| readme.txt - for libpng 0.89 |
| |
| This is a bug fix for the third beta version of libpng 1.0. The |
| changes from libpng-0.88 are bug fixes and some changes to the |
| API itself to increase robustness with shared libraries. This |
| release is based on libpng-0.88, but has been modified from that |
| version by Andreas Dilger <adilger@enel.ucalgary.ca> because the |
| original author, Guy Schalnat, has not been able to keep up with |
| the time demands of maintaining this library. |
| |
| The callback functions for the error/warning messages have changed |
| since the last release because their implementation was broken, |
| and it was thought best to change the API itself (which was only |
| introduced in libpng-0.88 itself) to alert the user to the change, |
| rather than mislead the user into thinking their application was |
| OK after re-compiling. This means that calls to png_set_message_fn() |
| no longer exist, because the previously suggested method of calling |
| them before png_read_init() or png_write_init() is now ineffective. |
| |
| The preferred method of setting the error and warning callbacks |
| has been incorporated into the allocation of the png_struct and |
| info_struct itself, which allow them to be safely used during the |
| initialization of the structure, as well as to keep the size of |
| the png_struct internal to the library, rather than at compile time |
| of the application. This will hopefully remove any problems with |
| dynamically linked libraries, and should be considered the preferred |
| method of creating these structures, although the previous |
| initialization API is still available for compatibility. See libpng.txt |
| for more information on the new API. |
| |
| The changes made to the library, and bugs fixed are based on discussions |
| on the PNG implementation mailing list <png-implement@dworking.wustl.edu> |
| and not on material submitted to Guy. |
| |
| For a detailed description on using libpng, read libpng.txt. For |
| usage information and restrictions (what little they are) on libpng, |
| see png.h. For a description on using zlib (the compression library |
| used by libpng) and zlib's restrictions, see zlib.h |
| |
| I have included a general makefile, as well as several machine and compiler |
| specific ones, but you may have to modify one for your own needs. |
| |
| You will need zlib 0.95 or later to run this. zlib is a compression |
| library that is useful for more things then just png files. If |
| you need a compression library, check out zlib.h. There was a bug in |
| zlib <= 0.99 which caused it to generate invalid compression streams |
| on some occasions. Later versions of zlib do not have this problem. |
| |
| zlib should be available at the same place that libpng is. |
| If not, it should be at ftp.uu.net in /graphics/png |
| Eventually, it will be at ftp.uu.net in /pub/archiving/zip/zlib |
| |
| You may also want a copy of the PNG specification. It should |
| be available at the same place you picked up libpng. If it is |
| not there, try ftp.uu.net in the /graphics/png directory. |
| |
| This code is currently being archived at ftp.uu.net in the |
| /graphics/png directory, and on CompuServe, Lib 20 (PNG SUPPORT) |
| at GO GRAPHSUP. If you can't find it in any of those places, |
| e-mail me, and I'll help you find it. |
| |
| If you have any code changes, requests, problems, etc., please e-mail |
| them to me. Also, I'd appreciate any make files or project files, |
| and any modifications you needed to make to get libpng to compile, |
| along with a #define variable to tell what compiler/system you are on. |
| If you needed to add transformations to libpng, or wish libpng would |
| provide the image in a different way, drop me a note (and code, if |
| possible), so I can consider supporting the transformation. |
| Finally, if you get any warning messages when compiling libpng |
| (note: not zlib), and they are easy to fix, I'd appreciate the |
| fix. Please mention "libpng" somewhere in the subject line. Thanks. |
| |
| This release was created and will be supported by myself, and the |
| PNG group. |
| |
| adilger@enel.ucalgary.ca |
| png-implement@dworkin.wustl.edu |
| |
| You can reach Guy, the original libpng author, at (internet preferred): |
| |
| internet: schalnat@group42.com |
| CompuServe: 75501,1625 |
| |
| Please do not send general questions about PNG. Send them to |
| the address in the specification. At the same time, please do |
| not send libpng questions to that address, send them to me. I'll |
| get them in the end anyway. If you have a question about something |
| in the PNG specification that is related to using libpng, send it |
| to me. Send me any questions that start with "I was using libpng, |
| and ...". If in doubt, send questions to me. I'll bounce them |
| to others, if necessary. |
| |
| Please do not send suggestions on how to change PNG. We have |
| been discussing PNG for over a year now, and it is official and |
| finished. If you have suggestions for libpng, however, I'll |
| gladly listen. Even if your suggestion is not used for version |
| 1.0, it may be used later. |
| |
| Good luck, and happy coding. |
| |
| -Guy Eric Schalnat |
| Group 42, Inc. |
| Internet: schalnat@group42.com |
| CompuServe: 75501,1625 |
| Web: www.group42.com |
| |