Glenn Randers-Pehrson | b6ce43d | 1998-01-01 07:13:13 -0600 | [diff] [blame^] | 1 | README for libpng 1.10 |
Andreas Dilger | 02ad0ef | 1997-01-17 01:34:35 -0600 | [diff] [blame] | 2 | |
Glenn Randers-Pehrson | b6ce43d | 1998-01-01 07:13:13 -0600 | [diff] [blame^] | 3 | This first official release of libpng. Don't let the fact that |
| 4 | it's the first release fool you. The libpng library has been in |
| 5 | extensive use and testing for about two years. However, it's |
| 6 | finally gotten to the stage where there haven't been significant |
| 7 | changes to the API in some time, and people have a bad feeling about |
| 8 | libraries with versions < 1.0. |
| 9 | |
| 10 | Note that the version number is 1.10 to avoid potential problems |
| 11 | with shared libraries created for Linux ELF under version 0.89, |
| 12 | which mistakenly used 1.0.89 as the library version number in |
| 13 | false anticipation of an imminent 1.0 release. |
Andreas Dilger | 02ad0ef | 1997-01-17 01:34:35 -0600 | [diff] [blame] | 14 | |
Andreas Dilger | 47a0c42 | 1997-05-16 02:46:07 -0500 | [diff] [blame] | 15 | **** |
| 16 | Note that some of the changes to the png_info structure render this |
| 17 | version of the library binary incompatible with libpng-0.89 or |
| 18 | earlier versions if you are using a shared library. The type of the |
| 19 | "filler" parameter for png_set_filler() has changed from png_byte to |
| 20 | png_uint_32, which will affect shared-library applications which use |
| 21 | this function. |
Andreas Dilger | 02ad0ef | 1997-01-17 01:34:35 -0600 | [diff] [blame] | 22 | |
Andreas Dilger | 47a0c42 | 1997-05-16 02:46:07 -0500 | [diff] [blame] | 23 | To avoid problems with changes to the internals of png_info_struct, |
| 24 | new APIs have been made available in 0.95 to avoid direct application |
| 25 | access to info_ptr. These functions are the png_set_<chunk> and |
| 26 | png_get_<chunk> functions. These functions should be used when |
| 27 | accessing/storing the info_struct data, rather than manipulating it |
| 28 | directly, to avoid such problems in the future. |
Glenn Randers-Pehrson | b6ce43d | 1998-01-01 07:13:13 -0600 | [diff] [blame^] | 29 | |
| 30 | It is important to note that the APIs do not make current programs |
| 31 | which access the info struct directly incompatible with the new |
| 32 | library. However, it is strongly suggested that new programs use |
| 33 | the new APIs (as shown in example.c), and older programs be converted |
| 34 | to the new format, to facilitate upgrades in the future. |
Andreas Dilger | 47a0c42 | 1997-05-16 02:46:07 -0500 | [diff] [blame] | 35 | **** |
Andreas Dilger | 02ad0ef | 1997-01-17 01:34:35 -0600 | [diff] [blame] | 36 | |
Andreas Dilger | 47a0c42 | 1997-05-16 02:46:07 -0500 | [diff] [blame] | 37 | Additions since 0.90 include the ability to compile libpng as a |
| 38 | Windows DLL, and new APIs for accessing data in the info struct. |
| 39 | Experimental functions include the ability to set weighting and cost |
| 40 | factors for row filter selection, direct reads of integers from buffers |
| 41 | on big-endian processors that support misaligned data access, faster |
| 42 | methods of doing alpha composition, and more accurate 16->8 bit color |
| 43 | conversion. |
Andreas Dilger | 02ad0ef | 1997-01-17 01:34:35 -0600 | [diff] [blame] | 44 | |
Andreas Dilger | 47a0c42 | 1997-05-16 02:46:07 -0500 | [diff] [blame] | 45 | The additions since 0.89 include the ability to read from a PNG stream |
| 46 | which has had some (or all) of the signature bytes read by the calling |
| 47 | application. This also allows the reading of embedded PNG streams that |
| 48 | do not have the PNG file signature. As well, it is now possible to set |
| 49 | the library action on the detection of chunk CRC errors. It is possible |
| 50 | to set different actions based on whether the CRC error occurred in a |
| 51 | critical or an ancillary chunk. |
Andreas Dilger | 02ad0ef | 1997-01-17 01:34:35 -0600 | [diff] [blame] | 52 | |
| 53 | The changes made to the library, and bugs fixed are based on discussions |
| 54 | on the PNG implementation mailing list <png-implement@dworking.wustl.edu> |
| 55 | and not on material submitted to Guy. |
| 56 | |
| 57 | For a detailed description on using libpng, read libpng.txt. For |
Andreas Dilger | 47a0c42 | 1997-05-16 02:46:07 -0500 | [diff] [blame] | 58 | examples of libpng in a program, see example.c and pngtest.c. For usage |
| 59 | information and restrictions (what little they are) on libpng, see |
| 60 | png.h. For a description on using zlib (the compression library used by |
| 61 | libpng) and zlib's restrictions, see zlib.h |
Andreas Dilger | 02ad0ef | 1997-01-17 01:34:35 -0600 | [diff] [blame] | 62 | |
Andreas Dilger | 47a0c42 | 1997-05-16 02:46:07 -0500 | [diff] [blame] | 63 | I have included a general makefile, as well as several machine and |
| 64 | compiler specific ones, but you may have to modify one for your own needs. |
Andreas Dilger | 02ad0ef | 1997-01-17 01:34:35 -0600 | [diff] [blame] | 65 | |
| 66 | You should use zlib 1.0.4 or later to run this, but it MAY work with |
| 67 | versions as old as zlib 0.95. Even so, there are bugs in older zlib |
| 68 | versions which can cause the output of invalid compression streams for |
| 69 | some images. You will definitely need zlib 1.0.4 or later if you are |
| 70 | taking advantage of the MS-DOS "far" structure allocation for the small |
| 71 | and medium memory models. You should also note that zlib is a |
| 72 | compression library that is useful for more things than just PNG files. |
| 73 | You can use zlib as a drop-in replacement for fread() and fwrite() if |
| 74 | you are so inclined. |
| 75 | |
| 76 | zlib should be available at the same place that libpng is. |
| 77 | If not, it should be at ftp.uu.net in /graphics/png |
| 78 | Eventually, it will be at ftp.uu.net in /pub/archiving/zip/zlib |
| 79 | |
| 80 | You may also want a copy of the PNG specification. It is available |
| 81 | as an Internet Draft, and RFC, and a W3C Recommendation. Failing |
| 82 | these resources you can try ftp.uu.net in the /graphics/png directory. |
| 83 | |
| 84 | This code is currently being archived at ftp.uu.net in the |
| 85 | /graphics/png directory, and on CompuServe, Lib 20 (PNG SUPPORT) |
| 86 | at GO GRAPHSUP. If you can't find it in any of those places, |
| 87 | e-mail me, and I'll help you find it. |
| 88 | |
| 89 | If you have any code changes, requests, problems, etc., please e-mail |
| 90 | them to me. Also, I'd appreciate any make files or project files, |
| 91 | and any modifications you needed to make to get libpng to compile, |
| 92 | along with a #define variable to tell what compiler/system you are on. |
| 93 | If you needed to add transformations to libpng, or wish libpng would |
| 94 | provide the image in a different way, drop me a note (and code, if |
| 95 | possible), so I can consider supporting the transformation. |
| 96 | Finally, if you get any warning messages when compiling libpng |
| 97 | (note: not zlib), and they are easy to fix, I'd appreciate the |
| 98 | fix. Please mention "libpng" somewhere in the subject line. Thanks. |
| 99 | |
| 100 | This release was created and will be supported by myself (of course |
| 101 | based in a large way on Guy's earlier work), and the PNG group. |
| 102 | |
| 103 | adilger@enel.ucalgary.ca |
| 104 | png-implement@dworkin.wustl.edu |
| 105 | |
| 106 | You can reach Guy, the original libpng author, at (internet preferred): |
| 107 | |
| 108 | internet: schalnat@group42.com |
| 109 | CompuServe: 75501,1625 |
| 110 | |
| 111 | Please do not send general questions about PNG. Send them to |
| 112 | the address in the specification. At the same time, please do |
| 113 | not send libpng questions to that address, send them to me. I'll |
| 114 | get them in the end anyway. If you have a question about something |
| 115 | in the PNG specification that is related to using libpng, send it |
| 116 | to me. Send me any questions that start with "I was using libpng, |
| 117 | and ...". If in doubt, send questions to me. I'll bounce them |
| 118 | to others, if necessary. |
| 119 | |
| 120 | Please do not send suggestions on how to change PNG. We have |
| 121 | been discussing PNG for a couple years now, and it is official and |
| 122 | finished. If you have suggestions for libpng, however, I'll |
| 123 | gladly listen. Even if your suggestion is not used for version |
| 124 | 1.0, it may be used later. |
| 125 | |
| 126 | Files in this distribution: |
| 127 | |
Andreas Dilger | 47a0c42 | 1997-05-16 02:46:07 -0500 | [diff] [blame] | 128 | CHANGES => Description of changes between libpng versions |
Andreas Dilger | 02ad0ef | 1997-01-17 01:34:35 -0600 | [diff] [blame] | 129 | README => This file |
| 130 | TODO => Things not implemented in the current library |
| 131 | ansi2knr.c => Converts files to K&R style function declarations |
| 132 | build.bat => MS-DOS batch file for Borland compiler |
| 133 | descrip.mms => VMS project file |
| 134 | example.c => Example code for using libpng functions |
| 135 | libpng.txt => Description of libpng and its functions |
Andreas Dilger | 47a0c42 | 1997-05-16 02:46:07 -0500 | [diff] [blame] | 136 | makefile => Default Unixish makefile |
Andreas Dilger | 02ad0ef | 1997-01-17 01:34:35 -0600 | [diff] [blame] | 137 | makefile.aco => ACORN makefile |
| 138 | makefile.ama => Amiga makefile |
| 139 | makefile.atr => Atari makefile |
| 140 | makefile.bor => Borland makefile |
| 141 | makefile.dj2 => DJGPP 2 makefile |
| 142 | makefile.elf => Unix ELF makefile |
| 143 | makefile.knr => Makefile which calls ansi2knr to convert files |
| 144 | makefile.mip => MIPS makefile |
| 145 | makefile.msc => Microsoft C makefile |
| 146 | makefile.std => Standard Unix makefile |
| 147 | makefile.tc => Turbo C makefile |
| 148 | makevms.com => VMS make program |
| 149 | png.c => Basic interface functions common to library |
| 150 | png.h => Library function and interface declarations |
| 151 | pngconf.h => System specific library configuration |
| 152 | pngerror.c => Error/warning message I/O functions |
| 153 | pngmem.c => Memory handling functions |
| 154 | pngpread.c => Progressive reading functions |
Andreas Dilger | 02ad0ef | 1997-01-17 01:34:35 -0600 | [diff] [blame] | 155 | pngread.c => Read data/helper high-level functions |
| 156 | pngrio.c => Lowest-level data read I/O functions |
| 157 | pngrtran.c => Read data transformation functions |
| 158 | pngrutil.c => Read data utility functions |
Andreas Dilger | 47a0c42 | 1997-05-16 02:46:07 -0500 | [diff] [blame] | 159 | pngset.c => Functions for storing data into the info_struct |
Andreas Dilger | 02ad0ef | 1997-01-17 01:34:35 -0600 | [diff] [blame] | 160 | pngtest.c => Library test program |
| 161 | pngtest.png => Library test sample image |
| 162 | pngtrans.c => Common data transformation functions |
| 163 | pngwio.c => Lowest-level write I/O functions |
| 164 | pngwrite.c => High-level write functions |
| 165 | pngwtran.c => Write data transformations |
| 166 | pngwutil.c => Write utility functions |
| 167 | |
| 168 | Good luck, and happy coding. |
| 169 | |
| 170 | -Andreas Eric Dilger |
Andreas Dilger | 02ad0ef | 1997-01-17 01:34:35 -0600 | [diff] [blame] | 171 | Internet: adilger@enel.ucalgary.ca |
Andreas Dilger | 47a0c42 | 1997-05-16 02:46:07 -0500 | [diff] [blame] | 172 | Web: http://www-mddsp.enel.ucalgary.ca/People/adilger/ |
Andreas Dilger | 02ad0ef | 1997-01-17 01:34:35 -0600 | [diff] [blame] | 173 | |
| 174 | -Guy Eric Schalnat |
| 175 | Group 42, Inc. |
| 176 | Internet: schalnat@group42.com |
| 177 | CompuServe: 75501,1625 |
Andreas Dilger | 47a0c42 | 1997-05-16 02:46:07 -0500 | [diff] [blame] | 178 | Web: http://www.group42.com/ |
Andreas Dilger | 02ad0ef | 1997-01-17 01:34:35 -0600 | [diff] [blame] | 179 | |