/* png.h - header file for PNG reference library
 *
 * libpng version 1.2.8 - December 3, 2004
 * Copyright (c) 1998-2004 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
 * Authors and maintainers:
 *  libpng versions 0.71, May 1995, through 0.88, January 1996: Guy Schalnat
 *  libpng versions 0.89c, June 1996, through 0.96, May 1997: Andreas Dilger
 *  libpng versions 0.97, January 1998, through 1.2.8 - December 3, 2004: Glenn
 *  See also "Contributing Authors", below.
 *
 * Note about libpng version numbers:
 *
 *    Due to various miscommunications, unforeseen code incompatibilities
 *    and occasional factors outside the authors' control, version numbering
 *    on the library has not always been consistent and straightforward.
 *    The following table summarizes matters since version 0.89c, which was
 *    the first widely used release:
 *
 *    source                 png.h  png.h  shared-lib
 *    version                string   int  version
 *    -------                ------ -----  ----------
 *    0.89c "1.0 beta 3"     0.89      89  1.0.89
 *    0.90  "1.0 beta 4"     0.90      90  0.90  [should have been 2.0.90]
 *    0.95  "1.0 beta 5"     0.95      95  0.95  [should have been 2.0.95]
 *    0.96  "1.0 beta 6"     0.96      96  0.96  [should have been 2.0.96]
 *    0.97b "1.00.97 beta 7" 1.00.97   97  1.0.1 [should have been 2.0.97]
 *    0.97c                  0.97      97  2.0.97
 *    0.98                   0.98      98  2.0.98
 *    0.99                   0.99      98  2.0.99
 *    0.99a-m                0.99      99  2.0.99
 *    1.00                   1.00     100  2.1.0 [100 should be 10000]
 *    1.0.0      (from here on, the   100  2.1.0 [100 should be 10000]
 *    1.0.1       png.h string is   10001  2.1.0
 *    1.0.1a-e    identical to the  10002  from here on, the shared library
 *    1.0.2       source version)   10002  is 2.V where V is the source code
 *    1.0.2a-b                      10003  version, except as noted.
 *    1.0.3                         10003
 *    1.0.3a-d                      10004
 *    1.0.4                         10004
 *    1.0.4a-f                      10005
 *    1.0.5 (+ 2 patches)           10005
 *    1.0.5a-d                      10006
 *    1.0.5e-r                      10100 (not source compatible)
 *    1.0.5s-v                      10006 (not binary compatible)
 *    1.0.6 (+ 3 patches)           10006 (still binary incompatible)
 *    1.0.6d-f                      10007 (still binary incompatible)
 *    1.0.6g                        10007
 *    1.0.6h                        10007  10.6h (testing xy.z so-numbering)
 *    1.0.6i                        10007  10.6i
 *    1.0.6j                        10007  2.1.0.6j (incompatible with 1.0.0)
 *    1.0.7beta11-14        DLLNUM  10007  2.1.0.7beta11-14 (binary compatible)
 *    1.0.7beta15-18           1    10007  2.1.0.7beta15-18 (binary compatible)
 *    1.0.7rc1-2               1    10007  2.1.0.7rc1-2 (binary compatible)
 *    1.0.7                    1    10007  (still compatible)
 *    1.0.8beta1-4             1    10008  2.1.0.8beta1-4
 *    1.0.8rc1                 1    10008  2.1.0.8rc1
 *    1.0.8                    1    10008  2.1.0.8
 *    1.0.9beta1-6             1    10009  2.1.0.9beta1-6
 *    1.0.9rc1                 1    10009  2.1.0.9rc1
 *    1.0.9beta7-10            1    10009  2.1.0.9beta7-10
 *    1.0.9rc2                 1    10009  2.1.0.9rc2
 *    1.0.9                    1    10009  2.1.0.9
 *    1.0.10beta1              1    10010  2.1.0.10beta1
 *    1.0.10rc1                1    10010  2.1.0.10rc1
 *    1.0.10                   1    10010  2.1.0.10
 *    1.0.11beta1-3            1    10011  2.1.0.11beta1-3
 *    1.0.11rc1                1    10011  2.1.0.11rc1
 *    1.0.11                   1    10011  2.1.0.11
 *    1.0.12beta1-2            2    10012  2.1.0.12beta1-2
 *    1.0.12rc1                2    10012  2.1.0.12rc1
 *    1.0.12                   2    10012  2.1.0.12
 *    1.1.0a-f                 -    10100  2.1.1.0a-f (branch abandoned)
 *    1.2.0beta1-2             2    10200  2.1.2.0beta1-2
 *    1.2.0beta3-5             3    10200  3.1.2.0beta3-5
 *    1.2.0rc1                 3    10200  3.1.2.0rc1
 *    1.2.0                    3    10200  3.1.2.0
 *    1.2.1beta1-4             3    10201  3.1.2.1beta1-4
 *    1.2.1rc1-2               3    10201  3.1.2.1rc1-2
 *    1.2.1                    3    10201  3.1.2.1
 *    1.2.2beta1-6            12    10202  12.so.0.1.2.2beta1-6
 *    1.0.13beta1             10    10013  10.so.0.1.0.13beta1
 *    1.0.13rc1               10    10013  10.so.0.1.0.13rc1
 *    1.2.2rc1                12    10202  12.so.0.1.2.2rc1
 *    1.0.13                  10    10013  10.so.0.1.0.13
 *    1.2.2                   12    10202  12.so.0.1.2.2
 *    1.2.3rc1-6              12    10203  12.so.0.1.2.3rc1-6
 *    1.2.3                   12    10203  12.so.0.1.2.3
 *    1.2.4beta1-3            13    10204  12.so.0.1.2.4beta1-3
 *    1.0.14rc1               13    10014  10.so.0.1.0.14rc1
 *    1.2.4rc1                13    10204  12.so.0.1.2.4rc1
 *    1.0.14                  10    10014  10.so.0.1.0.14
 *    1.2.4                   13    10204  12.so.0.1.2.4
 *    1.2.5beta1-2            13    10205  12.so.0.1.2.5beta1-2
 *    1.0.15rc1-3             10    10015  10.so.0.1.0.15rc1-3
 *    1.2.5rc1-3              13    10205  12.so.0.1.2.5rc1-3
 *    1.0.15                  10    10015  10.so.0.1.0.15
 *    1.2.5                   13    10205  12.so.0.1.2.5
 *    1.2.6beta1-4            13    10206  12.so.0.1.2.6beta1-4
 *    1.0.16                  10    10016  10.so.0.1.0.16
 *    1.2.6                   13    10206  12.so.0.1.2.6
 *    1.2.7beta1-2            13    10207  12.so.0.1.2.7beta1-2
 *    1.0.17rc1               10    10017  12.so.0.1.0.17rc1
 *    1.2.7rc1                13    10207  12.so.0.1.2.7rc1
 *    1.0.17                  10    10017  12.so.0.1.0.17
 *    1.2.7                   13    10207  12.so.0.1.2.7
 *    1.2.8beta1-5            13    10208  12.so.0.1.2.8beta1-5
 *    1.0.18rc1-5             10    10018  12.so.0.1.0.18rc1-5
 *    1.2.8rc1-5              13    10208  12.so.0.1.2.8rc1-5
 *    1.0.18                  10    10018  12.so.0.1.0.18
 *    1.2.8                   13    10208  12.so.0.1.2.8
 *
 *    Henceforth the source version will match the shared-library major
 *    and minor numbers; the shared-library major version number will be
 *    used for changes in backward compatibility, as it is intended.  The
 *    PNG_LIBPNG_VER macro, which is not used within libpng but is available
 *    for applications, is an unsigned integer of the form xyyzz corresponding
 *    to the source version x.y.z (leading zeros in y and z).  Beta versions
 *    were given the previous public release number plus a letter, until
 *    version 1.0.6j; from then on they were given the upcoming public
 *    release number plus "betaNN" or "rcN".
 *
 *    Binary incompatibility exists only when applications make direct access
 *    to the info_ptr or png_ptr members through png.h, and the compiled
 *    application is loaded with a different version of the library.
 *
 *    DLLNUM will change each time there are forward or backward changes
 *    in binary compatibility (e.g., when a new feature is added).
 *
 * See libpng.txt or libpng.3 for more information.  The PNG specification
 * is available as a W3C Recommendation and as an ISO Specification,
 * <http://www.w3.org/TR/2003/REC-PNG-20031110/
 */

/*
 * COPYRIGHT NOTICE, DISCLAIMER, and LICENSE:
 *
 * If you modify libpng you may insert additional notices immediately following
 * this sentence.
 *
 * libpng versions 1.2.6, August 15, 2004, through 1.2.8, December 3, 2004, are
 * Copyright (c) 2004 Glenn Randers-Pehrson, and are
 * distributed according to the same disclaimer and license as libpng-1.2.5
 * with the following individual added to the list of Contributing Authors:
 *
 *    Cosmin Truta
 *
 * libpng versions 1.0.7, July 1, 2000, through 1.2.5, October 3, 2002, are
 * Copyright (c) 2000-2002 Glenn Randers-Pehrson, and are
 * distributed according to the same disclaimer and license as libpng-1.0.6
 * with the following individuals added to the list of Contributing Authors:
 *
 *    Simon-Pierre Cadieux
 *    Eric S. Raymond
 *    Gilles Vollant
 *
 * and with the following additions to the disclaimer:
 *
 *    There is no warranty against interference with your enjoyment of the
 *    library or against infringement.  There is no warranty that our
 *    efforts or the library will fulfill any of your particular purposes
 *    or needs.  This library is provided with all faults, and the entire
 *    risk of satisfactory quality, performance, accuracy, and effort is with
 *    the user.
 *
 * libpng versions 0.97, January 1998, through 1.0.6, March 20, 2000, are
 * Copyright (c) 1998, 1999, 2000 Glenn Randers-Pehrson, and are
 * distributed according to the same disclaimer and license as libpng-0.96,
 * with the following individuals added to the list of Contributing Authors:
 *
 *    Tom Lane
 *    Glenn Randers-Pehrson
 *    Willem van Schaik
 *
 * libpng versions 0.89, June 1996, through 0.96, May 1997, are
 * Copyright (c) 1996, 1997 Andreas Dilger
 * Distributed according to the same disclaimer and license as libpng-0.88,
 * with the following individuals added to the list of Contributing Authors:
 *
 *    John Bowler
 *    Kevin Bracey
 *    Sam Bushell
 *    Magnus Holmgren
 *    Greg Roelofs
 *    Tom Tanner
 *
 * libpng versions 0.5, May 1995, through 0.88, January 1996, are
 * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
 *
 * For the purposes of this copyright and license, "Contributing Authors"
 * is defined as the following set of individuals:
 *
 *    Andreas Dilger
 *    Dave Martindale
 *    Guy Eric Schalnat
 *    Paul Schmidt
 *    Tim Wegner
 *
 * The PNG Reference Library is supplied "AS IS".  The Contributing Authors
 * and Group 42, Inc. disclaim all warranties, expressed or implied,
 * including, without limitation, the warranties of merchantability and of
 * fitness for any purpose.  The Contributing Authors and Group 42, Inc.
 * assume no liability for direct, indirect, incidental, special, exemplary,
 * or consequential damages, which may result from the use of the PNG
 * Reference Library, even if advised of the possibility of such damage.
 *
 * Permission is hereby granted to use, copy, modify, and distribute this
 * source code, or portions hereof, for any purpose, without fee, subject
 * to the following restrictions:
 *
 * 1. The origin of this source code must not be misrepresented.
 *
 * 2. Altered versions must be plainly marked as such and
 * must not be misrepresented as being the original source.
 *
 * 3. This Copyright notice may not be removed or altered from
 *    any source or altered source distribution.
 *
 * The Contributing Authors and Group 42, Inc. specifically permit, without
 * fee, and encourage the use of this source code as a component to
 * supporting the PNG file format in commercial products.  If you use this
 * source code in a product, acknowledgment is not required but would be
 * appreciated.
 */

/*
 * A "png_get_copyright" function is available, for convenient use in "about"
 * boxes and the like:
 *
 * printf("%s",png_get_copyright(NULL));
 *
 * Also, the PNG logo (in PNG format, of course) is supplied in the
 * files "pngbar.png" and "pngbar.jpg (88x31) and "pngnow.png" (98x31).
 */

/*
 * Libpng is OSI Certified Open Source Software.  OSI Certified is a
 * certification mark of the Open Source Initiative.
 */

/*
 * The contributing authors would like to thank all those who helped
 * with testing, bug fixes, and patience.  This wouldn't have been
 * possible without all of you.
 *
 * Thanks to Frank J. T. Wojcik for helping with the documentation.
 */

/*
 * Y2K compliance in libpng:
 * =========================
 *
 *    December 3, 2004
 *
 *    Since the PNG Development group is an ad-hoc body, we can't make
 *    an official declaration.
 *
 *    This is your unofficial assurance that libpng from version 0.71 and
 *    upward through 1.2.8 are Y2K compliant.  It is my belief that earlier
 *    versions were also Y2K compliant.
 *
 *    Libpng only has three year fields.  One is a 2-byte unsigned integer
 *    that will hold years up to 65535.  The other two hold the date in text
 *    format, and will hold years up to 9999.
 *
 *    The integer is
 *        "png_uint_16 year" in png_time_struct.
 *
 *    The strings are
 *        "png_charp time_buffer" in png_struct and
 *        "near_time_buffer", which is a local character string in png.c.
 *
 *    There are seven time-related functions:
 *        png.c: png_convert_to_rfc_1123() in png.c
 *          (formerly png_convert_to_rfc_1152() in error)
 *        png_convert_from_struct_tm() in pngwrite.c, called in pngwrite.c
 *        png_convert_from_time_t() in pngwrite.c
 *        png_get_tIME() in pngget.c
 *        png_handle_tIME() in pngrutil.c, called in pngread.c
 *        png_set_tIME() in pngset.c
 *        png_write_tIME() in pngwutil.c, called in pngwrite.c
 *
 *    All handle dates properly in a Y2K environment.  The
 *    png_convert_from_time_t() function calls gmtime() to convert from system
 *    clock time, which returns (year - 1900), which we properly convert to
 *    the full 4-digit year.  There is a possibility that applications using
 *    libpng are not passing 4-digit years into the png_convert_to_rfc_1123()
 *    function, or that they are incorrectly passing only a 2-digit year
 *    instead of "year - 1900" into the png_convert_from_struct_tm() function,
 *    but this is not under our control.  The libpng documentation has always
 *    stated that it works with 4-digit years, and the APIs have been
 *    documented as such.
 *
 *    The tIME chunk itself is also Y2K compliant.  It uses a 2-byte unsigned
 *    integer to hold the year, and can hold years as large as 65535.
 *
 *    zlib, upon which libpng depends, is also Y2K compliant.  It contains
 *    no date-related code.
 *
 *       Glenn Randers-Pehrson
 *       libpng maintainer
 *       PNG Development Group
 */

#ifndef PNG_H
#define PNG_H

/* This is not the place to learn how to use libpng.  The file libpng.txt
 * describes how to use libpng, and the file example.c summarizes it
 * with some code on which to build.  This file is useful for looking
 * at the actual function definitions and structure components.
 */

/* Version information for png.h - this should match the version in png.c */
#define PNG_LIBPNG_VER_STRING "1.2.8"
#define PNG_HEADER_VERSION_STRING \
   " libpng version 1.2.8 - December 3, 2004 (header)\n"

#define PNG_LIBPNG_VER_SONUM   0
#define PNG_LIBPNG_VER_DLLNUM  13

/* These should match the first 3 components of PNG_LIBPNG_VER_STRING: */
#define PNG_LIBPNG_VER_MAJOR   1
#define PNG_LIBPNG_VER_MINOR   2
#define PNG_LIBPNG_VER_RELEASE 8
/* This should match the numeric part of the final component of
 * PNG_LIBPNG_VER_STRING, omitting any leading zero: */

#define PNG_LIBPNG_VER_BUILD  0

/* Release Status */
#define PNG_LIBPNG_BUILD_ALPHA    1
#define PNG_LIBPNG_BUILD_BETA     2
#define PNG_LIBPNG_BUILD_RC       3
#define PNG_LIBPNG_BUILD_STABLE   4
#define PNG_LIBPNG_BUILD_RELEASE_STATUS_MASK 7
  
/* Release-Specific Flags */
#define PNG_LIBPNG_BUILD_PATCH    8 /* Can be OR'ed with
                                       PNG_LIBPNG_BUILD_STABLE only */
#define PNG_LIBPNG_BUILD_PRIVATE 16 /* Cannot be OR'ed with
                                       PNG_LIBPNG_BUILD_SPECIAL */
#define PNG_LIBPNG_BUILD_SPECIAL 32 /* Cannot be OR'ed with
                                       PNG_LIBPNG_BUILD_PRIVATE */

#define PNG_LIBPNG_BUILD_BASE_TYPE PNG_LIBPNG_BUILD_STABLE

/* Careful here.  At one time, Guy wanted to use 082, but that would be octal.
 * We must not include leading zeros.
 * Versions 0.7 through 1.0.0 were in the range 0 to 100 here (only
 * version 1.0.0 was mis-numbered 100 instead of 10000).  From
 * version 1.0.1 it's    xxyyzz, where x=major, y=minor, z=release */
#define PNG_LIBPNG_VER 10208 /* 1.2.8 */

#ifndef PNG_VERSION_INFO_ONLY
/* include the compression library's header */
#include "zlib.h"
#endif

/* include all user configurable info, including optional assembler routines */
#include "pngconf.h"

/*
 * Added at libpng-1.2.8 */
/* Ref MSDN: Private as priority over Special
 * VS_FF_PRIVATEBUILD File *was not* built using standard release
 * procedures. If this value is given, the StringFileInfo block must
 * contain a PrivateBuild string. 
 *
 * VS_FF_SPECIALBUILD File *was* built by the original company using
 * standard release procedures but is a variation of the standard
 * file of the same version number. If this value is given, the
 * StringFileInfo block must contain a SpecialBuild string. 
 */

#if defined(PNG_USER_PRIVATEBUILD)
#  define PNG_LIBPNG_BUILD_TYPE PNG_LIBPNG_BUILD_BASE_TYPE | \
          PNG_LIBPNG_BUILD_PRIVATE
#else
#  if defined(PNG_LIBPNG_SPECIALBUILD)
#    define PNG_LIBPNG_BUILD_TYPE PNG_LIBPNG_BUILD_BASE_TYPE | \
            PNG_LIBPNG_BUILD_SPECIAL
#  else
#    define PNG_LIBPNG_BUILD_TYPE PNG_LIBPNG_BUILD_BASE_TYPE
#  endif
#endif

#ifndef PNG_VERSION_INFO_ONLY

/* Inhibit C++ name-mangling for libpng functions but not for system calls. */
#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */

/* This file is arranged in several sections.  The first section contains
 * structure and type definitions.  The second section contains the external
 * library functions, while the third has the internal library functions,
 * which applications aren't expected to use directly.
 */

#ifndef PNG_NO_TYPECAST_NULL
#define int_p_NULL                (int *)NULL
#define png_bytep_NULL            (png_bytep)NULL
#define png_bytepp_NULL           (png_bytepp)NULL
#define png_doublep_NULL          (png_doublep)NULL
#define png_error_ptr_NULL        (png_error_ptr)NULL
#define png_flush_ptr_NULL        (png_flush_ptr)NULL
#define png_free_ptr_NULL         (png_free_ptr)NULL
#define png_infopp_NULL           (png_infopp)NULL
#define png_malloc_ptr_NULL       (png_malloc_ptr)NULL
#define png_read_status_ptr_NULL  (png_read_status_ptr)NULL
#define png_rw_ptr_NULL           (png_rw_ptr)NULL
#define png_structp_NULL          (png_structp)NULL
#define png_uint_16p_NULL         (png_uint_16p)NULL
#define png_voidp_NULL            (png_voidp)NULL
#define png_write_status_ptr_NULL (png_write_status_ptr)NULL
#else
#define int_p_NULL                NULL
#define png_bytep_NULL            NULL
#define png_bytepp_NULL           NULL
#define png_doublep_NULL          NULL
#define png_error_ptr_NULL        NULL
#define png_flush_ptr_NULL        NULL
#define png_free_ptr_NULL         NULL
#define png_infopp_NULL           NULL
#define png_malloc_ptr_NULL       NULL
#define png_read_status_ptr_NULL  NULL
#define png_rw_ptr_NULL           NULL
#define png_structp_NULL          NULL
#define png_uint_16p_NULL         NULL
#define png_voidp_NULL            NULL
#define png_write_status_ptr_NULL NULL
#endif

/* variables declared in png.c - only it needs to define PNG_NO_EXTERN */
#if !defined(PNG_NO_EXTERN) || defined(PNG_ALWAYS_EXTERN)
/* Version information for C files, stored in png.c.  This had better match
 * the version above.
 */
#ifdef PNG_USE_GLOBAL_ARRAYS
PNG_EXPORT_VAR (const char) png_libpng_ver[18];
  /* need room for 99.99.99beta99z */
#else
#define png_libpng_ver png_get_header_ver(NULL)
#endif

#ifdef PNG_USE_GLOBAL_ARRAYS
/* This was removed in version 1.0.5c */
/* Structures to facilitate easy interlacing.  See png.c for more details */
PNG_EXPORT_VAR (const int FARDATA) png_pass_start[7];
PNG_EXPORT_VAR (const int FARDATA) png_pass_inc[7];
PNG_EXPORT_VAR (const int FARDATA) png_pass_ystart[7];
PNG_EXPORT_VAR (const int FARDATA) png_pass_yinc[7];
PNG_EXPORT_VAR (const int FARDATA) png_pass_mask[7];
PNG_EXPORT_VAR (const int FARDATA) png_pass_dsp_mask[7];
#ifdef PNG_HAVE_ASSEMBLER_COMBINE_ROW
PNG_EXPORT_VAR (const int FARDATA) png_pass_width[7];
#endif
/* This isn't currently used.  If you need it, see png.c for more details.
PNG_EXPORT_VAR (const int FARDATA) png_pass_height[7];
*/
#endif

#endif /* PNG_NO_EXTERN */

/* Three color definitions.  The order of the red, green, and blue, (and the
 * exact size) is not important, although the size of the fields need to
 * be png_byte or png_uint_16 (as defined below).
 */
typedef struct png_color_struct
{
   png_byte red;
   png_byte green;
   png_byte blue;
} png_color;
typedef png_color FAR * png_colorp;
typedef png_color FAR * FAR * png_colorpp;

typedef struct png_color_16_struct
{
   png_byte index;    /* used for palette files */
   png_uint_16 red;   /* for use in red green blue files */
   png_uint_16 green;
   png_uint_16 blue;
   png_uint_16 gray;  /* for use in grayscale files */
} png_color_16;
typedef png_color_16 FAR * png_color_16p;
typedef png_color_16 FAR * FAR * png_color_16pp;

typedef struct png_color_8_struct
{
   png_byte red;   /* for use in red green blue files */
   png_byte green;
   png_byte blue;
   png_byte gray;  /* for use in grayscale files */
   png_byte alpha; /* for alpha channel files */
} png_color_8;
typedef png_color_8 FAR * png_color_8p;
typedef png_color_8 FAR * FAR * png_color_8pp;

/*
 * The following two structures are used for the in-core representation
 * of sPLT chunks.
 */
typedef struct png_sPLT_entry_struct
{
   png_uint_16 red;
   png_uint_16 green;
   png_uint_16 blue;
   png_uint_16 alpha;
   png_uint_16 frequency;
} png_sPLT_entry;
typedef png_sPLT_entry FAR * png_sPLT_entryp;
typedef png_sPLT_entry FAR * FAR * png_sPLT_entrypp;

/*  When the depth of the sPLT palette is 8 bits, the color and alpha samples
 *  occupy the LSB of their respective members, and the MSB of each member
 *  is zero-filled.  The frequency member always occupies the full 16 bits.
 */

typedef struct png_sPLT_struct
{
   png_charp name;           /* palette name */
   png_byte depth;           /* depth of palette samples */
   png_sPLT_entryp entries;  /* palette entries */
   png_int_32 nentries;      /* number of palette entries */
} png_sPLT_t;
typedef png_sPLT_t FAR * png_sPLT_tp;
typedef png_sPLT_t FAR * FAR * png_sPLT_tpp;

#ifdef PNG_TEXT_SUPPORTED
/* png_text holds the contents of a text/ztxt/itxt chunk in a PNG file,
 * and whether that contents is compressed or not.  The "key" field
 * points to a regular zero-terminated C string.  The "text", "lang", and
 * "lang_key" fields can be regular C strings, empty strings, or NULL pointers.
 * However, the * structure returned by png_get_text() will always contain
 * regular zero-terminated C strings (possibly empty), never NULL pointers,
 * so they can be safely used in printf() and other string-handling functions.
 */
typedef struct png_text_struct
{
   int  compression;       /* compression value:
                             -1: tEXt, none
                              0: zTXt, deflate
                              1: iTXt, none
                              2: iTXt, deflate  */
   png_charp key;          /* keyword, 1-79 character description of "text" */
   png_charp text;         /* comment, may be an empty string (ie "")
                              or a NULL pointer */
   png_size_t text_length; /* length of the text string */
#ifdef PNG_iTXt_SUPPORTED
   png_size_t itxt_length; /* length of the itxt string */
   png_charp lang;         /* language code, 0-79 characters
                              or a NULL pointer */
   png_charp lang_key;     /* keyword translated UTF-8 string, 0 or more
                              chars or a NULL pointer */
#endif
} png_text;
typedef png_text FAR * png_textp;
typedef png_text FAR * FAR * png_textpp;
#endif

/* Supported compression types for text in PNG files (tEXt, and zTXt).
 * The values of the PNG_TEXT_COMPRESSION_ defines should NOT be changed. */
#define PNG_TEXT_COMPRESSION_NONE_WR -3
#define PNG_TEXT_COMPRESSION_zTXt_WR -2
#define PNG_TEXT_COMPRESSION_NONE    -1
#define PNG_TEXT_COMPRESSION_zTXt     0
#define PNG_ITXT_COMPRESSION_NONE     1
#define PNG_ITXT_COMPRESSION_zTXt     2
#define PNG_TEXT_COMPRESSION_LAST     3  /* Not a valid value */

/* png_time is a way to hold the time in an machine independent way.
 * Two conversions are provided, both from time_t and struct tm.  There
 * is no portable way to convert to either of these structures, as far
 * as I know.  If you know of a portable way, send it to me.  As a side
 * note - PNG has always been Year 2000 compliant!
 */
typedef struct png_time_struct
{
   png_uint_16 year; /* full year, as in, 1995 */
   png_byte month;   /* month of year, 1 - 12 */
   png_byte day;     /* day of month, 1 - 31 */
   png_byte hour;    /* hour of day, 0 - 23 */
   png_byte minute;  /* minute of hour, 0 - 59 */
   png_byte second;  /* second of minute, 0 - 60 (for leap seconds) */
} png_time;
typedef png_time FAR * png_timep;
typedef png_time FAR * FAR * png_timepp;

#if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED)
/* png_unknown_chunk is a structure to hold queued chunks for which there is
 * no specific support.  The idea is that we can use this to queue
 * up private chunks for output even though the library doesn't actually
 * know about their semantics.
 */
typedef struct png_unknown_chunk_t
{
    png_byte name[5];
    png_byte *data;
    png_size_t size;

    /* libpng-using applications should NOT directly modify this byte. */
    png_byte location; /* mode of operation at read time */
}
png_unknown_chunk;
typedef png_unknown_chunk FAR * png_unknown_chunkp;
typedef png_unknown_chunk FAR * FAR * png_unknown_chunkpp;
#endif

/* png_info is a structure that holds the information in a PNG file so
 * that the application can find out the characteristics of the image.
 * If you are reading the file, this structure will tell you what is
 * in the PNG file.  If you are writing the file, fill in the information
 * you want to put into the PNG file, then call png_write_info().
 * The names chosen should be very close to the PNG specification, so
 * consult that document for information about the meaning of each field.
 *
 * With libpng < 0.95, it was only possible to directly set and read the
 * the values in the png_info_struct, which meant that the contents and
 * order of the values had to remain fixed.  With libpng 0.95 and later,
 * however, there are now functions that abstract the contents of
 * png_info_struct from the application, so this makes it easier to use
 * libpng with dynamic libraries, and even makes it possible to use
 * libraries that don't have all of the libpng ancillary chunk-handing
 * functionality.
 *
 * In any case, the order of the parameters in png_info_struct should NOT
 * be changed for as long as possible to keep compatibility with applications
 * that use the old direct-access method with png_info_struct.
 *
 * The following members may have allocated storage attached that should be
 * cleaned up before the structure is discarded: palette, trans, text,
 * pcal_purpose, pcal_units, pcal_params, hist, iccp_name, iccp_profile,
 * splt_palettes, scal_unit, row_pointers, and unknowns.   By default, these
 * are automatically freed when the info structure is deallocated, if they were
 * allocated internally by libpng.  This behavior can be changed by means
 * of the png_data_freer() function.
 *
 * More allocation details: all the chunk-reading functions that
 * change these members go through the corresponding png_set_*
 * functions.  A function to clear these members is available: see
 * png_free_data().  The png_set_* functions do not depend on being
 * able to point info structure members to any of the storage they are
 * passed (they make their own copies), EXCEPT that the png_set_text
 * functions use the same storage passed to them in the text_ptr or
 * itxt_ptr structure argument, and the png_set_rows and png_set_unknowns
 * functions do not make their own copies.
 */
typedef struct png_info_struct
{
   /* the following are necessary for every PNG file */
   png_uint_32 width;       /* width of image in pixels (from IHDR) */
   png_uint_32 height;      /* height of image in pixels (from IHDR) */
   png_uint_32 valid;       /* valid chunk data (see PNG_INFO_ below) */
   png_uint_32 rowbytes;    /* bytes needed to hold an untransformed row */
   png_colorp palette;      /* array of color values (valid & PNG_INFO_PLTE) */
   png_uint_16 num_palette; /* number of color entries in "palette" (PLTE) */
   png_uint_16 num_trans;   /* number of transparent palette color (tRNS) */
   png_byte bit_depth;      /* 1, 2, 4, 8, or 16 bits/channel (from IHDR) */
   png_byte color_type;     /* see PNG_COLOR_TYPE_ below (from IHDR) */
   /* The following three should have been named *_method not *_type */
   png_byte compression_type; /* must be PNG_COMPRESSION_TYPE_BASE (IHDR) */
   png_byte filter_type;    /* must be PNG_FILTER_TYPE_BASE (from IHDR) */
   png_byte interlace_type; /* One of PNG_INTERLACE_NONE, PNG_INTERLACE_ADAM7 */

   /* The following is informational only on read, and not used on writes. */
   png_byte channels;       /* number of data channels per pixel (1, 2, 3, 4) */
   png_byte pixel_depth;    /* number of bits per pixel */
   png_byte spare_byte;     /* to align the data, and for future use */
   png_byte signature[8];   /* magic bytes read by libpng from start of file */

   /* The rest of the data is optional.  If you are reading, check the
    * valid field to see if the information in these are valid.  If you
    * are writing, set the valid field to those chunks you want written,
    * and initialize the appropriate fields below.
    */

#if defined(PNG_gAMA_SUPPORTED) && defined(PNG_FLOATING_POINT_SUPPORTED)
   /* The gAMA chunk describes the gamma characteristics of the system
    * on which the image was created, normally in the range [1.0, 2.5].
    * Data is valid if (valid & PNG_INFO_gAMA) is non-zero.
    */
   float gamma; /* gamma value of image, if (valid & PNG_INFO_gAMA) */
#endif

#if defined(PNG_sRGB_SUPPORTED)
    /* GR-P, 0.96a */
    /* Data valid if (valid & PNG_INFO_sRGB) non-zero. */
   png_byte srgb_intent; /* sRGB rendering intent [0, 1, 2, or 3] */
#endif

#if defined(PNG_TEXT_SUPPORTED)
   /* The tEXt, and zTXt chunks contain human-readable textual data in
    * uncompressed, compressed, and optionally compressed forms, respectively.
    * The data in "text" is an array of pointers to uncompressed,
    * null-terminated C strings. Each chunk has a keyword that describes the
    * textual data contained in that chunk.  Keywords are not required to be
    * unique, and the text string may be empty.  Any number of text chunks may
    * be in an image.
    */
   int num_text; /* number of comments read/to write */
   int max_text; /* current size of text array */
   png_textp text; /* array of comments read/to write */
#endif /* PNG_TEXT_SUPPORTED */

#if defined(PNG_tIME_SUPPORTED)
   /* The tIME chunk holds the last time the displayed image data was
    * modified.  See the png_time struct for the contents of this struct.
    */
   png_time mod_time;
#endif

#if defined(PNG_sBIT_SUPPORTED)
   /* The sBIT chunk specifies the number of significant high-order bits
    * in the pixel data.  Values are in the range [1, bit_depth], and are
    * only specified for the channels in the pixel data.  The contents of
    * the low-order bits is not specified.  Data is valid if
    * (valid & PNG_INFO_sBIT) is non-zero.
    */
   png_color_8 sig_bit; /* significant bits in color channels */
#endif

#if defined(PNG_tRNS_SUPPORTED) || defined(PNG_READ_EXPAND_SUPPORTED) || \
defined(PNG_READ_BACKGROUND_SUPPORTED)
   /* The tRNS chunk supplies transparency data for paletted images and
    * other image types that don't need a full alpha channel.  There are
    * "num_trans" transparency values for a paletted image, stored in the
    * same order as the palette colors, starting from index 0.  Values
    * for the data are in the range [0, 255], ranging from fully transparent
    * to fully opaque, respectively.  For non-paletted images, there is a
    * single color specified that should be treated as fully transparent.
    * Data is valid if (valid & PNG_INFO_tRNS) is non-zero.
    */
   png_bytep trans; /* transparent values for paletted image */
   png_color_16 trans_values; /* transparent color for non-palette image */
#endif

#if defined(PNG_bKGD_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
   /* The bKGD chunk gives the suggested image background color if the
    * display program does not have its own background color and the image
    * is needs to composited onto a background before display.  The colors
    * in "background" are normally in the same color space/depth as the
    * pixel data.  Data is valid if (valid & PNG_INFO_bKGD) is non-zero.
    */
   png_color_16 background;
#endif

#if defined(PNG_oFFs_SUPPORTED)
   /* The oFFs chunk gives the offset in "offset_unit_type" units rightwards
    * and downwards from the top-left corner of the display, page, or other
    * application-specific co-ordinate space.  See the PNG_OFFSET_ defines
    * below for the unit types.  Valid if (valid & PNG_INFO_oFFs) non-zero.
    */
   png_int_32 x_offset; /* x offset on page */
   png_int_32 y_offset; /* y offset on page */
   png_byte offset_unit_type; /* offset units type */
#endif

#if defined(PNG_pHYs_SUPPORTED)
   /* The pHYs chunk gives the physical pixel density of the image for
    * display or printing in "phys_unit_type" units (see PNG_RESOLUTION_
    * defines below).  Data is valid if (valid & PNG_INFO_pHYs) is non-zero.
    */
   png_uint_32 x_pixels_per_unit; /* horizontal pixel density */
   png_uint_32 y_pixels_per_unit; /* vertical pixel density */
   png_byte phys_unit_type; /* resolution type (see PNG_RESOLUTION_ below) */
#endif

#if defined(PNG_hIST_SUPPORTED)
   /* The hIST chunk contains the relative frequency or importance of the
    * various palette entries, so that a viewer can intelligently select a
    * reduced-color palette, if required.  Data is an array of "num_palette"
    * values in the range [0,65535]. Data valid if (valid & PNG_INFO_hIST)
    * is non-zero.
    */
   png_uint_16p hist;
#endif

#ifdef PNG_cHRM_SUPPORTED
   /* The cHRM chunk describes the CIE color characteristics of the monitor
    * on which the PNG was created.  This data allows the viewer to do gamut
    * mapping of the input image to ensure that the viewer sees the same
    * colors in the image as the creator.  Values are in the range
    * [0.0, 0.8].  Data valid if (valid & PNG_INFO_cHRM) non-zero.
    */
#ifdef PNG_FLOATING_POINT_SUPPORTED
   float x_white;
   float y_white;
   float x_red;
   float y_red;
   float x_green;
   float y_green;
   float x_blue;
   float y_blue;
#endif
#endif

#if defined(PNG_pCAL_SUPPORTED)
   /* The pCAL chunk describes a transformation between the stored pixel
    * values and original physical data values used to create the image.
    * The integer range [0, 2^bit_depth - 1] maps to the floating-point
    * range given by [pcal_X0, pcal_X1], and are further transformed by a
    * (possibly non-linear) transformation function given by "pcal_type"
    * and "pcal_params" into "pcal_units".  Please see the PNG_EQUATION_
    * defines below, and the PNG-Group's PNG extensions document for a
    * complete description of the transformations and how they should be
    * implemented, and for a description of the ASCII parameter strings.
    * Data values are valid if (valid & PNG_INFO_pCAL) non-zero.
    */
   png_charp pcal_purpose;  /* pCAL chunk description string */
   png_int_32 pcal_X0;      /* minimum value */
   png_int_32 pcal_X1;      /* maximum value */
   png_charp pcal_units;    /* Latin-1 string giving physical units */
   png_charpp pcal_params;  /* ASCII strings containing parameter values */
   png_byte pcal_type;      /* equation type (see PNG_EQUATION_ below) */
   png_byte pcal_nparams;   /* number of parameters given in pcal_params */
#endif

/* New members added in libpng-1.0.6 */
#ifdef PNG_FREE_ME_SUPPORTED
   png_uint_32 free_me;     /* flags items libpng is responsible for freeing */
#endif

#if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED)
   /* storage for unknown chunks that the library doesn't recognize. */
   png_unknown_chunkp unknown_chunks;
   png_size_t unknown_chunks_num;
#endif

#if defined(PNG_iCCP_SUPPORTED)
   /* iCCP chunk data. */
   png_charp iccp_name;     /* profile name */
   png_charp iccp_profile;  /* International Color Consortium profile data */
                            /* Note to maintainer: should be png_bytep */
   png_uint_32 iccp_proflen;  /* ICC profile data length */
   png_byte iccp_compression; /* Always zero */
#endif

#if defined(PNG_sPLT_SUPPORTED)
   /* data on sPLT chunks (there may be more than one). */
   png_sPLT_tp splt_palettes;
   png_uint_32 splt_palettes_num;
#endif

#if defined(PNG_sCAL_SUPPORTED)
   /* The sCAL chunk describes the actual physical dimensions of the
    * subject matter of the graphic.  The chunk contains a unit specification
    * a byte value, and two ASCII strings representing floating-point
    * values.  The values are width and height corresponsing to one pixel
    * in the image.  This external representation is converted to double
    * here.  Data values are valid if (valid & PNG_INFO_sCAL) is non-zero.
    */
   png_byte scal_unit;         /* unit of physical scale */
#ifdef PNG_FLOATING_POINT_SUPPORTED
   double scal_pixel_width;    /* width of one pixel */
   double scal_pixel_height;   /* height of one pixel */
#endif
#ifdef PNG_FIXED_POINT_SUPPORTED
   png_charp scal_s_width;     /* string containing height */
   png_charp scal_s_height;    /* string containing width */
#endif
#endif

#if defined(PNG_INFO_IMAGE_SUPPORTED)
   /* Memory has been allocated if (valid & PNG_ALLOCATED_INFO_ROWS) non-zero */
   /* Data valid if (valid & PNG_INFO_IDAT) non-zero */
   png_bytepp row_pointers;        /* the image bits */
#endif

#if defined(PNG_FIXED_POINT_SUPPORTED) && defined(PNG_gAMA_SUPPORTED)
   png_fixed_point int_gamma; /* gamma of image, if (valid & PNG_INFO_gAMA) */
#endif

#if defined(PNG_cHRM_SUPPORTED) && defined(PNG_FIXED_POINT_SUPPORTED)
   png_fixed_point int_x_white;
   png_fixed_point int_y_white;
   png_fixed_point int_x_red;
   png_fixed_point int_y_red;
   png_fixed_point int_x_green;
   png_fixed_point int_y_green;
   png_fixed_point int_x_blue;
   png_fixed_point int_y_blue;
#endif

} png_info;

typedef png_info FAR * png_infop;
typedef png_info FAR * FAR * png_infopp;

/* Maximum positive integer used in PNG is (2^31)-1 */
#define PNG_UINT_31_MAX ((png_uint_32)0x7fffffffL)
#define PNG_UINT_32_MAX ((png_uint_32)(-1))
#define PNG_SIZE_MAX ((png_size_t)(-1))
/* PNG_MAX_UINT is deprecated; use PNG_UINT_31_MAX instead. */
#define PNG_MAX_UINT PNG_UINT_31_MAX

/* These describe the color_type field in png_info. */
/* color type masks */
#define PNG_COLOR_MASK_PALETTE    1
#define PNG_COLOR_MASK_COLOR      2
#define PNG_COLOR_MASK_ALPHA      4

/* color types.  Note that not all combinations are legal */
#define PNG_COLOR_TYPE_GRAY 0
#define PNG_COLOR_TYPE_PALETTE  (PNG_COLOR_MASK_COLOR | PNG_COLOR_MASK_PALETTE)
#define PNG_COLOR_TYPE_RGB        (PNG_COLOR_MASK_COLOR)
#define PNG_COLOR_TYPE_RGB_ALPHA  (PNG_COLOR_MASK_COLOR | PNG_COLOR_MASK_ALPHA)
#define PNG_COLOR_TYPE_GRAY_ALPHA (PNG_COLOR_MASK_ALPHA)
/* aliases */
#define PNG_COLOR_TYPE_RGBA  PNG_COLOR_TYPE_RGB_ALPHA
#define PNG_COLOR_TYPE_GA  PNG_COLOR_TYPE_GRAY_ALPHA

/* This is for compression type. PNG 1.0-1.2 only define the single type. */
#define PNG_COMPRESSION_TYPE_BASE 0 /* Deflate method 8, 32K window */
#define PNG_COMPRESSION_TYPE_DEFAULT PNG_COMPRESSION_TYPE_BASE

/* This is for filter type. PNG 1.0-1.2 only define the single type. */
#define PNG_FILTER_TYPE_BASE      0 /* Single row per-byte filtering */
#define PNG_INTRAPIXEL_DIFFERENCING 64 /* Used only in MNG datastreams */
#define PNG_FILTER_TYPE_DEFAULT   PNG_FILTER_TYPE_BASE

/* These are for the interlacing type.  These values should NOT be changed. */
#define PNG_INTERLACE_NONE        0 /* Non-interlaced image */
#define PNG_INTERLACE_ADAM7       1 /* Adam7 interlacing */
#define PNG_INTERLACE_LAST        2 /* Not a valid value */

/* These are for the oFFs chunk.  These values should NOT be changed. */
#define PNG_OFFSET_PIXEL          0 /* Offset in pixels */
#define PNG_OFFSET_MICROMETER     1 /* Offset in micrometers (1/10^6 meter) */
#define PNG_OFFSET_LAST           2 /* Not a valid value */

/* These are for the pCAL chunk.  These values should NOT be changed. */
#define PNG_EQUATION_LINEAR       0 /* Linear transformation */
#define PNG_EQUATION_BASE_E       1 /* Exponential base e transform */
#define PNG_EQUATION_ARBITRARY    2 /* Arbitrary base exponential transform */
#define PNG_EQUATION_HYPERBOLIC   3 /* Hyperbolic sine transformation */
#define PNG_EQUATION_LAST         4 /* Not a valid value */

/* These are for the sCAL chunk.  These values should NOT be changed. */
#define PNG_SCALE_UNKNOWN         0 /* unknown unit (image scale) */
#define PNG_SCALE_METER           1 /* meters per pixel */
#define PNG_SCALE_RADIAN          2 /* radians per pixel */
#define PNG_SCALE_LAST            3 /* Not a valid value */

/* These are for the pHYs chunk.  These values should NOT be changed. */
#define PNG_RESOLUTION_UNKNOWN    0 /* pixels/unknown unit (aspect ratio) */
#define PNG_RESOLUTION_METER      1 /* pixels/meter */
#define PNG_RESOLUTION_LAST       2 /* Not a valid value */

/* These are for the sRGB chunk.  These values should NOT be changed. */
#define PNG_sRGB_INTENT_PERCEPTUAL 0
#define PNG_sRGB_INTENT_RELATIVE   1
#define PNG_sRGB_INTENT_SATURATION 2
#define PNG_sRGB_INTENT_ABSOLUTE   3
#define PNG_sRGB_INTENT_LAST       4 /* Not a valid value */

/* This is for text chunks */
#define PNG_KEYWORD_MAX_LENGTH     79

/* Maximum number of entries in PLTE/sPLT/tRNS arrays */
#define PNG_MAX_PALETTE_LENGTH    256

/* These determine if an ancillary chunk's data has been successfully read
 * from the PNG header, or if the application has filled in the corresponding
 * data in the info_struct to be written into the output file.  The values
 * of the PNG_INFO_<chunk> defines should NOT be changed.
 */
#define PNG_INFO_gAMA 0x0001
#define PNG_INFO_sBIT 0x0002
#define PNG_INFO_cHRM 0x0004
#define PNG_INFO_PLTE 0x0008
#define PNG_INFO_tRNS 0x0010
#define PNG_INFO_bKGD 0x0020
#define PNG_INFO_hIST 0x0040
#define PNG_INFO_pHYs 0x0080
#define PNG_INFO_oFFs 0x0100
#define PNG_INFO_tIME 0x0200
#define PNG_INFO_pCAL 0x0400
#define PNG_INFO_sRGB 0x0800   /* GR-P, 0.96a */
#define PNG_INFO_iCCP 0x1000   /* ESR, 1.0.6 */
#define PNG_INFO_sPLT 0x2000   /* ESR, 1.0.6 */
#define PNG_INFO_sCAL 0x4000   /* ESR, 1.0.6 */
#define PNG_INFO_IDAT 0x8000L  /* ESR, 1.0.6 */

/* This is used for the transformation routines, as some of them
 * change these values for the row.  It also should enable using
 * the routines for other purposes.
 */
typedef struct png_row_info_struct
{
   png_uint_32 width; /* width of row */
   png_uint_32 rowbytes; /* number of bytes in row */
   png_byte color_type; /* color type of row */
   png_byte bit_depth; /* bit depth of row */
   png_byte channels; /* number of channels (1, 2, 3, or 4) */
   png_byte pixel_depth; /* bits per pixel (depth * channels) */
} png_row_info;

typedef png_row_info FAR * png_row_infop;
typedef png_row_info FAR * FAR * png_row_infopp;

/* These are the function types for the I/O functions and for the functions
 * that allow the user to override the default I/O functions with his or her
 * own.  The png_error_ptr type should match that of user-supplied warning
 * and error functions, while the png_rw_ptr type should match that of the
 * user read/write data functions.
 */
typedef struct png_struct_def png_struct;
typedef png_struct FAR * png_structp;

typedef void (PNGAPI *png_error_ptr) PNGARG((png_structp, png_const_charp));
typedef void (PNGAPI *png_rw_ptr) PNGARG((png_structp, png_bytep, png_size_t));
typedef void (PNGAPI *png_flush_ptr) PNGARG((png_structp));
typedef void (PNGAPI *png_read_status_ptr) PNGARG((png_structp, png_uint_32,
   int));
typedef void (PNGAPI *png_write_status_ptr) PNGARG((png_structp, png_uint_32,
   int));

#ifdef PNG_PROGRESSIVE_READ_SUPPORTED
typedef void (PNGAPI *png_progressive_info_ptr) PNGARG((png_structp, png_infop));
typedef void (PNGAPI *png_progressive_end_ptr) PNGARG((png_structp, png_infop));
typedef void (PNGAPI *png_progressive_row_ptr) PNGARG((png_structp, png_bytep,
   png_uint_32, int));
#endif

#if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) || \
    defined(PNG_WRITE_USER_TRANSFORM_SUPPORTED) || \
    defined(PNG_LEGACY_SUPPORTED)
typedef void (PNGAPI *png_user_transform_ptr) PNGARG((png_structp,
    png_row_infop, png_bytep));
#endif

#if defined(PNG_USER_CHUNKS_SUPPORTED)
typedef int (PNGAPI *png_user_chunk_ptr) PNGARG((png_structp, png_unknown_chunkp));
#endif
#if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED)
typedef void (PNGAPI *png_unknown_chunk_ptr) PNGARG((png_structp));
#endif

/* Transform masks for the high-level interface */
#define PNG_TRANSFORM_IDENTITY       0x0000    /* read and write */
#define PNG_TRANSFORM_STRIP_16       0x0001    /* read only */
#define PNG_TRANSFORM_STRIP_ALPHA    0x0002    /* read only */
#define PNG_TRANSFORM_PACKING        0x0004    /* read and write */
#define PNG_TRANSFORM_PACKSWAP       0x0008    /* read and write */
#define PNG_TRANSFORM_EXPAND         0x0010    /* read only */
#define PNG_TRANSFORM_INVERT_MONO    0x0020    /* read and write */
#define PNG_TRANSFORM_SHIFT          0x0040    /* read and write */
#define PNG_TRANSFORM_BGR            0x0080    /* read and write */
#define PNG_TRANSFORM_SWAP_ALPHA     0x0100    /* read and write */
#define PNG_TRANSFORM_SWAP_ENDIAN    0x0200    /* read and write */
#define PNG_TRANSFORM_INVERT_ALPHA   0x0400    /* read and write */
#define PNG_TRANSFORM_STRIP_FILLER   0x0800    /* WRITE only */

/* Flags for MNG supported features */
#define PNG_FLAG_MNG_EMPTY_PLTE     0x01
#define PNG_FLAG_MNG_FILTER_64      0x04
#define PNG_ALL_MNG_FEATURES        0x05

typedef png_voidp (*png_malloc_ptr) PNGARG((png_structp, png_size_t));
typedef void (*png_free_ptr) PNGARG((png_structp, png_voidp));

/* The structure that holds the information to read and write PNG files.
 * The only people who need to care about what is inside of this are the
 * people who will be modifying the library for their own special needs.
 * It should NOT be accessed directly by an application, except to store
 * the jmp_buf.
 */

struct png_struct_def
{
#ifdef PNG_SETJMP_SUPPORTED
   jmp_buf jmpbuf;            /* used in png_error */
#endif
   png_error_ptr error_fn;    /* function for printing errors and aborting */
   png_error_ptr warning_fn;  /* function for printing warnings */
   png_voidp error_ptr;       /* user supplied struct for error functions */
   png_rw_ptr write_data_fn;  /* function for writing output data */
   png_rw_ptr read_data_fn;   /* function for reading input data */
   png_voidp io_ptr;          /* ptr to application struct for I/O functions */

#if defined(PNG_READ_USER_TRANSFORM_SUPPORTED)
   png_user_transform_ptr read_user_transform_fn; /* user read transform */
#endif

#if defined(PNG_WRITE_USER_TRANSFORM_SUPPORTED)
   png_user_transform_ptr write_user_transform_fn; /* user write transform */
#endif

/* These were added in libpng-1.0.2 */
#if defined(PNG_USER_TRANSFORM_PTR_SUPPORTED)
#if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) || \
    defined(PNG_WRITE_USER_TRANSFORM_SUPPORTED)
   png_voidp user_transform_ptr; /* user supplied struct for user transform */
   png_byte user_transform_depth;    /* bit depth of user transformed pixels */
   png_byte user_transform_channels; /* channels in user transformed pixels */
#endif
#endif

   png_uint_32 mode;          /* tells us where we are in the PNG file */
   png_uint_32 flags;         /* flags indicating various things to libpng */
   png_uint_32 transformations; /* which transformations to perform */

   z_stream zstream;          /* pointer to decompression structure (below) */
   png_bytep zbuf;            /* buffer for zlib */
   png_size_t zbuf_size;      /* size of zbuf */
   int zlib_level;            /* holds zlib compression level */
   int zlib_method;           /* holds zlib compression method */
   int zlib_window_bits;      /* holds zlib compression window bits */
   int zlib_mem_level;        /* holds zlib compression memory level */
   int zlib_strategy;         /* holds zlib compression strategy */

   png_uint_32 width;         /* width of image in pixels */
   png_uint_32 height;        /* height of image in pixels */
   png_uint_32 num_rows;      /* number of rows in current pass */
   png_uint_32 usr_width;     /* width of row at start of write */
   png_uint_32 rowbytes;      /* size of row in bytes */
   png_uint_32 irowbytes;     /* size of current interlaced row in bytes */
   png_uint_32 iwidth;        /* width of current interlaced row in pixels */
   png_uint_32 row_number;    /* current row in interlace pass */
   png_bytep prev_row;        /* buffer to save previous (unfiltered) row */
   png_bytep row_buf;         /* buffer to save current (unfiltered) row */
   png_bytep sub_row;         /* buffer to save "sub" row when filtering */
   png_bytep up_row;          /* buffer to save "up" row when filtering */
   png_bytep avg_row;         /* buffer to save "avg" row when filtering */
   png_bytep paeth_row;       /* buffer to save "Paeth" row when filtering */
   png_row_info row_info;     /* used for transformation routines */…