CHANGES - changes for libpng

version 0.2
  added reader into png.h
  fixed small problems in stub file

version 0.3
  added pull reader
  split up pngwrite.c to several files
  added pnglib.txt
  added example.c
  cleaned up writer, adding a few new tranformations
  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
  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 consistant
  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
  interfaced with zlib 0.8
  fixed many reading and writing bugs
  saved using 3 spaces instead of tabs

version 0.6
  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
  cleaned up lots of bugs
  finished dithering and other stuff
  added test program
  changed name from pnglib to libpng

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

version 0.8
  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 [July, 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 0.90 [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 stream.  ****This affects the size
     of info_struct and invalidates all programs that use a shared libpng****
  fixed png_filler() declarations
  fixed? background color conversions
  fixed order of error function pointers to match documentation
  current chunk name is now available in png_struct to reduce the number
     of nearly identical error messages (will simplify multi-lingual
     support when available)
  try to get ready for unknown-chunk callback functions:
     - previously read critical chunks are flagged, so the chunk handling
       routines can determine if the chunk is in the right place
     - all chunk handling routines have the same prototypes, so we will
       be able to handle all chunks via a callback mechanism
  try to fix Linux "setjmp" buffer size problems
  removed png_large_malloc, png_large_free, and png_realloc functions.

version 0.95 [March, 1997]
  fixed bug in pngwutil.c allocating "up_row" twice and "avg_row" never
  fixed bug in PNG file signature compares when start != 0
  changed parameter type of png_set_filler(...filler...) from png_byte
     to png_uint_32
  added test for MACOS to ensure that both math.h and fp.h are not #included
  added macros for libpng to be compiled as a Windows DLL (Andreas Kupries)
  added "packswap" transformation, which changes the endianness of
     packed-pixel bytes (Kevin Bracey)
  added "strip_alpha" transformation, which removes the alpha channel of
     input images without using it (not neccesarily a good idea)
  added "swap_alpha" transformation, which puts the alpha channel in front
     of the color bytes instead of after
  removed all implicit variable tests which assume NULL == 0 (I think)
  changed several variables to "png_size_t" to show 16/32-bit limitations
  added new pCAL chunk read/write support
  added experimental filter selection weighting (Greg Roelofs)
  removed old png_set_rgbx() and png_set_xrgb() functions that have been
     obsolete for about 2 years now (use png_set_filler() instead)
  added macros to read 16- and 32-bit ints directly from buffer, to be
     used only on those systems that support it (namely PowerPC and 680x0)
     With some testing, this may become the default for MACOS/PPC systems.
  only calculate CRC on data if we are going to use it
  added macros for zTXt compression type PNG_zTXt_COMPRESSION_???
  added macros for simple libpng debugging output selectable at compile time
  removed PNG_READ_END_MODE in progressive reader (Smarasderagd)
  more description of info_struct in libpng.txt and png.h
  more instructions in example.c
  more chunk types tested in pngtest.c
  renamed pngrcb.c to pngset.c, and all png_read_<chunk> functions to be
     png_set_<chunk>.  We now have corresponding png_get_<chunk>
     functions in pngget.c to get infomation in info_ptr.  This isolates
     the application from the internal organization of png_info_struct
     (good for shared library implementations).

version 0.96 [May, 1997]
  fixed serious bug with < 8bpp images introduced in 0.95
  fixed 256-color transparency bug (Greg Roelofs)
  fixed up documentation (Greg Roelofs, Laszlo Nyul)
  fixed "error" in pngconf.h for Linux setjmp() behaviour
  fixed DOS medium model support (Tim Wegner)
  fixed png_check_keyword() for case with error in static string text
  added read of CRC after IEND chunk for embedded PNGs (Laszlo Nyul)
  added typecasts to quiet compiler errors
  added more debugging info

version 0.97 [January, 1998]
  removed PNG_USE_OWN_CRC capability
  relocated png_set_crc_action from pngrutil.c to pngrtran.c
  fixed typecasts of "new_key", etc. (Andreas Dilger)
  added RFC 1152 [sic] date support
  fixed bug in gamma handling of 4-bit grayscale
  added 2-bit grayscale gamma handling (Glenn R-P)
  added more typecasts. 65536L becomes (png_uint_32)65536L, etc. (Glenn R-P)
  minor corrections in libpng.txt
  added simple sRGB support (Glenn R-P)
  easier conditional compiling, e.g. define PNG_READ/WRITE_NOT_FULLY_SUPPORTED;
     all configurable options can be selected from command-line instead
     of having to edit pngconf.h (Glenn R-P)
  fixed memory leak in pngwrite.c (free info_ptr->text) (Glenn R-P)
  added more conditions for png_do_background, to avoid changing
     black pixels to background when a background is supplied and
     no pixels are transparent
  repaired PNG_NO_STDIO behaviour
  tested NODIV support and made it default behaviour (Greg Roelofs)
  added "-m" option and PNGTEST_DEBUG_MEMORY to pngtest (John Bowler)
  regularized version numbering scheme and bumped shared-library major
     version number to 2 to avoid problems with libpng 0.89 apps (Greg Roelofs)

version 0.98 [January, 1998]
  cleaned up some typos in libpng.txt and in code documentation
  fixed memory leaks in pCAL chunk processing (Glenn R-P and John Bowler)
  cosmetic change "display_gamma" to "screen_gamma" in pngrtran.c
  changed recommendation about file_gamma for PC images to .51 from .45,
     in example.c and libpng.txt, added comments to distinguish between
     screen_gamma, viewing_gamma, and display_gamma.
  changed all references to RFC1152 to read RFC1123 and changed the
     PNG_TIME_RFC1152_SUPPORTED macro to PNG_TIME_RFC1123_SUPPORTED
  added png_invert_alpha capability (Glenn R-P -- suggestion by Jon Vincent)
  changed srgb_intent from png_byte to int to avoid compiler bugs

version 0.99 [January 30, 1998]
  free info_ptr->text instead of end_info_ptr->text in pngread.c (John Bowler)
  fixed a longstanding "packswap" bug in pngtrans.c
  fixed some inconsistencies in pngconf.h that prevented compiling with
     PNG_READ_GAMMA_SUPPORTED and PNG_READ_hIST_SUPPORTED undefined
  fixed some typos and made other minor rearrangement of libpng.txt (Andreas)