense that most JFIF decoders should -be able to read the most common variant of SPIFF. SPIFF has some technical -advantages over JFIF, but its major claim to fame is simply that it is an -official standard rather than an informal one. At this point it is unclear -whether SPIFF will supersede JFIF or whether JFIF will remain the de-facto -standard. IJG intends to support SPIFF once the standard is frozen, but we -have not decided whether it should become our default output format or not. -(In any case, our decoder will remain capable of reading JFIF indefinitely.) - -Various proprietary file formats incorporating JPEG compression also exist. -We have little or no sympathy for the existence of these formats. Indeed, -one of the original reasons for developing this free software was to help -force convergence on common, open format standards for JPEG files. Don't -use a proprietary file format! - - -TO DO -===== - -In future versions, we are considering supporting some of the upcoming JPEG -Part 3 extensions --- principally, variable quantization and the SPIFF file -format. - -Tuning the software for better behavior at low quality/high compression -settings is also of interest. The current method for scaling the -quantization tables is known not to be very good at low Q values. - -As always, speeding things up is high on our priority list. - -Please send bug reports, offers of help, etc. to jpeg-info@uunet.uu.net. |