| 1 | README for libpng version 1.2.54 - November 12, 2015 (shared library 12.0)
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| 2 | See the note about version numbers near the top of png.h
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| 3 |
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| 4 | See INSTALL for instructions on how to install libpng.
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| 5 |
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| 6 | Libpng comes in several distribution formats. Get libpng-*.tar.gz,
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| 7 | libpng-*.tar.xz, or libpng-*.tar.bz2 if you want UNIX-style line
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| 8 | endings in the text files, or lpng*.7z or lpng*.zip if you want DOS-style
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| 9 | line endings. You can get UNIX-style line endings from the *.zip file
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| 10 | by using "unzip -a" but there seems to be no simple way to recover
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| 11 | UNIX-style line endings from the *.7z file. The *.tar.xz file is
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| 12 | recommended for *NIX users instead.
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| 13 |
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| 14 | Version 0.89 was the first official release of libpng. Don't let the
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| 15 | fact that it's the first release fool you. The libpng library has been in
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| 16 | extensive use and testing since mid-1995. By late 1997 it had
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| 17 | finally gotten to the stage where there hadn't been significant
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| 18 | changes to the API in some time, and people have a bad feeling about
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| 19 | libraries with versions < 1.0. Version 1.0.0 was released in
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| 20 | March 1998.
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| 21 |
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| 22 | ****
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| 23 | Note that some of the changes to the png_info structure render this
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| 24 | version of the library binary incompatible with libpng-0.89 or
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| 25 | earlier versions if you are using a shared library. The type of the
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| 26 | "filler" parameter for png_set_filler() has changed from png_byte to
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| 27 | png_uint_32, which will affect shared-library applications that use
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| 28 | this function.
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| 29 |
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| 30 | To avoid problems with changes to the internals of png_info_struct,
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| 31 | new APIs have been made available in 0.95 to avoid direct application
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| 32 | access to info_ptr. These functions are the png_set_<chunk> and
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| 33 | png_get_<chunk> functions. These functions should be used when
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| 34 | accessing/storing the info_struct data, rather than manipulating it
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| 35 | directly, to avoid such problems in the future.
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| 36 |
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| 37 | It is important to note that the APIs do not make current programs
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| 38 | that access the info struct directly incompatible with the new
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| 39 | library. However, it is strongly suggested that new programs use
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| 40 | the new APIs (as shown in example.c and pngtest.c), and older programs
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| 41 | be converted to the new format, to facilitate upgrades in the future.
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| 42 | ****
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| 43 |
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| 44 | Additions since 0.90 include the ability to compile libpng as a
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| 45 | Windows DLL, and new APIs for accessing data in the info struct.
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| 46 | Experimental functions include the ability to set weighting and cost
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| 47 | factors for row filter selection, direct reads of integers from buffers
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| 48 | on big-endian processors that support misaligned data access, faster
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| 49 | methods of doing alpha composition, and more accurate 16->8 bit color
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| 50 | conversion.
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| 51 |
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| 52 | The additions since 0.89 include the ability to read from a PNG stream
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| 53 | which has had some (or all) of the signature bytes read by the calling
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| 54 | application. This also allows the reading of embedded PNG streams that
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| 55 | do not have the PNG file signature. As well, it is now possible to set
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| 56 | the library action on the detection of chunk CRC errors. It is possible
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| 57 | to set different actions based on whether the CRC error occurred in a
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| 58 | critical or an ancillary chunk.
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| 59 |
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| 60 | The changes made to the library, and bugs fixed are based on discussions
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| 61 | on the png-mng-implement mailing list and not on material submitted
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| 62 | privately to Guy, Andreas, or Glenn. They will forward any good
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| 63 | suggestions to the list.
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| 64 |
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| 65 | For a detailed description on using libpng, read libpng.txt. For
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| 66 | examples of libpng in a program, see example.c and pngtest.c. For usage
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| 67 | information and restrictions (what little they are) on libpng, see
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| 68 | png.h. For a description on using zlib (the compression library used by
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| 69 | libpng) and zlib's restrictions, see zlib.h
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| 70 |
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| 71 | I have included a general makefile, as well as several machine and
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| 72 | compiler specific ones, but you may have to modify one for your own needs.
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| 73 |
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| 74 | You should use zlib 1.0.4 or later to run this, but it MAY work with
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| 75 | versions as old as zlib 0.95. Even so, there are bugs in older zlib
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| 76 | versions which can cause the output of invalid compression streams for
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| 77 | some images. You will definitely need zlib 1.0.4 or later if you are
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| 78 | taking advantage of the MS-DOS "far" structure allocation for the small
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| 79 | and medium memory models. You should also note that zlib is a
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| 80 | compression library that is useful for more things than just PNG files.
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| 81 | You can use zlib as a drop-in replacement for fread() and fwrite() if
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| 82 | you are so inclined.
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| 83 |
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| 84 | zlib should be available at the same place that libpng is, or at
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| 85 | ftp://ftp.simplesystems.org/pub/png/src/
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| 86 |
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| 87 | You may also want a copy of the PNG specification. It is available
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| 88 | as an RFC, a W3C Recommendation, and an ISO/IEC Standard. You can find
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| 89 | these at http://www.libpng.org/pub/png/pngdocs.html
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| 90 |
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| 91 | This code is currently being archived at libpng.sf.net in the
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| 92 | [DOWNLOAD] area, and on CompuServe, Lib 20 (PNG SUPPORT)
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| 93 | at GO GRAPHSUP. If you can't find it in any of those places,
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| 94 | e-mail me, and I'll help you find it.
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| 95 |
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| 96 | I am not a lawyer, but I believe that the Export Control Classification
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| 97 | Number (ECCN) for libpng is EAR99, which means not subject to export
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| 98 | controls or International Traffic in Arms Regulations (ITAR) because it
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| 99 | is open source, publicly available software, that does not contain any
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| 100 | encryption software. See the EAR, paragraphs 734.3(b)(3) and 734.7(b).
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| 101 |
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| 102 | If you have any code changes, requests, problems, etc., please e-mail
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| 103 | them to me. Also, I'd appreciate any make files or project files,
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| 104 | and any modifications you needed to make to get libpng to compile,
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| 105 | along with a #define variable to tell what compiler/system you are on.
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| 106 | If you needed to add transformations to libpng, or wish libpng would
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| 107 | provide the image in a different way, drop me a note (and code, if
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| 108 | possible), so I can consider supporting the transformation.
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| 109 | Finally, if you get any warning messages when compiling libpng
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| 110 | (note: not zlib), and they are easy to fix, I'd appreciate the
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| 111 | fix. Please mention "libpng" somewhere in the subject line. Thanks.
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| 112 |
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| 113 | This release was created and will be supported by myself (of course
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| 114 | based in a large way on Guy's and Andreas' earlier work), and the PNG
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| 115 | development group.
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| 116 |
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| 117 | Send comments/corrections/commendations to png-mng-implement at lists.sf.net
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| 118 | (subscription required; visit
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| 119 | https://lists.sourceforge.net/lists/listinfo/png-mng-implement
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| 120 | to subscribe) or to glennrp at users.sourceforge.net
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| 121 |
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| 122 | You can't reach Guy, the original libpng author, at the addresses
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| 123 | given in previous versions of this document. He and Andreas will
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| 124 | read mail addressed to the png-mng-implement list, however.
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| 125 |
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| 126 | Please do not send general questions about PNG. Send them to
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| 127 | the (png-mng-misc at lists.sourceforge.net, subscription required, visit
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| 128 | https://lists.sourceforge.net/lists/listinfo/png-mng-misc to
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| 129 | subscribe). On the other hand, please do not send libpng questions to
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| 130 | that address, send them to me or to the png-mng-implement list. I'll
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| 131 | get them in the end anyway. If you have a question about something
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| 132 | in the PNG specification that is related to using libpng, send it
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| 133 | to me. Send me any questions that start with "I was using libpng,
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| 134 | and ...". If in doubt, send questions to me. I'll bounce them
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| 135 | to others, if necessary.
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| 136 |
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| 137 | Please do not send suggestions on how to change PNG. We have
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| 138 | been discussing PNG for twenty years now, and it is official and
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| 139 | finished. If you have suggestions for libpng, however, I'll
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| 140 | gladly listen. Even if your suggestion is not used immediately,
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| 141 | it may be used later.
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| 142 |
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| 143 | Files in this distribution:
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| 144 |
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| 145 | ANNOUNCE => Announcement of this version, with recent changes
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| 146 | CHANGES => Description of changes between libpng versions
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| 147 | KNOWNBUG => List of known bugs and deficiencies
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| 148 | LICENSE => License to use and redistribute libpng
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| 149 | README => This file
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| 150 | TODO => Things not implemented in the current library
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| 151 | Y2KINFO => Statement of Y2K compliance
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| 152 | example.c => Example code for using libpng functions
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| 153 | libpng-*-*-diff.txt => Diff from previous release
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| 154 | libpng.3 => manual page for libpng (includes libpng.txt)
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| 155 | libpng.txt => Description of libpng and its functions
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| 156 | libpngpf.3 => manual page for libpng's private functions
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| 157 | png.5 => manual page for the PNG format
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| 158 | png.c => Basic interface functions common to library
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| 159 | png.h => Library function and interface declarations
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| 160 | pngconf.h => System specific library configuration
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| 161 | pngerror.c => Error/warning message I/O functions
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| 162 | pngget.c => Functions for retrieving info from struct
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| 163 | pngmem.c => Memory handling functions
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| 164 | pngbar.png => PNG logo, 88x31
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| 165 | pngnow.png => PNG logo, 98x31
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| 166 | pngpread.c => Progressive reading functions
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| 167 | pngread.c => Read data/helper high-level functions
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| 168 | pngrio.c => Lowest-level data read I/O functions
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| 169 | pngrtran.c => Read data transformation functions
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| 170 | pngrutil.c => Read data utility functions
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| 171 | pngset.c => Functions for storing data into the info_struct
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| 172 | pngtest.c => Library test program
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| 173 | pngtest.png => Library test sample image
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| 174 | pngtrans.c => Common data transformation functions
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| 175 | pngwio.c => Lowest-level write I/O functions
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| 176 | pngwrite.c => High-level write functions
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| 177 | pngwtran.c => Write data transformations
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| 178 | pngwutil.c => Write utility functions
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| 179 | contrib => Contributions
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| 180 | gregbook => source code for PNG reading and writing, from
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| 181 | Greg Roelofs' "PNG: The Definitive Guide",
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| 182 | O'Reilly, 1999
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| 183 | pngminim => Minimal pnm2pngm and png2pnmm programs
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| 184 | pngminus => Simple pnm2png and png2pnm programs
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| 185 | pngsuite => Test images
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| 186 | visupng => Contains a MSVC workspace for VisualPng
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| 187 | projects => Contains project files and workspaces for
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| 188 | building a DLL
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| 189 | beos => Contains a Beos workspace for building libpng
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| 190 | c5builder => Contains a Borland workspace for building
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| 191 | libpng and zlib
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| 192 | MacOSX => Contains a MacOSX workspace for building libpng
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| 193 | netware.txt => Contains instructions for downloading a set
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| 194 | of project files for building libpng and
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| 195 | zlib on Netware.
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| 196 | visualc6 => Contains a Microsoft Visual C++ (MSVC)
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| 197 | workspace for building libpng and zlib
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| 198 | visualc71 => Contains a Microsoft Visual C++ (MSVC)
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| 199 | workspace for building libpng and zlib
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| 200 | wince.txt => Contains instructions for downloading a
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| 201 | Microsoft Visual C++ (Windows CD Toolkit)
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| 202 | workspace for building libpng and zlib on
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| 203 | WindowsCE
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| 204 | xcode => Contains xcode project files
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| 205 | scripts => Directory containing scripts for building libpng:
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| 206 | descrip.mms => VMS makefile for MMS or MMK
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| 207 | makefile.std => Generic UNIX makefile (cc, creates static
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| 208 | libpng.a)
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| 209 | makefile.elf => Linux/ELF gcc makefile symbol versioning,
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| 210 | creates libpng12.so.0.1.2.54)
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| 211 | makefile.linux => Linux/ELF makefile (gcc, creates
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| 212 | libpng12.so.0.1.2.54)
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| 213 | makefile.gcmmx => Linux/ELF makefile (gcc, creates
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| 214 | libpng12.so.0.1.2.54, previously
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| 215 | used assembler code tuned for Intel MMX
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| 216 | platform)
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| 217 | makefile.gcc => Generic makefile (gcc, creates static
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| 218 | libpng.a)
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| 219 | makefile.knr => Archaic UNIX Makefile that converts files
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| 220 | with ansi2knr (Requires ansi2knr.c from
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| 221 | ftp://ftp.cs.wisc.edu/ghost)
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| 222 | makefile.aix => AIX makefile
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| 223 | makefile.cygwin => Cygwin/gcc makefile
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| 224 | makefile.darwin => Darwin makefile
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| 225 | makefile.dec => DEC Alpha UNIX makefile
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| 226 | makefile.freebsd => FreeBSD makefile
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| 227 | makefile.hpgcc => HPUX makefile using gcc
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| 228 | makefile.hpux => HPUX (10.20 and 11.00) makefile
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| 229 | makefile.hp64 => HPUX (10.20 and 11.00) makefile, 64 bit
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| 230 | makefile.ibmc => IBM C/C++ version 3.x for Win32 and OS/2
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| 231 | (static)
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| 232 | makefile.intel => Intel C/C++ version 4.0 and later
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| 233 | libpng.icc => Project file, IBM VisualAge/C++ 4.0 or later
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| 234 | makefile.netbsd => NetBSD/cc makefile, makes libpng.so.
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| 235 | makefile.ne12bsd => NetBSD/cc makefile, makes libpng12.so
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| 236 | makefile.openbsd => OpenBSD makefile
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| 237 | makefile.sgi => Silicon Graphics IRIX (cc, creates static lib)
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| 238 | makefile.sggcc => Silicon Graphics
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| 239 | (gcc, creates libpng12.so.0.1.2.54)
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| 240 | makefile.sunos => Sun makefile
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| 241 | makefile.solaris => Solaris 2.X makefile
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| 242 | (gcc, creates libpng12.so.0.1.2.54)
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| 243 | makefile.so9 => Solaris 9 makefile
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| 244 | (gcc, creates libpng12.so.0.1.2.54)
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| 245 | makefile.32sunu => Sun Ultra 32-bit makefile
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| 246 | makefile.64sunu => Sun Ultra 64-bit makefile
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| 247 | makefile.sco => For SCO OSr5 ELF and Unixware 7 with Native cc
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| 248 | makefile.mips => MIPS makefile
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| 249 | makefile.acorn => Acorn makefile
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| 250 | makefile.amiga => Amiga makefile
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| 251 | smakefile.ppc => AMIGA smakefile for SAS C V6.58/7.00 PPC
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| 252 | compiler (Requires SCOPTIONS, copied from
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| 253 | scripts/SCOPTIONS.ppc)
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| 254 | makefile.atari => Atari makefile
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| 255 | makefile.beos => BEOS makefile for X86
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| 256 | makefile.bor => Borland makefile (uses bcc)
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| 257 | makefile.bc32 => 32-bit Borland C++ (all modules compiled in C mode)
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| 258 | makefile.tc3 => Turbo C 3.0 makefile
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| 259 | makefile.dj2 => DJGPP 2 makefile
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| 260 | makefile.msc => Microsoft C makefile
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| 261 | makefile.vcawin32=> makefile for Microsoft Visual C++ 5.0 and
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| 262 | later (previously used assembler code tuned
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| 263 | for Intel MMX platform)
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| 264 | makefile.vcwin32 => makefile for Microsoft Visual C++ 4.0 and
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| 265 | later (does not use assembler code)
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| 266 | makefile.os2 => OS/2 Makefile (gcc and emx, requires pngos2.def)
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| 267 | pngos2.def => OS/2 module definition file used by makefile.os2
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| 268 | makefile.watcom => Watcom 10a+ Makefile, 32-bit flat memory model
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| 269 | makevms.com => VMS build script
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| 270 | SCOPTIONS.ppc => Used with smakefile.ppc
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| 271 |
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| 272 | Good luck, and happy coding.
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| 273 |
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| 274 | -Glenn Randers-Pehrson (current maintainer, since 1998)
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| 275 | Internet: glennrp at users.sourceforge.net
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| 276 |
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| 277 | -Andreas Eric Dilger (former maintainer, 1996-1997)
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| 278 | Internet: adilger at enel.ucalgary.ca
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| 279 | Web: http://members.shaw.ca/adilger/
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| 280 |
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| 281 | -Guy Eric Schalnat (original author and former maintainer, 1995-1996)
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| 282 | (formerly of Group 42, Inc)
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| 283 | Internet: gschal at infinet.com
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