libpng/1.6.37

The official PNG reference C library

README for libpng version 1.6.37 - April 14, 2019
=================================================

See the note about version numbers near the top of png.h.
See INSTALL for instructions on how to install libpng.

Libpng comes in several distribution formats.  Get libpng-*.tar.gz or
libpng-*.tar.xz or if you want UNIX-style line endings in the text
files, or lpng*.7z or lpng*.zip if you want DOS-style line endings.

Version 0.89 was the first official release of libpng.  Don't let the
fact that... More

Depends (1)

Builds

Changes

CHANGES - changes for libpng

version 0.1 [March 29, 1995]
  initial work-in-progress release

version 0.2 [April 1, 1995]
  added reader into png.h
  fixed small problems in stub file

version 0.3 [April 8, 1995]
  added pull reader
  split up pngwrite.c to several files
  added pnglib.txt
  added example.c
  cleaned up writer, adding a few new transformations
  fixed some bugs in writer
  interfaced with zlib 0.5
  added K&R support
  added check for 64 KB blocks for 16 bit machines

version 0.4 [April 26, 1995]
  cleaned up code and commented code
  simplified time handling into png_time
  created png_color_16 and png_color_8 to handle color needs
  cleaned up color type defines
  fixed various bugs
  made various names more consistent
  interfaced with zlib 0.71
  cleaned up zTXt reader and writer (using zlib's Reset functions)
  split transformations into pngrtran.c and pngwtran.c

version 0.5 [April 30, 1995]
  interfaced with zlib 0.8
  fixed many reading and writing bugs
  saved using 3 spaces instead of tabs

version 0.6 [May 1, 1995]
  first beta release
  added png_large_malloc() and png_large_free()
  added png_size_t
  cleaned up some compiler warnings
  added png_start_read_image()

version 0.7 [June 24, 1995]
  cleaned up lots of bugs
  finished dithering and other stuff
  added test program
  changed name from pnglib to libpng

version 0.71 [June 26, 1995]
  changed pngtest.png for zlib 0.93
  fixed error in libpng.txt and example.c

version 0.8 [August 20, 1995]
  cleaned up some bugs
  added png_set_filler()
  split up pngstub.c into pngmem.c, pngio.c, and pngerror.c
  added #define's to remove unwanted code
  moved png_info_init() to png.c
  added old_size into png_realloc()
  added functions to manually set filtering and compression info
  changed compression parameters based on image type
  optimized filter selection code
  added version info
  changed external functions passing floats to doubles (k&r problems?)
  put all the configurable stuff in pngconf.h
  enabled png_set_shift to work with paletted images on read
  added png_read_update_info() - updates info structure with transformations

Version 0.81 [August, 1995]
  incorporated Tim Wegner's medium model code (thanks, Tim)

Version 0.82 [September, 1995]
  [unspecified changes]

Version 0.85 [December, 1995]
  added more medium model code (almost everything's a far)
  added i/o, error, and memory callback functions
  fixed some bugs (16-bit, 4-bit interlaced, etc.)
  added first run progressive reader (barely tested)

Version 0.86 [January, 1996]
  fixed bugs
  improved documentation

Version 0.87 [January, 1996]
  fixed medium model bugs
  fixed other bugs introduced in 0.85 and 0.86
  added some minor documentation

Version 0.88 [January, 1996]
  fixed progressive bugs
  replaced tabs with spaces
  cleaned up documentation
  added callbacks for read/write and warning/error functions

Version 0.89 [June 5, 1996]
  Added new initialization API to make libpng work better with shared libs
    we now have png_create_read_struct(), png_create_write_struct(),
    png_create_info_struct(), png_destroy_read_struct(), and
    png_destroy_write_struct() instead of the separate calls to
    malloc and png_read_init(), png_info_init(), and png_write_init()
  Changed warning/error callback functions to fix bug - this means you
    should use the new initialization API if you were using the old
    png_set_message_fn() calls, and that the old API no longer exists
    so that people are aware that they need to change their code
  Changed filter selection API to allow selection of multiple filters
    since it didn't work in previous versions of libpng anyways
  Optimized filter selection code
  Fixed png_set_background() to allow using an arbitrary RGB color for
    paletted images
  Fixed gamma and background correction for paletted images, so
    png_correct_palette is not needed unless you are correcting an
    external palette (you will need to #define PNG_CORRECT_PALETTE_SUPPORTED
    in pngconf.h) - if nobody uses this, it may disappear in the future.
  Fixed bug with Borland 64K memory allocation (Alexander Lehmann)
  Fixed bug in interlace handling (Smarasderagd, I think)
  Added more error checking for writing and image to reduce invalid files
  Separated read and write functions so that they won't both be linked
    into a binary when only reading or writing functionality is used
  New pngtest image also has interlacing and zTXt
  Updated documentation to reflect new API

Version 0.89c [June 17, 1996]
  Bug fixes.

Version 0.90 [January, 1997]
  Made CRC errors/warnings on critical and ancillary chunks configurable
  libpng will use the zlib CRC routines by (compile-time) default
  Changed DOS small/medium model memory support - needs zlib 1.04 (Tim Wegner)
  Added external C++ wrapper statements to png.h (Gilles Dauphin)
  Allow PNG file to be read when some or all of file signature has already
    been read from the beginning of the... More