changes

一个国人自己实现图像库的程序（有参考价值）

  Renamed "PNG_GLOBAL_ARRAYS" to "PNG_USE_GLOBAL_ARRAYS" and made available
    to applications a macro "PNG_USE_LOCAL_ARRAYS".
  #ifdef out all the new declarations when PNG_USE_GLOBAL_ARRAYS is defined.
  Added PNG_EXPORT_VAR macro to accommodate making DLL's.
version 1.0.5e [November 30, 1999]
  Added iCCP, iTXt, and sPLT support; added "lang" member to the png_text
    structure; refactored the inflate/deflate support to make adding new chunks
    with trailing compressed parts easier in the future, and added new functions
    png_free_iCCP, png_free_pCAL, png_free_sPLT, png_free_text, png_get_iCCP,
    png_get_spalettes, png_set_iCCP, png_set_spalettes (Eric S. Raymond).
  NOTE: Applications that write text chunks MUST define png_text->lang
    before calling png_set_text(). It must be set to NULL if you want to
    write tEXt or zTXt chunks.  If you want your application to be able to
    run with older versions of libpng, use

      #ifdef PNG_iTXt_SUPPORTED
         png_text[i].lang = NULL;
      #endif

  Changed png_get_oFFs() and png_set_oFFs() to use signed rather than unsigned
    offsets (Eric S. Raymond).
  Combined PNG_READ_cHNK_SUPPORTED and PNG_WRITE_cHNK_SUPPORTED macros into
    PNG_cHNK_SUPPORTED and combined the three types of PNG_text_SUPPORTED
    macros, leaving the separate macros also available.
  Removed comments on #endifs at the end of many short, non-nested #if-blocks.
version 1.0.5f [December 6, 1999]
  Changed makefile.solaris to issue a warning about potential problems when
    the ucb "ld" is in the path ahead of the ccs "ld".
  Removed "- [date]" from the "synopsis" line in libpng.3 and libpngpf.3.
  Added sCAL chunk support (Eric S. Raymond).
version 1.0.5g [December 7, 1999]
  Fixed "png_free_spallettes" typo in png.h
  Added code to handle new chunks in pngpread.c
  Moved PNG_CHNK string macro definitions outside of PNG_NO_EXTERN block
  Added "translated_key" to png_text structure and png_write_iTXt().
  Added code in pngwrite.c to work around a newly discovered zlib bug.
version 1.0.5h [December 10, 1999]
  NOTE: regarding the note for version 1.0.5e, the following must also
    be included in your code:
        png_text[i].translated_key = NULL;
  Unknown chunk handling is now supported.
  Option to eliminate all floating point support was added.  Some new
    fixed-point functions such as png_set_gAMA_fixed() were added.
  Expanded tabs and removed trailing blanks in source files.
version 1.0.5i [December 13, 1999]
  Added some type casts to silence compiler warnings.
  Renamed "png_free_spalette" to "png_free_spalettes" for consistency.
  Removed leading blanks from a #define in pngvcrd.c
  Added some parameters to the new png_set_keep_unknown_chunks() function.
  Added a test for up->location != 0 in the first instance of writing
    unknown chunks in pngwrite.c
  Changed "num" to "i" in png_free_spalettes() and png_free_unknowns() to
    prevent recursion.
  Added png_free_hIST() function.
  Various patches to fix bugs in the sCAL and integer cHRM processing,
    and to add some convenience macros for use with sCAL.
version 1.0.5j [December 21, 1999]
  Changed "unit" parameter of png_write_sCAL from png_byte to int, to work
    around buggy compilers.
  Added new type "png_fixed_point" for integers that hold float*100000 values
  Restored backward compatibility of tEXt/zTXt chunk processing:
    Restored the first four members of png_text to the same order as v.1.0.5d.
    Added members "lang_key" and "itxt_length" to png_text struct.  Set
    text_length=0 when "text" contains iTXt data.  Use the "compression"
    member to distinguish among tEXt/zTXt/iTXt types.  Added
    PNG_ITXT_COMPRESSION_NONE (1) and PNG_ITXT_COMPRESSION_zTXt(2) macros.
    The "Note" above, about backward incompatibility of libpng-1.0.5e, no
    longer applies.
  Fixed png_read|write_iTXt() to read|write parameters in the right order,
    and to write the iTXt chunk after IDAT if it appears in the end_ptr.
  Added pnggccrd.c, version of pngvcrd.c Intel assembler for gcc (Greg Roelofs)
  Reversed the order of trying to write floating-point and fixed-point gAMA.
version 1.0.5k [December 27, 1999]
  Added many parentheses, e.g., "if (a && b & c)" becomes "if (a && (b & c))"
  Added png_handle_as_unknown() function (Glenn)
  Added png_free_chunk_list() function and chunk_list and num_chunk_list members
    of png_ptr.
  Eliminated erroneous warnings about multiple sPLT chunks and sPLT-after-PLTE.
  Fixed a libpng-1.0.5h bug in pngrutil.c that was issuing erroneous warnings
    about ignoring incorrect gAMA with sRGB (gAMA was in fact not ignored)
  Added png_free_tRNS(); png_set_tRNS() now malloc's its own trans array (ESR).
  Define png_get_int_32 when oFFs chunk is supported as well as when pCAL is.
  Changed type of proflen from png_int_32 to png_uint_32 in png_get_iCCP().
version 1.0.5l [January 1, 2000]
  Added functions png_set_read_user_chunk_fn() and png_get_user_chunk_ptr()
    for setting a callback function to handle unknown chunks and for
    retrieving the associated user pointer (Glenn).
version 1.0.5m [January 7, 2000]
  Added high-level functions png_read_png(), png_write_png(), png_free_pixels().
version 1.0.5n [January 9, 2000]
  Added png_free_PLTE() function, and modified png_set_PLTE() to malloc its
    own memory for info_ptr->palette.  This makes it safe for the calling
    application to free its copy of the palette any time after it calls
    png_set_PLTE().
version 1.0.5o [January 20, 2000]
  Cosmetic changes only (removed some trailing blanks and TABs)
version 1.0.5p [January 31, 2000]
  Renamed pngdll.mak to makefile.bd32
  Cosmetic changes in pngtest.c
version 1.0.5q [February 5, 2000]
  Relocated the makefile.solaris warning about PATH problems.
  Fixed pngvcrd.c bug by pushing/popping registers in mmxsupport (Bruce Oberg)
  Revised makefile.gcmmx
  Added PNG_SETJMP_SUPPORTED, PNG_SETJMP_NOT_SUPPORTED, and PNG_ABORT() macros
version 1.0.5r [February 7, 2000]
  Removed superfluous prototype for png_get_itxt from png.h
  Fixed a bug in pngrtran.c that improperly expanded the background color.
  Return *num_text=0 from png_get_text() when appropriate, and fix documentation
    of png_get_text() in libpng.txt/libpng.3.
version 1.0.5s [February 18, 2000]
  Added "png_jmp_env()" macro to pngconf.h, to help people migrate to the
    new error handler that's planned for the next libpng release, and changed
    example.c, pngtest.c, and contrib programs to use this macro.
  Revised some of the DLL-export macros in pngconf.h (Greg Roelofs)
  Fixed a bug in png_read_png() that caused it to fail to expand some images
    that it should have expanded.
  Fixed some mistakes in the unused and undocumented INCH_CONVERSIONS functions
    in pngget.c
  Changed the allocation of palette, history, and trans arrays back to
    the version 1.0.5 method (linking instead of copying) which restores
    backward compatibility with version 1.0.5.  Added some remarks about
    that in example.c.  Added "free_me" member to info_ptr and png_ptr
    and added png_free_data() function.
  Updated makefile.linux and makefile.gccmmx to make directories conditionally.
  Made cosmetic changes to pngasmrd.h
  Added png_set_rows() and png_get_rows(), for use with png_read|write_png().
  Modified png_read_png() to allocate info_ptr->row_pointers only if it
    hasn't already been allocated.
version 1.0.5t [March 4, 2000]
  Changed png_jmp_env() migration aiding macro to png_jmpbuf().
  Fixed "interlace" typo (should be "interlaced") in contrib/gregbook/read2-x.c
  Fixed bug with use of PNG_BEFORE_IHDR bit in png_ptr->mode, introduced when
    PNG_FLAG_HAVE_CHUNK_HEADER was moved into png_ptr->mode in version 1.0.5b
  Files in contrib/gregbook were revised to use png_jmpbuf() and to select
    a 24-bit visual if one is available, and to allow abbreviated options.
  Files in contrib/pngminus were revised to use the png_jmpbuf() macro.
  Removed spaces in makefile.linux and makefile.gcmmx, introduced in 1.0.5s
version 1.0.5u [March 5, 2000]
  Simplified the code that detects old png.h in png.c and pngtest.c
  Renamed png_spalette (_p, _pp) to png_sPLT_t (_tp, _tpp)
  Increased precision of rgb_to_gray calculations from 8 to 15 bits and
    added png_set_rgb_to_gray_fixed() function.
  Added makefile.bc32 (32-bit Borland C++, C mode)
version 1.0.5v [March 11, 2000]
  Added some parentheses to the png_jmpbuf macro definition.
  Updated references to the zlib home page, which has moved to freesoftware.com.
  Corrected bugs in documentation regarding png_read_row() and png_write_row().
  Updated documentation of png_rgb_to_gray calculations in libpng.3/libpng.txt.
  Renamed makefile.borland,turboc3 back to makefile.bor,tc3 as in version 1.0.3,
    revised borland makefiles; added makefile.ibmvac3 and makefile.gcc (Cosmin)
version 1.0.6 [March 20, 2000]
  Minor revisions of makefile.bor, libpng.txt, and gregbook/rpng2-win.c
  Added makefile.sggcc (SGI IRIX with gcc)
version 1.0.6d [April 7, 2000]
  Changed sprintf() to strcpy() in png_write_sCAL_s() to work without STDIO
  Added data_length parameter to png_decompress_chunk() function
  Revised documentation to remove reference to abandoned png_free_chnk functions
  Fixed an error in png_rgb_to_gray_fixed()
  Revised example.c, usage of png_destroy_write_struct().
  Renamed makefile.ibmvac3 to makefile.ibmc, added libpng.icc IBM project file
  Added a check for info_ptr->free_me&PNG_FREE_TEXT when freeing text in png.c
  Simplify png_sig_bytes() function to remove use of non-ISO-C strdup().
version 1.0.6e [April 9, 2000]
  Added png_data_freer() function.
  In the code that checks for over-length tRNS chunks, added check of
    info_ptr->num_trans as well as png_ptr->num_trans (Matthias Benckmann)
  Minor revisions of libpng.txt/libpng.3.
  Check for existing data and free it if the free_me flag is set, in png_set_*()
    and png_handle_*().
  Only define PNG_WEIGHTED_FILTERS_SUPPORTED when PNG_FLOATING_POINT_SUPPORTED
    is defined.
  Changed several instances of PNG_NO_CONSOLE_ID to PNG_NO_STDIO in pngrutil.c
    and mentioned the purposes of the two macros in libpng.txt/libpng.3.
version 1.0.6f [April 14, 2000]
  Revised png_set_iCCP() and png_set_rows() to avoid prematurely freeing data.
  Add checks in png_set_text() for NULL members of the input text structure.
  Revised libpng.txt/libpng.3.
  Removed superfluous prototype for png_set_itxt from png.h
  Removed "else" from pngread.c, after png_error(), and changed "0" to "length".
  Changed several png_errors about malformed ancillary chunks to png_warnings.
version 1.0.6g [April 24, 2000]
  Added png_pass-* arrays to pnggccrd.c when PNG_USE_LOCAL_ARRAYS is defined.
  Relocated paragraph about png_set_background() in libpng.3/libpng.txt
    and other revisions (Matthias Benckmann)
  Relocated info_ptr->free_me, png_ptr->free_me, and other info_ptr and
    png_ptr members to restore binary compatibility with libpng-1.0.5
    (breaks compatibility with libpng-1.0.6).
version 1.0.6h [April 24, 2000]
  Changed shared library so-number pattern from 2.x.y.z to xy.z (this builds
    libpng.so.10 & libpng.so.10.6h instead of libpng.so.2 & libpng.so.2.1.0.6h)
    This is a temporary change for test purposes.
version 1.0.6i [May 2, 2000]
  Rearranged some members at the end of png_info and png_struct, to put
    unknown_chunks_num and free_me within the original size of the png_structs
    and free_me, png_read_user_fn, and png_free_fn within the original png_info,
    because some old applications allocate the structs directly instead of
    using png_create_*().
  Added documentation of user memory functions in libpng.txt/libpng.3
  Modified png_read_png so that it will use user_allocated row_pointers
    if present, unless free_me directs that it be freed, and added description
    of the use of png_set_rows() and png_get_rows() in libpng.txt/libpng.3.
  Added PNG_LEGACY_SUPPORTED macro, and #ifdef out all new (since version
    1.00) members of png_struct and png_info, to regain binary compatibility
    when you define this macro.  Capabilities lost in this event
    are user transforms (new in version 1.0.0),the user transform pointer
    (new in version 1.0.2), rgb_to_gray (new in 1.0.5), iCCP, sCAL, sPLT,
    the high-level interface, and unknown chunks support (all new in 1.0.6).
    This was necessary because of old applications that allocate the structs
    directly as authors were instructed to do in libpng-0.88 and earlier,
    instead of using png_create_*().
  Added modes PNG_CREATED_READ_STRUCT and PNG_CREATED_WRITE_STRUCT which
    can be used to detect codes that directly allocate the structs, and
    code to check these modes in png_read_init() and png_write_init() and
    generate a libpng error if the modes aren't set and PNG_LEGACY_SUPPORTED
    was not defined.
  Added makefile.intel and updated makefile.watcom (Pawel Mrochen)
version 1.0.6j [May 3, 2000]
  Overloaded png_read_init() and png_write_init() with macros that convert
    calls to png_read_init_2() or png_write_init_2() that check the version
    and structure sizes.
version 1.0.7beta11 [May 7, 2000]
  Removed the new PNG_CREATED_READ_STRUCT and PNG_CREATED_WRITE_STRUCT modes
    which are no longer used.
  Eliminated the three new members of png_text when PNG_LEGACY_SUPPORTED is
    defined or when neither PNG_READ_iTXt_SUPPORTED nor PNG_WRITE_iTXT_SUPPORTED
    is defined.
  Made PNG_NO_READ|WRITE_iTXt the default setting, to avoid memory
    overrun when old applications fill the info_ptr->text structure directly.
  Added PNGAPI macro, and added it to the definitions of all exported functions.
  Relocated version macro definitions ahead of the includes of zlib.h and
    pngconf.h in png.h.
version 1.0.7beta12 [May 12, 2000]
  Revised pngset.c to avoid a problem with expanding the png_debug macro.
  Deleted some extraneous defines from pngconf.h
  Made PNG_NO_CONSOLE_IO the default condition when PNG_BUILD_DLL is defined.
  Use MSC _RPTn debugging instead of fprintf if _MSC_VER is defined.
  Added png_access_version_number() function.
  Check for mask&PNG_FREE_CHNK (for TEXT, SCAL, PCAL) in png_free_data().
  Expanded libpng.3/libpng.txt information about png_data_freer().
version 1.0.7beta14 [May 17, 2000] (beta13 was not published)
  Changed pnggccrd.c and pngvcrd.c to handle bad adaptive filter types as
    warnings instead of errors, as pngrutil.c does.
  Set the PNG_INFO_IDAT valid flag in png_set_rows() so png_write_png()
    will actually write IDATs.
  Made the default PNG_USE_LOCAL_ARRAYS depend on PNG_DLL instead of WIN32.
  Make png_free_data() ignore its final parameter except when freeing data
    that can have multiple instances (text, sPLT, unknowns).
  Fixed a new bug in png_set_rows().
  Removed info_ptr->valid tests from png_free_data(), as in version 1.0.5.
  Added png_set_invalid() function.
  Fixed incorrect illustrations of png_destroy_write_struct() in example.c.
version 1.0.7beta15 [May 30, 2000]
  Revised the deliberately erroneous Linux setjmp code in pngconf.h to produce
    fewer error messages.
  Rearranged checks for Z_OK to check the most likely path first in pngpread.c
    and pngwutil.c.