1README for libpng version 1.6.10 - March 6, 2014 (shared library 16.0)
2See the note about version numbers near the top of png.h
3
4See INSTALL for instructions on how to install libpng.
5
6Libpng comes in several distribution formats. Get libpng-*.tar.gz or
7libpng-*.tar.xz or if you want UNIX-style line endings in the text files,
8or lpng*.7z or lpng*.zip if you want DOS-style line endings.
9
10Version 0.89 was the first official release of libpng. Don't let the
11fact that it's the first release fool you. The libpng library has been in
12extensive use and testing since mid-1995. By late 1997 it had
13finally gotten to the stage where there hadn't been significant
14changes to the API in some time, and people have a bad feeling about
15libraries with versions < 1.0. Version 1.0.0 was released in
16March 1998.
17
18****
19Note that some of the changes to the png_info structure render this
20version of the library binary incompatible with libpng-0.89 or
21earlier versions if you are using a shared library. The type of the
22"filler" parameter for png_set_filler() has changed from png_byte to
23png_uint_32, which will affect shared-library applications that use
24this function.
25
26To avoid problems with changes to the internals of png_info_struct,
27new APIs have been made available in 0.95 to avoid direct application
28access to info_ptr. These functions are the png_set_<chunk> and
29png_get_<chunk> functions. These functions should be used when
30accessing/storing the info_struct data, rather than manipulating it
31directly, to avoid such problems in the future.
32
33It is important to note that the APIs do not make current programs
34that access the info struct directly incompatible with the new
35library. However, it is strongly suggested that new programs use
36the new APIs (as shown in example.c and pngtest.c), and older programs
37be converted to the new format, to facilitate upgrades in the future.
38****
39
40Additions since 0.90 include the ability to compile libpng as a
41Windows DLL, and new APIs for accessing data in the info struct.
42Experimental functions include the ability to set weighting and cost
43factors for row filter selection, direct reads of integers from buffers
44on big-endian processors that support misaligned data access, faster
45methods of doing alpha composition, and more accurate 16->8 bit color
46conversion.
47
48The additions since 0.89 include the ability to read from a PNG stream
49which has had some (or all) of the signature bytes read by the calling
50application. This also allows the reading of embedded PNG streams that
51do not have the PNG file signature. As well, it is now possible to set
52the library action on the detection of chunk CRC errors. It is possible
53to set different actions based on whether the CRC error occurred in a
54critical or an ancillary chunk.
55
56The changes made to the library, and bugs fixed are based on discussions
57on the PNG-implement mailing list and not on material submitted
58privately to Guy, Andreas, or Glenn. They will forward any good
59suggestions to the list.
60
61For a detailed description on using libpng, read libpng-manual.txt. For
62examples of libpng in a program, see example.c and pngtest.c. For usage
63information and restrictions (what little they are) on libpng, see
64png.h. For a description on using zlib (the compression library used by
65libpng) and zlib's restrictions, see zlib.h
66
67I have included a general makefile, as well as several machine and
68compiler specific ones, but you may have to modify one for your own needs.
69
70You should use zlib 1.0.4 or later to run this, but it MAY work with
71versions as old as zlib 0.95. Even so, there are bugs in older zlib
72versions which can cause the output of invalid compression streams for
73some images. You will definitely need zlib 1.0.4 or later if you are
74taking advantage of the MS-DOS "far" structure allocation for the small
75and medium memory models. You should also note that zlib is a
76compression library that is useful for more things than just PNG files.
77You can use zlib as a drop-in replacement for fread() and fwrite() if
78you are so inclined.
79
80zlib should be available at the same place that libpng is, or at zlib.net.
81
82You may also want a copy of the PNG specification. It is available
83as an RFC, a W3C Recommendation, and an ISO/IEC Standard. You can find
84these at http://www.libpng.org/pub/png/documents/
85
86This code is currently being archived at libpng.sf.net in the
87[DOWNLOAD] area, and at ftp://ftp.simplesystems.org. If you can't find it
88in any of those places, e-mail me, and I'll help you find it.
89
90If you have any code changes, requests, problems, etc., please e-mail
91them to me. Also, I'd appreciate any make files or project files,
92and any modifications you needed to make to get libpng to compile,
93along with a #define variable to tell what compiler/system you are on.
94If you needed to add transformations to libpng, or wish libpng would
95provide the image in a different way, drop me a note (and code, if
96possible), so I can consider supporting the transformation.
97Finally, if you get any warning messages when compiling libpng
98(note: not zlib), and they are easy to fix, I'd appreciate the
99fix. Please mention "libpng" somewhere in the subject line. Thanks.
100
101This release was created and will be supported by myself (of course
102based in a large way on Guy's and Andreas' earlier work), and the PNG
103development group.
104
105Send comments/corrections/commendations to png-mng-implement at
106lists.sourceforge.net (subscription required; visit
107https://lists.sourceforge.net/lists/listinfo/png-mng-implement
108to subscribe) or to glennrp at users.sourceforge.net
109
110You can't reach Guy, the original libpng author, at the addresses
111given in previous versions of this document. He and Andreas will
112read mail addressed to the png-implement list, however.
113
114Please do not send general questions about PNG. Send them to
115png-mng-misc at lists.sf.net (subscription required; visit
116https://lists.sourceforge.net/lists/listinfo/png-mng-misc to
117subscribe). If you have a question about something
118in the PNG specification that is related to using libpng, send it
119to me. Send me any questions that start with "I was using libpng,
120and ...". If in doubt, send questions to me. I'll bounce them
121to others, if necessary.
122
123Please do not send suggestions on how to change PNG. We have
124been discussing PNG for nineteen years now, and it is official and
125finished. If you have suggestions for libpng, however, I'll
126gladly listen. Even if your suggestion is not used immediately,
127it may be used later.
128
129Files in this distribution:
130
131 ANNOUNCE => Announcement of this version, with recent changes
132 CHANGES => Description of changes between libpng versions
133 KNOWNBUG => List of known bugs and deficiencies
134 LICENSE => License to use and redistribute libpng
135 README => This file
136 TODO => Things not implemented in the current library
137 Y2KINFO => Statement of Y2K compliance
138 example.c => Example code for using libpng functions
139 libpng.3 => manual page for libpng (includes libpng-manual.txt)
140 libpng-manual.txt => Description of libpng and its functions
141 libpngpf.3 => manual page for libpng's private functions
142 png.5 => manual page for the PNG format
143 png.c => Basic interface functions common to library
144 png.h => Library function and interface declarations (public)
145 pngpriv.h => Library function and interface declarations (private)
146 pngconf.h => System specific library configuration (public)
147 pngstruct.h => png_struct declaration (private)
148 pnginfo.h => png_info struct declaration (private)
149 pngdebug.h => debugging macros (private)
150 pngerror.c => Error/warning message I/O functions
151 pngget.c => Functions for retrieving info from struct
152 pngmem.c => Memory handling functions
153 pngbar.png => PNG logo, 88x31
154 pngnow.png => PNG logo, 98x31
155 pngpread.c => Progressive reading functions
156 pngread.c => Read data/helper high-level functions
157 pngrio.c => Lowest-level data read I/O functions
158 pngrtran.c => Read data transformation functions
159 pngrutil.c => Read data utility functions
160 pngset.c => Functions for storing data into the info_struct
161 pngtest.c => Library test program
162 pngtest.png => Library test sample image
163 pngtrans.c => Common data transformation functions
164 pngwio.c => Lowest-level write I/O functions
165 pngwrite.c => High-level write functions
166 pngwtran.c => Write data transformations
167 pngwutil.c => Write utility functions
168 arm => Contains optimized code for the ARM platform
169 contrib => Contributions
170 examples => Example programs
171 gregbook => source code for PNG reading and writing, from
172 Greg Roelofs' "PNG: The Definitive Guide",
173 O'Reilly, 1999
174 libtests => Test programs
175 pngminim => Minimal decoder, encoder, and progressive decoder
176 programs demonstrating use of pngusr.dfa
177 pngminus => Simple pnm2png and png2pnm programs
178 pngsuite => Test images
179 tools => Various tools
180 visupng => Contains a MSVC workspace for VisualPng
181 projects => Contains project files and workspaces for
182 building a DLL
183 owatcom => Contains a WATCOM project for building libpng
184 visualc71 => Contains a Microsoft Visual C++ (MSVC)
185 workspace for building libpng and zlib
186 vstudio => Contains a Microsoft Visual C++ (MSVC)
187 workspace for building libpng and zlib
188 scripts => Directory containing scripts for building libpng:
189 (see scripts/README.txt for the list of scripts)
190
191Good luck, and happy coding.
192
193-Glenn Randers-Pehrson (current maintainer, since 1998)
194 Internet: glennrp at users.sourceforge.net
195
196-Andreas Eric Dilger (former maintainer, 1996-1997)
197 Internet: adilger at enel.ucalgary.ca
198 Web: http://www-mddsp.enel.ucalgary.ca/People/adilger/
199
200-Guy Eric Schalnat (original author and former maintainer, 1995-1996)
201 (formerly of Group 42, Inc)
202 Internet: gschal at infinet.com
203
