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1 README for libpng version 1.2.51 - February 6, 2014 (shared library 12.0)
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
8 endings in the text files, or lpng*.7z or lpng*.zip if you want DOS-style
9 line endings. You can get UNIX-style line endings from the *.zip file
10 by using "unzip -a" but there seems to be no simple way to recover
11 UNIX-style line endings from the *.7z file. The *.tar.xz file is
12 recommended for *NIX users instead.
14 Version 0.89 was the first official release of libpng. Don't let the
15 fact that it's the first release fool you. The libpng library has been in
16 extensive use and testing since mid-1995. By late 1997 it had
17 finally gotten to the stage where there hadn't been significant
18 changes to the API in some time, and people have a bad feeling about
19 libraries with versions < 1.0. Version 1.0.0 was released in
20 March 1998.
22 ****
23 Note that some of the changes to the png_info structure render this
24 version of the library binary incompatible with libpng-0.89 or
25 earlier versions if you are using a shared library. The type of the
26 "filler" parameter for png_set_filler() has changed from png_byte to
27 png_uint_32, which will affect shared-library applications that use
28 this function.
30 To avoid problems with changes to the internals of png_info_struct,
31 new APIs have been made available in 0.95 to avoid direct application
32 access to info_ptr. These functions are the png_set_<chunk> and
33 png_get_<chunk> functions. These functions should be used when
34 accessing/storing the info_struct data, rather than manipulating it
35 directly, to avoid such problems in the future.
37 It is important to note that the APIs do not make current programs
38 that access the info struct directly incompatible with the new
39 library. However, it is strongly suggested that new programs use
40 the new APIs (as shown in example.c and pngtest.c), and older programs
41 be converted to the new format, to facilitate upgrades in the future.
42 ****
44 Additions since 0.90 include the ability to compile libpng as a
45 Windows DLL, and new APIs for accessing data in the info struct.
46 Experimental functions include the ability to set weighting and cost
47 factors for row filter selection, direct reads of integers from buffers
48 on big-endian processors that support misaligned data access, faster
49 methods of doing alpha composition, and more accurate 16->8 bit color
50 conversion.
52 The additions since 0.89 include the ability to read from a PNG stream
53 which has had some (or all) of the signature bytes read by the calling
54 application. This also allows the reading of embedded PNG streams that
55 do not have the PNG file signature. As well, it is now possible to set
56 the library action on the detection of chunk CRC errors. It is possible
57 to set different actions based on whether the CRC error occurred in a
58 critical or an ancillary chunk.
60 The changes made to the library, and bugs fixed are based on discussions
61 on the png-mng-implement mailing list and not on material submitted
62 privately to Guy, Andreas, or Glenn. They will forward any good
63 suggestions to the list.
65 For a detailed description on using libpng, read libpng.txt. For
66 examples of libpng in a program, see example.c and pngtest.c. For usage
67 information and restrictions (what little they are) on libpng, see
68 png.h. For a description on using zlib (the compression library used by
69 libpng) and zlib's restrictions, see zlib.h
71 I have included a general makefile, as well as several machine and
72 compiler specific ones, but you may have to modify one for your own needs.
74 You should use zlib 1.0.4 or later to run this, but it MAY work with
75 versions as old as zlib 0.95. Even so, there are bugs in older zlib
76 versions which can cause the output of invalid compression streams for
77 some images. You will definitely need zlib 1.0.4 or later if you are
78 taking advantage of the MS-DOS "far" structure allocation for the small
79 and medium memory models. You should also note that zlib is a
80 compression library that is useful for more things than just PNG files.
81 You can use zlib as a drop-in replacement for fread() and fwrite() if
82 you are so inclined.
84 zlib should be available at the same place that libpng is, or at
85 ftp://ftp.simplesystems.org/pub/png/src/
87 You may also want a copy of the PNG specification. It is available
88 as an RFC, a W3C Recommendation, and an ISO/IEC Standard. You can find
89 these at http://www.libpng.org/pub/png/pngdocs.html
91 This code is currently being archived at libpng.sf.net in the
92 [DOWNLOAD] area, and on CompuServe, Lib 20 (PNG SUPPORT)
93 at GO GRAPHSUP. If you can't find it in any of those places,
94 e-mail me, and I'll help you find it.
96 If you have any code changes, requests, problems, etc., please e-mail
97 them to me. Also, I'd appreciate any make files or project files,
98 and any modifications you needed to make to get libpng to compile,
99 along with a #define variable to tell what compiler/system you are on.
100 If you needed to add transformations to libpng, or wish libpng would
101 provide the image in a different way, drop me a note (and code, if
102 possible), so I can consider supporting the transformation.
103 Finally, if you get any warning messages when compiling libpng
104 (note: not zlib), and they are easy to fix, I'd appreciate the
105 fix. Please mention "libpng" somewhere in the subject line. Thanks.
107 This release was created and will be supported by myself (of course
108 based in a large way on Guy's and Andreas' earlier work), and the PNG
109 development group.
111 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
112 (subscription required; visit
113 https://lists.sourceforge.net/lists/listinfo/png-mng-implement
114 to subscribe) or to glennrp at users.sourceforge.net
116 You can't reach Guy, the original libpng author, at the addresses
117 given in previous versions of this document. He and Andreas will
118 read mail addressed to the png-mng-implement list, however.
120 Please do not send general questions about PNG. Send them to
121 the (png-mng-misc at lists.sourceforge.net, subscription required, visit
122 https://lists.sourceforge.net/lists/listinfo/png-mng-misc to
123 subscribe). On the other hand, please do not send libpng questions to
124 that address, send them to me or to the png-mng-implement list. I'll
125 get them in the end anyway. If you have a question about something
126 in the PNG specification that is related to using libpng, send it
127 to me. Send me any questions that start with "I was using libpng,
128 and ...". If in doubt, send questions to me. I'll bounce them
129 to others, if necessary.
131 Please do not send suggestions on how to change PNG. We have
132 been discussing PNG for nineteen years now, and it is official and
133 finished. If you have suggestions for libpng, however, I'll
134 gladly listen. Even if your suggestion is not used immediately,
135 it may be used later.
137 Files in this distribution:
139 ANNOUNCE => Announcement of this version, with recent changes
140 CHANGES => Description of changes between libpng versions
141 KNOWNBUG => List of known bugs and deficiencies
142 LICENSE => License to use and redistribute libpng
143 README => This file
144 TODO => Things not implemented in the current library
145 Y2KINFO => Statement of Y2K compliance
146 example.c => Example code for using libpng functions
147 libpng-*-*-diff.txt => Diff from previous release
148 libpng.3 => manual page for libpng (includes libpng.txt)
149 libpng.txt => Description of libpng and its functions
150 libpngpf.3 => manual page for libpng's private functions
151 png.5 => manual page for the PNG format
152 png.c => Basic interface functions common to library
153 png.h => Library function and interface declarations
154 pngconf.h => System specific library configuration
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",
176 O'Reilly, 1999
177 pngminim => Minimal pnm2pngm and png2pnmm programs
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
182 building a DLL
183 beos => Contains a Beos workspace for building libpng
184 c5builder => Contains a Borland workspace for building
185 libpng and zlib
186 MacOSX => Contains a MacOSX workspace for building libpng
187 netware.txt => Contains instructions for downloading a set
188 of project files for building libpng and
189 zlib on Netware.
190 visualc6 => Contains a Microsoft Visual C++ (MSVC)
191 workspace for building libpng and zlib
192 visualc71 => Contains a Microsoft Visual C++ (MSVC)
193 workspace for building libpng and zlib
194 wince.txt => Contains instructions for downloading a
195 Microsoft Visual C++ (Windows CD Toolkit)
196 workspace for building libpng and zlib on
197 WindowsCE
198 xcode => Contains xcode project files
199 scripts => Directory containing scripts for building libpng:
200 descrip.mms => VMS makefile for MMS or MMK
201 makefile.std => Generic UNIX makefile (cc, creates static
202 libpng.a)
203 makefile.elf => Linux/ELF gcc makefile symbol versioning,
204 creates libpng12.so.0.1.2.51)
205 makefile.linux => Linux/ELF makefile (gcc, creates
206 libpng12.so.0.1.2.51)
207 makefile.gcmmx => Linux/ELF makefile (gcc, creates
208 libpng12.so.0.1.2.51, previously
209 used assembler code tuned for Intel MMX
210 platform)
211 makefile.gcc => Generic makefile (gcc, creates static
212 libpng.a)
213 makefile.knr => Archaic UNIX Makefile that converts files
214 with ansi2knr (Requires ansi2knr.c from
215 ftp://ftp.cs.wisc.edu/ghost)
216 makefile.aix => AIX makefile
217 makefile.cygwin => Cygwin/gcc makefile
218 makefile.darwin => Darwin makefile
219 makefile.dec => DEC Alpha UNIX makefile
220 makefile.freebsd => FreeBSD makefile
221 makefile.hpgcc => HPUX makefile using gcc
222 makefile.hpux => HPUX (10.20 and 11.00) makefile
223 makefile.hp64 => HPUX (10.20 and 11.00) makefile, 64 bit
224 makefile.ibmc => IBM C/C++ version 3.x for Win32 and OS/2
225 (static)
226 makefile.intel => Intel C/C++ version 4.0 and later
227 libpng.icc => Project file, IBM VisualAge/C++ 4.0 or later
228 makefile.netbsd => NetBSD/cc makefile, makes libpng.so.
229 makefile.ne12bsd => NetBSD/cc makefile, makes libpng12.so
230 makefile.openbsd => OpenBSD makefile
231 makefile.sgi => Silicon Graphics IRIX (cc, creates static lib)
232 makefile.sggcc => Silicon Graphics
233 (gcc, creates libpng12.so.0.1.2.51)
234 makefile.sunos => Sun makefile
235 makefile.solaris => Solaris 2.X makefile
236 (gcc, creates libpng12.so.0.1.2.51)
237 makefile.so9 => Solaris 9 makefile
238 (gcc, creates libpng12.so.0.1.2.51)
239 makefile.32sunu => Sun Ultra 32-bit makefile
240 makefile.64sunu => Sun Ultra 64-bit makefile
241 makefile.sco => For SCO OSr5 ELF and Unixware 7 with Native cc
242 makefile.mips => MIPS makefile
243 makefile.acorn => Acorn makefile
244 makefile.amiga => Amiga makefile
245 smakefile.ppc => AMIGA smakefile for SAS C V6.58/7.00 PPC
246 compiler (Requires SCOPTIONS, copied from
247 scripts/SCOPTIONS.ppc)
248 makefile.atari => Atari makefile
249 makefile.beos => BEOS makefile for X86
250 makefile.bor => Borland makefile (uses bcc)
251 makefile.bc32 => 32-bit Borland C++ (all modules compiled in C mode)
252 makefile.tc3 => Turbo C 3.0 makefile
253 makefile.dj2 => DJGPP 2 makefile
254 makefile.msc => Microsoft C makefile
255 makefile.vcawin32=> makefile for Microsoft Visual C++ 5.0 and
256 later (previously used assembler code tuned
257 for Intel MMX platform)
258 makefile.vcwin32 => makefile for Microsoft Visual C++ 4.0 and
259 later (does not use assembler code)
260 makefile.os2 => OS/2 Makefile (gcc and emx, requires pngos2.def)
261 pngos2.def => OS/2 module definition file used by makefile.os2
262 makefile.watcom => Watcom 10a+ Makefile, 32-bit flat memory model
263 makevms.com => VMS build script
264 SCOPTIONS.ppc => Used with smakefile.ppc
266 Good luck, and happy coding.
268 -Glenn Randers-Pehrson (current maintainer, since 1998)
269 Internet: glennrp at users.sourceforge.net
271 -Andreas Eric Dilger (former maintainer, 1996-1997)
272 Internet: adilger at enel.ucalgary.ca
273 Web: http://members.shaw.ca/adilger/
275 -Guy Eric Schalnat (original author and former maintainer, 1995-1996)
276 (formerly of Group 42, Inc)
277 Internet: gschal at infinet.com