README 9.1 KB

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  1. README for libpng version 1.6.38.git
  2. ====================================
  3. See the note about version numbers near the top of png.h.
  4. See INSTALL for instructions on how to install libpng.
  5. Libpng comes in several distribution formats. Get libpng-*.tar.gz or
  6. libpng-*.tar.xz or if you want UNIX-style line endings in the text
  7. files, or lpng*.7z or lpng*.zip if you want DOS-style line endings.
  8. Version 0.89 was the first official release of libpng. Don't let the
  9. fact that it's the first release fool you. The libpng library has been
  10. in extensive use and testing since mid-1995. By late 1997 it had
  11. finally gotten to the stage where there hadn't been significant
  12. changes to the API in some time, and people have a bad feeling about
  13. libraries with versions < 1.0. Version 1.0.0 was released in
  14. March 1998.
  15. ****
  16. Note that some of the changes to the png_info structure render this
  17. version of the library binary incompatible with libpng-0.89 or
  18. earlier versions if you are using a shared library. The type of the
  19. "filler" parameter for png_set_filler() has changed from png_byte to
  20. png_uint_32, which will affect shared-library applications that use
  21. this function.
  22. To avoid problems with changes to the internals of the png info_struct,
  23. new APIs have been made available in 0.95 to avoid direct application
  24. access to info_ptr. These functions are the png_set_<chunk> and
  25. png_get_<chunk> functions. These functions should be used when
  26. accessing/storing the info_struct data, rather than manipulating it
  27. directly, to avoid such problems in the future.
  28. It is important to note that the APIs did not make current programs
  29. that access the info struct directly incompatible with the new
  30. library, through libpng-1.2.x. In libpng-1.4.x, which was meant to
  31. be a transitional release, members of the png_struct and the
  32. info_struct can still be accessed, but the compiler will issue a
  33. warning about deprecated usage. Since libpng-1.5.0, direct access
  34. to these structs is not allowed, and the definitions of the structs
  35. reside in private pngstruct.h and pnginfo.h header files that are not
  36. accessible to applications. It is strongly suggested that new
  37. programs use the new APIs (as shown in example.c and pngtest.c), and
  38. older programs be converted to the new format, to facilitate upgrades
  39. in the future.
  40. ****
  41. Additions since 0.90 include the ability to compile libpng as a
  42. Windows DLL, and new APIs for accessing data in the info struct.
  43. Experimental functions include the ability to set weighting and cost
  44. factors for row filter selection, direct reads of integers from buffers
  45. on big-endian processors that support misaligned data access, faster
  46. methods of doing alpha composition, and more accurate 16->8 bit color
  47. conversion.
  48. The additions since 0.89 include the ability to read from a PNG stream
  49. which has had some (or all) of the signature bytes read by the calling
  50. application. This also allows the reading of embedded PNG streams that
  51. do not have the PNG file signature. As well, it is now possible to set
  52. the library action on the detection of chunk CRC errors. It is possible
  53. to set different actions based on whether the CRC error occurred in a
  54. critical or an ancillary chunk.
  55. For a detailed description on using libpng, read libpng-manual.txt.
  56. For examples of libpng in a program, see example.c and pngtest.c. For
  57. usage information and restrictions (what little they are) on libpng,
  58. see png.h. For a description on using zlib (the compression library
  59. used by libpng) and zlib's restrictions, see zlib.h
  60. I have included a general makefile, as well as several machine and
  61. compiler specific ones, but you may have to modify one for your own
  62. needs.
  63. You should use zlib 1.0.4 or later to run this, but it MAY work with
  64. versions as old as zlib 0.95. Even so, there are bugs in older zlib
  65. versions which can cause the output of invalid compression streams for
  66. some images.
  67. You should also note that zlib is a compression library that is useful
  68. for more things than just PNG files. You can use zlib as a drop-in
  69. replacement for fread() and fwrite(), if you are so inclined.
  70. zlib should be available at the same place that libpng is, or at
  71. https://zlib.net.
  72. You may also want a copy of the PNG specification. It is available
  73. as an RFC, a W3C Recommendation, and an ISO/IEC Standard. You can find
  74. these at http://www.libpng.org/pub/png/pngdocs.html .
  75. This code is currently being archived at libpng.sourceforge.io in the
  76. [DOWNLOAD] area, and at http://libpng.download/src .
  77. This release, based in a large way on Glenn's, Guy's and Andreas'
  78. earlier work, was created and will be supported by myself and the PNG
  79. development group.
  80. Send comments/corrections/commendations to png-mng-implement at
  81. lists.sourceforge.net (subscription required; visit
  82. https://lists.sourceforge.net/lists/listinfo/png-mng-implement
  83. to subscribe).
  84. Send general questions about the PNG specification to png-mng-misc
  85. at lists.sourceforge.net (subscription required; visit
  86. https://lists.sourceforge.net/lists/listinfo/png-mng-misc to
  87. subscribe).
  88. Files in this distribution:
  89. ANNOUNCE => Announcement of this version, with recent changes
  90. AUTHORS => List of contributing authors
  91. CHANGES => Description of changes between libpng versions
  92. KNOWNBUG => List of known bugs and deficiencies
  93. LICENSE => License to use and redistribute libpng
  94. README => This file
  95. TODO => Things not implemented in the current library
  96. TRADEMARK => Trademark information
  97. example.c => Example code for using libpng functions
  98. libpng.3 => manual page for libpng (includes libpng-manual.txt)
  99. libpng-manual.txt => Description of libpng and its functions
  100. libpngpf.3 => manual page for libpng's private functions
  101. png.5 => manual page for the PNG format
  102. png.c => Basic interface functions common to library
  103. png.h => Library function and interface declarations (public)
  104. pngpriv.h => Library function and interface declarations (private)
  105. pngconf.h => System specific library configuration (public)
  106. pngstruct.h => png_struct declaration (private)
  107. pnginfo.h => png_info struct declaration (private)
  108. pngdebug.h => debugging macros (private)
  109. pngerror.c => Error/warning message I/O functions
  110. pngget.c => Functions for retrieving info from struct
  111. pngmem.c => Memory handling functions
  112. pngbar.png => PNG logo, 88x31
  113. pngnow.png => PNG logo, 98x31
  114. pngpread.c => Progressive reading functions
  115. pngread.c => Read data/helper high-level functions
  116. pngrio.c => Lowest-level data read I/O functions
  117. pngrtran.c => Read data transformation functions
  118. pngrutil.c => Read data utility functions
  119. pngset.c => Functions for storing data into the info_struct
  120. pngtest.c => Library test program
  121. pngtest.png => Library test sample image
  122. pngtrans.c => Common data transformation functions
  123. pngwio.c => Lowest-level write I/O functions
  124. pngwrite.c => High-level write functions
  125. pngwtran.c => Write data transformations
  126. pngwutil.c => Write utility functions
  127. arm => Contains optimized code for the ARM platform
  128. powerpc => Contains optimized code for the PowerPC platform
  129. contrib => Contributions
  130. arm-neon => Optimized code for ARM-NEON platform
  131. powerpc-vsx => Optimized code for POWERPC-VSX platform
  132. examples => Example programs
  133. gregbook => source code for PNG reading and writing, from
  134. Greg Roelofs' "PNG: The Definitive Guide",
  135. O'Reilly, 1999
  136. libtests => Test programs
  137. mips-msa => Optimized code for MIPS-MSA platform
  138. pngminim => Minimal decoder, encoder, and progressive decoder
  139. programs demonstrating use of pngusr.dfa
  140. pngminus => Simple pnm2png and png2pnm programs
  141. pngsuite => Test images
  142. testpngs
  143. tools => Various tools
  144. visupng => Contains a MSVC workspace for VisualPng
  145. intel => Optimized code for INTEL-SSE2 platform
  146. mips => Optimized code for MIPS platform
  147. projects => Contains project files and workspaces for
  148. building a DLL
  149. owatcom => Contains a WATCOM project for building libpng
  150. visualc71 => Contains a Microsoft Visual C++ (MSVC)
  151. workspace for building libpng and zlib
  152. vstudio => Contains a Microsoft Visual C++ (MSVC)
  153. workspace for building libpng and zlib
  154. scripts => Directory containing scripts for building libpng:
  155. (see scripts/README.txt for the list of scripts)
  156. Good luck, and happy coding!
  157. * Cosmin Truta (current maintainer, since 2018)
  158. * Glenn Randers-Pehrson (former maintainer, 1998-2018)
  159. * Andreas Eric Dilger (former maintainer, 1996-1997)
  160. * Guy Eric Schalnat (original author and former maintainer, 1995-1996)
  161. (formerly of Group 42, Inc.)