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a626cc03 | 1 | README for libpng 1.0.3 - January 14, 1999 (shared library 2.1) |
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2 | See the note about version numbers near the top of png.h |
3 | ||
4 | See INSTALL for instructions on how to install libpng. | |
5 | ||
6 | This is the first official release of libpng. Don't let the fact that | |
7 | it's the first release fool you. The libpng library has been in | |
8 | extensive use and testing for about two and a half years. However, it's | |
9 | finally gotten to the stage where there haven't been significant | |
10 | changes to the API in some time, and people have a bad feeling about | |
11 | libraries with versions < 1.0. | |
12 | ||
13 | **** | |
14 | Note that some of the changes to the png_info structure render this | |
15 | version of the library binary incompatible with libpng-0.89 or | |
16 | earlier versions if you are using a shared library. The type of the | |
17 | "filler" parameter for png_set_filler() has changed from png_byte to | |
18 | png_uint_32, which will affect shared-library applications that use | |
19 | this function. | |
20 | ||
21 | To avoid problems with changes to the internals of png_info_struct, | |
22 | new APIs have been made available in 0.95 to avoid direct application | |
23 | access to info_ptr. These functions are the png_set_<chunk> and | |
24 | png_get_<chunk> functions. These functions should be used when | |
25 | accessing/storing the info_struct data, rather than manipulating it | |
26 | directly, to avoid such problems in the future. | |
27 | ||
28 | It is important to note that the APIs do not make current programs | |
29 | that access the info struct directly incompatible with the new | |
30 | library. However, it is strongly suggested that new programs use | |
31 | the new APIs (as shown in example.c), and older programs be converted | |
32 | to the new format, to facilitate upgrades in the future. | |
33 | **** | |
34 | ||
35 | Additions since 0.90 include the ability to compile libpng as a | |
36 | Windows DLL, and new APIs for accessing data in the info struct. | |
37 | Experimental functions include the ability to set weighting and cost | |
38 | factors for row filter selection, direct reads of integers from buffers | |
39 | on big-endian processors that support misaligned data access, faster | |
40 | methods of doing alpha composition, and more accurate 16->8 bit color | |
41 | conversion. | |
42 | ||
43 | The additions since 0.89 include the ability to read from a PNG stream | |
44 | which has had some (or all) of the signature bytes read by the calling | |
45 | application. This also allows the reading of embedded PNG streams that | |
46 | do not have the PNG file signature. As well, it is now possible to set | |
47 | the library action on the detection of chunk CRC errors. It is possible | |
48 | to set different actions based on whether the CRC error occurred in a | |
49 | critical or an ancillary chunk. | |
50 | ||
51 | The changes made to the library, and bugs fixed are based on discussions | |
52 | on the PNG implementation mailing list <png-implement@dworking.wustl.edu> | |
53 | and not on material submitted to Guy. | |
54 | ||
55 | For a detailed description on using libpng, read libpng.txt. For | |
56 | examples of libpng in a program, see example.c and pngtest.c. For usage | |
57 | information and restrictions (what little they are) on libpng, see | |
58 | png.h. For a description on using zlib (the compression library used by | |
59 | libpng) and zlib's restrictions, see zlib.h | |
60 | ||
61 | I have included a general makefile, as well as several machine and | |
62 | compiler specific ones, but you may have to modify one for your own needs. | |
63 | ||
64 | You should use zlib 1.0.4 or later to run this, but it MAY work with | |
65 | versions as old as zlib 0.95. Even so, there are bugs in older zlib | |
66 | versions which can cause the output of invalid compression streams for | |
67 | some images. You will definitely need zlib 1.0.4 or later if you are | |
68 | taking advantage of the MS-DOS "far" structure allocation for the small | |
69 | and medium memory models. You should also note that zlib is a | |
70 | compression library that is useful for more things than just PNG files. | |
71 | You can use zlib as a drop-in replacement for fread() and fwrite() if | |
72 | you are so inclined. | |
73 | ||
74 | zlib should be available at the same place that libpng is. | |
75 | If not, it should be at ftp.uu.net in /graphics/png | |
76 | Eventually, it will be at ftp.uu.net in /pub/archiving/zip/zlib | |
77 | ||
78 | You may also want a copy of the PNG specification. It is available | |
79 | as an RFC and a W3C Recommendation. Failing | |
80 | these resources you can try ftp.uu.net in the /graphics/png directory. | |
81 | ||
82 | This code is currently being archived at ftp.uu.net in the | |
83 | /graphics/png directory, and on CompuServe, Lib 20 (PNG SUPPORT) | |
84 | at GO GRAPHSUP. If you can't find it in any of those places, | |
85 | e-mail me, and I'll help you find it. | |
86 | ||
87 | If you have any code changes, requests, problems, etc., please e-mail | |
88 | them to me. Also, I'd appreciate any make files or project files, | |
89 | and any modifications you needed to make to get libpng to compile, | |
90 | along with a #define variable to tell what compiler/system you are on. | |
91 | If you needed to add transformations to libpng, or wish libpng would | |
92 | provide the image in a different way, drop me a note (and code, if | |
93 | possible), so I can consider supporting the transformation. | |
94 | Finally, if you get any warning messages when compiling libpng | |
95 | (note: not zlib), and they are easy to fix, I'd appreciate the | |
96 | fix. Please mention "libpng" somewhere in the subject line. Thanks. | |
97 | ||
98 | This release was created and will be supported by myself (of course | |
99 | based in a large way on Guy's and Andreas' earlier work), and the PNG group. | |
100 | ||
101 | randeg@alumni.rpi.edu | |
102 | png-implement@dworkin.wustl.edu | |
103 | ||
104 | You can't reach Guy, the original libpng author, at the addresses | |
105 | given in previous versions of this document. He and Andreas will read mail | |
106 | addressed to the png-implement list, however. | |
107 | ||
108 | Please do not send general questions about PNG. Send them to | |
109 | the address in the specification (png-group@w3.org). At the same | |
110 | time, please do not send libpng questions to that address, send them to me | |
111 | or to png-implement@dworkin.wustl.edu. I'll | |
112 | get them in the end anyway. If you have a question about something | |
113 | in the PNG specification that is related to using libpng, send it | |
114 | to me. Send me any questions that start with "I was using libpng, | |
115 | and ...". If in doubt, send questions to me. I'll bounce them | |
116 | to others, if necessary. | |
117 | ||
118 | Please do not send suggestions on how to change PNG. We have | |
119 | been discussing PNG for three years now, and it is official and | |
120 | finished. If you have suggestions for libpng, however, I'll | |
121 | gladly listen. Even if your suggestion is not used for version | |
122 | 1.0, it may be used later. | |
123 | ||
124 | Files in this distribution: | |
125 | ||
126 | CHANGES => Description of changes between libpng versions | |
127 | README => This file | |
128 | TODO => Things not implemented in the current library | |
129 | ansi2knr.1 => Manual page for ansi2knr | |
130 | ansi2knr.c => Converts files to K&R style function declarations | |
131 | build.bat => MS-DOS batch file for Borland compiler | |
132 | descrip.mms => VMS project file | |
133 | example.c => Example code for using libpng functions | |
134 | libpng.3 => manual page for libpng | |
135 | libpng.txt => Description of libpng and its functions | |
136 | libpngpf.3 => manual page for libpng's private functions | |
137 | png.5 => manual page for the PNG format | |
138 | png.c => Basic interface functions common to library | |
139 | png.h => Library function and interface declarations | |
140 | pngconf.h => System specific library configuration | |
141 | pngerror.c => Error/warning message I/O functions | |
142 | pngget.c => Functions for retrieving info from struct | |
143 | pngmem.c => Memory handling functions | |
144 | pngpread.c => Progressive reading functions | |
145 | pngread.c => Read data/helper high-level functions | |
146 | pngrio.c => Lowest-level data read I/O functions | |
147 | pngrtran.c => Read data transformation functions | |
148 | pngrutil.c => Read data utility functions | |
149 | pngset.c => Functions for storing data into the info_struct | |
150 | pngtest.c => Library test program | |
151 | pngtest.png => Library test sample image | |
152 | pngtrans.c => Common data transformation functions | |
153 | pngwio.c => Lowest-level write I/O functions | |
154 | pngwrite.c => High-level write functions | |
155 | pngwtran.c => Write data transformations | |
156 | pngwutil.c => Write utility functions | |
157 | scripts => Directory containing scripts for building libpng: | |
158 | descrip.mms => VMS makefile for MMS or MMK | |
159 | makefile.std => Generic UNIX makefile | |
160 | makefile.knr => Archaic UNIX Makefile that converts files with ansi2knr | |
161 | makefile.dec => DEC Alpha UNIX makefile | |
a626cc03 | 162 | makefile.hux => HPUX (10.20 and 11.00) makefile |
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163 | makefile.sgi => Silicon Graphics IRIX makefile |
164 | makefile.sun => Sun makefile | |
165 | makefile.s2x => Solaris 2.X makefile (gcc, creates libpng.so.2.1.0) | |
166 | makefile.lnx => Linux/ELF makefile (gcc, creates libpng.so.2.1.0) | |
167 | makefile.mip => MIPS makefile | |
168 | makefile.aco => Acorn makefile | |
169 | makefile.ama => Amiga makefile | |
170 | smakefile.ppc => AMIGA smakefile for SAS C V6.58/7.00 PPC compiler | |
171 | (Requires SCOPTIONS, copied from scripts/SCOPTIONS.ppc) | |
172 | makefile.atr => Atari makefile | |
173 | makefile.bor => Borland makefile | |
174 | build.bat => MS-DOS batch file for Borland compiler | |
175 | makefile.dj2 => DJGPP 2 makefile | |
176 | makefile.msc => Microsoft C makefile | |
a626cc03 | 177 | makefile.w32 => makefile for Microsoft Visual C++ 4.0 and later |
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178 | makefile.tc3 => Turbo C 3.0 makefile |
179 | makefile.os2 => OS/2 Makefile (gcc and emx, requires pngos2.def) | |
180 | makefile.wat => Watcom 10a+ Makefile, 32-bit flat memory model | |
181 | pngos2.def => OS/2 module definition file used by makefile.os2 | |
182 | makevms.com => VMS build script | |
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183 | pngdll.mak => To make a png32bd.dll with Borland C++ 4.5 |
184 | pngdef.pas => Defines for a png32bd.dll with Borland C++ 4.5 | |
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185 | |
186 | Good luck, and happy coding. | |
187 | ||
188 | -Glenn Randers-Pehrson | |
189 | Internet: randeg@alumni.rpi.edu | |
190 | Web: http://www.rpi.edu/~randeg/index.html | |
191 | ||
192 | -Andreas Eric Dilger | |
193 | Internet: adilger@enel.ucalgary.ca | |
194 | Web: http://www-mddsp.enel.ucalgary.ca/People/adilger/ | |
195 | ||
196 | -Guy Eric Schalnat | |
197 | (formerly of Group 42, Inc) | |
198 | Internet: gschal@infinet.com |