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/* png.h - header file for PNG reference library
 * libpng version 1.6.34, September 29, 2017
 * Copyright (c) 1998-2002,2004,2006-2017 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.)
 * This code is released under the libpng license (See LICENSE, below)
 * Authors and maintainers:
 *   libpng versions 0.71, May 1995, through 0.88, January 1996: Guy Schalnat
 *   libpng versions 0.89, June 1996, through 0.96, May 1997: Andreas Dilger
 *   libpng versions 0.97, January 1998, through 1.6.34, September 29, 2017:
 *     Glenn Randers-Pehrson.
 *   See also "Contributing Authors", below.
 * COPYRIGHT NOTICE, DISCLAIMER, and LICENSE:
 * If you modify libpng you may insert additional notices immediately following
 * this sentence.
 * This code is released under the libpng license.
 * libpng versions 1.0.7, July 1, 2000 through 1.6.34, September 29, 2017 are
 * Copyright (c) 2000-2002, 2004, 2006-2017 Glenn Randers-Pehrson, are
 * derived from libpng-1.0.6, 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
 *    Mans Rullgard
 *    Cosmin Truta
 *    Gilles Vollant
 *    James Yu
 *    Mandar Sahastrabuddhe
 *    Google Inc.
 *    Vadim Barkov
 * 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.
 * Some files in the "contrib" directory and some configure-generated
 * files that are distributed with libpng have other copyright owners and
 * are released under other open source licenses.
 * libpng versions 0.97, January 1998, through 1.0.6, March 20, 2000, are
 * Copyright (c) 1998-2000 Glenn Randers-Pehrson, are derived from
 * libpng-0.96, 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, are derived from libpng-0.88,
 * and are 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
 * Some files in the "scripts" directory have other copyright owners
 * but are released under this license.
 * 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.
 * END OF COPYRIGHT NOTICE, DISCLAIMER, and LICENSE.
 * TRADEMARK:
 * The name "libpng" has not been registered by the Copyright owner
 * as a trademark in any jurisdiction.  However, because libpng has
 * been distributed and maintained world-wide, continually since 1995,
 * the Copyright owner claims "common-law trademark protection" in any
 * jurisdiction where common-law trademark is recognized.
 * OSI CERTIFICATION:
 * Libpng is OSI Certified Open Source Software.  OSI Certified Open Source is
 * a certification mark of the Open Source Initiative. OSI has not addressed
 * the additional disclaimers inserted at version 1.0.7.
 * EXPORT CONTROL:
 * The Copyright owner believes that the Export Control Classification
 * Number (ECCN) for libpng is EAR99, which means not subject to export
 * controls or International Traffic in Arms Regulations (ITAR) because
 * it is open source, publicly available software, that does not contain
 * any encryption software.  See the EAR, paragraphs 734.3(b)(3) and
 * 734.7(b).
 * 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).
 * 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.
/* 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]
 *    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.
 *    1.0.5 (+ 2 patches)           10005
 *    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)
 *    1.0.6h                        10007  10.6h (testing xy.z so-numbering)
 *    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)
 *    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 "rcNN".
 *    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,
 * <https://www.w3.org/TR/2003/REC-PNG-20031110/
 * Y2K compliance in libpng:
 * =========================
 *    September 29, 2017
 *    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 1.6.34 are Y2K compliant.  It is my belief that
 *    earlier versions were also Y2K compliant.
 *    Libpng only has two year fields.  One is a 2-byte unsigned integer
 *    that will hold years up to 65535.  The other, which is deprecated,
 *    holds the date in text format, and will hold years up to 9999.
 *    The integer is
 *        "png_uint_16 year" in png_time_struct.
 *    The string is
 *        "char time_buffer[29]" in png_struct.  This is no longer used
 *    in libpng-1.6.x and will be removed from libpng-1.7.0.
 *    There are seven time-related functions:
 *        png.c: png_convert_to_rfc_1123_buffer() in png.c
 *          (formerly png_convert_to_rfc_1123() prior to libpng-1.5.x and
 *          png_convert_to_rfc_1152() in error prior to libpng-0.98)
 *        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 libpng applications
 *    are not passing 4-digit years into the png_convert_to_rfc_1123_buffer()
 *    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-manual.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.  If that
 * file has been stripped from your copy of libpng, you can find it at
 * <http://www.libpng.org/pub/png/libpng-manual.txt>
 * If you just need to read a PNG file and don't want to read the documentation
 * skip to the end of this file and read the section entitled 'simplified API'.
/* Version information for png.h - this should match the version in png.c */
#define PNG_LIBPNG_VER_STRING "1.6.34"
#define PNG_HEADER_VERSION_STRING " libpng version 1.6.34 - September 29, 2017\n"
#define PNG_LIBPNG_VER_SONUM   16
#define PNG_LIBPNG_VER_DLLNUM  16
/* These should match the first 3 components of PNG_LIBPNG_VER_STRING: */
#define PNG_LIBPNG_VER_MAJOR   1
#define PNG_LIBPNG_VER_MINOR   6
#define PNG_LIBPNG_VER_RELEASE 34
/* 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 10634 /* 1.6.34 */
/* Library configuration: these options cannot be changed after
 * the library has been built.
#ifndef PNGLCONF_H
/* If pnglibconf.h is missing, you can
 * copy scripts/pnglibconf.h.prebuilt to pnglibconf.h
#   include "pnglibconf.h"
#ifndef PNG_VERSION_INFO_ONLY
/* Machine specific configuration. */
#  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.
#ifdef PNG_USER_PRIVATEBUILD /* From pnglibconf.h */
#  define PNG_LIBPNG_BUILD_TYPE \
       (PNG_LIBPNG_BUILD_BASE_TYPE | PNG_LIBPNG_BUILD_PRIVATE)
#  ifdef PNG_LIBPNG_SPECIALBUILD
#    define PNG_LIBPNG_BUILD_TYPE \
         (PNG_LIBPNG_BUILD_BASE_TYPE | PNG_LIBPNG_BUILD_SPECIAL)
#    define PNG_LIBPNG_BUILD_TYPE (PNG_LIBPNG_BUILD_BASE_TYPE)
#ifndef PNG_VERSION_INFO_ONLY
/* Inhibit C++ name-mangling for libpng functions but not for system calls. */
#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */
/* Version information for C files, stored in png.c.  This had better match
 * the version above.
#define png_libpng_ver png_get_header_ver(NULL)
/* This file is arranged in several sections:
 * 1. [omitted]
 * 2. Any configuration options that can be specified by for the application
 *    code when it is built.  (Build time configuration is in pnglibconf.h)
 * 3. Type definitions (base types are defined in pngconf.h), structure
 *    definitions.
 * 4. Exported library functions.
 * 5. Simplified API.
 * 6. Implementation options.
 * The library source code has additional files (principally pngpriv.h) that
 * allow configuration of the library.
/* Section 1: [omitted] */
/* Section 2: run time configuration
 * See pnglibconf.h for build time configuration
 * Run time configuration allows the application to choose between
 * implementations of certain arithmetic APIs.  The default is set
 * at build time and recorded in pnglibconf.h, but it is safe to
 * override these (and only these) settings.  Note that this won't
 * change what the library does, only application code, and the
 * settings can (and probably should) be made on a per-file basis
 * by setting the #defines before including png.h
 * Use macros to read integers from PNG data or use the exported
 * functions?
 *   PNG_USE_READ_MACROS: use the macros (see below)  Note that
 *     the macros evaluate their argument multiple times.
 *   PNG_NO_USE_READ_MACROS: call the relevant library function.
 * Use the alternative algorithm for compositing alpha samples that
 * does not use division?
 *   PNG_READ_COMPOSITE_NODIV_SUPPORTED: use the 'no division'
 *      algorithm.
 *   PNG_NO_READ_COMPOSITE_NODIV: use the 'division' algorithm.
 * How to handle benign errors if PNG_ALLOW_BENIGN_ERRORS is
 *   PNG_ALLOW_BENIGN_ERRORS: map calls to the benign error
 *      APIs to png_warning.
 * Otherwise the calls are mapped to png_error.
/* Section 3: type definitions, including structures and compile time
 * constants.
 * See pngconf.h for base types that vary by machine/system
/* This triggers a compiler error in png.c, if png.c and png.h
 * do not agree upon the version number.
typedef char* png_libpng_version_1_6_34;
/* Basic control structions.  Read libpng-manual.txt or libpng.3 for more info.
 * png_struct is the cache of information used while reading or writing a single
 * PNG file.  One of these is always required, although the simplified API
 * (below) hides the creation and destruction of it.
typedef struct png_struct_def png_struct;
typedef const png_struct * png_const_structp;
typedef png_struct * png_structp;
typedef png_struct * * png_structpp;
/* png_info contains information read from or to be written to a PNG file.  One
 * or more of these must exist while reading or creating a PNG file.  The
 * information is not used by libpng during read but is used to control what
 * gets written when a PNG file is created.  "png_get_" function calls read
 * information during read and "png_set_" functions calls write information
 * when creating a PNG.
 * been moved into a separate header file that is not accessible to
 * applications.  Read libpng-manual.txt or libpng.3 for more info.
typedef struct png_info_def png_info;
typedef png_info * png_infop;
typedef const png_info * png_const_infop;
typedef png_info * * png_infopp;
/* Types with names ending 'p' are pointer types.  The corresponding types with
 * names ending 'rp' are identical pointer types except that the pointer is
 * marked 'restrict', which means that it is the only pointer to the object
 * passed to the function.  Applications should not use the 'restrict' types;
 * it is always valid to pass 'p' to a pointer with a function argument of the
 * corresponding 'rp' type.  Different compilers have different rules with
 * regard to type matching in the presence of 'restrict'.  For backward
 * compatibility libpng callbacks never have 'restrict' in their parameters and,
 * consequentially, writing portable application code is extremely difficult if
 * an attempt is made to use 'restrict'.
typedef png_struct * PNG_RESTRICT png_structrp;
typedef const png_struct * PNG_RESTRICT png_const_structrp;
typedef png_info * PNG_RESTRICT png_inforp;
typedef const png_info * PNG_RESTRICT png_const_inforp;
/* 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 * png_colorp;
typedef const png_color * png_const_colorp;
typedef png_color * * 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 * png_color_16p;
typedef const png_color_16 * png_const_color_16p;
typedef png_color_16 * * 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 * png_color_8p;
typedef const png_color_8 * png_const_color_8p;
typedef png_color_8 * * 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 * png_sPLT_entryp;
typedef const png_sPLT_entry * png_const_sPLT_entryp;
typedef png_sPLT_entry * * 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 * png_sPLT_tp;
typedef const png_sPLT_t * png_const_sPLT_tp;
typedef png_sPLT_t * * 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" fields can be a
 * regular C string, an empty string, or a NULL pointer.
 * However, the structure returned by png_get_text() will always contain
 * the "text" field as a regular zero-terminated C string (possibly
 * empty), never a NULL pointer, so it can be safely used in printf() and
 * other string-handling functions.  Note that the "itxt_length", "lang", and
 * "lang_key" members of the structure only exist when the library is built
 * with iTXt chunk support.  Prior to libpng-1.4.0 the library was built by
 * default without iTXt support. Also note that when iTXt *is* supported,
 * the "lang" and "lang_key" fields contain NULL pointers when the
 * "compression" field contains * PNG_TEXT_COMPRESSION_NONE or
 * PNG_TEXT_COMPRESSION_zTXt. Note that the "compression value" is not the
 * same as what appears in the PNG tEXt/zTXt/iTXt chunk's "compression flag"
 * which is always 0 or 1, or its "compression method" which is always 0.
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 */
   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 */
} png_text;
typedef png_text * png_textp;
typedef const png_text * png_const_textp;
typedef png_text * * png_textpp;
/* 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 * png_timep;
typedef const png_time * png_const_timep;
typedef png_time * * png_timepp;
#if defined(PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED) ||\
   defined(PNG_USER_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.
 * The data in the structure is set by libpng on read and used on write.
typedef struct png_unknown_chunk_t
   png_byte name[5]; /* Textual chunk name with '\0' terminator */
   png_byte *data;   /* Data, should not be modified on read! */
   png_size_t size;
   /* On write 'location' must be set using the flag values listed below.
    * Notice that on read it is set by libpng however the values stored have
    * more bits set than are listed below.  Always treat the value as a
    * bitmask.  On write set only one bit - setting multiple bits may cause the
    * chunk to be written in multiple places.
   png_byte location; /* mode of operation at read time */
png_unknown_chunk;
typedef png_unknown_chunk * png_unknown_chunkp;
typedef const png_unknown_chunk * png_const_unknown_chunkp;
typedef png_unknown_chunk * * png_unknown_chunkpp;
/* Flag values for the unknown chunk location byte. */
#define PNG_HAVE_IHDR  0x01
#define PNG_HAVE_PLTE  0x02
#define PNG_AFTER_IDAT 0x08
/* 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))
/* These are constants for fixed point values encoded in the
 * PNG specification manner (x100000)
#define PNG_FP_1    100000
#define PNG_FP_HALF  50000
#define PNG_FP_MAX  ((png_fixed_point)0x7fffffffL)
#define PNG_FP_MIN  (-PNG_FP_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 0x0001U
#define PNG_INFO_sBIT 0x0002U
#define PNG_INFO_cHRM 0x0004U
#define PNG_INFO_PLTE 0x0008U
#define PNG_INFO_tRNS 0x0010U
#define PNG_INFO_bKGD 0x0020U
#define PNG_INFO_hIST 0x0040U
#define PNG_INFO_pHYs 0x0080U
#define PNG_INFO_oFFs 0x0100U
#define PNG_INFO_tIME 0x0200U
#define PNG_INFO_pCAL 0x0400U
#define PNG_INFO_sRGB 0x0800U  /* GR-P, 0.96a */
#define PNG_INFO_iCCP 0x1000U  /* ESR, 1.0.6 */
#define PNG_INFO_sPLT 0x2000U  /* ESR, 1.0.6 */
#define PNG_INFO_sCAL 0x4000U  /* ESR, 1.0.6 */
#define PNG_INFO_IDAT 0x8000U  /* ESR, 1.0.6 */
#define PNG_INFO_eXIf 0x10000U /* GR-P, 1.6.31 */
/* 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_size_t 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 * png_row_infop;
typedef png_row_info * * 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.  Note that the 'write' function must not
 * modify the buffer it is passed. The 'read' function, on the other hand, is
 * expected to return the read data in the buffer.
typedef PNG_CALLBACK(void, *png_error_ptr, (png_structp, png_const_charp));
typedef PNG_CALLBACK(void, *png_rw_ptr, (png_structp, png_bytep, png_size_t));
typedef PNG_CALLBACK(void, *png_flush_ptr, (png_structp));
typedef PNG_CALLBACK(void, *png_read_status_ptr, (png_structp, png_uint_32,
typedef PNG_CALLBACK(void, *png_write_status_ptr, (png_structp, png_uint_32,
#ifdef PNG_PROGRESSIVE_READ_SUPPORTED
typedef PNG_CALLBACK(void, *png_progressive_info_ptr, (png_structp, png_infop));
typedef PNG_CALLBACK(void, *png_progressive_end_ptr, (png_structp, png_infop));
/* The following callback receives png_uint_32 row_number, int pass for the
 * png_bytep data of the row.  When transforming an interlaced image the
 * row number is the row number within the sub-image of the interlace pass, so
 * the value will increase to the height of the sub-image (not the full image)
 * then reset to 0 for the next pass.
 * Use PNG_ROW_FROM_PASS_ROW(row, pass) and PNG_COL_FROM_PASS_COL(col, pass) to
 * find the output pixel (x,y) given an interlaced sub-image pixel
 * (row,col,pass).  (See below for these macros.)
typedef PNG_CALLBACK(void, *png_progressive_row_ptr, (png_structp, png_bytep,
    png_uint_32, int));
#if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) || \
    defined(PNG_WRITE_USER_TRANSFORM_SUPPORTED)
typedef PNG_CALLBACK(void, *png_user_transform_ptr, (png_structp, png_row_infop,
    png_bytep));
#ifdef PNG_USER_CHUNKS_SUPPORTED
typedef PNG_CALLBACK(int, *png_user_chunk_ptr, (png_structp,
    png_unknown_chunkp));
#ifdef PNG_UNKNOWN_CHUNKS_SUPPORTED
/* not used anywhere */
/* typedef PNG_CALLBACK(void, *png_unknown_chunk_ptr, (png_structp)); */
#ifdef PNG_SETJMP_SUPPORTED
/* This must match the function definition in <setjmp.h>, and the application
 * must include this before png.h to obtain the definition of jmp_buf.  The
 * function is required to be PNG_NORETURN, but this is not checked.  If the
 * function does return the application will crash via an abort() or similar
 * system level call.
 * If you get a warning here while building the library you may need to make
 * changes to ensure that pnglibconf.h records the calling convention used by
 * your compiler.  This may be very difficult - try using a different compiler
 * to build the library!
PNG_FUNCTION(void, (PNGCAPI *png_longjmp_ptr), PNGARG((jmp_buf, int)), typedef);
/* 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 */
/* Added to libpng-1.2.34 */
#define PNG_TRANSFORM_STRIP_FILLER_BEFORE PNG_TRANSFORM_STRIP_FILLER
#define PNG_TRANSFORM_STRIP_FILLER_AFTER 0x1000 /* write only */
/* Added to libpng-1.4.0 */
#define PNG_TRANSFORM_GRAY_TO_RGB   0x2000      /* read only */
/* Added to libpng-1.5.4 */
#define PNG_TRANSFORM_EXPAND_16     0x4000      /* read only */
#if INT_MAX >= 0x8000 /* else this might break */
#define PNG_TRANSFORM_SCALE_16      0x8000      /* read 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
/* NOTE: prior to 1.5 these functions had no 'API' style declaration,
 * this allowed the zlib default functions to be used on Windows
 * platforms.  In 1.5 the zlib default malloc (which just calls malloc and
 * ignores the first argument) should be completely compatible with the
 * following.
typedef PNG_CALLBACK(png_voidp, *png_malloc_ptr, (png_structp,
    png_alloc_size_t));
typedef PNG_CALLBACK(void, *png_free_ptr, (png_structp, png_voidp));
/* Section 4: exported functions
 * Here are the function definitions most commonly used.  This is not
 * the place to find out how to use libpng.  See libpng-manual.txt for the
 * full explanation, see example.c for the summary.  This just provides
 * a simple one line description of the use of each function.
 * The PNG_EXPORT() and PNG_EXPORTA() macros used below are defined in
 * pngconf.h and in the *.dfn files in the scripts directory.
 *   PNG_EXPORT(ordinal, type, name, (args));
 *       ordinal:    ordinal that is used while building
 *                   *.def files. The ordinal value is only
 *                   relevant when preprocessing png.h with
 *                   the *.dfn files for building symbol table
 *                   entries, and are removed by pngconf.h.
 *       type:       return type of the function
 *       name:       function name
 *       args:       function arguments, with types
 * When we wish to append attributes to a function prototype we use
 * the PNG_EXPORTA() macro instead.
 *   PNG_EXPORTA(ordinal, type, name, (args), attributes);
 *       ordinal, type, name, and args: same as in PNG_EXPORT().
 *       attributes: function attributes
/* Returns the version number of the library */
PNG_EXPORT(1, png_uint_32, png_access_version_number, (void));
/* Tell lib we have already handled the first <num_bytes> magic bytes.
 * Handling more than 8 bytes from the beginning of the file is an error.
PNG_EXPORT(2, void, png_set_sig_bytes, (png_structrp png_ptr, int num_bytes));
/* Check sig[start] through sig[start + num_to_check - 1] to see if it's a
 * PNG file.  Returns zero if the supplied bytes match the 8-byte PNG
 * signature, and non-zero otherwise.  Having num_to_check == 0 or
 * start > 7 will always fail (ie return non-zero).
PNG_EXPORT(3, int, png_sig_cmp, (png_const_bytep sig, png_size_t start,
    png_size_t num_to_check));
/* Simple signature checking function.  This is the same as calling
 * png_check_sig(sig, n) := !png_sig_cmp(sig, 0, n).
#define png_check_sig(sig, n) !png_sig_cmp((sig), 0, (n))
/* Allocate and initialize png_ptr struct for reading, and any other memory. */
PNG_EXPORTA(4, png_structp, png_create_read_struct,
    (png_const_charp user_png_ver, png_voidp error_ptr,
    png_error_ptr error_fn, png_error_ptr warn_fn),
    PNG_ALLOCATED);
/* Allocate and initialize png_ptr struct for writing, and any other memory */
PNG_EXPORTA(5, png_structp, png_create_write_struct,
    (png_const_charp user_png_ver, png_voidp error_ptr, png_error_ptr error_fn,
    png_error_ptr warn_fn),
    PNG_ALLOCATED);
PNG_EXPORT(6, png_size_t, png_get_compression_buffer_size,
    (png_const_structrp png_ptr));
PNG_EXPORT(7, void, png_set_compression_buffer_size, (png_structrp png_ptr,
    png_size_t size));
/* Moved from pngconf.h in 1.4.0 and modified to ensure setjmp/longjmp
 * match up.
#ifdef PNG_SETJMP_SUPPORTED
/* This function returns the jmp_buf built in to *png_ptr.  It must be
 * supplied with an appropriate 'longjmp' function to use on that jmp_buf
 * unless the default error function is overridden in which case NULL is
 * acceptable.  The size of the jmp_buf is checked against the actual size
 * allocated by the library - the call will return NULL on a mismatch
 * indicating an ABI mismatch.
PNG_EXPORT(8, jmp_buf*, png_set_longjmp_fn, (png_structrp png_ptr,
    png_longjmp_ptr longjmp_fn, size_t jmp_buf_size));
#  define png_jmpbuf(png_ptr) \
      (*png_set_longjmp_fn((png_ptr), longjmp, (sizeof (jmp_buf))))
#  define png_jmpbuf(png_ptr) \
      (LIBPNG_WAS_COMPILED_WITH__PNG_NO_SETJMP)
/* This function should be used by libpng applications in place of
 * longjmp(png_ptr->jmpbuf, val).  If longjmp_fn() has been set, it
 * will use it; otherwise it will call PNG_ABORT().  This function was
 * added in libpng-1.5.0.
PNG_EXPORTA(9, void, png_longjmp, (png_const_structrp png_ptr, int val),
    PNG_NORETURN);
#ifdef PNG_READ_SUPPORTED
/* Reset the compression stream */
PNG_EXPORTA(10, int, png_reset_zstream, (png_structrp png_ptr), PNG_DEPRECATED);
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