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1 README for libpng version 1.6.3 - July 18, 2013 (shared library 16.0)
2 See the note about version numbers near the top of png.h
4 See INSTALL for instructions on how to install libpng.
6 Libpng comes in several distribution formats. Get libpng-*.tar.gz or
7 libpng-*.tar.xz or if you want UNIX-style line endings in the text files,
8 or lpng*.7z or lpng*.zip if you want DOS-style line endings.
10 Version 0.89 was the first official release of libpng. Don't let the
11 fact that it's the first release fool you. The libpng library has been in
12 extensive use and testing since mid-1995. By late 1997 it had
13 finally gotten to the stage where there hadn't been significant
14 changes to the API in some time, and people have a bad feeling about
15 libraries with versions < 1.0. Version 1.0.0 was released in
16 March 1998.
18 ****
19 Note that some of the changes to the png_info structure render this
20 version of the library binary incompatible with libpng-0.89 or
21 earlier 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
23 png_uint_32, which will affect shared-library applications that use
24 this function.
26 To avoid problems with changes to the internals of png_info_struct,
27 new APIs have been made available in 0.95 to avoid direct application
28 access to info_ptr. These functions are the png_set_<chunk> and
29 png_get_<chunk> functions. These functions should be used when
30 accessing/storing the info_struct data, rather than manipulating it
31 directly, to avoid such problems in the future.
33 It is important to note that the APIs do not make current programs
34 that access the info struct directly incompatible with the new
35 library. However, it is strongly suggested that new programs use
36 the new APIs (as shown in example.c and pngtest.c), and older programs
37 be converted to the new format, to facilitate upgrades in the future.
38 ****
40 Additions since 0.90 include the ability to compile libpng as a
41 Windows DLL, and new APIs for accessing data in the info struct.
42 Experimental functions include the ability to set weighting and cost
43 factors for row filter selection, direct reads of integers from buffers
44 on big-endian processors that support misaligned data access, faster
45 methods of doing alpha composition, and more accurate 16->8 bit color
46 conversion.
48 The additions since 0.89 include the ability to read from a PNG stream
49 which has had some (or all) of the signature bytes read by the calling
50 application. This also allows the reading of embedded PNG streams that
51 do not have the PNG file signature. As well, it is now possible to set
52 the library action on the detection of chunk CRC errors. It is possible
53 to set different actions based on whether the CRC error occurred in a
54 critical or an ancillary chunk.
56 The changes made to the library, and bugs fixed are based on discussions
57 on the PNG-implement mailing list and not on material submitted
58 privately to Guy, Andreas, or Glenn. They will forward any good
59 suggestions to the list.
61 For a detailed description on using libpng, read libpng-manual.txt. For
62 examples of libpng in a program, see example.c and pngtest.c. For usage
63 information and restrictions (what little they are) on libpng, see
64 png.h. For a description on using zlib (the compression library used by
65 libpng) and zlib's restrictions, see zlib.h
67 I have included a general makefile, as well as several machine and
68 compiler specific ones, but you may have to modify one for your own needs.
70 You should use zlib 1.0.4 or later to run this, but it MAY work with
71 versions as old as zlib 0.95. Even so, there are bugs in older zlib
72 versions which can cause the output of invalid compression streams for
73 some images. You will definitely need zlib 1.0.4 or later if you are
74 taking advantage of the MS-DOS "far" structure allocation for the small
75 and medium memory models. You should also note that zlib is a
76 compression library that is useful for more things than just PNG files.
77 You can use zlib as a drop-in replacement for fread() and fwrite() if
78 you are so inclined.
80 zlib should be available at the same place that libpng is, or at zlib.net.
82 You may also want a copy of the PNG specification. It is available
83 as an RFC, a W3C Recommendation, and an ISO/IEC Standard. You can find
84 these at http://www.libpng.org/pub/png/documents/
86 This 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
88 in any of those places, e-mail me, and I'll help you find it.
90 If you have any code changes, requests, problems, etc., please e-mail
91 them to me. Also, I'd appreciate any make files or project files,
92 and any modifications you needed to make to get libpng to compile,
93 along with a #define variable to tell what compiler/system you are on.
94 If you needed to add transformations to libpng, or wish libpng would
95 provide the image in a different way, drop me a note (and code, if
96 possible), so I can consider supporting the transformation.
97 Finally, if you get any warning messages when compiling libpng
98 (note: not zlib), and they are easy to fix, I'd appreciate the
99 fix. Please mention "libpng" somewhere in the subject line. Thanks.
101 This release was created and will be supported by myself (of course
102 based in a large way on Guy's and Andreas' earlier work), and the PNG
103 development group.
105 Send comments/corrections/commendations to png-mng-implement at
106 lists.sourceforge.net (subscription required; visit
107 https://lists.sourceforge.net/lists/listinfo/png-mng-implement
108 to subscribe) or to glennrp at users.sourceforge.net
110 You can't reach Guy, the original libpng author, at the addresses
111 given in previous versions of this document. He and Andreas will
112 read mail addressed to the png-implement list, however.
114 Please do not send general questions about PNG. Send them to
115 png-mng-misc at lists.sf.net (subscription required; visit
116 https://lists.sourceforge.net/lists/listinfo/png-mng-misc to
117 subscribe). If you have a question about something
118 in the PNG specification that is related to using libpng, send it
119 to me. Send me any questions that start with "I was using libpng,
120 and ...". If in doubt, send questions to me. I'll bounce them
121 to others, if necessary.
123 Please do not send suggestions on how to change PNG. We have
124 been discussing PNG for eighteen years now, and it is official and
125 finished. If you have suggestions for libpng, however, I'll
126 gladly listen. Even if your suggestion is not used immediately,
127 it may be used later.
129 Files in this distribution:
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)
191 Good luck, and happy coding.
193 -Glenn Randers-Pehrson (current maintainer, since 1998)
194 Internet: glennrp at users.sourceforge.net
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/
200 -Guy Eric Schalnat (original author and former maintainer, 1995-1996)
201 (formerly of Group 42, Inc)
202 Internet: gschal at infinet.com