The Independent JPEG Group's JPEG software v5
diff --git a/README b/README
index 99c4d36..c882ffb 100644
--- a/README
+++ b/README
@@ -1,51 +1,65 @@
The Independent JPEG Group's JPEG software
==========================================
-README for release 4A of 18-Feb-93
-==================================
+README for release 5 of 24-Sep-94
+=================================
-This distribution contains a BETA TEST release of the Independent JPEG
+This distribution contains the fifth 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.
-For installation instructions, see file SETUP.
-
-For usage instructions, see file USAGE (or the cjpeg.1 and djpeg.1 manual
-pages; but USAGE contains a "hints" section not found in the manual pages).
-Useful information can also be found in the JPEG FAQ (Frequently Asked
-Questions) article; see ARCHIVE LOCATIONS below to obtain the FAQ article.
-
-This software is still undergoing revision. Updated versions may be obtained
-by FTP or UUCP to UUNET and other archive sites; see ARCHIVE LOCATIONS below
-for details.
-
Serious users of this software (particularly those incorporating it into
larger programs) should contact 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, Lee
-Crocker, George Phillips, Ge' Weijers, and other members of the Independent
-JPEG Group.
+This software is the work of Tom Lane, Philip Gladstone, Luis Ortiz, Jim
+Boucher, Lee Crocker, George Phillips, Davide Rossi, Ge' Weijers, and other
+members of the Independent JPEG Group.
+
+IJG is not associated with the official ISO JPEG standards committee.
-DISCLAIMER
-==========
+DOCUMENTATION ROADMAP
+=====================
-THIS SOFTWARE IS NOT COMPLETE NOR FULLY DEBUGGED. It is not guaranteed to be
-useful for anything, nor to be compatible with subsequent releases, nor to be
-an accurate implementation of the JPEG standard. (See LEGAL ISSUES for even
-more disclaimers.)
+This file contains the following sections:
-Despite that, we believe that this software is pretty good, and if you find
-any problems with it, we'd like to know about them. Please report problems
-by e-mail to jpeg-info@uunet.uu.net.
+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, rdjpgcom, wrjpgcom.
+ *.1 Unix-style man pages for programs (same info as usage.doc).
+ 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.
-WHAT'S HERE
-===========
+OVERVIEW
+========
-This distribution contains C software to implement JPEG image compression and
+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; cartoons and other non-realistic images are not its
@@ -57,19 +71,27 @@
For more details, see the references, or just experiment with various
compression settings.
-The software implements JPEG baseline and extended-sequential compression
+We provide a set of library routines for reading and writing JPEG image files,
+plus two simple 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.
+
+This software implements JPEG baseline and extended-sequential 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 process; see
LEGAL ISSUES. At present we have made no provision for supporting the
progressive, hierarchical, or lossless processes defined in the standard.
+(Support for progressive mode may be offered in a future release.)
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 if not
-required for a particular application.
+colormapped displays. These extra functions can be compiled out of the
+library if not required for a particular application. We have also included
+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,
@@ -78,258 +100,31 @@
package will someday be industrial-strength code, much remains to be done in
performance tuning and in improving the capabilities of individual modules.
-
-This software can be used on several levels:
-
-* As canned software for JPEG compression and decompression. Just edit the
- Makefile and configuration files as needed (see file SETUP), compile and go.
- Members of the Independent JPEG Group will improve the out-of-the-box
- functionality and speed as time goes on.
-
-* As the basis for other JPEG programs. For example, you could incorporate
- the decompressor into a general image viewing package by replacing the
- output module with write-to-screen functions. For an implementation on
- specific hardware, you might want to replace some of the inner loops with
- assembly code. For a non-command-line-driven system, you might want a
- different user interface. (Members of the group will be producing Macintosh
- and Amiga versions with more appropriate user interfaces, for example.)
-
-* As a toolkit for experimentation with JPEG and JPEG-like algorithms. Most
- of the individual decisions you might want to mess with are packaged up into
- separate modules. For example, the details of color-space conversion and
- subsampling techniques are each localized in one compressor and one
- decompressor module. You'd probably also want to extend the user interface
- to give you more detailed control over the JPEG compression parameters.
-
-In particular, we welcome the use of this software as a component of commercial
-products; no royalty is required.
-
-
-ARCHIVE LOCATIONS
-=================
-
-[Version 4A is a beta-test release and will not be publicly archived.
-The following paragraphs refer to the most recent official release.]
-
-The "official" archive site for this software is ftp.uu.net (Internet
-address 137.39.1.9 or 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 jpegsrc.v4.tar.Z. If you are on the Internet, you can
-retrieve files from UUNET by anonymous FTP. If you don't have FTP access,
-UUNET's archives are also available via UUCP; contact postmaster@uunet.uu.net
-for information on retrieving files that way.
-
-Numerous Internet sites maintain copies of the UUNET files; in particular,
-you can probably find a copy at any site that archives comp.sources.misc
-submissions. However, only ftp.uu.net is guaranteed to have the latest
-official version.
-
-You can also obtain this software from CompuServe, in the GRAPHSUPPORT forum
-(GO PICS), library 15; this version will be file jpsrc4.zip. Again,
-CompuServe is not guaranteed to have the very latest version.
-
-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, news.answers, and other groups. You
-can always obtain the latest version from the news.answers archive at
-rtfm.mit.edu (18.172.1.27). By FTP, fetch /pub/usenet/news.answers/jpeg-faq.
-If you don't have FTP, send e-mail to mail-server@rtfm.mit.edu with body
-"send usenet/news.answers/jpeg-faq".
-
-
-SUPPORTING SOFTWARE
-===================
-
-You will probably want Jef Poskanzer's 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 FTP
-this free software from export.lcs.mit.edu (contrib/pbmplus*.tar.Z) or
-ftp.ee.lbl.gov (pbmplus*.tar.Z). Unfortunately PBMPLUS is not nearly as
-portable as the JPEG software is; you are likely to have difficulty making it
-work on any non-Unix machine.
-
-If you are using X Windows you might want to use the xv or xloadimage viewers
-to save yourself the trouble of converting PPM to some other format. Both of
-these can be found in the contrib directory at export.lcs.mit.edu. Actually,
-xv version 2.00 and up incorporates our software and thus can read and write
-JPEG files directly. (NOTE: since xv internally reduces all images to 8
-bits/pixel, a JPEG file written by xv will not be very high quality; and xv
-cannot fully exploit a 24-bit display. These problems are expected to go away
-in the next xv release, planned for early 1993. In the meantime, use
-xloadimage for 24-bit displays.)
-
-For DOS machines, Lee Crocker's free Piclab program is a useful companion to
-the JPEG software. The latest version, currently 1.91, is available by FTP
-from SIMTEL20 and its various mirror sites, file <msdos.graphics>piclb191.zip.
-CompuServe also has it, in the same library as the JPEG software.
-
-
-SOFTWARE THAT'S NO HELP AT ALL
-==============================
-
-Handmade Software's shareware PC program GIF2JPG produces files that are
-totally incompatible with our programs. They use a proprietary format that is
-an amalgam of GIF and JPEG representations. However, you can force GIF2JPG
-to produce compatible files with its -j switch, and their decompression
-program JPG2GIF can read our files (at least ones produced with our default
-option settings).
-
-Some commercial JPEG implementations are also incompatible as of this writing,
-especially programs released before summer 1991. 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 we expect
-that it will become the de facto standard. JFIF is a minimal representation;
-work is also going forward to incorporate JPEG compression into the TIFF 6.0
-standard, for use in "high end" applications that need to record a lot of
-additional data about an image. We intend to support TIFF 6.0 in the future.
-We hope that these two formats will be sufficient and that other, incompatible
-JPEG file formats will not proliferate.
-
-Indeed, part of the reason for developing and releasing this free software is
-to help force rapid convergence to de facto standards for JPEG file formats.
-SUPPORT STANDARD, NON-PROPRIETARY FORMATS: demand JFIF or TIFF 6.0!
-
-
-USING JPEG AS A SUBROUTINE IN A LARGER PROGRAM
-==============================================
-
-You can readily incorporate the JPEG compression and decompression routines in
-a larger program. The file example.c provides a skeleton of the interface
-routines you'll need for this purpose. Essentially, you replace jcmain.c (for
-compression) and/or jdmain.c (for decompression) with your own code. Note
-that the fewer JPEG options you allow the user to twiddle, the less code you
-need; all the default options are set up automatically. (Alternately, if you
-know a lot about JPEG or have a special application, you may want to twiddle
-the default options even more extensively than jcmain/jdmain do.)
-
-Most likely, you will want the uncompressed image to come from memory (for
-compression) or go to memory or the screen (for decompression). For this
-purpose you must provide image reading or writing routines that match the
-interface used by the image file I/O modules (jrdXXX or jwrXXX); again,
-example.c shows a skeleton of what is required. In this situation, you
-won't need any of the non-JPEG image file I/O modules used by cjpeg and djpeg.
-
-By default, any error detected inside the JPEG routines will cause a message
-to be printed on stderr, followed by exit(). You can override this behavior
-by supplying your own message-printing and/or error-exit routines; again,
-example.c shows how.
-
-We recommend you create libjpeg.a as shown in the Makefile, then link that
-with your surrounding program. (If your linker is at all reasonable, only the
-code you actually need will get loaded.) Include the files jconfig.h and
-jpegdata.h in C files that need to call the JPEG routines.
-
-CAUTION: some people have tried to compile JPEG and their surrounding code
-with different compilers, e.g., cc for JPEG and c++ or gcc for the rest. This
-is a Real Bad Move and you will deserve what happens to you if you try it.
-(Hint: the parameter structures can get laid out differently with no warning.)
-
-Read our "architecture" file for more info. If it seems to you that the
-software structure doesn't accommodate what you want to do, please contact
-the authors.
-
-Beginning with version 3, we will endeavor to hold the interface described by
-example.c constant, so that you can plug in updated versions of the JPEG code
-just by recompiling. However, we can't guarantee this, especially if you
-choose to twiddle any JPEG options not listed in example.c. Check the
-CHANGELOG when installing any new version, and compare example.c against the
-prior version. Recompile your calling software (don't just relink), as we may
-add or subtract fields in the parameter structures.
-
-
-REFERENCES
-==========
-
-We highly recommend reading one or more of these references before trying to
-understand the innards of any 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 the article is
-available at ftp.uu.net, graphics/jpeg/wallace.ps.Z. The file (actually a
-preprint for an article to appear 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...
-
-A new textbook about JPEG is "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. This 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 I highly
-recommend it. If you read the entire book, you will probably know more about
-JPEG than I do.
-
-The JPEG standard itself is not available electronically; you must order a
-paper copy through ISO. (Unless you are concerned about having a certified
-official copy, I recommend buying the Pennebaker and Mitchell book instead;
-it's much cheaper and includes a great deal of useful explanatory material.)
-In the US, copies of the standard may be ordered from ANSI Sales at (212)
-642-4900. It's not cheap: as of 1992, Part 1 is $95 and Part 2 is $47, plus
-7% shipping/handling. The standard is divided into two parts, Part 1 being
-the actual specification, while Part 2 covers compliance testing methods.
-As of early 1992, Part 1 has Draft International Standard status. It is
-titled "Digital Compression and Coding of Continuous-tone Still Images, Part
-1: Requirements and guidelines" and has document number ISO/IEC DIS 10918-1.
-Part 2 is still at Committee Draft status. It is titled "Digital Compression
-and Coding of Continuous-tone Still Images, Part 2: Compliance testing" and
-has document number ISO/IEC CD 10918-2. (NOTE: I'm told that the final
-version of Part 2 will differ considerably from the CD draft.)
-
-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.
- 399A West Trimble Road
- San Jose, CA 95131
- (408) 944-6300
-A PostScript version of this document is available at ftp.uu.net, file
-graphics/jpeg/jfif.ps.Z. 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. It should be noted that the TIFF 6.0 spec
-of 3-June-92 has a number of serious problems in its JPEG features. A
-clarification note will probably be needed to ensure that TIFF JPEG files are
-compatible across different implementations. The IJG does not intend to
-support TIFF 6.0 until these problems are resolved.
-
-If you want to understand this implementation, start by reading the
-"architecture" documentation file. Please read "codingrules" if you want to
-contribute any code.
+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, 1992, Thomas G. Lane.
+This software is copyright (C) 1991, 1992, 1993, 1994, Thomas G. Lane.
All Rights Reserved except as specified below.
Permission is hereby granted to use, copy, modify, and distribute this
@@ -346,6 +141,10 @@
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
@@ -362,44 +161,189 @@
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 JPEG code, this does not limit you more than
+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 by GNU Autoconf. Again,
+the FSF copyright terms apply only to configure, not to the IJG code; and
+again, that does not limit your use of the object code.
It appears that the arithmetic coding option of the JPEG spec is covered by
-patents owned by IBM and AT&T, as well as a pending Japanese patent of
-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
-implementors will support it. If you do obtain the necessary licenses,
-contact jpeg-info@uunet.uu.net for a copy of our arithmetic coding modules.)
+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.
-
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 to appear 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. (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 US,
+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 number ISO/IEC IS 10918-1. As of mid-1994,
+Part 2 is still at Draft International Standard status. It is titled "Digital
+Compression and Coding of Continuous-tone Still Images, Part 2: Compliance
+testing" and has document number ISO/IEC DIS 10918-2. (The document number
+will change to IS 10918-2 when final approval is obtained.) A Part 3,
+covering extensions, is likely to appear in draft form in late 1994.
+
+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. It should be noted that the TIFF 6.0 spec
+of 3-June-92 has a number of serious problems in its JPEG features. A
+redesign effort is currently underway to correct these problems; it is
+expected to result in a new, incompatible, spec. IJG intends to support the
+corrected version of TIFF when the new spec is issued.
+
+
+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.v5.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; in particular,
+you can probably find a copy at any site that archives comp.sources.misc
+submissions. However, only ftp.uu.net is guaranteed to have the latest
+official version.
+
+You can also obtain this software from CompuServe, in the GRAPHSUPPORT forum
+(GO GRAPHSUP); this version will be file jpsrc5.zip in library 15. Again,
+CompuServe is not guaranteed to have the very latest version.
+
+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, news.answers, and other groups. You
+can always obtain the latest version from the news.answers archive at
+rtfm.mit.edu (18.181.0.24). By FTP, fetch /pub/usenet/news.answers/jpeg-faq.
+If you don't have FTP, send e-mail to mail-server@rtfm.mit.edu with body
+"send usenet/news.answers/jpeg-faq".
+
+
+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
+implements a larger subset of the JPEG standard. In particular, it supports
+lossless JPEG.
+
+
+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.
+Work is also going forward to incorporate JPEG compression into the TIFF
+standard, for use in "high end" applications that need to record a lot of
+additional data about an image. We intend to support TIFF in the future.
+We hope that these two formats will be sufficient and that other,
+incompatible JPEG file formats will not proliferate.
+
+Indeed, part of the reason for developing and releasing this free software is
+to help force rapid convergence to de facto standards for JPEG file formats.
+SUPPORT STANDARD, NON-PROPRIETARY FORMATS: demand JFIF or TIFF/JPEG!
+
+
TO DO
=====
-The next major release will probably be a significant rewrite to allow use of
-this code in conjunction with Sam Leffler's free TIFF library (assuming the
-bugs in the TIFF 6.0 specification get resolved).
+In future versions, we are considering supporting progressive JPEG
+compression, the upcoming JPEG Part 3 extensions, and other improvements.
-Many of the modules need fleshing out to provide more complete
-implementations, or to provide faster paths for common cases.
-Speeding things up is still high on our priority list.
-
-We'd appreciate it if people would compile and check out the code on as wide a
-variety of systems as possible, and report any portability problems
-encountered (with solutions, if possible). Checks of file compatibility with
-other JPEG implementations would also be of interest. Finally, we would
-appreciate code profiles showing where the most time is spent, especially on
-unusual systems.
+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.