1README for libpng version 1.2.45 - July 7, 2011 (shared library 12.0)
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,
7libpng-*.tar.xz, or libpng-*.tar.bz2 if you want UNIX-style line
8endings in the text files, or lpng*.7z or lpng*.zip if you want DOS-style
9line endings. You can get UNIX-style line endings from the *.zip file
10by using "unzip -a" but there seems to be no simple way to recover
11UNIX-style line endings from the *.7z file. The *.tar.xz file is
12recommended for *NIX users instead.
13
14Version 0.89 was the first official release of libpng. Don't let the
15fact that it's the first release fool you. The libpng library has been in
16extensive use and testing since mid-1995. By late 1997 it had
17finally gotten to the stage where there hadn't been significant
18changes to the API in some time, and people have a bad feeling about
19libraries with versions < 1.0. Version 1.0.0 was released in
20March 1998.
21
22****
23Note that some of the changes to the png_info structure render this
24version of the library binary incompatible with libpng-0.89 or
25earlier 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
27png_uint_32, which will affect shared-library applications that use
28this function.
29
30To avoid problems with changes to the internals of png_info_struct,
31new APIs have been made available in 0.95 to avoid direct application
32access to info_ptr. These functions are the png_set_<chunk> and
33png_get_<chunk> functions. These functions should be used when
34accessing/storing the info_struct data, rather than manipulating it
35directly, to avoid such problems in the future.
36
37It is important to note that the APIs do not make current programs
38that access the info struct directly incompatible with the new
39library. However, it is strongly suggested that new programs use
40the new APIs (as shown in example.c and pngtest.c), and older programs
41be converted to the new format, to facilitate upgrades in the future.
42****
43
44Additions since 0.90 include the ability to compile libpng as a
45Windows DLL, and new APIs for accessing data in the info struct.
46Experimental functions include the ability to set weighting and cost
47factors for row filter selection, direct reads of integers from buffers
48on big-endian processors that support misaligned data access, faster
49methods of doing alpha composition, and more accurate 16->8 bit color
50conversion.
51
52The additions since 0.89 include the ability to read from a PNG stream
53which has had some (or all) of the signature bytes read by the calling
54application. This also allows the reading of embedded PNG streams that
55do not have the PNG file signature. As well, it is now possible to set
56the library action on the detection of chunk CRC errors. It is possible
57to set different actions based on whether the CRC error occurred in a
58critical or an ancillary chunk.
59
60The changes made to the library, and bugs fixed are based on discussions
61on the png-mng-implement mailing list and not on material submitted
62privately to Guy, Andreas, or Glenn. They will forward any good
63suggestions to the list.
64
65For a detailed description on using libpng, read libpng.txt. For
66examples of libpng in a program, see example.c and pngtest.c. For usage
67information and restrictions (what little they are) on libpng, see
68png.h. For a description on using zlib (the compression library used by
69libpng) and zlib's restrictions, see zlib.h
70
71I have included a general makefile, as well as several machine and
72compiler specific ones, but you may have to modify one for your own needs.
73
74You should use zlib 1.0.4 or later to run this, but it MAY work with
75versions as old as zlib 0.95. Even so, there are bugs in older zlib
76versions which can cause the output of invalid compression streams for
77some images. You will definitely need zlib 1.0.4 or later if you are
78taking advantage of the MS-DOS "far" structure allocation for the small
79and medium memory models. You should also note that zlib is a
80compression library that is useful for more things than just PNG files.
81You can use zlib as a drop-in replacement for fread() and fwrite() if
82you are so inclined.
83
84zlib should be available at the same place that libpng is, or at
85ftp://ftp.simplesystems.org/pub/png/src/
86
87You may also want a copy of the PNG specification. It is available
88as an RFC, a W3C Recommendation, and an ISO/IEC Standard. You can find
89these at http://www.libpng.org/pub/png/pngdocs.html
90
91This code is currently being archived at libpng.sf.net in the
92[DOWNLOAD] area, and on CompuServe, Lib 20 (PNG SUPPORT)
93at GO GRAPHSUP. If you can't find it in any of those places,
94e-mail me, and I'll help you find it.
95
96If you have any code changes, requests, problems, etc., please e-mail
97them to me. Also, I'd appreciate any make files or project files,
98and any modifications you needed to make to get libpng to compile,
99along with a #define variable to tell what compiler/system you are on.
100If you needed to add transformations to libpng, or wish libpng would
101provide the image in a different way, drop me a note (and code, if
102possible), so I can consider supporting the transformation.
103Finally, if you get any warning messages when compiling libpng
104(note: not zlib), and they are easy to fix, I'd appreciate the
105fix. Please mention "libpng" somewhere in the subject line. Thanks.
106
107This release was created and will be supported by myself (of course
108based in a large way on Guy's and Andreas' earlier work), and the PNG
109development group.
110
111Send comments/corrections/commendations to png-mng-implement at lists.sf.net
112(subscription required; visit
113https://lists.sourceforge.net/lists/listinfo/png-mng-implement
114to subscribe) or to glennrp at users.sourceforge.net
115
116You can't reach Guy, the original libpng author, at the addresses
117given in previous versions of this document. He and Andreas will
118read mail addressed to the png-mng-implement list, however.
119
120Please do not send general questions about PNG. Send them to
121the (png-mng-misc at lists.sourceforge.net, subscription required, visit
122https://lists.sourceforge.net/lists/listinfo/png-mng-misc to
123subscribe). On the other hand, please do not send libpng questions to
124that address, send them to me or to the png-mng-implement list. I'll
125get them in the end anyway. If you have a question about something
126in the PNG specification that is related to using libpng, send it
127to me. Send me any questions that start with "I was using libpng,
128and ...". If in doubt, send questions to me. I'll bounce them
129to others, if necessary.
130
131Please do not send suggestions on how to change PNG. We have
132been discussing PNG for twelve years now, and it is official and
133finished. If you have suggestions for libpng, however, I'll
134gladly listen. Even if your suggestion is not used immediately,
135it may be used later.
136
137Files in this distribution:
138
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 msvctest => Builds and runs pngtest using a MSVC workspace
178 pngminim => Simple pnm2pngm and png2pnmm programs
179 pngminus => Simple pnm2png and png2pnm programs
180 pngsuite => Test images
181 visupng => Contains a MSVC workspace for VisualPng
182 projects => Contains project files and workspaces for
183 building a DLL
184 beos => Contains a Beos workspace for building libpng
185 c5builder => Contains a Borland workspace for building
186 libpng and zlib
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 wince.txt => Contains instructions for downloading a
193 Microsoft Visual C++ (Windows CD Toolkit)
194 workspace for building libpng and zlib on
195 WindowsCE
196 xcode => Contains xcode project files
197 scripts => Directory containing scripts for building libpng:
198 descrip.mms => VMS makefile for MMS or MMK
199 makefile.std => Generic UNIX makefile (cc, creates static
200 libpng.a)
201 makefile.elf => Linux/ELF gcc makefile symbol versioning,
202 creates libpng12.so.0.1.2.45)
203 makefile.linux => Linux/ELF makefile (gcc, creates
204 libpng12.so.0.1.2.45)
205 makefile.gcmmx => Linux/ELF makefile (gcc, creates
206 libpng12.so.0.1.2.45, previously
207 used assembler code tuned for Intel MMX
208 platform)
209 makefile.gcc => Generic makefile (gcc, creates static
210 libpng.a)
211 makefile.knr => Archaic UNIX Makefile that converts files
212 with ansi2knr (Requires ansi2knr.c from
213 ftp://ftp.cs.wisc.edu/ghost)
214 makefile.aix => AIX makefile
215 makefile.cygwin => Cygwin/gcc makefile
216 makefile.darwin => Darwin makefile
217 makefile.dec => DEC Alpha UNIX makefile
218 makefile.freebsd => FreeBSD makefile
219 makefile.hpgcc => HPUX makefile using gcc
220 makefile.hpux => HPUX (10.20 and 11.00) makefile
221 makefile.hp64 => HPUX (10.20 and 11.00) makefile, 64 bit
222 makefile.ibmc => IBM C/C++ version 3.x for Win32 and OS/2
223 (static)
224 makefile.intel => Intel C/C++ version 4.0 and later
225 libpng.icc => Project file, IBM VisualAge/C++ 4.0 or later
226 makefile.netbsd => NetBSD/cc makefile, makes libpng.so.
227 makefile.ne12bsd => NetBSD/cc makefile, makes libpng12.so
228 makefile.openbsd => OpenBSD makefile
229 makefile.sgi => Silicon Graphics IRIX (cc, creates static lib)
230 makefile.sggcc => Silicon Graphics
231 (gcc, creates libpng12.so.0.1.2.45)
232 makefile.sunos => Sun makefile
233 makefile.solaris => Solaris 2.X makefile
234 (gcc, creates libpng12.so.0.1.2.45)
235 makefile.so9 => Solaris 9 makefile
236 (gcc, creates libpng12.so.0.1.2.45)
237 makefile.32sunu => Sun Ultra 32-bit makefile
238 makefile.64sunu => Sun Ultra 64-bit makefile
239 makefile.sco => For SCO OSr5 ELF and Unixware 7 with Native cc
240 makefile.mips => MIPS makefile
241 makefile.acorn => Acorn makefile
242 makefile.amiga => Amiga makefile
243 smakefile.ppc => AMIGA smakefile for SAS C V6.58/7.00 PPC
244 compiler (Requires SCOPTIONS, copied from
245 scripts/SCOPTIONS.ppc)
246 makefile.atari => Atari makefile
247 makefile.beos => BEOS makefile for X86
248 makefile.bor => Borland makefile (uses bcc)
249 makefile.bc32 => 32-bit Borland C++ (all modules compiled in C mode)
250 makefile.tc3 => Turbo C 3.0 makefile
251 makefile.dj2 => DJGPP 2 makefile
252 makefile.msc => Microsoft C makefile
253 makefile.vcawin32=> makefile for Microsoft Visual C++ 5.0 and
254 later (previously used assembler code tuned
255 for Intel MMX platform)
256 makefile.vcwin32 => makefile for Microsoft Visual C++ 4.0 and
257 later (does not use assembler code)
258 makefile.os2 => OS/2 Makefile (gcc and emx, requires pngos2.def)
259 pngos2.def => OS/2 module definition file used by makefile.os2
260 makefile.watcom => Watcom 10a+ Makefile, 32-bit flat memory model
261 makevms.com => VMS build script
262 SCOPTIONS.ppc => Used with smakefile.ppc
263
264Good luck, and happy coding.
265
266-Glenn Randers-Pehrson (current maintainer, since 1998)
267 Internet: glennrp at users.sourceforge.net
268
269-Andreas Eric Dilger (former maintainer, 1996-1997)
270 Internet: adilger at enel.ucalgary.ca
271 Web: http://members.shaw.ca/adilger/
272
273-Guy Eric Schalnat (original author and former maintainer, 1995-1996)
274 (formerly of Group 42, Inc)
275 Internet: gschal at infinet.com
276
