| readme.txt - for libpng 0.90 |
| |
| This is the fourth beta version of libpng 1.0. The changes from |
| libpng-0.89 include bug fixes, a C++ wrapper for png.h, some |
| additions to the API, as well as internal changes to the library. |
| |
| ** |
| Note that some of the changes to the png_info structure render |
| this version of the library binary incompatible with libpng-0.89 |
| if you are using a shared library. Re-compiling the application |
| should be enough to remove this problem. |
| ** |
| |
| The additions to 0.89 include the ability to read from a PNG stream |
| which has had some (or all) of the signature bytes read by the |
| calling application. This also allows the reading of embedded PNG |
| streams that do not have the PNG file signature. As well, it is |
| now possible to set the library action on the detection of chunk |
| CRC errors. It is possible to set different actions based on |
| whether the error occurred in a critical or an ancillary chunk. |
| |
| The callback functions for the error/warning messages have changed |
| since the 0.88 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 should use zlib 1.0.4 or later to run this, but it MAY work with |
| versions as old as zlib 0.95. Even so, there are bugs in older zlib |
| versions which can cause the output of invalid compression streams for |
| some images. You will definitely need zlib 1.0.4 or later if you are |
| taking advantage of the MS-DOS "far" structure allocation for the small |
| and medium memory models. You should also note that zlib is a |
| compression library that is useful for more things than just PNG files. |
| You can use zlib as a drop-in replacement for fread() and fwrite() if |
| you are so inclined. |
| |
| 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 is available |
| as an Internet Draft, and RFC, and a W3C Recommendation. Failing |
| these resources you can 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 (of course |
| based in a large way on Guy's earlier work), 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 a couple years 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. |
| |
| Files in this distribution: |
| |
| CHANGES.txt => Description of changes between libpng versions |
| README => This file |
| TODO => Things not implemented in the current library |
| ansi2knr.c => Converts files to K&R style function declarations |
| build.bat => MS-DOS batch file for Borland compiler |
| descrip.mms => VMS project file |
| example.c => Example code for using libpng functions |
| libpng.txt => Description of libpng and its functions |
| makefile => Defualt makefile |
| makefile.aco => ACORN makefile |
| makefile.ama => Amiga makefile |
| makefile.atr => Atari makefile |
| makefile.bor => Borland makefile |
| makefile.dj2 => DJGPP 2 makefile |
| makefile.elf => Unix ELF makefile |
| makefile.knr => Makefile which calls ansi2knr to convert files |
| makefile.mip => MIPS makefile |
| makefile.msc => Microsoft C makefile |
| makefile.std => Standard Unix makefile |
| makefile.tc => Turbo C makefile |
| makevms.com => VMS make program |
| png.c => Basic interface functions common to library |
| png.h => Library function and interface declarations |
| pngconf.h => System specific library configuration |
| pngerror.c => Error/warning message I/O functions |
| pngmem.c => Memory handling functions |
| pngpread.c => Progressive reading functions |
| pngrcb.c => Read callback (data handling) low-level functions |
| pngread.c => Read data/helper high-level functions |
| pngrio.c => Lowest-level data read I/O functions |
| pngrtran.c => Read data transformation functions |
| pngrutil.c => Read data utility functions |
| pngtest.c => Library test program |
| pngtest.png => Library test sample image |
| pngtrans.c => Common data transformation functions |
| pngwio.c => Lowest-level write I/O functions |
| pngwrite.c => High-level write functions |
| pngwtran.c => Write data transformations |
| pngwutil.c => Write utility functions |
| |
| Good luck, and happy coding. |
| |
| -Andreas Eric Dilger |
| University of Calgary |
| Internet: adilger@enel.ucalgary.ca |
| Web: www-mddsp.enel.ucalgary.ca/People/adilger/ |
| |
| -Guy Eric Schalnat |
| Group 42, Inc. |
| Internet: schalnat@group42.com |
| CompuServe: 75501,1625 |
| Web: www.group42.com |
| |