media/libpng/README@97036ab72558 (annotated)
media/libpng/README
Tue, 06 Jan 2015 21:39:09 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Tue, 06 Jan 2015 21:39:09 +0100
- branch
- TOR_BUG_9701
- changeset 8
- 97036ab72558
- permissions
- -rw-r--r--
Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.
| michael@0 | 1 | README for libpng version 1.6.10 - March 6, 2014 (shared library 16.0) |
| michael@0 | 2 | See the note about version numbers near the top of png.h |
| michael@0 | 3 | |
| michael@0 | 4 | See INSTALL for instructions on how to install libpng. |
| michael@0 | 5 | |
| michael@0 | 6 | Libpng comes in several distribution formats. Get libpng-*.tar.gz or |
| michael@0 | 7 | libpng-*.tar.xz or if you want UNIX-style line endings in the text files, |
| michael@0 | 8 | or lpng*.7z or lpng*.zip if you want DOS-style line endings. |
| michael@0 | 9 | |
| michael@0 | 10 | Version 0.89 was the first official release of libpng. Don't let the |
| michael@0 | 11 | fact that it's the first release fool you. The libpng library has been in |
| michael@0 | 12 | extensive use and testing since mid-1995. By late 1997 it had |
| michael@0 | 13 | finally gotten to the stage where there hadn't been significant |
| michael@0 | 14 | changes to the API in some time, and people have a bad feeling about |
| michael@0 | 15 | libraries with versions < 1.0. Version 1.0.0 was released in |
| michael@0 | 16 | March 1998. |
| michael@0 | 17 | |
| michael@0 | 18 | **** |
| michael@0 | 19 | Note that some of the changes to the png_info structure render this |
| michael@0 | 20 | version of the library binary incompatible with libpng-0.89 or |
| michael@0 | 21 | earlier versions if you are using a shared library. The type of the |
| michael@0 | 22 | "filler" parameter for png_set_filler() has changed from png_byte to |
| michael@0 | 23 | png_uint_32, which will affect shared-library applications that use |
| michael@0 | 24 | this function. |
| michael@0 | 25 | |
| michael@0 | 26 | To avoid problems with changes to the internals of png_info_struct, |
| michael@0 | 27 | new APIs have been made available in 0.95 to avoid direct application |
| michael@0 | 28 | access to info_ptr. These functions are the png_set_<chunk> and |
| michael@0 | 29 | png_get_<chunk> functions. These functions should be used when |
| michael@0 | 30 | accessing/storing the info_struct data, rather than manipulating it |
| michael@0 | 31 | directly, to avoid such problems in the future. |
| michael@0 | 32 | |
| michael@0 | 33 | It is important to note that the APIs do not make current programs |
| michael@0 | 34 | that access the info struct directly incompatible with the new |
| michael@0 | 35 | library. However, it is strongly suggested that new programs use |
| michael@0 | 36 | the new APIs (as shown in example.c and pngtest.c), and older programs |
| michael@0 | 37 | be converted to the new format, to facilitate upgrades in the future. |
| michael@0 | 38 | **** |
| michael@0 | 39 | |
| michael@0 | 40 | Additions since 0.90 include the ability to compile libpng as a |
| michael@0 | 41 | Windows DLL, and new APIs for accessing data in the info struct. |
| michael@0 | 42 | Experimental functions include the ability to set weighting and cost |
| michael@0 | 43 | factors for row filter selection, direct reads of integers from buffers |
| michael@0 | 44 | on big-endian processors that support misaligned data access, faster |
| michael@0 | 45 | methods of doing alpha composition, and more accurate 16->8 bit color |
| michael@0 | 46 | conversion. |
| michael@0 | 47 | |
| michael@0 | 48 | The additions since 0.89 include the ability to read from a PNG stream |
| michael@0 | 49 | which has had some (or all) of the signature bytes read by the calling |
| michael@0 | 50 | application. This also allows the reading of embedded PNG streams that |
| michael@0 | 51 | do not have the PNG file signature. As well, it is now possible to set |
| michael@0 | 52 | the library action on the detection of chunk CRC errors. It is possible |
| michael@0 | 53 | to set different actions based on whether the CRC error occurred in a |
| michael@0 | 54 | critical or an ancillary chunk. |
| michael@0 | 55 | |
| michael@0 | 56 | The changes made to the library, and bugs fixed are based on discussions |
| michael@0 | 57 | on the PNG-implement mailing list and not on material submitted |
| michael@0 | 58 | privately to Guy, Andreas, or Glenn. They will forward any good |
| michael@0 | 59 | suggestions to the list. |
| michael@0 | 60 | |
| michael@0 | 61 | For a detailed description on using libpng, read libpng-manual.txt. For |
| michael@0 | 62 | examples of libpng in a program, see example.c and pngtest.c. For usage |
| michael@0 | 63 | information and restrictions (what little they are) on libpng, see |
| michael@0 | 64 | png.h. For a description on using zlib (the compression library used by |
| michael@0 | 65 | libpng) and zlib's restrictions, see zlib.h |
| michael@0 | 66 | |
| michael@0 | 67 | I have included a general makefile, as well as several machine and |
| michael@0 | 68 | compiler specific ones, but you may have to modify one for your own needs. |
| michael@0 | 69 | |
| michael@0 | 70 | You should use zlib 1.0.4 or later to run this, but it MAY work with |
| michael@0 | 71 | versions as old as zlib 0.95. Even so, there are bugs in older zlib |
| michael@0 | 72 | versions which can cause the output of invalid compression streams for |
| michael@0 | 73 | some images. You will definitely need zlib 1.0.4 or later if you are |
| michael@0 | 74 | taking advantage of the MS-DOS "far" structure allocation for the small |
| michael@0 | 75 | and medium memory models. You should also note that zlib is a |
| michael@0 | 76 | compression library that is useful for more things than just PNG files. |
| michael@0 | 77 | You can use zlib as a drop-in replacement for fread() and fwrite() if |
| michael@0 | 78 | you are so inclined. |
| michael@0 | 79 | |
| michael@0 | 80 | zlib should be available at the same place that libpng is, or at zlib.net. |
| michael@0 | 81 | |
| michael@0 | 82 | You may also want a copy of the PNG specification. It is available |
| michael@0 | 83 | as an RFC, a W3C Recommendation, and an ISO/IEC Standard. You can find |
| michael@0 | 84 | these at http://www.libpng.org/pub/png/documents/ |
| michael@0 | 85 | |
| michael@0 | 86 | This code is currently being archived at libpng.sf.net in the |
| michael@0 | 87 | [DOWNLOAD] area, and at ftp://ftp.simplesystems.org. If you can't find it |
| michael@0 | 88 | in any of those places, e-mail me, and I'll help you find it. |
| michael@0 | 89 | |
| michael@0 | 90 | If you have any code changes, requests, problems, etc., please e-mail |
| michael@0 | 91 | them to me. Also, I'd appreciate any make files or project files, |
| michael@0 | 92 | and any modifications you needed to make to get libpng to compile, |
| michael@0 | 93 | along with a #define variable to tell what compiler/system you are on. |
| michael@0 | 94 | If you needed to add transformations to libpng, or wish libpng would |
| michael@0 | 95 | provide the image in a different way, drop me a note (and code, if |
| michael@0 | 96 | possible), so I can consider supporting the transformation. |
| michael@0 | 97 | Finally, if you get any warning messages when compiling libpng |
| michael@0 | 98 | (note: not zlib), and they are easy to fix, I'd appreciate the |
| michael@0 | 99 | fix. Please mention "libpng" somewhere in the subject line. Thanks. |
| michael@0 | 100 | |
| michael@0 | 101 | This release was created and will be supported by myself (of course |
| michael@0 | 102 | based in a large way on Guy's and Andreas' earlier work), and the PNG |
| michael@0 | 103 | development group. |
| michael@0 | 104 | |
| michael@0 | 105 | Send comments/corrections/commendations to png-mng-implement at |
| michael@0 | 106 | lists.sourceforge.net (subscription required; visit |
| michael@0 | 107 | https://lists.sourceforge.net/lists/listinfo/png-mng-implement |
| michael@0 | 108 | to subscribe) or to glennrp at users.sourceforge.net |
| michael@0 | 109 | |
| michael@0 | 110 | You can't reach Guy, the original libpng author, at the addresses |
| michael@0 | 111 | given in previous versions of this document. He and Andreas will |
| michael@0 | 112 | read mail addressed to the png-implement list, however. |
| michael@0 | 113 | |
| michael@0 | 114 | Please do not send general questions about PNG. Send them to |
| michael@0 | 115 | png-mng-misc at lists.sf.net (subscription required; visit |
| michael@0 | 116 | https://lists.sourceforge.net/lists/listinfo/png-mng-misc to |
| michael@0 | 117 | subscribe). If you have a question about something |
| michael@0 | 118 | in the PNG specification that is related to using libpng, send it |
| michael@0 | 119 | to me. Send me any questions that start with "I was using libpng, |
| michael@0 | 120 | and ...". If in doubt, send questions to me. I'll bounce them |
| michael@0 | 121 | to others, if necessary. |
| michael@0 | 122 | |
| michael@0 | 123 | Please do not send suggestions on how to change PNG. We have |
| michael@0 | 124 | been discussing PNG for nineteen years now, and it is official and |
| michael@0 | 125 | finished. If you have suggestions for libpng, however, I'll |
| michael@0 | 126 | gladly listen. Even if your suggestion is not used immediately, |
| michael@0 | 127 | it may be used later. |
| michael@0 | 128 | |
| michael@0 | 129 | Files in this distribution: |
| michael@0 | 130 | |
| michael@0 | 131 | ANNOUNCE => Announcement of this version, with recent changes |
| michael@0 | 132 | CHANGES => Description of changes between libpng versions |
| michael@0 | 133 | KNOWNBUG => List of known bugs and deficiencies |
| michael@0 | 134 | LICENSE => License to use and redistribute libpng |
| michael@0 | 135 | README => This file |
| michael@0 | 136 | TODO => Things not implemented in the current library |
| michael@0 | 137 | Y2KINFO => Statement of Y2K compliance |
| michael@0 | 138 | example.c => Example code for using libpng functions |
| michael@0 | 139 | libpng.3 => manual page for libpng (includes libpng-manual.txt) |
| michael@0 | 140 | libpng-manual.txt => Description of libpng and its functions |
| michael@0 | 141 | libpngpf.3 => manual page for libpng's private functions |
| michael@0 | 142 | png.5 => manual page for the PNG format |
| michael@0 | 143 | png.c => Basic interface functions common to library |
| michael@0 | 144 | png.h => Library function and interface declarations (public) |
| michael@0 | 145 | pngpriv.h => Library function and interface declarations (private) |
| michael@0 | 146 | pngconf.h => System specific library configuration (public) |
| michael@0 | 147 | pngstruct.h => png_struct declaration (private) |
| michael@0 | 148 | pnginfo.h => png_info struct declaration (private) |
| michael@0 | 149 | pngdebug.h => debugging macros (private) |
| michael@0 | 150 | pngerror.c => Error/warning message I/O functions |
| michael@0 | 151 | pngget.c => Functions for retrieving info from struct |
| michael@0 | 152 | pngmem.c => Memory handling functions |
| michael@0 | 153 | pngbar.png => PNG logo, 88x31 |
| michael@0 | 154 | pngnow.png => PNG logo, 98x31 |
| michael@0 | 155 | pngpread.c => Progressive reading functions |
| michael@0 | 156 | pngread.c => Read data/helper high-level functions |
| michael@0 | 157 | pngrio.c => Lowest-level data read I/O functions |
| michael@0 | 158 | pngrtran.c => Read data transformation functions |
| michael@0 | 159 | pngrutil.c => Read data utility functions |
| michael@0 | 160 | pngset.c => Functions for storing data into the info_struct |
| michael@0 | 161 | pngtest.c => Library test program |
| michael@0 | 162 | pngtest.png => Library test sample image |
| michael@0 | 163 | pngtrans.c => Common data transformation functions |
| michael@0 | 164 | pngwio.c => Lowest-level write I/O functions |
| michael@0 | 165 | pngwrite.c => High-level write functions |
| michael@0 | 166 | pngwtran.c => Write data transformations |
| michael@0 | 167 | pngwutil.c => Write utility functions |
| michael@0 | 168 | arm => Contains optimized code for the ARM platform |
| michael@0 | 169 | contrib => Contributions |
| michael@0 | 170 | examples => Example programs |
| michael@0 | 171 | gregbook => source code for PNG reading and writing, from |
| michael@0 | 172 | Greg Roelofs' "PNG: The Definitive Guide", |
| michael@0 | 173 | O'Reilly, 1999 |
| michael@0 | 174 | libtests => Test programs |
| michael@0 | 175 | pngminim => Minimal decoder, encoder, and progressive decoder |
| michael@0 | 176 | programs demonstrating use of pngusr.dfa |
| michael@0 | 177 | pngminus => Simple pnm2png and png2pnm programs |
| michael@0 | 178 | pngsuite => Test images |
| michael@0 | 179 | tools => Various tools |
| michael@0 | 180 | visupng => Contains a MSVC workspace for VisualPng |
| michael@0 | 181 | projects => Contains project files and workspaces for |
| michael@0 | 182 | building a DLL |
| michael@0 | 183 | owatcom => Contains a WATCOM project for building libpng |
| michael@0 | 184 | visualc71 => Contains a Microsoft Visual C++ (MSVC) |
| michael@0 | 185 | workspace for building libpng and zlib |
| michael@0 | 186 | vstudio => Contains a Microsoft Visual C++ (MSVC) |
| michael@0 | 187 | workspace for building libpng and zlib |
| michael@0 | 188 | scripts => Directory containing scripts for building libpng: |
| michael@0 | 189 | (see scripts/README.txt for the list of scripts) |
| michael@0 | 190 | |
| michael@0 | 191 | Good luck, and happy coding. |
| michael@0 | 192 | |
| michael@0 | 193 | -Glenn Randers-Pehrson (current maintainer, since 1998) |
| michael@0 | 194 | Internet: glennrp at users.sourceforge.net |
| michael@0 | 195 | |
| michael@0 | 196 | -Andreas Eric Dilger (former maintainer, 1996-1997) |
| michael@0 | 197 | Internet: adilger at enel.ucalgary.ca |
| michael@0 | 198 | Web: http://www-mddsp.enel.ucalgary.ca/People/adilger/ |
| michael@0 | 199 | |
| michael@0 | 200 | -Guy Eric Schalnat (original author and former maintainer, 1995-1996) |
| michael@0 | 201 | (formerly of Group 42, Inc) |
| michael@0 | 202 | Internet: gschal at infinet.com |
