1 README for libpng version 1.6.35 - July 15, 2018 (shared library 16.0)
2 See the note about version numbers near the top of png.h
3
4 See INSTALL for instructions on how to install libpng.
5
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.
9
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.
17
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.
25
26 To avoid problems with changes to the internals of the 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.
32
43 older programs be converted to the new format, to facilitate upgrades
44 in the future.
45 ****
46
47 Additions since 0.90 include the ability to compile libpng as a
48 Windows DLL, and new APIs for accessing data in the info struct.
49 Experimental functions include the ability to set weighting and cost
50 factors for row filter selection, direct reads of integers from buffers
51 on big-endian processors that support misaligned data access, faster
52 methods of doing alpha composition, and more accurate 16->8 bit color
53 conversion.
54
55 The additions since 0.89 include the ability to read from a PNG stream
56 which has had some (or all) of the signature bytes read by the calling
57 application. This also allows the reading of embedded PNG streams that
58 do not have the PNG file signature. As well, it is now possible to set
59 the library action on the detection of chunk CRC errors. It is possible
60 to set different actions based on whether the CRC error occurred in a
61 critical or an ancillary chunk.
62
63 The changes made to the library, and bugs fixed are based on discussions
64 on the PNG-implement mailing list and not on material submitted
65 privately to Guy, Andreas, or Glenn. They will forward any good
66 suggestions to the list.
67
68 For a detailed description on using libpng, read libpng-manual.txt. For
69 examples of libpng in a program, see example.c and pngtest.c. For usage
70 information and restrictions (what little they are) on libpng, see
71 png.h. For a description on using zlib (the compression library used by
72 libpng) and zlib's restrictions, see zlib.h
73
74 I have included a general makefile, as well as several machine and
75 compiler specific ones, but you may have to modify one for your own needs.
76
77 You should use zlib 1.0.4 or later to run this, but it MAY work with
78 versions as old as zlib 0.95. Even so, there are bugs in older zlib
79 versions which can cause the output of invalid compression streams for
80 some images. You will definitely need zlib 1.0.4 or later if you are
81 taking advantage of the MS-DOS "far" structure allocation for the small
82 and medium memory models. You should also note that zlib is a
83 compression library that is useful for more things than just PNG files.
84 You can use zlib as a drop-in replacement for fread() and fwrite() if
85 you are so inclined.
86
87 zlib should be available at the same place that libpng is, or at zlib.net.
88
89 You may also want a copy of the PNG specification. It is available
90 as an RFC, a W3C Recommendation, and an ISO/IEC Standard. You can find
91 these at http://www.libpng.org/pub/png/pngdocs.html .
92
93 This code is currently being archived at libpng.sourceforge.io in the
94 [DOWNLOAD] area, and at http://libpng.download/src . If you
95 can't find it in any of those places, e-mail me, and I'll help you find it.
96
97 I am not a lawyer, but I believe that the Export Control Classification
98 Number (ECCN) for libpng is EAR99, which means not subject to export
99 controls or International Traffic in Arms Regulations (ITAR) because it
100 is open source, publicly available software, that does not contain any
101 encryption software. See the EAR, paragraphs 734.3(b)(3) and 734.7(b).
102
103 If you have any code changes, requests, problems, etc., please e-mail
104 them to me. Also, I'd appreciate any make files or project files,
105 and any modifications you needed to make to get libpng to compile,
106 along with a #define variable to tell what compiler/system you are on.
107 If you needed to add transformations to libpng, or wish libpng would
108 provide the image in a different way, drop me a note (and code, if
109 possible), so I can consider supporting the transformation.
110 Finally, if you get any warning messages when compiling libpng
111 (note: not zlib), and they are easy to fix, I'd appreciate the
112 fix. Please mention "libpng" somewhere in the subject line. Thanks.
113
114 This release was created and will be supported by myself (of course
115 based in a large way on Guy's and Andreas' earlier work), and the PNG
116 development group.
117
118 Send comments/corrections/commendations to png-mng-implement at
119 lists.sourceforge.net (subscription required; visit
120 https://lists.sourceforge.net/lists/listinfo/png-mng-implement
121 to subscribe).
122
123 You can't reach Guy, the original libpng author, at the addresses
124 given in previous versions of this document. He and Andreas will
125 read mail addressed to the png-implement list, however.
126
127 Please do not send general questions about PNG. Send them to
128 png-mng-misc at lists.sf.net (subscription required; visit
129 https://lists.sourceforge.net/lists/listinfo/png-mng-misc to
130 subscribe). If you have a question about something
131 in the PNG specification that is related to using libpng, send it
132 to me. Send me any questions that start with "I was using libpng,
133 and ...". If in doubt, send questions to me. I'll bounce them
134 to others, if necessary.
135
136 Please do not send suggestions on how to change PNG. We have
137 been discussing PNG for twenty years now, and it is official and
138 finished. If you have suggestions for libpng, however, I'll
139 gladly listen. Even if your suggestion is not used immediately,
140 it may be used later.
141
142 Files in this distribution:
143
144 ANNOUNCE => Announcement of this version, with recent changes
145 CHANGES => Description of changes between libpng versions
146 KNOWNBUG => List of known bugs and deficiencies
147 LICENSE => License to use and redistribute libpng
148 README => This file
149 TODO => Things not implemented in the current library
150 Y2KINFO => Statement of Y2K compliance
151 example.c => Example code for using libpng functions
152 libpng.3 => manual page for libpng (includes libpng-manual.txt)
153 libpng-manual.txt => Description of libpng and its functions
154 libpngpf.3 => manual page for libpng's private functions
155 png.5 => manual page for the PNG format
156 png.c => Basic interface functions common to library
157 png.h => Library function and interface declarations (public)
158 pngpriv.h => Library function and interface declarations (private)
159 pngconf.h => System specific library configuration (public)
160 pngstruct.h => png_struct declaration (private)
161 pnginfo.h => png_info struct declaration (private)
162 pngdebug.h => debugging macros (private)
163 pngerror.c => Error/warning message I/O functions
164 pngget.c => Functions for retrieving info from struct
165 pngmem.c => Memory handling functions
166 pngbar.png => PNG logo, 88x31
167 pngnow.png => PNG logo, 98x31
168 pngpread.c => Progressive reading functions
169 pngread.c => Read data/helper high-level functions
170 pngrio.c => Lowest-level data read I/O functions
191 mips-msa => Optimized code for MIPS-MSA platform
192 pngminim => Minimal decoder, encoder, and progressive decoder
193 programs demonstrating use of pngusr.dfa
194 pngminus => Simple pnm2png and png2pnm programs
195 pngsuite => Test images
196 testpngs
197 tools => Various tools
198 visupng => Contains a MSVC workspace for VisualPng
199 intel => Optimized code for INTEL-SSE2 platform
200 mips => Optimized code for MIPS platform
201 projects => Contains project files and workspaces for
202 building a DLL
203 owatcom => Contains a WATCOM project for building libpng
204 visualc71 => Contains a Microsoft Visual C++ (MSVC)
205 workspace for building libpng and zlib
206 vstudio => Contains a Microsoft Visual C++ (MSVC)
207 workspace for building libpng and zlib
208 scripts => Directory containing scripts for building libpng:
209 (see scripts/README.txt for the list of scripts)
210
211 Good luck, and happy coding.
212
213 -Glenn Randers-Pehrson (current maintainer, since 1998)
214 Internet: glennrp at users.sourceforge.net
215
216 -Andreas Eric Dilger (former maintainer, 1996-1997)
217 Internet: adilger at enel.ucalgary.ca
218 Web: http://www-mddsp.enel.ucalgary.ca/People/adilger/
219
220 -Guy Eric Schalnat (original author and former maintainer, 1995-1996)
221 (formerly of Group 42, Inc)
222 Internet: gschal at infinet.com
|
1 README for libpng version 1.6.37 - April 14, 2019
2 =================================================
3
4 See the note about version numbers near the top of png.h.
5 See INSTALL for instructions on how to install libpng.
6
7 Libpng comes in several distribution formats. Get libpng-*.tar.gz or
8 libpng-*.tar.xz or if you want UNIX-style line endings in the text
9 files, or lpng*.7z or lpng*.zip if you want DOS-style line endings.
10
11 Version 0.89 was the first official release of libpng. Don't let the
12 fact that it's the first release fool you. The libpng library has been
13 in extensive use and testing since mid-1995. By late 1997 it had
14 finally gotten to the stage where there hadn't been significant
15 changes to the API in some time, and people have a bad feeling about
16 libraries with versions < 1.0. Version 1.0.0 was released in
17 March 1998.
18
19 ****
20 Note that some of the changes to the png_info structure render this
21 version of the library binary incompatible with libpng-0.89 or
22 earlier versions if you are using a shared library. The type of the
23 "filler" parameter for png_set_filler() has changed from png_byte to
24 png_uint_32, which will affect shared-library applications that use
25 this function.
26
27 To avoid problems with changes to the internals of the png info_struct,
28 new APIs have been made available in 0.95 to avoid direct application
29 access to info_ptr. These functions are the png_set_<chunk> and
30 png_get_<chunk> functions. These functions should be used when
31 accessing/storing the info_struct data, rather than manipulating it
32 directly, to avoid such problems in the future.
33
44 older programs be converted to the new format, to facilitate upgrades
45 in the future.
46 ****
47
48 Additions since 0.90 include the ability to compile libpng as a
49 Windows DLL, and new APIs for accessing data in the info struct.
50 Experimental functions include the ability to set weighting and cost
51 factors for row filter selection, direct reads of integers from buffers
52 on big-endian processors that support misaligned data access, faster
53 methods of doing alpha composition, and more accurate 16->8 bit color
54 conversion.
55
56 The additions since 0.89 include the ability to read from a PNG stream
57 which has had some (or all) of the signature bytes read by the calling
58 application. This also allows the reading of embedded PNG streams that
59 do not have the PNG file signature. As well, it is now possible to set
60 the library action on the detection of chunk CRC errors. It is possible
61 to set different actions based on whether the CRC error occurred in a
62 critical or an ancillary chunk.
63
64 For a detailed description on using libpng, read libpng-manual.txt.
65 For examples of libpng in a program, see example.c and pngtest.c. For
66 usage information and restrictions (what little they are) on libpng,
67 see png.h. For a description on using zlib (the compression library
68 used by libpng) and zlib's restrictions, see zlib.h
69
70 I have included a general makefile, as well as several machine and
71 compiler specific ones, but you may have to modify one for your own
72 needs.
73
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.
78
79 You should also note that zlib is a compression library that is useful
80 for more things than just PNG files. You can use zlib as a drop-in
81 replacement for fread() and fwrite(), if you are so inclined.
82
83 zlib should be available at the same place that libpng is, or at
84 https://zlib.net.
85
86 You may also want a copy of the PNG specification. It is available
87 as an RFC, a W3C Recommendation, and an ISO/IEC Standard. You can find
88 these at http://www.libpng.org/pub/png/pngdocs.html .
89
90 This code is currently being archived at libpng.sourceforge.io in the
91 [DOWNLOAD] area, and at http://libpng.download/src .
92
93 This release, based in a large way on Glenn's, Guy's and Andreas'
94 earlier work, was created and will be supported by myself and the PNG
95 development group.
96
97 Send comments/corrections/commendations to png-mng-implement at
98 lists.sourceforge.net (subscription required; visit
99 https://lists.sourceforge.net/lists/listinfo/png-mng-implement
100 to subscribe).
101
102 Send general questions about the PNG specification to png-mng-misc
103 at lists.sourceforge.net (subscription required; visit
104 https://lists.sourceforge.net/lists/listinfo/png-mng-misc to
105 subscribe).
106
107 Files in this distribution:
108
109 ANNOUNCE => Announcement of this version, with recent changes
110 AUTHORS => List of contributing authors
111 CHANGES => Description of changes between libpng versions
112 KNOWNBUG => List of known bugs and deficiencies
113 LICENSE => License to use and redistribute libpng
114 README => This file
115 TODO => Things not implemented in the current library
116 TRADEMARK => Trademark information
117 example.c => Example code for using libpng functions
118 libpng.3 => manual page for libpng (includes libpng-manual.txt)
119 libpng-manual.txt => Description of libpng and its functions
120 libpngpf.3 => manual page for libpng's private functions
121 png.5 => manual page for the PNG format
122 png.c => Basic interface functions common to library
123 png.h => Library function and interface declarations (public)
124 pngpriv.h => Library function and interface declarations (private)
125 pngconf.h => System specific library configuration (public)
126 pngstruct.h => png_struct declaration (private)
127 pnginfo.h => png_info struct declaration (private)
128 pngdebug.h => debugging macros (private)
129 pngerror.c => Error/warning message I/O functions
130 pngget.c => Functions for retrieving info from struct
131 pngmem.c => Memory handling functions
132 pngbar.png => PNG logo, 88x31
133 pngnow.png => PNG logo, 98x31
134 pngpread.c => Progressive reading functions
135 pngread.c => Read data/helper high-level functions
136 pngrio.c => Lowest-level data read I/O functions
157 mips-msa => Optimized code for MIPS-MSA platform
158 pngminim => Minimal decoder, encoder, and progressive decoder
159 programs demonstrating use of pngusr.dfa
160 pngminus => Simple pnm2png and png2pnm programs
161 pngsuite => Test images
162 testpngs
163 tools => Various tools
164 visupng => Contains a MSVC workspace for VisualPng
165 intel => Optimized code for INTEL-SSE2 platform
166 mips => Optimized code for MIPS platform
167 projects => Contains project files and workspaces for
168 building a DLL
169 owatcom => Contains a WATCOM project for building libpng
170 visualc71 => Contains a Microsoft Visual C++ (MSVC)
171 workspace for building libpng and zlib
172 vstudio => Contains a Microsoft Visual C++ (MSVC)
173 workspace for building libpng and zlib
174 scripts => Directory containing scripts for building libpng:
175 (see scripts/README.txt for the list of scripts)
176
177 Good luck, and happy coding!
178
179 * Cosmin Truta (current maintainer, since 2018)
180 * Glenn Randers-Pehrson (former maintainer, 1998-2018)
181 * Andreas Eric Dilger (former maintainer, 1996-1997)
182 * Guy Eric Schalnat (original author and former maintainer, 1995-1996)
183 (formerly of Group 42, Inc.)
|