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1 README for libpng 1.0.1 (shared library 2.1)
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
162 makefile.sgi => Silicon Graphics IRIX makefile
163 makefile.sun => Sun makefile
164 makefile.s2x => Solaris 2.X makefile (gcc, creates libpng.so.2.1.0)
165 makefile.lnx => Linux/ELF makefile (gcc, creates libpng.so.2.1.0)
166 makefile.mip => MIPS makefile
167 makefile.aco => Acorn makefile
168 makefile.ama => Amiga makefile
169 smakefile.ppc => AMIGA smakefile for SAS C V6.58/7.00 PPC compiler
170 (Requires SCOPTIONS, copied from scripts/SCOPTIONS.ppc)
171 makefile.atr => Atari makefile
172 makefile.bor => Borland makefile
173 build.bat => MS-DOS batch file for Borland compiler
174 makefile.dj2 => DJGPP 2 makefile
175 makefile.msc => Microsoft C makefile
176 makefile.tc3 => Turbo C 3.0 makefile
177 makefile.os2 => OS/2 Makefile (gcc and emx, requires pngos2.def)
178 makefile.wat => Watcom 10a+ Makefile, 32-bit flat memory model
179 pngos2.def => OS/2 module definition file used by makefile.os2
180 makevms.com => VMS build script
181
182 Good luck, and happy coding.
183
184 -Glenn Randers-Pehrson
185 Internet: randeg@alumni.rpi.edu
186 Web: http://www.rpi.edu/~randeg/index.html
187
188 -Andreas Eric Dilger
189 Internet: adilger@enel.ucalgary.ca
190 Web: http://www-mddsp.enel.ucalgary.ca/People/adilger/
191
192 -Guy Eric Schalnat
193 (formerly of Group 42, Inc)
194 Internet: gschal@infinet.com