| README for libpng 1.10 |
| |
| This first official release of libpng. Don't let the fact that |
| it's the first release fool you. The libpng library has been in |
| extensive use and testing for about two years. However, it's |
| finally gotten to the stage where there haven't been significant |
| changes to the API in some time, and people have a bad feeling about |
| libraries with versions < 1.0. |
| |
| Note that the version number is 1.10 to avoid potential problems |
| with shared libraries created for Linux ELF under version 0.89, |
| which mistakenly used 1.0.89 as the library version number in |
| false anticipation of an imminent 1.0 release. |
| |
| **** |
| Note that some of the changes to the png_info structure render this |
| version of the library binary incompatible with libpng-0.89 or |
| earlier versions if you are using a shared library. The type of the |
| "filler" parameter for png_set_filler() has changed from png_byte to |
| png_uint_32, which will affect shared-library applications which use |
| this function. |
| |
| To avoid problems with changes to the internals of png_info_struct, |
| new APIs have been made available in 0.95 to avoid direct application |
| access to info_ptr. These functions are the png_set_<chunk> and |
| png_get_<chunk> functions. These functions should be used when |
| accessing/storing the info_struct data, rather than manipulating it |
| directly, to avoid such problems in the future. |
| |
| It is important to note that the APIs do not make current programs |
| which access the info struct directly incompatible with the new |
| library. However, it is strongly suggested that new programs use |
| the new APIs (as shown in example.c), and older programs be converted |
| to the new format, to facilitate upgrades in the future. |
| **** |
| |
| Additions since 0.90 include the ability to compile libpng as a |
| Windows DLL, and new APIs for accessing data in the info struct. |
| Experimental functions include the ability to set weighting and cost |
| factors for row filter selection, direct reads of integers from buffers |
| on big-endian processors that support misaligned data access, faster |
| methods of doing alpha composition, and more accurate 16->8 bit color |
| conversion. |
| |
| The additions since 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 CRC error occurred in a |
| critical or an ancillary chunk. |
| |
| 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 |
| examples of libpng in a program, see example.c and pngtest.c. 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 => 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 => Default Unixish 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 |
| 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 |
| pngset.c => Functions for storing data into the info_struct |
| 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 |
| Internet: adilger@enel.ucalgary.ca |
| Web: http://www-mddsp.enel.ucalgary.ca/People/adilger/ |
| |
| -Guy Eric Schalnat |
| Group 42, Inc. |
| Internet: schalnat@group42.com |
| CompuServe: 75501,1625 |
| Web: http://www.group42.com/ |
| |