1 README for libpng version 1.5.2 - March 31, 2011 (shared library 15.0)
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,
7 libpng-*.tar.xz or libpng-*.tar.bz2 if you want UNIX-style line endings
8 in the text files, 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
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
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.
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
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
80 zlib should be available at the same place that libpng is, or at.
81 ftp://ftp.info-zip.org/pub/infozip/zlib
83 You may also want a copy of the PNG specification. It is available
84 as an RFC, a W3C Recommendation, and an ISO/IEC Standard. You can find
85 these at http://www.libpng.org/pub/png/documents/
87 This code is currently being archived at libpng.sf.net in the
88 [DOWNLOAD] area, and on CompuServe, Lib 20 (PNG SUPPORT)
89 at GO GRAPHSUP. If you can't find it in any of those places,
90 e-mail me, and I'll help you find it.
92 If you have any code changes, requests, problems, etc., please e-mail
93 them to me. Also, I'd appreciate any make files or project files,
94 and any modifications you needed to make to get libpng to compile,
95 along with a #define variable to tell what compiler/system you are on.
96 If you needed to add transformations to libpng, or wish libpng would
97 provide the image in a different way, drop me a note (and code, if
98 possible), so I can consider supporting the transformation.
99 Finally, if you get any warning messages when compiling libpng
100 (note: not zlib), and they are easy to fix, I'd appreciate the
101 fix. Please mention "libpng" somewhere in the subject line. Thanks.
103 This release was created and will be supported by myself (of course
104 based in a large way on Guy's and Andreas' earlier work), and the PNG
107 Send comments/corrections/commendations to png-mng-implement at
108 lists.sourceforge.net (subscription required; visit
109 https://lists.sourceforge.net/lists/listinfo/png-mng-implement
110 to subscribe) or to glennrp at users.sourceforge.net
112 You can't reach Guy, the original libpng author, at the addresses
113 given in previous versions of this document. He and Andreas will
114 read mail addressed to the png-implement list, however.
116 Please do not send general questions about PNG. Send them to
117 the (png-list at ccrc.wustl.edu, subscription required, write to
118 majordomo at ccrc.wustl.edu with "subscribe png-list" in your message).
120 please do not send libpng questions to that address, send them to me
121 or to the png-implement list. I'll
122 get them in the end anyway. If you have a question about something
123 in the PNG specification that is related to using libpng, send it
124 to me. Send me any questions that start with "I was using libpng,
125 and ...". If in doubt, send questions to me. I'll bounce them
126 to others, if necessary.
128 Please do not send suggestions on how to change PNG. We have
129 been discussing PNG for nine years now, and it is official and
130 finished. If you have suggestions for libpng, however, I'll
131 gladly listen. Even if your suggestion is not used immediately,
132 it may be used later.
134 Files in this distribution:
136 ANNOUNCE => Announcement of this version, with recent changes
137 CHANGES => Description of changes between libpng versions
138 KNOWNBUG => List of known bugs and deficiencies
139 LICENSE => License to use and redistribute libpng
141 TODO => Things not implemented in the current library
142 Y2KINFO => Statement of Y2K compliance
143 example.c => Example code for using libpng functions
144 libpng.3 => manual page for libpng (includes libpng-manual.txt)
145 libpng-manual.txt => Description of libpng and its functions
146 libpngpf.3 => manual page for libpng's private functions
147 png.5 => manual page for the PNG format
148 png.c => Basic interface functions common to library
149 png.h => Library function and interface declarations (public)
150 pngpriv.h => Library function and interface declarations (private)
151 pngconf.h => System specific library configuration (public)
152 pngstruct.h => png_struct declaration (private)
153 pnginfo.h => png_info struct declaration (private)
154 pngdebug.h => debugging macros (private)
155 pngerror.c => Error/warning message I/O functions
156 pngget.c => Functions for retrieving info from struct
157 pngmem.c => Memory handling functions
158 pngbar.png => PNG logo, 88x31
159 pngnow.png => PNG logo, 98x31
160 pngpread.c => Progressive reading functions
161 pngread.c => Read data/helper high-level functions
162 pngrio.c => Lowest-level data read I/O functions
163 pngrtran.c => Read data transformation functions
164 pngrutil.c => Read data utility functions
165 pngset.c => Functions for storing data into the info_struct
166 pngtest.c => Library test program
167 pngtest.png => Library test sample image
168 pngtrans.c => Common data transformation functions
169 pngwio.c => Lowest-level write I/O functions
170 pngwrite.c => High-level write functions
171 pngwtran.c => Write data transformations
172 pngwutil.c => Write utility functions
173 contrib => Contributions
174 gregbook => source code for PNG reading and writing, from
175 Greg Roelofs' "PNG: The Definitive Guide",
177 msvctest => Builds and runs pngtest using a MSVC workspace
178 pngminus => Simple pnm2png and png2pnm programs
179 pngsuite => Test images
180 visupng => Contains a MSVC workspace for VisualPng
181 projects => Contains project files and workspaces for
183 cbuilder5 => Contains a Borland workspace for building
185 visualc6 => Contains a Microsoft Visual C++ (MSVC)
186 workspace for building libpng and zlib
187 visualc71 => Contains a Microsoft Visual C++ (MSVC)
188 workspace for building libpng and zlib
189 xcode => Contains an Apple xcode
190 workspace for building libpng and zlib
191 scripts => Directory containing scripts for building libpng:
192 (see scripts/README.txt for the list of scripts)
194 Good luck, and happy coding.
196 -Glenn Randers-Pehrson (current maintainer, since 1998)
197 Internet: glennrp at users.sourceforge.net
199 -Andreas Eric Dilger (former maintainer, 1996-1997)
200 Internet: adilger at enel.ucalgary.ca
201 Web: http://www-mddsp.enel.ucalgary.ca/People/adilger/
203 -Guy Eric Schalnat (original author and former maintainer, 1995-1996)
204 (formerly of Group 42, Inc)
205 Internet: gschal at infinet.com