module libpng.png;
/* png.h - header file for PNG reference library
 *
 * libpng version 1.6.37 - April 14, 2019
 *
 * Copyright (c) 2018-2019 Cosmin Truta
 * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
 * Copyright (c) 1996-1997 Andreas Dilger
 * 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 1.6.35, July 2018:
 *     Glenn Randers-Pehrson
 *   libpng versions 1.6.36, December 2018, through 1.6.37, April 2019:
 *     Cosmin Truta
 *   See also "Contributing Authors", below.
 */

/*
 * COPYRIGHT NOTICE, DISCLAIMER, and LICENSE
 * =========================================
 *
 * This modified version of libpng code adds animated PNG support and is
 * released under the libpng license described below. The modifications are
 * Copyright (c) 2006-2007 Andrew Smith, Copyright (c) 2008-2019 Max Stepin,
 * and are delimited by "#ifdef PNG_APNG_SUPPORTED / #endif" directives
 * surrounding them in the modified libpng source files.
 *
 * PNG Reference Library License version 2
 * ---------------------------------------
 *
 *  * Copyright (c) 1995-2019 The PNG Reference Library Authors.
 *  * Copyright (c) 2018-2019 Cosmin Truta.
 *  * Copyright (c) 2000-2002, 2004, 2006-2018 Glenn Randers-Pehrson.
 *  * Copyright (c) 1996-1997 Andreas Dilger.
 *  * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
 *
 * The software is supplied "as is", without warranty of any kind,
 * express or implied, including, without limitation, the warranties
 * of merchantability, fitness for a particular purpose, title, and
 * non-infringement.  In no event shall the Copyright owners, or
 * anyone distributing the software, be liable for any damages or
 * other liability, whether in contract, tort or otherwise, arising
 * from, out of, or in connection with the software, or the use or
 * other dealings in the software, even if advised of the possibility
 * of such damage.
 *
 * Permission is hereby granted to use, copy, modify, and distribute
 * this software, or portions hereof, for any purpose, without fee,
 * subject to the following restrictions:
 *
 *  1. The origin of this software must not be misrepresented; you
 *     must not claim that you wrote the original software.  If you
 *     use this software in a product, an acknowledgment in the product
 *     documentation would be appreciated, but is not required.
 *
 *  2. Altered source versions must be plainly marked as such, and must
 *     not be misrepresented as being the original software.
 *
 *  3. This Copyright notice may not be removed or altered from any
 *     source or altered source distribution.
 *
 *
 * PNG Reference Library License version 1 (for libpng 0.5 through 1.6.35)
 * -----------------------------------------------------------------------
 *
 * libpng versions 1.0.7, July 1, 2000, through 1.6.35, July 15, 2018 are
 * Copyright (c) 2000-2002, 2004, 2006-2018 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 owners
 * as a trademark in any jurisdiction.  However, because libpng has
 * been distributed and maintained world-wide, continually since 1995,
 * the Copyright owners claim "common-law trademark protection" in any
 * jurisdiction where common-law trademark is recognized.
 */

/*
 * 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.
 */

/* 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)
 *    ...
 *    1.0.69                  10    10069  10.so.0.69[.0]
 *    ...
 *    1.2.59                  13    10259  12.so.0.59[.0]
 *    ...
 *    1.4.20                  14    10420  14.so.0.20[.0]
 *    ...
 *    1.5.30                  15    10530  15.so.15.30[.0]
 *    ...
 *    1.6.37                  16    10637  16.so.16.37[.0]
 *
 *    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/IEC Standard; see
 * <https://www.w3.org/TR/2003/REC-PNG-20031110/>
 */

/* 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 */
enum PNG_LIBPNG_VER_STRING = "1.6.37+apng";
enum PNG_HEADER_VERSION_STRING =
     " libpng version 1.6.37+apng - April 14, 2019\n";

enum PNG_LIBPNG_VER_SONUM  = 16;
enum PNG_LIBPNG_VER_DLLNUM = 16;

/* These should match the first 3 components of PNG_LIBPNG_VER_STRING: */
enum PNG_LIBPNG_VER_MAJOR   = 1;
enum PNG_LIBPNG_VER_MINOR   = 6;
enum PNG_LIBPNG_VER_RELEASE = 17;

/* This should be zero for a public release, or non-zero for a
 * development version.  [Deprecated]
 */
enum PNG_LIBPNG_VER_BUILD = 0;

/* Release Status */
enum PNG_LIBPNG_BUILD_ALPHA = 1;
enum PNG_LIBPNG_BUILD_BETA = 2;
enum PNG_LIBPNG_BUILD_RC = 3;
enum PNG_LIBPNG_BUILD_STABLE = 4;
enum PNG_LIBPNG_BUILD_RELEASE_STATUS_MASK = 7;

/* Release-Specific Flags */
enum PNG_LIBPNG_BUILD_PATCH = 8; /* Can be OR'ed with
                                       PNG_LIBPNG_BUILD_STABLE only */
enum PNG_LIBPNG_BUILD_PRIVATE = 16; /* Cannot be OR'ed with
                                       PNG_LIBPNG_BUILD_SPECIAL */
enum PNG_LIBPNG_BUILD_SPECIAL = 32; /* Cannot be OR'ed with
                                       PNG_LIBPNG_BUILD_PRIVATE */

alias 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 is:
 * XXYYZZ, where XX=major, YY=minor, ZZ=release
 */
enum PNG_LIBPNG_VER = 10637; /* 1.6.37 */

/* Library configuration: these options cannot be changed after
 * the library has been built.
 */
/* If pnglibconf.h is missing, you can
 * copy scripts/pnglibconf.h.prebuilt to pnglibconf.h
 */
import libpng.pnglibconf;

enum PNG_APNG_SUPPORTED         = 1;
enum PNG_READ_APNG_SUPPORTED    = 1;
enum PNG_WRITE_APNG_SUPPORTED   = 1;

static if (PNG_CONVERT_tIME_SUPPORTED){
import core.stdc.time;
}

version(PNG_VERSION_INFO_ONLY) {}
else{
/* Machine specific configuration. */
public import libpng.pngconf;
}

/*
 * 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.
 */

version(PNG_USER_PRIVATEBUILD) {/* From pnglibconf.h */
	enum PNG_LIBPNG_BUILD_TYPE =
       (PNG_LIBPNG_BUILD_BASE_TYPE | PNG_LIBPNG_BUILD_PRIVATE);
}
else {
	version(PNG_LIBPNG_SPECIALBUILD) {
		enum PNG_LIBPNG_BUILD_TYPE =
         (PNG_LIBPNG_BUILD_BASE_TYPE | PNG_LIBPNG_BUILD_SPECIAL);
	}
	else {
		enum PNG_LIBPNG_BUILD_TYPE = (PNG_LIBPNG_BUILD_BASE_TYPE);
	}
}

version(PNG_VERSION_INFO_ONLY) {}
else {

/* Inhibit C++ name-mangling for libpng functions but not for system calls. */
extern (C) {

/* Version information for C files, stored in png.c.  This had better match
 * the version above.
 */
@property auto png_libpng_ver() { return 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
 * false?
 *   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
 */

static if(PNG_APNG_SUPPORTED)
{
    /* dispose_op flags from inside fcTL */
    enum PNG_DISPOSE_OP_NONE        = 0x00;
    enum PNG_DISPOSE_OP_BACKGROUND  = 0x01;
    enum PNG_DISPOSE_OP_PREVIOUS    = 0x02;

    /* blend_op flags from inside fcTL */
    enum PNG_BLEND_OP_SOURCE        = 0x00;
    enum PNG_BLEND_OP_OVER          = 0x01;
}

/* This triggers a compiler error in png.c, if png.c and png.h
 * do not agree upon the version number.
 */
alias png_libpng_version_1_6_37 = char*;

/* 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.
 */
struct png_struct;
alias png_const_structp = const(png_struct)*;
alias png_structp = png_struct *;
alias png_structpp = png_struct * *;

/* 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.
 */
struct png_info;
alias png_infop = png_info*;
alias png_const_infop = const(png_info)*;
alias png_infopp = png_info**;

/* 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;

// D-bindings comment:  restrict keyword do not exist in D.
//    Just ignoring it works as it is only a hint to the C compiler
//    and has no relation with ABI
alias png_structrp = png_struct*;
alias png_const_structrp = const(png_struct)*;
alias png_inforp = png_info*;
alias png_const_inforp = const(png_info)*;

/* 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).
 */
struct png_color
{
   png_byte red;
   png_byte green;
   png_byte blue;
}
alias png_colorp = png_color *;
alias png_const_colorp = const(png_color) *;
alias png_colorpp = png_color * *;

struct png_color_16
{
   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 */
}
alias png_color_16p = png_color_16 *;
alias png_const_color_16p = const(png_color_16) *;
alias png_color_16pp = png_color_16 * *;

struct png_color_8
{
   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 */
}
alias png_color_8p = png_color_8 *;
alias png_const_color_8p = const(png_color_8) *;
alias png_color_8pp = png_color_8 * *;

/*
 * The following two structures are used for the in-core representation
 * of sPLT chunks.
 */
struct png_sPLT_entry
{
   png_uint_16 red;
   png_uint_16 green;
   png_uint_16 blue;
   png_uint_16 alpha;
   png_uint_16 frequency;
}
alias png_sPLT_entryp = png_sPLT_entry *;
alias png_const_sPLT_entryp = const(png_sPLT_entry) *;
alias png_sPLT_entrypp = png_sPLT_entry * *;

/*  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.
 */

struct png_sPLT_t
{
   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 */
}
alias png_sPLT_tp = png_sPLT_t *;
alias png_const_sPLT_tp = const(png_sPLT_t) *;
alias png_sPLT_tpp = png_sPLT_t * *;

static if(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.
 */
struct png_text
{
   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 */
   size_t text_length;     /* length of the text string */
   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 */
}
alias png_textp = png_text *;
alias png_const_textp = const(png_text) *;
alias png_textpp = png_text * *;
}

/* Supported compression types for text in PNG files (tEXt, and zTXt).
 * The values of the PNG_TEXT_COMPRESSION_ defines should NOT be changed. */
enum PNG_TEXT_COMPRESSION_NONE_WR = -3;
enum PNG_TEXT_COMPRESSION_zTXt_WR = -2;
enum PNG_TEXT_COMPRESSION_NONE = -1;
enum PNG_TEXT_COMPRESSION_zTXt = 0;
enum PNG_ITXT_COMPRESSION_NONE = 1;
enum PNG_ITXT_COMPRESSION_zTXt = 2;
enum 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!
 */
struct png_time
{
   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) */
}
alias png_timep = png_time *;
alias png_const_timep = const(png_time) *;
alias png_timepp = png_time * *;

static if(PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED || 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.
 */
struct png_unknown_chunk
{
    png_byte[5] name; /* 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 */
}
alias png_unknown_chunkp = png_unknown_chunk *;
alias png_const_unknown_chunkp = const(png_unknown_chunk) *;
alias png_unknown_chunkpp = png_unknown_chunk * *;
}

/* Flag values for the unknown chunk location byte. */
enum PNG_HAVE_IHDR = 0x01;
enum PNG_HAVE_PLTE = 0x02;
enum PNG_AFTER_IDAT = 0x08;


/* Maximum positive integer used in PNG is (2^31)-1 */
enum PNG_UINT_31_MAX = cast(uint)0x7fffffffL;
enum PNG_UINT_32_MAX = cast(uint)(-1);
enum PNG_SIZE_MAX = cast(size_t)(-1);

/* These are constants for fixed point values encoded in the
 * PNG specification manner (x100000)
 */
enum PNG_FP_1 = 100000;
enum PNG_FP_HALF = 50000;
enum PNG_FP_MAX = (cast(png_fixed_point)0x7fffffffL);
enum PNG_FP_MIN = (-PNG_FP_MAX);

/* These describe the color_type field in png_info. */
/* color type masks */
enum PNG_COLOR_MASK_PALETTE = 1;
enum PNG_COLOR_MASK_COLOR = 2;
enum PNG_COLOR_MASK_ALPHA = 4;

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

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

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

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

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

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

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

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

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

/* This is for text chunks */
enum PNG_KEYWORD_MAX_LENGTH = 79;

/* Maximum number of entries in PLTE/sPLT/tRNS arrays */
enum 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.
 */
enum PNG_INFO_gAMA = 0x0001U;
enum PNG_INFO_sBIT = 0x0002U;
enum PNG_INFO_cHRM = 0x0004U;
enum PNG_INFO_PLTE = 0x0008U;
enum PNG_INFO_tRNS = 0x0010U;
enum PNG_INFO_bKGD = 0x0020U;
enum PNG_INFO_hIST = 0x0040U;
enum PNG_INFO_pHYs = 0x0080U;
enum PNG_INFO_oFFs = 0x0100U;
enum PNG_INFO_tIME = 0x0200U;
enum PNG_INFO_pCAL = 0x0400U;
enum PNG_INFO_sRGB = 0x0800U;   /* GR-P, 0.96a */
enum PNG_INFO_iCCP = 0x1000U;   /* ESR, 1.0.6 */
enum PNG_INFO_sPLT = 0x2000U;   /* ESR, 1.0.6 */
enum PNG_INFO_sCAL = 0x4000U;   /* ESR, 1.0.6 */
enum PNG_INFO_IDAT = 0x8000U;   /* ESR, 1.0.6 */
enum PNG_INFO_eXIf = 0x10000U;  /* GR-P, 1.6.31 */
static if(PNG_APNG_SUPPORTED)
{
    enum PNG_INFO_acTL = 0x20000U;
    enum PNG_INFO_fcTL = 0x40000U;
}

/* 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.
 */
struct png_row_info
{
   uint width;    /* width of row */
   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) */
}

alias png_row_infop = png_row_info *;
alias png_row_infopp = png_row_info * *;


/* 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.
 */
alias png_error_ptr = void function(png_structp, png_const_charp);
alias png_rw_ptr = void function(png_structp, png_bytep, size_t);
alias png_flush_ptr = void function(png_structp);
alias png_read_status_ptr = void function(png_structp, uint, int);
alias png_write_status_ptr = void function(png_structp, uint, int);

static if(PNG_PROGRESSIVE_READ_SUPPORTED) {
alias png_progressive_info_ptr = void function(png_structp, png_infop);
alias png_progressive_end_ptr = void function(png_structp, png_infop);
static if(PNG_APNG_SUPPORTED) {
alias png_progressive_frame_ptr = void function(png_structp, png_uint_32);
}

/* The following callback receives uint 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.)
 */
alias png_progressive_row_ptr = void function(png_structp, png_bytep, uint, int);
}

static if(PNG_READ_USER_TRANSFORM_SUPPORTED || PNG_WRITE_USER_TRANSFORM_SUPPORTED){
alias png_user_transform_ptr = void function(png_structp, png_row_infop, png_bytep);
}

static if(PNG_USER_CHUNKS_SUPPORTED) {
alias png_user_chunk_ptr = int function(png_structp, png_unknown_chunkp);
}
static if(PNG_UNKNOWN_CHUNKS_SUPPORTED) {
/* not used anywhere */
/* alias void function(png_structp) png_unknown_chunk_ptr; */
}

static if(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, 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!
 */
//alias void function(PNGARG((jmp_buf, int)), alias) png_longjmp_ptr;
}

/* Transform masks for the high-level interface */
enum PNG_TRANSFORM_IDENTITY = 0x0000;    /* read and write */
enum PNG_TRANSFORM_STRIP_16 = 0x0001;    /* read only */
enum PNG_TRANSFORM_STRIP_ALPHA = 0x0002;    /* read only */
enum PNG_TRANSFORM_PACKING = 0x0004;    /* read and write */
enum PNG_TRANSFORM_PACKSWAP = 0x0008;    /* read and write */
enum PNG_TRANSFORM_EXPAND = 0x0010;    /* read only */
enum PNG_TRANSFORM_INVERT_MONO = 0x0020;    /* read and write */
enum PNG_TRANSFORM_SHIFT = 0x0040;    /* read and write */
enum PNG_TRANSFORM_BGR = 0x0080;    /* read and write */
enum PNG_TRANSFORM_SWAP_ALPHA = 0x0100;    /* read and write */
enum PNG_TRANSFORM_SWAP_ENDIAN = 0x0200;    /* read and write */
enum PNG_TRANSFORM_INVERT_ALPHA = 0x0400;    /* read and write */
enum PNG_TRANSFORM_STRIP_FILLER = 0x0800;    /* write only */
/* Added to libpng-1.2.34 */
alias PNG_TRANSFORM_STRIP_FILLER_BEFORE = PNG_TRANSFORM_STRIP_FILLER;
enum PNG_TRANSFORM_STRIP_FILLER_AFTER = 0x1000; /* write only */
/* Added to libpng-1.4.0 */
enum PNG_TRANSFORM_GRAY_TO_RGB = 0x2000;      /* read only */
/* Added to libpng-1.5.4 */
enum PNG_TRANSFORM_EXPAND_16 = 0x4000;      /* read only */
static if (int.max >= 0x8000) { /* else this might break */
enum PNG_TRANSFORM_SCALE_16 = 0x8000;      /* read only */
}

/* Flags for MNG supported features */
enum PNG_FLAG_MNG_EMPTY_PLTE = 0x01;
enum PNG_FLAG_MNG_FILTER_64 = 0x04;
enum 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.
 */
alias png_malloc_ptr = png_voidp function(png_structp, png_alloc_size_t);
alias png_free_ptr = void function(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 */
uint png_access_version_number();

/* 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.
 */
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).
 */
int png_sig_cmp(png_const_bytep sig, size_t start,
    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).
 */
auto png_check_sig(S,N)(S sig, N n) { return !png_sig_cmp((sig), 0, (n)); }

/* Allocate and initialize png_ptr struct for reading, and any other memory. */
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);

/* Allocate and initialize png_ptr struct for writing, and any other memory */
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);

size_t png_get_compression_buffer_size
    (png_const_structrp png_ptr);

void png_set_compression_buffer_size(png_structrp png_ptr,
    size_t size);

/* Moved from pngconf.h in 1.4.0 and modified to ensure setjmp/longjmp
 * match up.
 */
static if(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.
 */
//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)))
}else{
//#  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.
 */
void png_longjmp(png_const_structrp png_ptr, int val);

static if(PNG_READ_SUPPORTED){
/* Reset the compression stream */
deprecated int png_reset_zstream(png_structrp png_ptr);
}

/* New functions added in libpng-1.0.2 (not enabled by default until 1.2.0) */
static if(PNG_USER_MEM_SUPPORTED){
png_structp png_create_read_struct_2
    (png_const_charp user_png_ver, png_voidp error_ptr, png_error_ptr error_fn,
    png_error_ptr warn_fn,
    png_voidp mem_ptr, png_malloc_ptr malloc_fn, png_free_ptr free_fn);
png_structp png_create_write_struct_2
    (png_const_charp user_png_ver, png_voidp error_ptr, png_error_ptr error_fn,
    png_error_ptr warn_fn,
    png_voidp mem_ptr, png_malloc_ptr malloc_fn, png_free_ptr free_fn);
}

/* Write the PNG file signature. */
void png_write_sig(png_structrp png_ptr);

/* Write a PNG chunk - size, type, (optional) data, CRC. */
void png_write_chunk(png_structrp png_ptr, png_const_bytep
    chunk_name, png_const_bytep data, size_t length);

/* Write the start of a PNG chunk - length and chunk name. */
void png_write_chunk_start(png_structrp png_ptr,
    png_const_bytep chunk_name, uint length);

/* Write the data of a PNG chunk started with png_write_chunk_start(). */
void png_write_chunk_data(png_structrp png_ptr,
    png_const_bytep data, size_t length);

/* Finish a chunk started with png_write_chunk_start() (includes CRC). */
void png_write_chunk_end(png_structrp png_ptr);

/* Allocate and initialize the info structure */
png_infop png_create_info_struct(png_const_structrp png_ptr);

/* DEPRECATED: this function allowed init structures to be created using the
 * default allocation method (typically malloc).  Use is deprecated in 1.6.0 and
 * the API will be removed in the future.
 */
deprecated void png_info_init_3(png_infopp info_ptr,
    size_t png_info_struct_size);

/* Writes all the PNG information before the image. */
void png_write_info_before_PLTE
    (png_structrp png_ptr, png_const_inforp info_ptr);
void png_write_info
    (png_structrp png_ptr, png_const_inforp info_ptr);

static if(PNG_SEQUENTIAL_READ_SUPPORTED){
/* Read the information before the actual image data. */
void png_read_info
    (png_structrp png_ptr, png_inforp info_ptr);
}

static if(PNG_TIME_RFC1123_SUPPORTED){
   /* Convert to a US string format: there is no localization support in this
    * routine.  The original implementation used a 29 character buffer in
    * png_struct, this will be removed in future versions.
    */
static if(PNG_LIBPNG_VER < 10700) {
/* To do: remove this from libpng17 (and from libpng17/png.c and pngstruct.h) */
deprecated png_const_charp png_convert_to_rfc1123
    (png_structrp png_ptr, png_const_timep ptime);
}

int png_convert_to_rfc1123_buffer(char[29] out_, png_const_timep ptime);

}

static if(PNG_CONVERT_tIME_SUPPORTED){
/* Convert from a struct tm to png_time */
void png_convert_from_struct_tm(png_timep ptime,
    const(tm) * ttime);

/* Convert from time_t to png_time.  Uses gmtime() */
void png_convert_from_time_t
    (png_timep ptime, time_t ttime);
} /* PNG_CONVERT_tIME_SUPPORTED */

static if(PNG_READ_EXPAND_SUPPORTED){
/* Expand data to 24-bit RGB, or 8-bit grayscale, with alpha if available. */
void png_set_expand(png_structrp png_ptr);
void png_set_expand_gray_1_2_4_to_8(png_structrp png_ptr);
void png_set_palette_to_rgb(png_structrp png_ptr);
void png_set_tRNS_to_alpha(png_structrp png_ptr);
}

static if(PNG_READ_EXPAND_16_SUPPORTED){
/* Expand to 16-bit channels, forces conversion of palette to RGB and expansion
 * of a tRNS chunk if present.
 */
void png_set_expand_16(png_structrp png_ptr);
}

static if(PNG_READ_BGR_SUPPORTED || PNG_WRITE_BGR_SUPPORTED){
/* Use blue, green, red order for pixels. */
void png_set_bgr(png_structrp png_ptr);
}

static if(PNG_READ_GRAY_TO_RGB_SUPPORTED){
/* Expand the grayscale to 24-bit RGB if necessary. */
void png_set_gray_to_rgb(png_structrp png_ptr);
}

static if(PNG_READ_RGB_TO_GRAY_SUPPORTED){
/* Reduce RGB to grayscale. */
enum PNG_ERROR_ACTION_NONE = 1;
enum PNG_ERROR_ACTION_WARN = 2;
enum PNG_ERROR_ACTION_ERROR = 3;
enum PNG_RGB_TO_GRAY_DEFAULT = (-1);/*for red/green coefficients*/

void png_set_rgb_to_gray(png_structrp png_ptr,
    int error_action, double red, double green);
void png_set_rgb_to_gray_fixed(png_structrp png_ptr,
    int error_action, png_fixed_point red, png_fixed_point green);

png_byte png_get_rgb_to_gray_status(png_const_structrp
    png_ptr);
}

static if(PNG_BUILD_GRAYSCALE_PALETTE_SUPPORTED){
void png_build_grayscale_palette(int bit_depth,
    png_colorp palette);
}

static if(PNG_READ_ALPHA_MODE_SUPPORTED){
/* How the alpha channel is interpreted - this affects how the color channels
 * of a PNG file are returned to the calling application when an alpha channel,
 * or a tRNS chunk in a palette file, is present.
 *
 * This has no effect on the way pixels are written into a PNG output
 * datastream. The color samples in a PNG datastream are never premultiplied
 * with the alpha samples.
 *
 * The default is to return data according to the PNG specification: the alpha
 * channel is a linear measure of the contribution of the pixel to the
 * corresponding composited pixel, and the color channels are unassociated
 * (not premultiplied).  The gamma encoded color channels must be scaled
 * according to the contribution and to do this it is necessary to undo
 * the encoding, scale the color values, perform the composition and re-encode
 * the values.  This is the 'PNG' mode.
 *
 * The alternative is to 'associate' the alpha with the color information by
 * storing color channel values that have been scaled by the alpha.
 * image.  These are the 'STANDARD', 'ASSOCIATED' or 'PREMULTIPLIED' modes
 * (the latter being the two common names for associated alpha color channels).
 *
 * For the 'OPTIMIZED' mode, a pixel is treated as opaque only if the alpha
 * value is equal to the maximum value.
 *
 * The final choice is to gamma encode the alpha channel as well.  This is
 * broken because, in practice, no implementation that uses this choice
 * correctly undoes the encoding before handling alpha composition.  Use this
 * choice only if other serious errors in the software or hardware you use
 * mandate it; the typical serious error is for dark halos to appear around
 * opaque areas of the composited PNG image because of arithmetic overflow.
 *
 * The API function png_set_alpha_mode specifies which of these choices to use
 * with an enumerated 'mode' value and the gamma of the required output:
 */
enum PNG_ALPHA_PNG = 0; /* according to the PNG standard */
enum PNG_ALPHA_STANDARD = 1; /* according to Porter/Duff */
enum PNG_ALPHA_ASSOCIATED = 1; /* as above; this is the normal practice */
enum PNG_ALPHA_PREMULTIPLIED = 1; /* as above */
enum PNG_ALPHA_OPTIMIZED = 2; /* 'PNG' for opaque pixels, else 'STANDARD' */
enum PNG_ALPHA_BROKEN = 3; /* the alpha channel is gamma encoded */

void png_set_alpha_mode(png_structrp png_ptr, int mode,
    double output_gamma);
void png_set_alpha_mode_fixed(png_structrp png_ptr,
    int mode, png_fixed_point output_gamma);
}

static if(PNG_READ_GAMMA_SUPPORTED || PNG_READ_ALPHA_MODE_SUPPORTED){
/* The output_gamma value is a screen gamma in libpng terminology: it expresses
 * how to decode the output values, not how they are encoded.
 */
enum PNG_DEFAULT_sRGB = -1;       /* sRGB gamma and color space */
enum PNG_GAMMA_MAC_18 = -2;       /* Old Mac '1.8' gamma and color space */
enum PNG_GAMMA_sRGB = 220000;   /* Television standards--matches sRGB gamma */
alias PNG_GAMMA_LINEAR = PNG_FP_1; /* Linear */
}

/* The following are examples of calls to png_set_alpha_mode to achieve the
 * required overall gamma correction and, where necessary, alpha
 * premultiplication.
 *
 * png_set_alpha_mode(pp, PNG_ALPHA_PNG, PNG_DEFAULT_sRGB);
 *    This is the default libpng handling of the alpha channel - it is not
 *    pre-multiplied into the color components.  In addition the call states
 *    that the output is for a sRGB system and causes all PNG files without gAMA
 *    chunks to be assumed to be encoded using sRGB.
 *
 * png_set_alpha_mode(pp, PNG_ALPHA_PNG, PNG_GAMMA_MAC);
 *    In this case the output is assumed to be something like an sRGB conformant
 *    display preceded by a power-law lookup table of power 1.45.  This is how
 *    early Mac systems behaved.
 *
 * png_set_alpha_mode(pp, PNG_ALPHA_STANDARD, PNG_GAMMA_LINEAR);
 *    This is the classic Jim Blinn approach and will work in academic
 *    environments where everything is done by the book.  It has the shortcoming
 *    of assuming that input PNG data with no gamma information is linear - this
 *    is unlikely to be correct unless the PNG files where generated locally.
 *    Most of the time the output precision will be so low as to show
 *    significant banding in dark areas of the image.
 *
 * png_set_expand_16(pp);
 * png_set_alpha_mode(pp, PNG_ALPHA_STANDARD, PNG_DEFAULT_sRGB);
 *    This is a somewhat more realistic Jim Blinn inspired approach.  PNG files
 *    are assumed to have the sRGB encoding if not marked with a gamma value and
 *    the output is always 16 bits per component.  This permits accurate scaling
 *    and processing of the data.  If you know that your input PNG files were
 *    generated locally you might need to replace PNG_DEFAULT_sRGB with the
 *    correct value for your system.
 *
 * png_set_alpha_mode(pp, PNG_ALPHA_OPTIMIZED, PNG_DEFAULT_sRGB);
 *    If you just need to composite the PNG image onto an existing background
 *    and if you control the code that does this you can use the optimization
 *    setting.  In this case you just copy completely opaque pixels to the
 *    output.  For pixels that are not completely transparent (you just skip
 *    those) you do the composition math using png_composite or png_composite_16
 *    below then encode the resultant 8-bit or 16-bit values to match the output
 *    encoding.
 *
 * Other cases
 *    If neither the PNG nor the standard linear encoding work for you because
 *    of the software or hardware you use then you have a big problem.  The PNG
 *    case will probably result in halos around the image.  The linear encoding
 *    will probably result in a washed out, too bright, image (it's actually too
 *    contrasty.)  Try the ALPHA_OPTIMIZED mode above - this will probably
 *    substantially reduce the halos.  Alternatively try:
 *
 * png_set_alpha_mode(pp, PNG_ALPHA_BROKEN, PNG_DEFAULT_sRGB);
 *    This option will also reduce the halos, but there will be slight dark
 *    halos round the opaque parts of the image where the background is light.
 *    In the OPTIMIZED mode the halos will be light halos where the background
 *    is dark.  Take your pick - the halos are unavoidable unless you can get
 *    your hardware/software fixed!  (The OPTIMIZED approach is slightly
 *    faster.)
 *
 * When the default gamma of PNG files doesn't match the output gamma.
 *    If you have PNG files with no gamma information png_set_alpha_mode allows
 *    you to provide a default gamma, but it also sets the output gamma to the
 *    matching value.  If you know your PNG files have a gamma that doesn't
 *    match the output you can take advantage of the fact that
 *    png_set_alpha_mode always sets the output gamma but only sets the PNG
 *    default if it is not already set:
 *
 * png_set_alpha_mode(pp, PNG_ALPHA_PNG, PNG_DEFAULT_sRGB);
 * png_set_alpha_mode(pp, PNG_ALPHA_PNG, PNG_GAMMA_MAC);
 *    The first call sets both the default and the output gamma values, the
 *    second call overrides the output gamma without changing the default.  This
 *    is easier than achieving the same effect with png_set_gamma.  You must use
 *    PNG_ALPHA_PNG for the first call - internal checking in png_set_alpha will
 *    fire if more than one call to png_set_alpha_mode and png_set_background is
 *    made in the same read operation, however multiple calls with PNG_ALPHA_PNG
 *    are ignored.
 */

static if(PNG_READ_STRIP_ALPHA_SUPPORTED){
void png_set_strip_alpha(png_structrp png_ptr);
}

static if(PNG_READ_SWAP_ALPHA_SUPPORTED || PNG_WRITE_SWAP_ALPHA_SUPPORTED){
void png_set_swap_alpha(png_structrp png_ptr);
}

static if(PNG_READ_INVERT_ALPHA_SUPPORTED || PNG_WRITE_INVERT_ALPHA_SUPPORTED){
void png_set_invert_alpha(png_structrp png_ptr);
}

static if(PNG_READ_FILLER_SUPPORTED || PNG_WRITE_FILLER_SUPPORTED){
/* Add a filler byte to 8-bit or 16-bit Gray or 24-bit or 48-bit RGB images. */
void png_set_filler(png_structrp png_ptr, uint filler,
    int flags);
/* The values of the PNG_FILLER_ defines should NOT be changed */
enum PNG_FILLER_BEFORE = 0;
enum PNG_FILLER_AFTER = 1;
/* Add an alpha byte to 8-bit or 16-bit Gray or 24-bit or 48-bit RGB images. */
void png_set_add_alpha
    (png_structrp png_ptr, uint filler,
    int flags);
} /* PNG_READ_FILLER_SUPPORTED || PNG_WRITE_FILLER_SUPPORTED */

static if(PNG_READ_SWAP_SUPPORTED || PNG_WRITE_SWAP_SUPPORTED){
/* Swap bytes in 16-bit depth files. */
void png_set_swap(png_structrp png_ptr);
}

static if(PNG_READ_PACK_SUPPORTED || PNG_WRITE_PACK_SUPPORTED){
/* Use 1 byte per pixel in 1, 2, or 4-bit depth files. */
void png_set_packing(png_structrp png_ptr);
}

static if(PNG_READ_PACKSWAP_SUPPORTED || PNG_WRITE_PACKSWAP_SUPPORTED){
/* Swap packing order of pixels in bytes. */
void png_set_packswap(png_structrp png_ptr);
}

static if(PNG_READ_SHIFT_SUPPORTED || PNG_WRITE_SHIFT_SUPPORTED){
/* Converts files to legal bit depths. */
void png_set_shift(png_structrp png_ptr, png_const_color_8p
    true_bits);
}

static if(PNG_READ_INTERLACING_SUPPORTED || PNG_WRITE_INTERLACING_SUPPORTED){
/* Have the code handle the interlacing.  Returns the number of passes.
 * MUST be called before png_read_update_info or png_start_read_image,
 * otherwise it will not have the desired effect.  Note that it is still
 * necessary to call png_read_row or png_read_rows png_get_image_height
 * times for each pass.
*/
int png_set_interlace_handling(png_structrp png_ptr);
}

static if(PNG_READ_INVERT_SUPPORTED || PNG_WRITE_INVERT_SUPPORTED){
/* Invert monochrome files */
void png_set_invert_mono(png_structrp png_ptr);
}

static if(PNG_READ_BACKGROUND_SUPPORTED){
/* Handle alpha and tRNS by replacing with a background color.  Prior to
 * libpng-1.5.4 this API must not be called before the PNG file header has been
 * read.  Doing so will result in unexpected behavior and possible warnings or
 * errors if the PNG file contains a bKGD chunk.
 */
void png_set_background(png_structrp png_ptr,
    png_const_color_16p background_color, int background_gamma_code,
    int need_expand, double background_gamma);
void png_set_background_fixed (png_structrp png_ptr,
    png_const_color_16p background_color, int background_gamma_code,
    int need_expand, png_fixed_point background_gamma);
}
static if(PNG_READ_BACKGROUND_SUPPORTED){
enum PNG_BACKGROUND_GAMMA_UNKNOWN = 0;
enum PNG_BACKGROUND_GAMMA_SCREEN  = 1;
enum PNG_BACKGROUND_GAMMA_FILE    = 2;
enum PNG_BACKGROUND_GAMMA_UNIQUE  = 3;
}

static if(PNG_READ_SCALE_16_TO_8_SUPPORTED){
/* Scale a 16-bit depth file down to 8-bit, accurately. */
void png_set_scale_16(png_structrp png_ptr);
}

static if(PNG_READ_STRIP_16_TO_8_SUPPORTED){
enum PNG_READ_16_TO_8_SUPPORTED = 1; /* Name prior to 1.5.4 */
/* Strip the second byte of information from a 16-bit depth file. */
void png_set_strip_16(png_structrp png_ptr);
}

static if(PNG_READ_QUANTIZE_SUPPORTED){
/* Turn on quantizing, and reduce the palette to the number of colors
 * available.
 */
void png_set_quantize
    (png_structrp png_ptr, png_colorp palette,
    int num_palette, int maximum_colors, png_const_uint_16p histogram,
    int full_quantize);
}

static if(PNG_READ_GAMMA_SUPPORTED){
/* The threshold on gamma processing is configurable but hard-wired into the
 * library.  The following is the floating point variant.
 */
enum PNG_GAMMA_THRESHOLD = (PNG_GAMMA_THRESHOLD_FIXED*0.00001);

/* Handle gamma correction. Screen_gamma=(display_exponent).
 * NOTE: this API simply sets the screen and file gamma values. It will
 * therefore override the value for gamma in a PNG file if it is called after
 * the file header has been read - use with care  - call before reading the PNG
 * file for best results!
 *
 * These routines accept the same gamma values as png_set_alpha_mode (described
 * above).  The PNG_GAMMA_ defines and PNG_DEFAULT_sRGB can be passed to either
 * API (floating point or fixed.)  Notice, however, that the 'file_gamma' value
 * is the inverse of a 'screen gamma' value.
 */
void png_set_gamma
    (png_structrp png_ptr, double screen_gamma,
    double override_file_gamma);
void png_set_gamma_fixed(png_structrp png_ptr,
    png_fixed_point screen_gamma, png_fixed_point override_file_gamma);
}

static if(PNG_WRITE_FLUSH_SUPPORTED){
/* Set how many lines between output flushes - 0 for no flushing */
void png_set_flush(png_structrp png_ptr, int nrows);
/* Flush the current PNG output buffer */
void png_write_flush(png_structrp png_ptr);
}

/* Optional update palette with requested transformations */
void png_start_read_image(png_structrp png_ptr);

/* Optional call to update the users info structure */
void png_read_update_info
    (png_structrp png_ptr, png_inforp info_ptr);

static if(PNG_SEQUENTIAL_READ_SUPPORTED){
/* Read one or more rows of image data. */
void png_read_rows(png_structrp png_ptr, png_bytepp row,
    png_bytepp display_row, uint num_rows);
}

static if(PNG_SEQUENTIAL_READ_SUPPORTED){
/* Read a row of data. */
void png_read_row(png_structrp png_ptr, png_bytep row,
    png_bytep display_row);
}

static if(PNG_SEQUENTIAL_READ_SUPPORTED){
/* Read the whole image into memory at once. */
void png_read_image(png_structrp png_ptr, png_bytepp image);
}

/* Write a row of image data */
void png_write_row
    (png_structrp png_ptr, png_const_bytep row);

/* Write a few rows of image data: (*row) is not written; however, the type
 * is declared as writeable to maintain compatibility with previous versions
 * of libpng and to allow the 'display_row' array from read_rows to be passed
 * unchanged to write_rows.
 */
void png_write_rows(png_structrp png_ptr, in png_bytepp row,
    uint num_rows);

/* Write the image data */
void png_write_image
    (png_structrp png_ptr, in png_bytepp image);

/* Write the end of the PNG file. */
void png_write_end
    (png_structrp png_ptr, png_inforp info_ptr);

static if(PNG_SEQUENTIAL_READ_SUPPORTED){
/* Read the end of the PNG file. */
void png_read_end(png_structrp png_ptr, png_inforp info_ptr);
}

/* Free any memory associated with the png_info_struct */
void png_destroy_info_struct(png_const_structrp png_ptr,
    png_infopp info_ptr_ptr);

/* Free any memory associated with the png_struct and the png_info_structs */
void png_destroy_read_struct(png_structpp png_ptr_ptr,
    png_infopp info_ptr_ptr, png_infopp end_info_ptr_ptr);

/* Free any memory associated with the png_struct and the png_info_structs */
void png_destroy_write_struct(png_structpp png_ptr_ptr,
    png_infopp info_ptr_ptr);

/* Set the libpng method of handling chunk CRC errors */
void png_set_crc_action
    (png_structrp png_ptr, int crit_action, int ancil_action);

/* Values for png_set_crc_action() say how to handle CRC errors in
 * ancillary and critical chunks, and whether to use the data contained
 * therein.  Note that it is impossible to "discard" data in a critical
 * chunk.  For versions prior to 0.90, the action was always error/quit,
 * whereas in version 0.90 and later, the action for CRC errors in ancillary
 * chunks is warn/discard.  These values should NOT be changed.
 *
 *      value                       action:critical     action:ancillary
 */
enum PNG_CRC_DEFAULT = 0;  /* error/quit          warn/discard data */
enum PNG_CRC_ERROR_QUIT = 1;  /* error/quit          error/quit        */
enum PNG_CRC_WARN_DISCARD = 2;  /* (INVALID)           warn/discard data */
enum PNG_CRC_WARN_USE = 3;  /* warn/use data       warn/use data     */
enum PNG_CRC_QUIET_USE = 4;  /* quiet/use data      quiet/use data    */
enum PNG_CRC_NO_CHANGE = 5;  /* use current value   use current value */

static if(PNG_WRITE_SUPPORTED){
/* These functions give the user control over the scan-line filtering in
 * libpng and the compression methods used by zlib.  These functions are
 * mainly useful for testing, as the defaults should work with most users.
 * Those users who are tight on memory or want faster performance at the
 * expense of compression can modify them.  See the compression library
 * header file (zlib.h) for an explination of the compression functions.
 */

/* Set the filtering method(s) used by libpng.  Currently, the only valid
 * value for "method" is 0.
 */
void png_set_filter
    (png_structrp png_ptr, int method, int filters);
} /* WRITE */

/* Flags for png_set_filter() to say which filters to use.  The flags
 * are chosen so that they don't conflict with real filter types
 * below, in case they are supplied instead of the #defined constants.
 * These values should NOT be changed.
 */
enum PNG_NO_FILTERS = 0x00;
enum PNG_FILTER_NONE = 0x08;
enum PNG_FILTER_SUB = 0x10;
enum PNG_FILTER_UP = 0x20;
enum PNG_FILTER_AVG = 0x40;
enum PNG_FILTER_PAETH = 0x80;
enum PNG_FAST_FILTERS = (PNG_FILTER_NONE | PNG_FILTER_SUB | PNG_FILTER_UP);
enum PNG_ALL_FILTERS = (PNG_FAST_FILTERS | PNG_FILTER_AVG | PNG_FILTER_PAETH);

/* Filter values (not flags) - used in pngwrite.c, pngwutil.c for now.
 * These defines should NOT be changed.
 */
enum PNG_FILTER_VALUE_NONE = 0;
enum PNG_FILTER_VALUE_SUB = 1;
enum PNG_FILTER_VALUE_UP = 2;
enum PNG_FILTER_VALUE_AVG = 3;
enum PNG_FILTER_VALUE_PAETH = 4;
enum PNG_FILTER_VALUE_LAST = 5;

static if(PNG_WRITE_SUPPORTED){
static if(PNG_WRITE_WEIGHTED_FILTER_SUPPORTED){ /* DEPRECATED */
void png_set_filter_heuristics(png_structrp png_ptr,
    int heuristic_method, int num_weights, png_const_doublep filter_weights,
    png_const_doublep filter_costs);
void png_set_filter_heuristics_fixed
    (png_structrp png_ptr,
    int heuristic_method, int num_weights, png_const_fixed_point_p
    filter_weights, png_const_fixed_point_p filter_costs);
} /*  PNG_WRITE_WEIGHTED_FILTER_SUPPORTED */

/* The following are no longer used and will be removed from libpng-1.7: */
enum PNG_FILTER_HEURISTIC_DEFAULT = 0;  /* Currently "UNWEIGHTED" */
enum PNG_FILTER_HEURISTIC_UNWEIGHTED = 1;  /* Used by libpng < 0.95 */
enum PNG_FILTER_HEURISTIC_WEIGHTED = 2;  /* Experimental feature */
enum PNG_FILTER_HEURISTIC_LAST = 3;  /* Not a valid value */

/* Set the library compression level.  Currently, valid values range from
 * 0 - 9, corresponding directly to the zlib compression levels 0 - 9
 * (0 - no compression, 9 - "maximal" compression).  Note that tests have
 * shown that zlib compression levels 3-6 usually perform as well as level 9
 * for PNG images, and do considerably fewer caclulations.  In the future,
 * these values may not correspond directly to the zlib compression levels.
 */
static if(PNG_WRITE_CUSTOMIZE_COMPRESSION_SUPPORTED){
void png_set_compression_level
    (png_structrp png_ptr, int level);

void png_set_compression_mem_level(png_structrp png_ptr,
    int mem_level);

void png_set_compression_strategy(png_structrp png_ptr,
    int strategy);

/* If PNG_WRITE_OPTIMIZE_CMF_SUPPORTED is defined, libpng will use a
 * smaller value of window_bits if it can do so safely.
 */
void png_set_compression_window_bits(png_structrp png_ptr,
    int window_bits);

void png_set_compression_method(png_structrp png_ptr,
    int method);
} /* WRITE_CUSTOMIZE_COMPRESSION */

static if(PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED){
/* Also set zlib parameters for compressing non-IDAT chunks */
void png_set_text_compression_level
    (png_structrp png_ptr, int level);

void png_set_text_compression_mem_level(png_structrp png_ptr,
    int mem_level);

void png_set_text_compression_strategy(png_structrp png_ptr,
    int strategy);

/* If PNG_WRITE_OPTIMIZE_CMF_SUPPORTED is defined, libpng will use a
 * smaller value of window_bits if it can do so safely.
 */
void png_set_text_compression_window_bits(png_structrp
    png_ptr, int window_bits);

void png_set_text_compression_method(png_structrp png_ptr,
    int method);
} /* WRITE_CUSTOMIZE_ZTXT_COMPRESSION */
} /* WRITE */

/* These next functions are called for input/output, memory, and error
 * handling.  They are in the file pngrio.c, pngwio.c, and pngerror.c,
 * and call standard C I/O routines such as fread(), fwrite(), and
 * fprintf().  These functions can be made to use other I/O routines
 * at run time for those applications that need to handle I/O in a
 * different manner by calling png_set_???_fn().  See libpng-manual.txt for
 * more information.
 */

static if(PNG_STDIO_SUPPORTED){
/* Initialize the input/output for the PNG file to the default functions. */
void png_init_io(png_structrp png_ptr, png_FILE_p fp);
}

/* Replace the (error and abort), and warning functions with user
 * supplied functions.  If no messages are to be printed you must still
 * write and use replacement functions. The replacement error_fn should
 * still do a longjmp to the last setjmp location if you are using this
 * method of error handling.  If error_fn or warning_fn is NULL, the
 * default function will be used.
 */

void png_set_error_fn
    (png_structrp png_ptr, png_voidp error_ptr,
    png_error_ptr error_fn, png_error_ptr warning_fn);

/* Return the user pointer associated with the error functions */
png_voidp png_get_error_ptr(png_const_structrp png_ptr);

/* Replace the default data output functions with a user supplied one(s).
 * If buffered output is not used, then output_flush_fn can be set to NULL.
 * If PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile time
 * output_flush_fn will be ignored (and thus can be NULL).
 * It is probably a mistake to use NULL for output_flush_fn if
 * write_data_fn is not also NULL unless you have built libpng with
 * PNG_WRITE_FLUSH_SUPPORTED undefined, because in this case libpng's
 * default flush function, which uses the standard *FILE structure, will
 * be used.
 */
void png_set_write_fn(png_structrp png_ptr, png_voidp io_ptr,
    png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn);

/* Replace the default data input function with a user supplied one. */
void png_set_read_fn(png_structrp png_ptr, png_voidp io_ptr,
    png_rw_ptr read_data_fn);

/* Return the user pointer associated with the I/O functions */
png_voidp png_get_io_ptr(png_const_structrp png_ptr);

void png_set_read_status_fn(png_structrp png_ptr,
    png_read_status_ptr read_row_fn);

void png_set_write_status_fn(png_structrp png_ptr,
    png_write_status_ptr write_row_fn);

static if(PNG_USER_MEM_SUPPORTED){
/* Replace the default memory allocation functions with user supplied one(s). */
void png_set_mem_fn(png_structrp png_ptr, png_voidp mem_ptr,
    png_malloc_ptr malloc_fn, png_free_ptr free_fn);
/* Return the user pointer associated with the memory functions */
png_voidp png_get_mem_ptr(png_const_structrp png_ptr);
}

static if(PNG_READ_USER_TRANSFORM_SUPPORTED){
void png_set_read_user_transform_fn(png_structrp png_ptr,
    png_user_transform_ptr read_user_transform_fn);
}

static if(PNG_WRITE_USER_TRANSFORM_SUPPORTED){
void png_set_write_user_transform_fn(png_structrp png_ptr,
    png_user_transform_ptr write_user_transform_fn);
}

static if(PNG_USER_TRANSFORM_PTR_SUPPORTED){
void png_set_user_transform_info(png_structrp png_ptr,
    png_voidp user_transform_ptr, int user_transform_depth,
    int user_transform_channels);
/* Return the user pointer associated with the user transform functions */
png_voidp png_get_user_transform_ptr
    (png_const_structrp png_ptr);
}

static if(PNG_USER_TRANSFORM_INFO_SUPPORTED){
/* Return information about the row currently being processed.  Note that these
 * APIs do not fail but will return unexpected results if called outside a user
 * transform callback.  Also note that 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.)
 */
uint png_get_current_row_number(png_const_structrp);
png_byte png_get_current_pass_number(png_const_structrp);
}

static if(PNG_READ_USER_CHUNKS_SUPPORTED){
/* This callback is called only for *unknown* chunks.  If
 * PNG_HANDLE_AS_UNKNOWN_SUPPORTED is set then it is possible to set known
 * chunks to be treated as unknown, however in this case the callback must do
 * any processing required by the chunk (e.g. by calling the appropriate
 * png_set_ APIs.)
 *
 * There is no write support - on write, by default, all the chunks in the
 * 'unknown' list are written in the specified position.
 *
 * The integer return from the callback function is interpreted thus:
 *
 * negative: An error occurred, png_chunk_error will be called.
 *     zero: The chunk was not handled, the chunk will be saved. A critical
 *           chunk will cause an error at this point unless it is to be saved.
 * positive: The chunk was handled, libpng will ignore/discard it.
 *
 * See "INTERACTION WITH USER CHUNK CALLBACKS" below for important notes about
 * how this behavior will change in libpng 1.7
 */
void png_set_read_user_chunk_fn(png_structrp png_ptr,
    png_voidp user_chunk_ptr, png_user_chunk_ptr read_user_chunk_fn);
}

static if (PNG_USER_CHUNKS_SUPPORTED) {
png_voidp png_get_user_chunk_ptr(png_const_structrp png_ptr);
}

static if(PNG_PROGRESSIVE_READ_SUPPORTED){
/* Sets the function callbacks for the push reader, and a pointer to a
 * user-defined structure available to the callback functions.
 */
void png_set_progressive_read_fn(png_structrp png_ptr,
    png_voidp progressive_ptr, png_progressive_info_ptr info_fn,
    png_progressive_row_ptr row_fn, png_progressive_end_ptr end_fn);

/* Returns the user pointer associated with the push read functions */
png_voidp png_get_progressive_ptr(png_const_structrp png_ptr);

/* Function to be called when data becomes available */
void png_process_data
    (png_structrp png_ptr, png_inforp info_ptr,
    png_bytep buffer, size_t buffer_size);

/* A function which may be called *only* within png_process_data to stop the
 * processing of any more data.  The function returns the number of bytes
 * remaining, excluding any that libpng has cached internally.  A subsequent
 * call to png_process_data must supply these bytes again.  If the argument
 * 'save' is set to true the routine will first save all the pending data and
 * will always return 0.
 */
size_t png_process_data_pause(png_structrp, int save);

/* A function which may be called *only* outside (after) a call to
 * png_process_data.  It returns the number of bytes of data to skip in the
 * input.  Normally it will return 0, but if it returns a non-zero value the
 * application must skip than number of bytes of input data and pass the
 * following data to the next call to png_process_data.
 */
uint png_process_data_skip(png_structrp);

/* Function that combines rows.  'new_row' is a flag that should come from
 * the callback and be non-NULL if anything needs to be done; the library
 * stores its own version of the new data internally and ignores the passed
 * in value.
 */
void png_progressive_combine_row(png_const_structrp png_ptr,
    png_bytep old_row, png_const_bytep new_row);

} /* PNG_PROGRESSIVE_READ_SUPPORTED */

png_voidp png_malloc
    (png_const_structrp png_ptr, png_alloc_size_t size);
/* Added at libpng version 1.4.0 */
png_voidp png_calloc
    (png_const_structrp png_ptr, png_alloc_size_t size);

/* Added at libpng version 1.2.4 */
png_voidp png_malloc_warn(png_const_structrp png_ptr,
    png_alloc_size_t size);

/* Frees a pointer allocated by png_malloc() */
void png_free(png_const_structrp png_ptr, png_voidp ptr);

/* Free data that was allocated internally */
void png_free_data
    (png_const_structrp png_ptr, png_inforp info_ptr, uint free_me, int num);

/* Reassign responsibility for freeing existing data, whether allocated
 * by libpng or by the application; this works on the png_info structure passed
 * in, it does not change the state for other png_info structures.
 *
 * It is unlikely that this function works correctly as of 1.6.0 and using it
 * may result either in memory leaks or double free of allocated data.
 */
void png_data_freer
    (png_const_structrp png_ptr, png_inforp info_ptr, int freer, uint mask);

/* Assignments for png_data_freer */
enum PNG_DESTROY_WILL_FREE_DATA = 1;
enum PNG_SET_WILL_FREE_DATA = 1;
enum PNG_USER_WILL_FREE_DATA = 2;
/* Flags for png_ptr->free_me and info_ptr->free_me */
enum PNG_FREE_HIST = 0x0008U;
enum PNG_FREE_ICCP = 0x0010U;
enum PNG_FREE_SPLT = 0x0020U;
enum PNG_FREE_ROWS = 0x0040U;
enum PNG_FREE_PCAL = 0x0080U;
enum PNG_FREE_SCAL = 0x0100U;
static if (PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED) {
    enum PNG_FREE_UNKN = 0x0200U;
}
/*      PNG_FREE_LIST 0x0400    removed in 1.6.0 because it is ignored */
enum PNG_FREE_PLTE = 0x1000U;
enum PNG_FREE_TRNS = 0x2000U;
enum PNG_FREE_TEXT = 0x4000U;
enum PNG_FREE_EXIF = 0x8000U; /* Added at libpng-1.6.31 */
enum PNG_FREE_ALL = 0x7fffU;
enum PNG_FREE_MUL = 0x4220U; /* PNG_FREE_SPLT|PNG_FREE_TEXT|PNG_FREE_UNKN */

static if(PNG_USER_MEM_SUPPORTED){
deprecated png_voidp png_malloc_default(png_const_structrp png_ptr,
    png_alloc_size_t size);
deprecated void png_free_default(png_structrp png_ptr, png_voidp ptr);
}

static if(PNG_ERROR_TEXT_SUPPORTED){
/* Fatal error in PNG image of libpng - can't continue */
void png_error
    (png_const_structrp png_ptr, png_const_charp error_message);

/* The same, but the chunk name is prepended to the error string. */
void png_chunk_error(png_const_structrp png_ptr,
    png_const_charp error_mes);

}else{
/* Fatal error in PNG image of libpng - can't continue */
void png_err(png_const_structrp png);
void png_error(S1, S2) (S1 s1, S2 s2) { png_err(s1); }
void png_chunk_error(S1, S2) (S1 s1, S2 s2) { png_err(s1); }
}

static if(PNG_WARNINGS_SUPPORTED){
/* Non-fatal error in libpng.  Can continue, but may have a problem. */
void png_warning(png_const_structrp png_ptr,
    png_const_charp warning_message);

/* Non-fatal error in libpng, chunk name is prepended to message. */
void png_chunk_warning(png_const_structrp png_ptr,
    png_const_charp warning_message);
}
else {
void png_warning(S1, S2)(S1 s1, S2 s2) {}
void png_chunk_warning(S1, S2)(S1 s1, S2 s2) {}
}

static if(PNG_BENIGN_ERRORS_SUPPORTED){
/* Benign error in libpng.  Can continue, but may have a problem.
 * User can choose whether to handle as a fatal error or as a warning. */
//#  undef png_benign_error
void png_benign_error(png_const_structrp png_ptr,
    png_const_charp warning_message);

static if(PNG_READ_SUPPORTED) {
/* Same, chunk name is prepended to message (only during read) */
void png_chunk_benign_error (png_const_structrp png_ptr,
    png_const_charp warning_message);
}

void png_set_benign_errors
    (png_structrp png_ptr, int allowed);
}else{
  version(PNG_ALLOW_BENIGN_ERRORS){
    alias png_benign_error = png_warning;
    alias png_chunk_benign_error = png_chunk_warning;
  }else{
    alias png_benign_error = png_error;
    alias png_chunk_benign_error = png_chunk_error;
  }
}

/* The png_set_<chunk> functions are for storing values in the png_info_struct.
 * Similarly, the png_get_<chunk> calls are used to read values from the
 * png_info_struct, either storing the parameters in the passed variables, or
 * setting pointers into the png_info_struct where the data is stored.  The
 * png_get_<chunk> functions return a non-zero value if the data was available
 * in info_ptr, or return zero and do not change any of the parameters if the
 * data was not available.
 *
 * These functions should be used instead of directly accessing png_info
 * to avoid problems with future changes in the size and internal layout of
 * png_info_struct.
 */
/* Returns "flag" if chunk data is valid in info_ptr. */
uint png_get_valid
    (png_const_structrp png_ptr, png_const_inforp info_ptr,
    uint flag);

/* Returns number of bytes needed to hold a transformed row. */
size_t png_get_rowbytes(png_const_structrp png_ptr,
    png_const_inforp info_ptr);

static if(PNG_INFO_IMAGE_SUPPORTED){
/* Returns row_pointers, which is an array of pointers to scanlines that was
 * returned from png_read_png().
 */
png_bytepp png_get_rows
    (png_const_structrp png_ptr, png_const_inforp info_ptr);
/* Set row_pointers, which is an array of pointers to scanlines for use
 * by png_write_png().
 */
void png_set_rows(png_const_structrp png_ptr,
    png_inforp info_ptr, png_bytepp row_pointers);
}

/* Returns number of color channels in image. */
png_byte png_get_channels
    (png_const_structrp png_ptr, png_const_inforp info_ptr);

static if(PNG_EASY_ACCESS_SUPPORTED){
/* Returns image width in pixels. */
uint png_get_image_width(png_const_structrp png_ptr,
    png_const_inforp info_ptr);

/* Returns image height in pixels. */
uint png_get_image_height(png_const_structrp png_ptr,
    png_const_inforp info_ptr);

/* Returns image bit_depth. */
png_byte png_get_bit_depth
    (png_const_structrp png_ptr, png_const_inforp info_ptr);

/* Returns image color_type. */
png_byte png_get_color_type(png_const_structrp png_ptr,
    png_const_inforp info_ptr);

/* Returns image filter_type. */
png_byte png_get_filter_type(png_const_structrp png_ptr,
    png_const_inforp info_ptr);

/* Returns image interlace_type. */
png_byte png_get_interlace_type(png_const_structrp png_ptr,
    png_const_inforp info_ptr);

/* Returns image compression_type. */
png_byte png_get_compression_type(png_const_structrp png_ptr,
    png_const_inforp info_ptr);

/* Returns image resolution in pixels per meter, from pHYs chunk data. */
uint png_get_pixels_per_meter
    (png_const_structrp png_ptr, png_const_inforp info_ptr);
uint png_get_x_pixels_per_meter
    (png_const_structrp png_ptr, png_const_inforp info_ptr);
uint png_get_y_pixels_per_meter
    (png_const_structrp png_ptr, png_const_inforp info_ptr);

/* Returns pixel aspect ratio, computed from pHYs chunk data.  */
float png_get_pixel_aspect_ratio
    (png_const_structrp png_ptr, png_const_inforp info_ptr);
png_fixed_point png_get_pixel_aspect_ratio_fixed
    (png_const_structrp png_ptr, png_const_inforp info_ptr);

/* Returns image x, y offset in pixels or microns, from oFFs chunk data. */
png_int_32 png_get_x_offset_pixels
    (png_const_structrp png_ptr, png_const_inforp info_ptr);
png_int_32 png_get_y_offset_pixels
    (png_const_structrp png_ptr, png_const_inforp info_ptr);
png_int_32 png_get_x_offset_microns
    (png_const_structrp png_ptr, png_const_inforp info_ptr);
png_int_32 png_get_y_offset_microns
    (png_const_structrp png_ptr, png_const_inforp info_ptr);

} /* PNG_EASY_ACCESS_SUPPORTED */

static if(PNG_READ_SUPPORTED) {
/* Returns pointer to signature string read from PNG header */
png_const_bytep png_get_signature
    (png_const_structrp png_ptr, png_const_inforp info_ptr);
}

static if(PNG_bKGD_SUPPORTED){
uint png_get_bKGD
    (png_const_structrp png_ptr, png_inforp info_ptr,
    png_color_16p *background);
}

static if(PNG_bKGD_SUPPORTED){
void png_set_bKGD(png_const_structrp png_ptr, png_inforp info_ptr,
    png_const_color_16p background);
}

static if(PNG_cHRM_SUPPORTED){
png_uint_32 png_get_cHRM(png_const_structrp png_ptr,
   png_const_inforp info_ptr, double *white_x, double *white_y, double *red_x,
    double *red_y, double *green_x, double *green_y, double *blue_x,
    double *blue_y);
png_uint_32 png_get_cHRM_XYZ(png_const_structrp png_ptr,
    png_const_inforp info_ptr, double *red_X, double *red_Y, double *red_Z,
    double *green_X, double *green_Y, double *green_Z, double *blue_X,
    double *blue_Y, double *blue_Z);
static if(PNG_FIXED_POINT_SUPPORTED){ /* Otherwise not implemented */
uint png_get_cHRM_fixed
    (png_const_structrp png_ptr,
    png_const_inforp info_ptr, png_fixed_point *int_white_x,
    png_fixed_point *int_white_y, png_fixed_point *int_red_x,
    png_fixed_point *int_red_y, png_fixed_point *int_green_x,
    png_fixed_point *int_green_y, png_fixed_point *int_blue_x,
    png_fixed_point *int_blue_y);
}
uint png_get_cHRM_XYZ_fixed
    (png_const_structrp png_ptr, png_const_inforp info_ptr,
    png_fixed_point *int_red_X, png_fixed_point *int_red_Y,
    png_fixed_point *int_red_Z, png_fixed_point *int_green_X,
    png_fixed_point *int_green_Y, png_fixed_point *int_green_Z,
    png_fixed_point *int_blue_X, png_fixed_point *int_blue_Y,
    png_fixed_point *int_blue_Z);
}

static if(PNG_cHRM_SUPPORTED){
void png_set_cHRM
    (png_const_structrp png_ptr, png_inforp info_ptr,
    double white_x, double white_y, double red_x, double red_y, double green_x,
    double green_y, double blue_x, double blue_y);
void png_set_cHRM_XYZ(png_const_structrp png_ptr,
    png_inforp info_ptr, double red_X, double red_Y, double red_Z,
    double green_X, double green_Y, double green_Z, double blue_X,
    double blue_Y, double blue_Z);
void png_set_cHRM_fixed(png_const_structrp png_ptr,
    png_inforp info_ptr, png_fixed_point int_white_x,
    png_fixed_point int_white_y, png_fixed_point int_red_x,
    png_fixed_point int_red_y, png_fixed_point int_green_x,
    png_fixed_point int_green_y, png_fixed_point int_blue_x,
    png_fixed_point int_blue_y);
void png_set_cHRM_XYZ_fixed(png_const_structrp png_ptr,
    png_inforp info_ptr, png_fixed_point int_red_X, png_fixed_point int_red_Y,
    png_fixed_point int_red_Z, png_fixed_point int_green_X,
    png_fixed_point int_green_Y, png_fixed_point int_green_Z,
    png_fixed_point int_blue_X, png_fixed_point int_blue_Y,
    png_fixed_point int_blue_Z);
}

static if(PNG_eXIf_SUPPORTED){
png_uint_32 png_get_eXIf
    (png_const_structrp png_ptr, png_inforp info_ptr, png_bytep *exif);
void png_set_eXIf
    (png_const_structrp png_ptr, png_inforp info_ptr, png_bytep exif);

png_uint_32 png_get_eXIf_1
    (png_const_structrp png_ptr, png_const_inforp info_ptr, png_uint_32 *num_exif, png_bytep *exif);
void png_set_eXIf_1
    (png_const_structrp png_ptr, png_inforp info_ptr, png_uint_32 num_exif, png_bytep exif);
}

static if(PNG_gAMA_SUPPORTED){
png_uint_32 png_get_gAMA
    (png_const_structrp png_ptr, png_const_inforp info_ptr,
    double *file_gamma);
uint png_get_gAMA_fixed
    (png_const_structrp png_ptr, png_const_inforp info_ptr,
    png_fixed_point *int_file_gamma);
}

static if(PNG_gAMA_SUPPORTED){
void png_set_gAMA(png_const_structrp png_ptr,
    png_inforp info_ptr, double file_gamma);
void png_set_gAMA_fixed(png_const_structrp png_ptr,
    png_inforp info_ptr, png_fixed_point int_file_gamma);
}

static if(PNG_hIST_SUPPORTED){
uint png_get_hIST
    (png_const_structrp png_ptr, png_const_inforp info_ptr,
    png_uint_16p *hist);

void png_set_hIST(png_const_structrp png_ptr,
    png_inforp info_ptr, png_const_uint_16p hist);
}

uint png_get_IHDR
    (png_const_structrp png_ptr, png_const_inforp info_ptr,
    uint *width, uint *height, int *bit_depth, int *color_type,
    int *interlace_method, int *compression_method, int *filter_method);

void png_set_IHDR
    (png_const_structrp png_ptr, png_inforp info_ptr,
    uint width, uint height, int bit_depth, int color_type,
    int interlace_method, int compression_method, int filter_method);

static if(PNG_oFFs_SUPPORTED){
uint png_get_oFFs
    (png_const_structrp png_ptr, png_const_inforp info_ptr,
    png_int_32 *offset_x, png_int_32 *offset_y, int *unit_type);
}

static if(PNG_oFFs_SUPPORTED){
void png_set_oFFs
    (png_const_structrp png_ptr, png_inforp info_ptr,
    png_int_32 offset_x, png_int_32 offset_y, int unit_type);
}

static if(PNG_pCAL_SUPPORTED){
uint png_get_pCAL
    (png_const_structrp png_ptr, png_inforp info_ptr,
    png_charp *purpose, png_int_32 *X0, png_int_32 *X1, int *type,
    int *nparams,
    png_charp *units, png_charpp *params);
}

static if(PNG_pCAL_SUPPORTED){
void png_set_pCAL(png_const_structrp png_ptr,
    png_inforp info_ptr,
    png_const_charp purpose, png_int_32 X0, png_int_32 X1, int type,
    int nparams, png_const_charp units, png_charpp params);
}

static if(PNG_pHYs_SUPPORTED){
uint png_get_pHYs
    (png_const_structrp png_ptr, png_const_inforp info_ptr,
    uint *res_x, uint *res_y, int *unit_type);
}

static if(PNG_pHYs_SUPPORTED){
void png_set_pHYs
    (png_const_structrp png_ptr, png_inforp info_ptr,
    uint res_x, uint res_y, int unit_type);
}

uint png_get_PLTE
    (png_const_structrp png_ptr, png_inforp info_ptr,
    png_colorp *palette, int *num_palette);

void png_set_PLTE
    (png_structrp png_ptr, png_inforp info_ptr,
    png_const_colorp palette, int num_palette);

static if(PNG_sBIT_SUPPORTED){
uint png_get_sBIT
    (png_const_structrp png_ptr, png_inforp info_ptr,
    png_color_8p *sig_bit);
}

static if(PNG_sBIT_SUPPORTED){
void png_set_sBIT
    (png_const_structrp png_ptr, png_inforp info_ptr, png_const_color_8p sig_bit);
}

static if(PNG_sRGB_SUPPORTED){
uint png_get_sRGB(png_const_structrp png_ptr,
    png_const_inforp info_ptr, int *file_srgb_intent);
}

static if(PNG_sRGB_SUPPORTED){
void png_set_sRGB
    (png_const_structrp png_ptr, png_inforp info_ptr, int srgb_intent);
void png_set_sRGB_gAMA_and_cHRM(png_const_structrp png_ptr,
    png_inforp info_ptr, int srgb_intent);
}

static if(PNG_iCCP_SUPPORTED){
uint png_get_iCCP
    (png_const_structrp png_ptr, png_inforp info_ptr,
    png_charpp name, int *compression_type, png_bytepp profile,
    uint *proflen);
}

static if(PNG_iCCP_SUPPORTED){
void png_set_iCCP
    (png_const_structrp png_ptr, png_inforp info_ptr,
    png_const_charp name, int compression_type, png_const_bytep profile,
    uint proflen);
}

static if(PNG_sPLT_SUPPORTED){
uint png_get_sPLT
    (png_const_structrp png_ptr, png_inforp info_ptr,
    png_sPLT_tpp entries);
}

static if(PNG_sPLT_SUPPORTED){
void png_set_sPLT
    (png_const_structrp png_ptr, png_inforp info_ptr,
    png_const_sPLT_tp entries, int nentries);
}

static if(PNG_TEXT_SUPPORTED){
/* png_get_text also returns the number of text chunks in *num_text */
uint png_get_text
    (png_const_structrp png_ptr, png_inforp info_ptr,
    png_textp *text_ptr, int *num_text);
}

/* Note while png_set_text() will accept a structure whose text,
 * language, and  translated keywords are NULL pointers, the structure
 * returned by png_get_text will always contain regular
 * zero-terminated C strings.  They might be empty strings but
 * they will never be NULL pointers.
 */

static if(PNG_TEXT_SUPPORTED){
void png_set_text
    (png_const_structrp png_ptr, png_inforp info_ptr,
    png_const_textp text_ptr, int num_text);
}

static if(PNG_tIME_SUPPORTED){
uint png_get_tIME
    (png_const_structrp png_ptr, png_inforp info_ptr, png_timep *mod_time);
}

static if(PNG_tIME_SUPPORTED){
void png_set_tIME
    (png_const_structrp png_ptr, png_inforp info_ptr, png_const_timep mod_time);
}

static if(PNG_tRNS_SUPPORTED){
uint png_get_tRNS
    (png_const_structrp png_ptr, png_inforp info_ptr,
    png_bytep *trans_alpha, int *num_trans, png_color_16p *trans_color);
}

static if(PNG_tRNS_SUPPORTED){
void png_set_tRNS
    (png_structrp png_ptr, png_inforp info_ptr,
    png_const_bytep trans_alpha, int num_trans,
    png_const_color_16p trans_color);
}

static if(PNG_sCAL_SUPPORTED){
png_uint_32 png_get_sCAL
    (png_const_structrp png_ptr, png_const_inforp info_ptr,
    int *unit, double *width, double *height);
static if(PNG_FLOATING_ARITHMETIC_SUPPORTED || PNG_FLOATING_POINT_SUPPORTED){
/* NOTE: this API is currently implemented using floating point arithmetic,
 * consequently it can only be used on systems with floating point support.
 * In any case the range of values supported by png_fixed_point is small and it
 * is highly recommended that png_get_sCAL_s be used instead.
 */
uint png_get_sCAL_fixed
    (png_const_structrp png_ptr, png_const_inforp info_ptr, int *unit,
    png_fixed_point *width,
    png_fixed_point *height);
}
uint png_get_sCAL_s
    (png_const_structrp png_ptr, png_const_inforp info_ptr,
    int *unit, png_charpp swidth, png_charpp sheight);

void png_set_sCAL
    (png_const_structrp png_ptr, png_inforp info_ptr,
    int unit, double width, double height);
void png_const_set_sCAL_fixed (png_structrp png_ptr,
   png_inforp info_ptr, int unit, png_fixed_point width,
   png_fixed_point height);
void png_set_sCAL_s
    (png_const_structrp png_ptr, png_inforp info_ptr,
    int unit, png_const_charp swidth, png_const_charp sheight);
} /* PNG_sCAL_SUPPORTED */

static if(PNG_SET_UNKNOWN_CHUNKS_SUPPORTED){
/* Provide the default handling for all unknown chunks or, optionally, for
 * specific unknown chunks.
 *
 * NOTE: prior to 1.6.0 the handling specified for particular chunks on read was
 * ignored and the default was used, the per-chunk setting only had an effect on
 * write.  If you wish to have chunk-specific handling on read in code that must
 * work on earlier versions you must use a user chunk callback to specify the
 * desired handling (keep or discard.)
 *
 * The 'keep' parameter is a PNG_HANDLE_CHUNK_ value as listed below.  The
 * parameter is interpreted as follows:
 *
 * READ:
 *    PNG_HANDLE_CHUNK_AS_DEFAULT:
 *       Known chunks: do normal libpng processing, do not keep the chunk (but
 *          see the comments below about PNG_HANDLE_AS_UNKNOWN_SUPPORTED)
 *       Unknown chunks: for a specific chunk use the global default, when used
 *          as the default discard the chunk data.
 *    PNG_HANDLE_CHUNK_NEVER:
 *       Discard the chunk data.
 *    PNG_HANDLE_CHUNK_IF_SAFE:
 *       Keep the chunk data if the chunk is not critical else raise a chunk
 *       error.
 *    PNG_HANDLE_CHUNK_ALWAYS:
 *       Keep the chunk data.
 *
 * If the chunk data is saved it can be retrieved using png_get_unknown_chunks,
 * below.  Notice that specifying "AS_DEFAULT" as a global default is equivalent
 * to specifying "NEVER", however when "AS_DEFAULT" is used for specific chunks
 * it simply resets the behavior to the libpng default.
 *
 * INTERACTION WITH USER CHUNK CALLBACKS:
 * The per-chunk handling is always used when there is a png_user_chunk_ptr
 * callback and the callback returns 0; the chunk is then always stored *unless*
 * it is critical and the per-chunk setting is other than ALWAYS.  Notice that
 * the global default is *not* used in this case.  (In effect the per-chunk
 * value is incremented to at least IF_SAFE.)
 *
 * IMPORTANT NOTE: this behavior will change in libpng 1.7 - the global and
 * per-chunk defaults will be honored.  If you want to preserve the current
 * behavior when your callback returns 0 you must set PNG_HANDLE_CHUNK_IF_SAFE
 * as the default - if you don't do this libpng 1.6 will issue a warning.
 *
 * If you want unhandled unknown chunks to be discarded in libpng 1.6 and
 * earlier simply return '1' (handled).
 *
 * PNG_HANDLE_AS_UNKNOWN_SUPPORTED:
 *    If this is *not* set known chunks will always be handled by libpng and
 *    will never be stored in the unknown chunk list.  Known chunks listed to
 *    png_set_keep_unknown_chunks will have no effect.  If it is set then known
 *    chunks listed with a keep other than AS_DEFAULT will *never* be processed
 *    by libpng, in addition critical chunks must either be processed by the
 *    callback or saved.
 *
 *    The IHDR and IEND chunks must not be listed.  Because this turns off the
 *    default handling for chunks that would otherwise be recognized the
 *    behavior of libpng transformations may well become incorrect!
 *
 * WRITE:
 *    When writing chunks the options only apply to the chunks specified by
 *    png_set_unknown_chunks (below), libpng will *always* write known chunks
 *    required by png_set_ calls and will always write the core critical chunks
 *    (as required for PLTE).
 *
 *    Each chunk in the png_set_unknown_chunks list is looked up in the
 *    png_set_keep_unknown_chunks list to find the keep setting, this is then
 *    interpreted as follows:
 *
 *    PNG_HANDLE_CHUNK_AS_DEFAULT:
 *       Write safe-to-copy chunks and write other chunks if the global
 *       default is set to _ALWAYS, otherwise don't write this chunk.
 *    PNG_HANDLE_CHUNK_NEVER:
 *       Do not write the chunk.
 *    PNG_HANDLE_CHUNK_IF_SAFE:
 *       Write the chunk if it is safe-to-copy, otherwise do not write it.
 *    PNG_HANDLE_CHUNK_ALWAYS:
 *       Write the chunk.
 *
 * Note that the default behavior is effectively the opposite of the read case -
 * in read unknown chunks are not stored by default, in write they are written
 * by default.  Also the behavior of PNG_HANDLE_CHUNK_IF_SAFE is very different
 * - on write the safe-to-copy bit is checked, on read the critical bit is
 * checked and on read if the chunk is critical an error will be raised.
 *
 * num_chunks:
 * ===========
 *    If num_chunks is positive, then the "keep" parameter specifies the manner
 *    for handling only those chunks appearing in the chunk_list array,
 *    otherwise the chunk list array is ignored.
 *
 *    If num_chunks is 0 the "keep" parameter specifies the default behavior for
 *    unknown chunks, as described above.
 *
 *    If num_chunks is negative, then the "keep" parameter specifies the manner
 *    for handling all unknown chunks plus all chunks recognized by libpng
 *    except for the IHDR, PLTE, tRNS, IDAT, and IEND chunks (which continue to
 *    be processed by libpng.
 */
static if (PNG_HANDLE_AS_UNKNOWN_SUPPORTED){
void png_set_keep_unknown_chunks
    (png_structrp png_ptr, int keep,
    png_const_bytep chunk_list, int num_chunks);
} /* HANDLE_AS_UNKNOWN */

/* The "keep" PNG_HANDLE_CHUNK_ parameter for the specified chunk is returned;
 * the result is therefore true (non-zero) if special handling is required,
 * false for the default handling.
 */
int png_handle_as_unknown(png_const_structrp png_ptr,
    png_const_bytep chunk_name);
} /* SET_UNKNOWN_CHUNKS */
static if(PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED){
void png_set_unknown_chunks(png_const_structrp png_ptr,
    png_inforp info_ptr, png_const_unknown_chunkp unknowns,
    int num_unknowns);
   /* NOTE: prior to 1.6.0 this routine set the 'location' field of the added
    * unknowns to the location currently stored in the png_struct.  This is
    * invariably the wrong value on write.  To fix this call the following API
    * for each chunk in the list with the correct location.  If you know your
    * code won't be compiled on earlier versions you can rely on
    * png_set_unknown_chunks(write-ptr, png_get_unknown_chunks(read-ptr)) doing
    * the correct thing.
    */

void png_set_unknown_chunk_location
    (png_const_structrp png_ptr, png_inforp info_ptr, int chunk, int location);

int png_get_unknown_chunks(png_const_structrp png_ptr,
    png_inforp info_ptr, png_unknown_chunkpp entries);
}

/* Png_free_data() will turn off the "valid" flag for anything it frees.
 * If you need to turn it off for a chunk that your application has freed,
 * you can use png_set_invalid(png_ptr, info_ptr, PNG_INFO_CHNK);
 */
void png_set_invalid
    (png_const_structrp png_ptr, png_inforp info_ptr, int mask);

static if(PNG_INFO_IMAGE_SUPPORTED){
/* The "params" pointer is currently not used and is for future expansion. */
static if(PNG_SEQUENTIAL_READ_SUPPORTED){
void png_read_png(png_structrp png_ptr, png_inforp info_ptr,
    int transforms, png_voidp params);
}
static if(PNG_WRITE_SUPPORTED){
void png_write_png(png_structrp png_ptr, png_inforp info_ptr,
    int transforms, png_voidp params);
}
}

png_const_charp png_get_copyright
    (png_const_structrp png_ptr);
png_const_charp png_get_header_ver
    (png_const_structrp png_ptr);
png_const_charp png_get_header_version
    (png_const_structrp png_ptr);
png_const_charp png_get_libpng_ver
    (png_const_structrp png_ptr);

static if(PNG_MNG_FEATURES_SUPPORTED){
uint png_permit_mng_features(png_structrp png_ptr,
    uint mng_features_permitted);
}

/* For use in png_set_keep_unknown, added to version 1.2.6 */
enum PNG_HANDLE_CHUNK_AS_DEFAULT = 0;
enum PNG_HANDLE_CHUNK_NEVER = 1;
enum PNG_HANDLE_CHUNK_IF_SAFE = 2;
enum PNG_HANDLE_CHUNK_ALWAYS = 3;
enum PNG_HANDLE_CHUNK_LAST = 4;

/* Strip the prepended error numbers ("#nnn ") from error and warning
 * messages before passing them to the error or warning handler.
 */
static if(PNG_ERROR_NUMBERS_SUPPORTED){
void png_set_strip_error_numbers
    (png_structrp png_ptr,
    uint strip_mode);
}

/* Added in libpng-1.2.6 */
static if(PNG_SET_USER_LIMITS_SUPPORTED){
void png_set_user_limits(png_structrp png_ptr,
    uint user_width_max, uint user_height_max);
uint png_get_user_width_max
    (png_const_structrp png_ptr);
uint png_get_user_height_max
    (png_const_structrp png_ptr);
/* Added in libpng-1.4.0 */
void png_set_chunk_cache_max(png_structrp png_ptr,
    uint user_chunk_cache_max);
uint png_get_chunk_cache_max
    (png_const_structrp png_ptr);
/* Added in libpng-1.4.1 */
void png_set_chunk_malloc_max(png_structrp png_ptr,
    png_alloc_size_t user_chunk_cache_max);
png_alloc_size_t png_get_chunk_malloc_max
    (png_const_structrp png_ptr);
}

static if(PNG_INCH_CONVERSIONS_SUPPORTED){
uint png_get_pixels_per_inch
    (png_const_structrp png_ptr, png_const_inforp info_ptr);

uint png_get_x_pixels_per_inch
    (png_const_structrp png_ptr, png_const_inforp info_ptr);

uint png_get_y_pixels_per_inch
    (png_const_structrp png_ptr, png_const_inforp info_ptr);

float png_get_x_offset_inches
    (png_const_structrp png_ptr, png_const_inforp info_ptr);
static if(PNG_FIXED_POINT_SUPPORTED){ /* otherwise not implemented. */
png_fixed_point png_get_x_offset_inches_fixed
    (png_const_structrp png_ptr, png_const_inforp info_ptr);
}

float png_get_y_offset_inches(png_const_structrp png_ptr,
    png_const_inforp info_ptr);
static if(PNG_FIXED_POINT_SUPPORTED){ /* otherwise not implemented. */
png_fixed_point png_get_y_offset_inches_fixed
    (png_const_structrp png_ptr, png_const_inforp info_ptr);
}

static if(PNG_pHYs_SUPPORTED){
uint png_get_pHYs_dpi(png_const_structrp png_ptr,
    png_const_inforp info_ptr, uint *res_x, uint *res_y,
    int *unit_type);
} /* PNG_pHYs_SUPPORTED */
}  /* PNG_INCH_CONVERSIONS_SUPPORTED */

/* Added in libpng-1.4.0 */
static if(PNG_IO_STATE_SUPPORTED){
uint png_get_io_state(png_const_structrp png_ptr);

/* Removed from libpng 1.6; use png_get_io_chunk_type. */
/* deprecated png_const_bytep png_get_io_chunk_name
    (png_structrp png_ptr); */
uint png_get_io_chunk_type
    (png_const_structrp png_ptr);

/* The flags returned by png_get_io_state() are the following: */
enum PNG_IO_NONE = 0x0000;   /* no I/O at this moment */
enum PNG_IO_READING = 0x0001;   /* currently reading */
enum PNG_IO_WRITING = 0x0002;   /* currently writing */
enum PNG_IO_SIGNATURE = 0x0010;   /* currently at the file signature */
enum PNG_IO_CHUNK_HDR = 0x0020;   /* currently at the chunk header */
enum PNG_IO_CHUNK_DATA = 0x0040;   /* currently at the chunk data */
enum PNG_IO_CHUNK_CRC = 0x0080;   /* currently at the chunk crc */
enum PNG_IO_MASK_OP = 0x000f;   /* current operation: reading/writing */
enum PNG_IO_MASK_LOC = 0x00f0;   /* current location: sig/hdr/data/crc */
} /* ?PNG_IO_STATE_SUPPORTED */

/* Interlace support.  The following macros are always defined so that if
 * libpng interlace handling is turned off the macros may be used to handle
 * interlaced images within the application.
 */
enum PNG_INTERLACE_ADAM7_PASSES = 7;

/* Two macros to return the first row and first column of the original,
 * full, image which appears in a given pass.  'pass' is in the range 0
 * to 6 and the result is in the range 0 to 7.
 */
auto PNG_PASS_START_ROW(T)(T pass) { return (((1&~(pass))<<(3-((pass)>>1)))&7); }
auto PNG_PASS_START_COL(T)(T pass) { return (((1& (pass))<<(3-(((pass)+1)>>1)))&7); }

/* A macro to return the offset between pixels in the output row for a pair of
 * pixels in the input - effectively the inverse of the 'COL_SHIFT' macro that
 * follows.  Note that ROW_OFFSET is the offset from one row to the next whereas
 * COL_OFFSET is from one column to the next, within a row.
 */
auto PNG_PASS_ROW_OFFSET(T)(T pass) { return ((pass)>2?(8>>(((pass)-1)>>1)):8); }
auto PNG_PASS_COL_OFFSET(T)(T pass) { return (1<<((7-(pass))>>1)); }

/* Two macros to help evaluate the number of rows or columns in each
 * pass.  This is expressed as a shift - effectively log2 of the number or
 * rows or columns in each 8x8 tile of the original image.
 */
auto PNG_PASS_ROW_SHIFT(T)(T pass) { return ((pass)>2?(8-(pass))>>1:3); }
auto PNG_PASS_COL_SHIFT(T)(T pass) { return ((pass)>1?(7-(pass))>>1:3); }

/* Hence two macros to determine the number of rows or columns in a given
 * pass of an image given its height or width.  In fact these macros may
 * return non-zero even though the sub-image is empty, because the other
 * dimension may be empty for a small image.
 */
auto PNG_PASS_ROWS(S,T)(S height, T pass) { return (((height)+(((1<<PNG_PASS_ROW_SHIFT(pass))
   -1)-PNG_PASS_START_ROW(pass)))>>PNG_PASS_ROW_SHIFT(pass)); }
auto PNG_PASS_COLS(S,T)(S width, T pass) { return (((width)+(((1<<PNG_PASS_COL_SHIFT(pass))
   -1)-PNG_PASS_START_COL(pass)))>>PNG_PASS_COL_SHIFT(pass)); }

/* For the reader row callbacks (both progressive and sequential) it is
 * necessary to find the row in the output image given a row in an interlaced
 * image, so two more macros:
 */
auto PNG_ROW_FROM_PASS_ROW(S,T)(S y_in, T pass) { return
   (((y_in)<<PNG_PASS_ROW_SHIFT(pass))+PNG_PASS_START_ROW(pass)); }
auto PNG_COL_FROM_PASS_COL(S,T)(S x_in, T pass) { return
   (((x_in)<<PNG_PASS_COL_SHIFT(pass))+PNG_PASS_START_COL(pass)); }

/* Two macros which return a boolean (0 or 1) saying whether the given row
 * or column is in a particular pass.  These use a common utility macro that
 * returns a mask for a given pass - the offset 'off' selects the row or
 * column version.  The mask has the appropriate bit set for each column in
 * the tile.
 */
auto PNG_PASS_MASK(S,T)(S pass,T off) { return (
   ((0x110145AF>>(((7-(off))-(pass))<<2)) & 0xF) |
   ((0x01145AF0>>(((7-(off))-(pass))<<2)) & 0xF0)); }

auto PNG_ROW_IN_INTERLACE_PASS(T)(y, pass) { return
   ((PNG_PASS_MASK(pass,0) >> ((y)&7)) & 1); }
auto PNG_COL_IN_INTERLACE_PASS(T)(x, pass) { return
   ((PNG_PASS_MASK(pass,1) >> ((x)&7)) & 1); }

static if(PNG_READ_COMPOSITE_NODIV_SUPPORTED){
/* With these routines we avoid an integer divide, which will be slower on
 * most machines.  However, it does take more operations than the corresponding
 * divide method, so it may be slower on a few RISC systems.  There are two
 * shifts (by 8 or 16 bits) and an addition, versus a single integer divide.
 *
 * Note that the rounding factors are NOT supposed to be the same!  128 and
 * 32768 are correct for the NODIV code; 127 and 32767 are correct for the
 * standard method.
 *
 * [Optimized code by Greg Roelofs and Mark Adler...blame us for bugs. :-) ]
 */

 /* fg and bg should be in `gamma 1.0' space; alpha is the opacity */

static assert(0);

}else{  /* Standard method using integer division */

  auto png_composite(T)(out T composite, png_uint_16 fg, png_uint_16 alpha, png_uint_16 bg) {
     return (composite) = cast(png_byte)(((fg) * (alpha) +
     (bg) * (255 - (alpha)) +
     127) / 255); }

  auto png_composite_16(T)(out T composite, uint fg, uint alpha, uint bg) {
     return (composite) = cast(png_uint_16)(((fg) * (alpha) +
     (bg)*(65535 - (alpha)) +
     32767) / 65535); }
} /* PNG_READ_COMPOSITE_NODIV_SUPPORTED */

static if(PNG_READ_INT_FUNCTIONS_SUPPORTED){
png_uint_32 png_get_uint_32(png_const_bytep buf);
png_uint_16 png_get_uint_16(png_const_bytep buf);
png_int_32 png_get_int_32(png_const_bytep buf);
}

uint png_get_uint_31(png_const_structrp png_ptr,
    png_const_bytep buf);
/* No png_get_int_16 -- may be added if there's a real need for it. */

/* Place a 32-bit number into a buffer in PNG byte order (big-endian). */
static if(PNG_WRITE_INT_FUNCTIONS_SUPPORTED){
void png_save_uint_32(png_bytep buf, uint i);
}
static if(PNG_SAVE_INT_32_SUPPORTED){
void png_save_int_32(png_bytep buf, png_int_32 i);
}

/* Place a 16-bit number into a buffer in PNG byte order.
 * The parameter is declared unsigned int, not png_uint_16,
 * just to avoid potential problems on pre-ANSI C compilers.
 */
static if(PNG_WRITE_INT_FUNCTIONS_SUPPORTED){
void png_save_uint_16(png_bytep buf, uint i);
/* No png_save_int_16 -- may be added if there's a real need for it. */
}

version(PNG_USE_READ_MACROS){
/* Inline macros to do direct reads of bytes from the input buffer.
 * The png_get_int_32() routine assumes we are using two's complement
 * format for negative values, which is almost certainly true.
 */
    auto PNG_get_uint_32(png_const_bytep buf) pure { return
     ((cast(uint)(*(buf)) << 24) +
      (cast(uint)(*((buf) + 1)) << 16) +
      (cast(uint)(*((buf) + 2)) << 8) +
      (cast(uint)(*((buf) + 3)))); }

   /* From libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the
    * function) incorrectly returned a value of type uint.
    */
	auto PNG_get_uint_16(png_const_bytep buf) pure { return
     (cast(png_uint_16)
      ((cast(uint)(*(buf)) << 8) +
       (cast(uint)(*((buf) + 1))))); }

	auto PNG_get_int_32(T)(png_const_bytep buf) pure { return
     (cast(png_int_32)((*(buf) & 0x80)
      ? -(cast(png_int_32)(((png_get_uint_32(buf) ^ 0xffffffffU) + 1U) & 0x7fffffffU))
      : cast(png_int_32)png_get_uint_32(buf))); }

    static if (!PNG_PREFIX){
        auto png_get_uint_32(S)(S s) pure { return PNG_get_uint_32(s); }
        auto png_get_uint_16(S)(S s) pure { return PNG_get_uint_16(s); }
        auto png_get_int_32(S)(S s) pure { return PNG_get_int_32(s); }
    }
}
else {
    auto PNG_get_uint_32(S)(S s) pure { return png_get_uint_32(s); }
    auto PNG_get_uint_16(S)(S s) pure { return png_get_uint_16(s); }
    auto PNG_get_int_32(S)(S s) pure { return png_get_int_32(s); }
}

static if(PNG_CHECK_FOR_INVALID_INDEX_SUPPORTED){
void png_set_check_for_invalid_index(png_structp png_ptr, int allowed);
static if(PNG_GET_PALETTE_MAX_SUPPORTED){
int png_get_palette_max(png_const_structrp png_ptr, png_const_infop info_ptr);
}
} /* CHECK_FOR_INVALID_INDEX */

/*******************************************************************************
 * Section 5: SIMPLIFIED API
 *******************************************************************************
 *
 * Please read the documentation in libpng-manual.txt (TODO: write said
 * documentation) if you don't understand what follows.
 *
 * The simplified API hides the details of both libpng and the PNG file format
 * itself.  It allows PNG files to be read into a very limited number of
 * in-memory bitmap formats or to be written from the same formats.  If these
 * formats do not accommodate your needs then you can, and should, use the more
 * sophisticated APIs above - these support a wide variety of in-memory formats
 * and a wide variety of sophisticated transformations to those formats as well
 * as a wide variety of APIs to manipulate ancillary information.
 *
 * To read a PNG file using the simplified API:
 *
 * 1) Declare a 'png_image' structure (see below) on the stack, set the
 *    version field to PNG_IMAGE_VERSION and the 'opaque' pointer to NULL
 *    (this is REQUIRED, your program may crash if you don't do it.)
 * 2) Call the appropriate png_image_begin_read... function.
 * 3) Set the png_image 'format' member to the required sample format.
 * 4) Allocate a buffer for the image and, if required, the color-map.
 * 5) Call png_image_finish_read to read the image and, if required, the
 *    color-map into your buffers.
 *
 * There are no restrictions on the format of the PNG input itself; all valid
 * color types, bit depths, and interlace methods are acceptable, and the
 * input image is transformed as necessary to the requested in-memory format
 * during the png_image_finish_read() step.  The only caveat is that if you
 * request a color-mapped image from a PNG that is full-color or makes
 * complex use of an alpha channel the transformation is extremely lossy and the
 * result may look terrible.
 *
 * To write a PNG file using the simplified API:
 *
 * 1) Declare a 'png_image' structure on the stack and memset() it to all zero.
 * 2) Initialize the members of the structure that describe the image, setting
 *    the 'format' member to the format of the image samples.
 * 3) Call the appropriate png_image_write... function with a pointer to the
 *    image and, if necessary, the color-map to write the PNG data.
 *
 * png_image is a structure that describes the in-memory format of an image
 * when it is being read or defines the in-memory format of an image that you
 * need to write:
 */
static if (PNG_SIMPLIFIED_READ_SUPPORTED ||
    PNG_SIMPLIFIED_WRITE_SUPPORTED) {

enum PNG_IMAGE_VERSION = 1;

struct png_control;
alias png_controlp = png_control*;
struct png_image
{
   png_controlp opaque;    /* Initialize to NULL, free with png_image_free */
   png_uint_32  version_;   /* Set to PNG_IMAGE_VERSION */
   png_uint_32  width;     /* Image width in pixels (columns) */
   png_uint_32  height;    /* Image height in pixels (rows) */
   png_uint_32  format;    /* Image format as defined below */
   png_uint_32  flags;     /* A bit mask containing informational flags */
   png_uint_32  colormap_entries;
                           /* Number of entries in the color-map */

   png_uint_32  warning_or_error;

   char[64]     message;
};
alias png_imagep = png_image*;

   /* In the event of an error or warning the following field will be set to a
    * non-zero value and the 'message' field will contain a '\0' terminated
    * string with the libpng error or warning message.  If both warnings and
    * an error were encountered, only the error is recorded.  If there
    * are multiple warnings, only the first one is recorded.
    *
    * The upper 30 bits of this value are reserved, the low two bits contain
    * a value as follows:
    */
enum PNG_IMAGE_WARNING = 1;
enum PNG_IMAGE_ERROR = 2;
   /*
    * The result is a two-bit code such that a value more than 1 indicates
    * a failure in the API just called:
    *
    *    0 - no warning or error
    *    1 - warning
    *    2 - error
    *    3 - error preceded by warning
    */
bool PNG_IMAGE_FAILED(ref const(png_image)png_cntrl) { return (png_cntrl.warning_or_error&0x03) > 1; }

/* The samples of the image have one to four channels whose components have
 * original values in the range 0 to 1.0:
 *
 * 1: A single gray or luminance channel (G).
 * 2: A gray/luminance channel and an alpha channel (GA).
 * 3: Three red, green, blue color channels (RGB).
 * 4: Three color channels and an alpha channel (RGBA).
 *
 * The components are encoded in one of two ways:
 *
 * a) As a small integer, value 0..255, contained in a single byte.  For the
 * alpha channel the original value is simply value/255.  For the color or
 * luminance channels the value is encoded according to the sRGB specification
 * and matches the 8-bit format expected by typical display devices.
 *
 * The color/gray channels are not scaled (pre-multiplied) by the alpha
 * channel and are suitable for passing to color management software.
 *
 * b) As a value in the range 0..65535, contained in a 2-byte integer.  All
 * channels can be converted to the original value by dividing by 65535; all
 * channels are linear.  Color channels use the RGB encoding (RGB end-points) of
 * the sRGB specification.  This encoding is identified by the
 * PNG_FORMAT_FLAG_LINEAR flag below.
 *
 * When the simplified API needs to convert between sRGB and linear colorspaces,
 * the actual sRGB transfer curve defined in the sRGB specification (see the
 * article at <https://en.wikipedia.org/wiki/SRGB>) is used, not the gamma=1/2.2
 * approximation used elsewhere in libpng.
 *
 * When an alpha channel is present it is expected to denote pixel coverage
 * of the color or luminance channels and is returned as an associated alpha
 * channel: the color/gray channels are scaled (pre-multiplied) by the alpha
 * value.
 *
 * The samples are either contained directly in the image data, between 1 and 8
 * bytes per pixel according to the encoding, or are held in a color-map indexed
 * by bytes in the image data.  In the case of a color-map the color-map entries
 * are individual samples, encoded as above, and the image data has one byte per
 * pixel to select the relevant sample from the color-map.
 */

/* PNG_FORMAT_*
 *
 * #defines to be used in png_image::format.  Each #define identifies a
 * particular layout of sample data and, if present, alpha values.  There are
 * separate defines for each of the two component encodings.
 *
 * A format is built up using single bit flag values.  All combinations are
 * valid.  Formats can be built up from the flag values or you can use one of
 * the predefined values below.  When testing formats always use the FORMAT_FLAG
 * macros to test for individual features - future versions of the library may
 * add new flags.
 *
 * When reading or writing color-mapped images the format should be set to the
 * format of the entries in the color-map then png_image_{read,write}_colormap
 * called to read or write the color-map and set the format correctly for the
 * image data.  Do not set the PNG_FORMAT_FLAG_COLORMAP bit directly!
 *
 * NOTE: libpng can be built with particular features disabled. If you see
 * compiler errors because the definition of one of the following flags has been
 * compiled out it is because libpng does not have the required support.  It is
 * possible, however, for the libpng configuration to enable the format on just
 * read or just write; in that case you may see an error at run time.  You can
 * guard against this by checking for the definition of the appropriate
 * "_SUPPORTED" macro, one of:
 *
 *    PNG_SIMPLIFIED_{READ,WRITE}_{BGR,AFIRST}_SUPPORTED
 */
enum PNG_FORMAT_FLAG_ALPHA      = 0x01U; /* format with an alpha channel */
enum PNG_FORMAT_FLAG_COLOR      = 0x02U; /* color format: otherwise grayscale */
enum PNG_FORMAT_FLAG_LINEAR     = 0x04U; /* 2-byte channels else 1-byte */
enum PNG_FORMAT_FLAG_COLORMAP   = 0x08U; /* image data is color-mapped */

static if(PNG_FORMAT_BGR_SUPPORTED) {
enum PNG_FORMAT_FLAG_BGR        = 0x10U; /* BGR colors, else order is RGB */
}

static if(PNG_FORMAT_AFIRST_SUPPORTED) {
enum PNG_FORMAT_FLAG_AFIRST     = 0x20U; /* alpha channel comes first */
}

enum PNG_FORMAT_FLAG_ASSOCIATED_ALPHA = 0x40U; /* alpha channel is associated */

/* Commonly used formats have predefined macros.
 *
 * First the single byte (sRGB) formats:
 */
enum PNG_FORMAT_GRAY    = 0;
enum PNG_FORMAT_GA      = PNG_FORMAT_FLAG_ALPHA;
enum PNG_FORMAT_AG      = (PNG_FORMAT_GA|PNG_FORMAT_FLAG_AFIRST);
enum PNG_FORMAT_RGB     = PNG_FORMAT_FLAG_COLOR;
enum PNG_FORMAT_BGR     = (PNG_FORMAT_FLAG_COLOR|PNG_FORMAT_FLAG_BGR);
enum PNG_FORMAT_RGBA    = (PNG_FORMAT_RGB|PNG_FORMAT_FLAG_ALPHA);
enum PNG_FORMAT_ARGB    = (PNG_FORMAT_RGBA|PNG_FORMAT_FLAG_AFIRST);
enum PNG_FORMAT_BGRA    = (PNG_FORMAT_BGR|PNG_FORMAT_FLAG_ALPHA);
enum PNG_FORMAT_ABGR    = (PNG_FORMAT_BGRA|PNG_FORMAT_FLAG_AFIRST);

/* Then the linear 2-byte formats.  When naming these "Y" is used to
 * indicate a luminance (gray) channel.
 */
enum PNG_FORMAT_LINEAR_Y            = PNG_FORMAT_FLAG_LINEAR;
enum PNG_FORMAT_LINEAR_Y_ALPHA      = (PNG_FORMAT_FLAG_LINEAR|PNG_FORMAT_FLAG_ALPHA);
enum PNG_FORMAT_LINEAR_RGB          = (PNG_FORMAT_FLAG_LINEAR|PNG_FORMAT_FLAG_COLOR);
enum PNG_FORMAT_LINEAR_RGB_ALPHA    =
   (PNG_FORMAT_FLAG_LINEAR|PNG_FORMAT_FLAG_COLOR|PNG_FORMAT_FLAG_ALPHA);

/* With color-mapped formats the image data is one byte for each pixel, the byte
 * is an index into the color-map which is formatted as above.  To obtain a
 * color-mapped format it is sufficient just to add the PNG_FOMAT_FLAG_COLORMAP
 * to one of the above definitions, or you can use one of the definitions below.
 */
enum PNG_FORMAT_RGB_COLORMAP    = (PNG_FORMAT_RGB|PNG_FORMAT_FLAG_COLORMAP);
enum PNG_FORMAT_BGR_COLORMAP    = (PNG_FORMAT_BGR|PNG_FORMAT_FLAG_COLORMAP);
enum PNG_FORMAT_RGBA_COLORMAP   = (PNG_FORMAT_RGBA|PNG_FORMAT_FLAG_COLORMAP);
enum PNG_FORMAT_ARGB_COLORMAP   = (PNG_FORMAT_ARGB|PNG_FORMAT_FLAG_COLORMAP);
enum PNG_FORMAT_BGRA_COLORMAP   = (PNG_FORMAT_BGRA|PNG_FORMAT_FLAG_COLORMAP);
enum PNG_FORMAT_ABGR_COLORMAP   = (PNG_FORMAT_ABGR|PNG_FORMAT_FLAG_COLORMAP);

/* PNG_IMAGE macros
 *
 * These are convenience macros to derive information from a png_image
 * structure.  The PNG_IMAGE_SAMPLE_ macros return values appropriate to the
 * actual image sample values - either the entries in the color-map or the
 * pixels in the image.  The PNG_IMAGE_PIXEL_ macros return corresponding values
 * for the pixels and will always return 1 for color-mapped formats.  The
 * remaining macros return information about the rows in the image and the
 * complete image.
 *
 * NOTE: All the macros that take a png_image::format parameter are compile time
 * constants if the format parameter is, itself, a constant.  Therefore these
 * macros can be used in array declarations and case labels where required.
 * Similarly the macros are also pre-processor constants (sizeof is not used) so
 * they can be used in #if tests.
 *
 * First the information about the samples.
 */
auto PNG_IMAGE_SAMPLE_CHANNELS(F)(F fmt) pure { return
   (((fmt)&(PNG_FORMAT_FLAG_COLOR|PNG_FORMAT_FLAG_ALPHA))+1); }
   /* Return the total number of channels in a given format: 1..4 */

auto PNG_IMAGE_SAMPLE_COMPONENT_SIZE(F)(F fmt) pure { return
   ((((fmt) & PNG_FORMAT_FLAG_LINEAR) >> 2)+1); }
   /* Return the size in bytes of a single component of a pixel or color-map
    * entry (as appropriate) in the image: 1 or 2.
    */

auto PNG_IMAGE_SAMPLE_SIZE(F)(F fmt) pure { return
   (PNG_IMAGE_SAMPLE_CHANNELS(fmt) * PNG_IMAGE_SAMPLE_COMPONENT_SIZE(fmt)); }
   /* This is the size of the sample data for one sample.  If the image is
    * color-mapped it is the size of one color-map entry (and image pixels are
    * one byte in size), otherwise it is the size of one image pixel.
    */

auto PNG_IMAGE_MAXIMUM_COLORMAP_COMPONENTS(F)(F fmt) pure { return
   (PNG_IMAGE_SAMPLE_CHANNELS(fmt) * 256); }
   /* The maximum size of the color-map required by the format expressed in a
    * count of components.  This can be used to compile-time allocate a
    * color-map:
    *
    * png_uint_16 colormap[PNG_IMAGE_MAXIMUM_COLORMAP_COMPONENTS(linear_fmt)];
    *
    * png_byte colormap[PNG_IMAGE_MAXIMUM_COLORMAP_COMPONENTS(sRGB_fmt)];
    *
    * Alternatively use the PNG_IMAGE_COLORMAP_SIZE macro below to use the
    * information from one of the png_image_begin_read_ APIs and dynamically
    * allocate the required memory.
    */

/* Corresponding information about the pixels */
auto PNG_IMAGE_PIXEL_(string test, F)(F fmt) pure { return
   (((fmt)&PNG_FORMAT_FLAG_COLORMAP)?1:mixin(test~"(fmt)")); }

auto PNG_IMAGE_PIXEL_CHANNELS(F)(F fmt) pure { return
   PNG_IMAGE_PIXEL_!"PNG_IMAGE_SAMPLE_CHANNELS"(fmt); }
   /* The number of separate channels (components) in a pixel; 1 for a
    * color-mapped image.
    */

auto PNG_IMAGE_PIXEL_COMPONENT_SIZE(F)(F fmt) pure { return
   PNG_IMAGE_PIXEL_!"PNG_IMAGE_SAMPLE_COMPONENT_SIZE"(fmt); }
   /* The size, in bytes, of each component in a pixel; 1 for a color-mapped
    * image.
    */

auto PNG_IMAGE_PIXEL_SIZE(F)(F fmt) pure
{ return PNG_IMAGE_PIXEL_!"PNG_IMAGE_SAMPLE_SIZE"(fmt); }
   /* The size, in bytes, of a complete pixel; 1 for a color-mapped image. */

/* Information about the whole row, or whole image */
auto PNG_IMAGE_ROW_STRIDE(ref const(png_image) image) pure { return
   (PNG_IMAGE_PIXEL_CHANNELS((image).format) * (image).width); }
   /* Return the total number of components in a single row of the image; this
    * is the minimum 'row stride', the minimum count of components between each
    * row.  For a color-mapped image this is the minimum number of bytes in a
    * row.
    *
    * WARNING: this macro overflows for some images with more than one component
    * and very large image widths.  libpng will refuse to process an image where
    * this macro would overflow.
    */

auto PNG_IMAGE_BUFFER_SIZE(S)(ref const(png_image) image, S row_stride) pure { return
   (PNG_IMAGE_PIXEL_COMPONENT_SIZE((image).format)*(image).height*(row_stride)); }
   /* Return the size, in bytes, of an image buffer given a png_image and a row
    * stride - the number of components to leave space for in each row.
    *
    * WARNING: this macro overflows a 32-bit integer for some large PNG images,
    * libpng will refuse to process an image where such an overflow would occur.
    */

auto PNG_IMAGE_SIZE(ref const(png_image) image) pure { return
   PNG_IMAGE_BUFFER_SIZE(image, PNG_IMAGE_ROW_STRIDE(image)); }
   /* Return the size, in bytes, of the image in memory given just a png_image;
    * the row stride is the minimum stride required for the image.
    */

auto PNG_IMAGE_COLORMAP_SIZE(ref const(png_image) image) pure { return
   (PNG_IMAGE_SAMPLE_SIZE((image).format) * (image).colormap_entries); }
   /* Return the size, in bytes, of the color-map of this image.  If the image
    * format is not a color-map format this will return a size sufficient for
    * 256 entries in the given format; check PNG_FORMAT_FLAG_COLORMAP if
    * you don't want to allocate a color-map in this case.
    */

/* PNG_IMAGE_FLAG_*
 *
 * Flags containing additional information about the image are held in the
 * 'flags' field of png_image.
 */
enum PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB = 0x01;
   /* This indicates that the RGB values of the in-memory bitmap do not
    * correspond to the red, green and blue end-points defined by sRGB.
    */

enum PNG_IMAGE_FLAG_FAST = 0x02;
   /* On write emphasise speed over compression; the resultant PNG file will be
    * larger but will be produced significantly faster, particular for large
    * images.  Do not use this option for images which will be distributed, only
    * used it when producing intermediate files that will be read back in
    * repeatedly.  For a typical 24-bit image the option will double the read
    * speed at the cost of increasing the image size by 25%, however for many
    * more compressible images the PNG file can be 10 times larger with only a
    * slight speed gain.
    */

enum PNG_IMAGE_FLAG_16BIT_sRGB = 0x04;
   /* On read if the image is a 16-bit per component image and there is no gAMA
    * or sRGB chunk assume that the components are sRGB encoded.  Notice that
    * images output by the simplified API always have gamma information; setting
    * this flag only affects the interpretation of 16-bit images from an
    * external source.  It is recommended that the application expose this flag
    * to the user; the user can normally easily recognize the difference between
    * linear and sRGB encoding.  This flag has no effect on write - the data
    * passed to the write APIs must have the correct encoding (as defined
    * above.)
    *
    * If the flag is not set (the default) input 16-bit per component data is
    * assumed to be linear.
    *
    * NOTE: the flag can only be set after the png_image_begin_read_ call,
    * because that call initializes the 'flags' field.
    */

static if(PNG_SIMPLIFIED_READ_SUPPORTED){
/* READ APIs
 * ---------
 *
 * The png_image passed to the read APIs must have been initialized by setting
 * the png_controlp field 'opaque' to NULL (or, safer, memset the whole thing.)
 */
static if(PNG_STDIO_SUPPORTED){
int png_image_begin_read_from_file (png_imagep image,
   const char *file_name);
   /* The named file is opened for read and the image header is filled in
    * from the PNG header in the file.
    */

int png_image_begin_read_from_stdio (png_imagep image,
   FILE* file);
   /* The PNG header is read from the stdio FILE object. */
} /* STDIO */

int png_image_begin_read_from_memory (png_imagep image,
   png_const_voidp memory, size_t size);
   /* The PNG header is read from the given memory buffer. */

int png_image_finish_read (png_imagep image,
   png_const_colorp background, void *buffer, png_int_32 row_stride,
   void *colormap);
   /* Finish reading the image into the supplied buffer and clean up the
    * png_image structure.
    *
    * row_stride is the step, in byte or 2-byte units as appropriate,
    * between adjacent rows.  A positive stride indicates that the top-most row
    * is first in the buffer - the normal top-down arrangement.  A negative
    * stride indicates that the bottom-most row is first in the buffer.
    *
    * background need only be supplied if an alpha channel must be removed from
    * a png_byte format and the removal is to be done by compositing on a solid
    * color; otherwise it may be NULL and any composition will be done directly
    * onto the buffer.  The value is an sRGB color to use for the background,
    * for grayscale output the green channel is used.
    *
    * background must be supplied when an alpha channel must be removed from a
    * single byte color-mapped output format, in other words if:
    *
    * 1) The original format from png_image_begin_read_from_* had
    *    PNG_FORMAT_FLAG_ALPHA set.
    * 2) The format set by the application does not.
    * 3) The format set by the application has PNG_FORMAT_FLAG_COLORMAP set and
    *    PNG_FORMAT_FLAG_LINEAR *not* set.
    *
    * For linear output removing the alpha channel is always done by compositing
    * on black and background is ignored.
    *
    * colormap must be supplied when PNG_FORMAT_FLAG_COLORMAP is set.  It must
    * be at least the size (in bytes) returned by PNG_IMAGE_COLORMAP_SIZE.
    * image->colormap_entries will be updated to the actual number of entries
    * written to the colormap; this may be less than the original value.
    */

void png_image_free (png_imagep image);
   /* Free any data allocated by libpng in image->opaque, setting the pointer to
    * NULL.  May be called at any time after the structure is initialized.
    */
} /* SIMPLIFIED_READ */

static if(PNG_SIMPLIFIED_WRITE_SUPPORTED){
/* WRITE APIS
 * ----------
 * For write you must initialize a png_image structure to describe the image to
 * be written.  To do this use memset to set the whole structure to 0 then
 * initialize fields describing your image.
 *
 * version: must be set to PNG_IMAGE_VERSION
 * opaque: must be initialized to NULL
 * width: image width in pixels
 * height: image height in rows
 * format: the format of the data (image and color-map) you wish to write
 * flags: set to 0 unless one of the defined flags applies; set
 *    PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB for color format images where the RGB
 *    values do not correspond to the colors in sRGB.
 * colormap_entries: set to the number of entries in the color-map (0 to 256)
 */
static if (PNG_SIMPLIFIED_WRITE_STDIO_SUPPORTED) {
int png_image_write_to_file (png_imagep image,
   const char *file, int convert_to_8bit, const void *buffer,
   png_int_32 row_stride, const void *colormap);
   /* Write the image to the named file. */

int png_image_write_to_stdio (png_imagep image, FILE *file,
   int convert_to_8_bit, const void *buffer, png_int_32 row_stride,
   const void *colormap);
   /* Write the image to the given (FILE*). */
} /* SIMPLIFIED_WRITE_STDIO */

/* With all write APIs if image is in one of the linear formats with 16-bit
 * data then setting convert_to_8_bit will cause the output to be an 8-bit PNG
 * gamma encoded according to the sRGB specification, otherwise a 16-bit linear
 * encoded PNG file is written.
 *
 * With color-mapped data formats the colormap parameter point to a color-map
 * with at least image->colormap_entries encoded in the specified format.  If
 * the format is linear the written PNG color-map will be converted to sRGB
 * regardless of the convert_to_8_bit flag.
 *
 * With all APIs row_stride is handled as in the read APIs - it is the spacing
 * from one row to the next in component sized units (1 or 2 bytes) and if
 * negative indicates a bottom-up row layout in the buffer.  If row_stride is
 * zero, libpng will calculate it for you from the image width and number of
 * channels.
 *
 * Note that the write API does not support interlacing, sub-8-bit pixels or
 * most ancillary chunks.  If you need to write text chunks (e.g. for copyright
 * notices) you need to use one of the other APIs.
 */

int png_image_write_to_memory(png_imagep image, void *memory, png_alloc_size_t *memory_bytes,
        int convert_to_8_bit, const void *buffer, png_int_32 row_stride, const void *colormap);
   /* Write the image to the given memory buffer.  The function both writes the
    * whole PNG data stream to *memory and updates *memory_bytes with the count
    * of bytes written.
    *
    * 'memory' may be NULL.  In this case *memory_bytes is not read however on
    * success the number of bytes which would have been written will still be
    * stored in *memory_bytes.  On failure *memory_bytes will contain 0.
    *
    * If 'memory' is not NULL it must point to memory[*memory_bytes] of
    * writeable memory.
    *
    * If the function returns success memory[*memory_bytes] (if 'memory' is not
    * NULL) contains the written PNG data.  *memory_bytes will always be less
    * than or equal to the original value.
    *
    * If the function returns false and *memory_bytes was not changed an error
    * occurred during write.  If *memory_bytes was changed, or is not 0 if
    * 'memory' was NULL, the write would have succeeded but for the memory
    * buffer being too small.  *memory_bytes contains the required number of
    * bytes and will be bigger that the original value.
    */

int png_image_write_get_memory_size(png_image image, png_alloc_size_t size, int convert_to_8_bit,
        const void *buffer, png_int_32 row_stride, const void *colormap) {
    return png_image_write_to_memory(cast(png_imagep) &image, null, &size, convert_to_8_bit, buffer,
            row_stride, colormap);
}
   /* Return the amount of memory in 'size' required to compress this image.
    * The png_image structure 'image' must be filled in as in the above
    * function and must not be changed before the actual write call, the buffer
    * and all other parameters must also be identical to that in the final
    * write call.  The 'size' variable need not be initialized.
    *
    * NOTE: the macro returns true/false, if false is returned 'size' will be
    * set to zero and the write failed and probably will fail if tried again.
    */

/* You can pre-allocate the buffer by making sure it is of sufficient size
 * regardless of the amount of compression achieved.  The buffer size will
 * always be bigger than the original image and it will never be filled.  The
 * following macros are provided to assist in allocating the buffer.
 */
auto PNG_IMAGE_DATA_SIZE(ref const png_image image) {
    return PNG_IMAGE_SIZE(image)+(image).height;
   /* The number of uncompressed bytes in the PNG byte encoding of the image;
    * uncompressing the PNG IDAT data will give this number of bytes.
    *
    * NOTE: while PNG_IMAGE_SIZE cannot overflow for an image in memory this
    * macro can because of the extra bytes used in the PNG byte encoding.  You
    * need to avoid this macro if your image size approaches 2^30 in width or
    * height.  The same goes for the remainder of these macros; they all produce
    * bigger numbers than the actual in-memory image size.
    */
}

version (PNG_ZLIB_MAX_SIZE) {
} else {
    auto PNG_ZLIB_MAX_SIZE(S)(S b) {
        return b + (b + ((b + 7U) >> 3) + ((b + 63U) >> 6) + 11U);
   /* An upper bound on the number of compressed bytes given 'b' uncompressed
    * bytes.  This is based on deflateBounds() in zlib; different
    * implementations of zlib compression may conceivably produce more data so
    * if your zlib implementation is not zlib itself redefine this macro
    * appropriately.
    */
    }
}

auto PNG_IMAGE_COMPRESSED_SIZE_MAX(const ref png_image image) {
    return PNG_ZLIB_MAX_SIZE(cast(png_alloc_size_t) PNG_IMAGE_DATA_SIZE(image));
   /* An upper bound on the size of the data in the PNG IDAT chunks. */
}

auto PNG_IMAGE_PNG_SIZE_MAX_(S)(const ref png_image image, S image_size) {
    return ((8U/*sig*/+25U/*IHDR*/+16U/*gAMA*/+44U/*cHRM*/+12U/*IEND*/+
    (((image).format&PNG_FORMAT_FLAG_COLORMAP)?/*colormap: PLTE, tRNS*/
    12U+3U*(image).colormap_entries/*PLTE data*/+
    (((image).format&PNG_FORMAT_FLAG_ALPHA)?
    12U/*tRNS*/+(image).colormap_entries:0U):0U)+
    12U)+(12U*((image_size)/PNG_ZBUF_SIZE))/*IDAT*/+(image_size));
   /* A helper for the following macro; if your compiler cannot handle the
    * following macro use this one with the result of
    * PNG_IMAGE_COMPRESSED_SIZE_MAX(image) as the second argument (most
    * compilers should handle this just fine.)
    */
}

auto PNG_IMAGE_PNG_SIZE_MAX(const ref png_image image) {
    return PNG_IMAGE_PNG_SIZE_MAX_(image, PNG_IMAGE_COMPRESSED_SIZE_MAX(image));
   /* An upper bound on the total length of the PNG data stream for 'image'.
    * The result is of type png_alloc_size_t, on 32-bit systems this may
    * overflow even though PNG_IMAGE_DATA_SIZE does not overflow; the write will
    * run out of buffer space but return a corrected size which should work.
    */
}

} /* SIMPLIFIED_WRITE */
/*******************************************************************************
 *  END OF SIMPLIFIED API
 ******************************************************************************/
} /* SIMPLIFIED_{READ|WRITE} */

/*******************************************************************************
 * Section 6: IMPLEMENTATION OPTIONS
 *******************************************************************************
 *
 * Support for arbitrary implementation-specific optimizations.  The API allows
 * particular options to be turned on or off.  'Option' is the number of the
 * option and 'onoff' is 0 (off) or non-0 (on).  The value returned is given
 * by the PNG_OPTION_ defines below.
 *
 * HARDWARE: normally hardware capabilities, such as the Intel SSE instructions,
 *           are detected at run time, however sometimes it may be impossible
 *           to do this in user mode, in which case it is necessary to discover
 *           the capabilities in an OS specific way.  Such capabilities are
 *           listed here when libpng has support for them and must be turned
 *           ON by the application if present.
 *
 * SOFTWARE: sometimes software optimizations actually result in performance
 *           decrease on some architectures or systems, or with some sets of
 *           PNG images.  'Software' options allow such optimizations to be
 *           selected at run time.
 */
static if(PNG_SET_OPTION_SUPPORTED) {
static if(PNG_ARM_NEON_API_SUPPORTED) {
enum PNG_ARM_NEON = 0; /* HARDWARE: ARM Neon SIMD instructions supported */
}
enum PNG_MAXIMUM_INFLATE_WINDOW = 2; /* SOFTWARE: force maximum window */
enum PNG_SKIP_sRGB_CHECK_PROFILE = 4; /* SOFTWARE: Check ICC profile for sRGB */
version (PNG_MIPS_MSA_API_SUPPORTED) {
    enum PNG_MIPS_MSA = 6;
}
enum PNG_IGNORE_ADLER32 = 8;
static if (PNG_POWERPC_VSX_API_SUPPORTED) {
    enum PNG_POWERPC_VSX = 10;
}
enum PNG_OPTION_NEXT = 12; /* Next option - numbers must be even */

/* Return values: NOTE: there are four values and 'off' is *not* zero */
enum PNG_OPTION_UNSET   = 0; /* Unset - defaults to off */
enum PNG_OPTION_INVALID = 1; /* Option number out of range */
enum PNG_OPTION_OFF     = 2;
enum PNG_OPTION_ON      = 3;

int png_set_option (png_structrp png_ptr, int option,
   int onoff);
} /* SET_OPTION */

/*******************************************************************************
 *  END OF HARDWARE AND SOFTWARE OPTIONS
 ******************************************************************************/

static if (PNG_APNG_SUPPORTED) {
    png_uint_32 png_get_acTL(png_structp png_ptr, png_infop info_ptr, png_uint_32 *num_frames,
            png_uint_32 *num_plays);

    png_uint_32 png_set_acTL(png_structp png_ptr, png_infop info_ptr, png_uint_32 num_frames,
            png_uint_32 num_plays);

    png_uint_32 png_get_num_frames(png_structp png_ptr, png_infop info_ptr);

    png_uint_32 png_get_num_plays(png_structp png_ptr, png_infop info_ptr);

    png_uint_32 png_get_next_frame_fcTL(png_structp png_ptr, png_infop info_ptr, png_uint_32 *width,
            png_uint_32 *height, png_uint_32 *x_offset, png_uint_32 *y_offset, png_uint_16 *delay_num,
            png_uint_16 *delay_den, png_byte *dispose_op, png_byte *blend_op);

    png_uint_32 png_set_next_frame_fcTL(png_structp png_ptr, png_infop info_ptr, png_uint_32 width,
            png_uint_32 height, png_uint_32 x_offset, png_uint_32 y_offset, png_uint_16 delay_num,
            png_uint_16 delay_den, png_byte dispose_op, png_byte blend_op);

    png_uint_32 png_get_next_frame_width(png_structp png_ptr, png_infop info_ptr);
    png_uint_32 png_get_next_frame_height(png_structp png_ptr, png_infop info_ptr);
    png_uint_32 png_get_next_frame_x_offset(png_structp png_ptr, png_infop info_ptr);
    png_uint_32 png_get_next_frame_y_offset(png_structp png_ptr, png_infop info_ptr);
    png_uint_16 png_get_next_frame_delay_num(png_structp png_ptr, png_infop info_ptr);
    png_uint_16 png_get_next_frame_delay_den(png_structp png_ptr, png_infop info_ptr);
    png_byte png_get_next_frame_dispose_op(png_structp png_ptr, png_infop info_ptr);
    png_byte png_get_next_frame_blend_op(png_structp png_ptr, png_infop info_ptr);
    png_byte png_get_first_frame_is_hidden(png_structp png_ptr, png_infop info_ptr);
    png_uint_32 png_set_first_frame_is_hidden(png_structp png_ptr, png_infop info_ptr, png_byte is_hidden);

    static if (PNG_READ_APNG_SUPPORTED) {
        void png_read_frame_head(png_structp png_ptr, png_infop info_ptr);

        static if (PNG_PROGRESSIVE_READ_SUPPORTED) {
            void png_set_progressive_frame_fn(png_structp png_ptr,
                    png_progressive_frame_ptr frame_info_fn,
                    png_progressive_frame_ptr frame_end_fn);
        } /* PROGRESSIVE_READ */
    } /* READ_APNG */

    static if (PNG_WRITE_APNG_SUPPORTED) {
        void png_write_frame_head(png_structp png_ptr, png_infop info_ptr,
                png_bytepp row_pointers, png_uint_32 width, png_uint_32 height,
                png_uint_32 x_offset, png_uint_32 y_offset, png_uint_16 delay_num,
                png_uint_16 delay_den, png_byte dispose_op, png_byte blend_op);

        void png_write_frame_tail(png_structp png_ptr, png_infop info_ptr);
    } /* WRITE_APNG */
} /* APNG */

/* Maintainer: Put new public prototypes here ^, in libpng.3, and project
 * defs
 */

/* The last ordinal number (this is the *last* one already used; the next
 * one to use is one more than this.)  Maintainer, remember to add an entry to
 * scripts/symbols.def as well.
 */
// static if (PNG_EXPORT_LAST_ORDINAL) {
//     static if (PNG_APNG_SUPPORTED) {
//         PNG_EXPORT_LAST_ORDINAL(269);
//     } else {
//         PNG_EXPORT_LAST_ORDINAL(249);
//     }
// }

}//extern (C)

} /* PNG_VERSION_INFO_ONLY */
/* Do not put anything past this line */