text: 
  /* pngpriv.h - private declarations for use inside libpng
   *
   * For conditions of distribution and use, see copyright notice in png.h
   * Copyright (c) 1998-2014 Glenn Randers-Pehrson
   * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
   * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
   *
   * Last changed in libpng 1.6.10 [March 6, 1014]]
   *
   * This code is released under the libpng license.
   * For conditions of distribution and use, see the disclaimer
   * and license in png.h
   */
  
  /* The symbols declared in this file (including the functions declared
   * as extern) are PRIVATE.  They are not part of the libpng public
   * interface, and are not recommended for use by regular applications.
   * Some of them may become public in the future; others may stay private,
   * change in an incompatible way, or even disappear.
   * Although the libpng users are not forbidden to include this header,
   * they should be well aware of the issues that may arise from doing so.
   */
  
  #ifndef PNGPRIV_H
  #define PNGPRIV_H
  
  /* Feature Test Macros.  The following are defined here to ensure that correctly
   * implemented libraries reveal the APIs libpng needs to build and hide those
   * that are not needed and potentially damaging to the compilation.
   *
   * Feature Test Macros must be defined before any system header is included (see
   * POSIX 1003.1 2.8.2 "POSIX Symbols."
   *
   * These macros only have an effect if the operating system supports either
   * POSIX 1003.1 or C99, or both.  On other operating systems (particularly
   * Windows/Visual Studio) there is no effect; the OS specific tests below are
   * still required (as of 2011-05-02.)
   */
  #define _POSIX_SOURCE 1 /* Just the POSIX 1003.1 and C89 APIs */
  
  #ifndef PNG_VERSION_INFO_ONLY
  /* Standard library headers not required by png.h: */
  #  include <stdlib.h>
  #  include <string.h>
  #endif
  
  #define PNGLIB_BUILD /*libpng is being built, not used*/
  
  /* If HAVE_CONFIG_H is defined during the build then the build system must
   * provide an appropriate "config.h" file on the include path.  The header file
   * must provide definitions as required below (search for "HAVE_CONFIG_H");
   * see configure.ac for more details of the requirements.  The macro
   * "PNG_NO_CONFIG_H" is provided for maintainers to test for dependencies on
   * 'configure'; define this macro to prevent the configure build including the
   * configure generated config.h.  Libpng is expected to compile without *any*
   * special build system support on a reasonably ANSI-C compliant system.
   */
  #if defined(HAVE_CONFIG_H) && !defined(PNG_NO_CONFIG_H)
  #  include <config.h>
  
     /* Pick up the definition of 'restrict' from config.h if it was read: */
  #  define PNG_RESTRICT restrict
  #endif
  
  /* To support symbol prefixing it is necessary to know *before* including png.h
   * whether the fixed point (and maybe other) APIs are exported, because if they
   * are not internal definitions may be required.  This is handled below just
   * before png.h is included, but load the configuration now if it is available.
   */
  #ifndef PNGLCONF_H
  #  include "pnglibconf.h"
  #endif
  
  /* Local renames may change non-exported API functions from png.h */
  #if defined(PNG_PREFIX) && !defined(PNGPREFIX_H)
  #  include "pngprefix.h"
  #endif
  
  #ifdef PNG_USER_CONFIG
  #  include "pngusr.h"
     /* These should have been defined in pngusr.h */
  #  ifndef PNG_USER_PRIVATEBUILD
  #    define PNG_USER_PRIVATEBUILD "Custom libpng build"
  #  endif
  #  ifndef PNG_USER_DLLFNAME_POSTFIX
  #    define PNG_USER_DLLFNAME_POSTFIX "Cb"
  #  endif
  #endif
  
  /* Compile time options.
   * =====================
   * In a multi-arch build the compiler may compile the code several times for the
   * same object module, producing different binaries for different architectures.
   * When this happens configure-time setting of the target host options cannot be
   * done and this interferes with the handling of the ARM NEON optimizations, and
   * possibly other similar optimizations.  Put additional tests here; in general
   * this is needed when the same option can be changed at both compile time and
   * run time depending on the target OS (i.e. iOS vs Android.)
   *
   * NOTE: symbol prefixing does not pass $(CFLAGS) to the preprocessor, because
   * this is not possible with certain compilers (Oracle SUN OS CC), as a result
   * it is necessary to ensure that all extern functions that *might* be used
   * regardless of $(CFLAGS) get declared in this file.  The test on __ARM_NEON__
   * below is one example of this behavior because it is controlled by the
   * presence or not of -mfpu=neon on the GCC command line, it is possible to do
   * this in $(CC), e.g. "CC=gcc -mfpu=neon", but people who build libpng rarely
   * do this.
   */
  #ifndef PNG_ARM_NEON_OPT
     /* ARM NEON optimizations are being controlled by the compiler settings,
      * typically the target FPU.  If the FPU has been set to NEON (-mfpu=neon
      * with GCC) then the compiler will define __ARM_NEON__ and we can rely
      * unconditionally on NEON instructions not crashing, otherwise we must
      * disable use of NEON instructions.
      *
      * NOTE: at present these optimizations depend on 'ALIGNED_MEMORY', so they
      * can only be turned on automatically if that is supported too.  If
      * PNG_ARM_NEON_OPT is set in CPPFLAGS (to >0) then arm/arm_init.c will fail
      * to compile with an appropriate #error if ALIGNED_MEMORY has been turned
      * off.
      *
      * Note that gcc-4.9 defines __ARM_NEON instead of __ARM_NEON__, so we
      * check both variants.
      */
  // https://blog.csdn.net/weixin_42330265/article/details/80484978
  /*#  if (defined(__ARM_NEON__) || defined(__ARM_NEON)) && \*/
  #  if defined(PNG_ARM_NEON) && (defined(__ARM_NEON__) || defined(__ARM_NEON)) && \
     defined(PNG_ALIGNED_MEMORY_SUPPORTED)
  #     define PNG_ARM_NEON_OPT 2
  #  else
  #     define PNG_ARM_NEON_OPT 0
  #  endif
  #endif
  
  #if PNG_ARM_NEON_OPT > 0
     /* NEON optimizations are to be at least considered by libpng, so enable the
      * callbacks to do this.
      */
  #  define PNG_FILTER_OPTIMIZATIONS png_init_filter_functions_neon
  
     /* By default the 'intrinsics' code in arm/filter_neon_intrinsics.c is used
      * if possible - if __ARM_NEON__ is set and the compiler version is not known
      * to be broken.  This is controlled by PNG_ARM_NEON_IMPLEMENTATION which can
      * be:
      *
      *    1  The intrinsics code (the default with __ARM_NEON__)
      *    2  The hand coded assembler (the default without __ARM_NEON__)
      *
      * It is possible to set PNG_ARM_NEON_IMPLEMENTATION in CPPFLAGS, however
      * this is *NOT* supported and may cease to work even after a minor revision
      * to libpng.  It *is* valid to do this for testing purposes, e.g. speed
      * testing or a new compiler, but the results should be communicated to the
      * libpng implementation list for incorporation in the next minor release.
      */
  #  ifndef PNG_ARM_NEON_IMPLEMENTATION
  #     if defined(__ARM_NEON__) || defined(__ARM_NEON)
  #        if defined(__clang__)
              /* At present it is unknown by the libpng developers which versions
               * of clang support the intrinsics, however some or perhaps all
               * versions do not work with the assembler so this may be
               * irrelevant, so just use the default (do nothing here.)
               */
  #        elif defined(__GNUC__)
              /* GCC 4.5.4 NEON support is known to be broken.  4.6.3 is known to
               * work, so if this *is* GCC, or G++, look for a version >4.5
               */
  #           if __GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 6)
  #              define PNG_ARM_NEON_IMPLEMENTATION 2
  #           endif /* no GNUC support */
  #        endif /* __GNUC__ */
  #     else /* !defined __ARM_NEON__ */
           /* The 'intrinsics' code simply won't compile without this -mfpu=neon:
            */
  #        define PNG_ARM_NEON_IMPLEMENTATION 2
  #     endif /* __ARM_NEON__ */
  #  endif /* !PNG_ARM_NEON_IMPLEMENTATION */
  
  #  ifndef PNG_ARM_NEON_IMPLEMENTATION
        /* Use the intrinsics code by default. */
  #     define PNG_ARM_NEON_IMPLEMENTATION 1
  #  endif
  #endif /* PNG_ARM_NEON_OPT > 0 */
  
  /* Is this a build of a DLL where compilation of the object modules requires
   * different preprocessor settings to those required for a simple library?  If
   * so PNG_BUILD_DLL must be set.
   *
   * If libpng is used inside a DLL but that DLL does not export the libpng APIs
   * PNG_BUILD_DLL must not be set.  To avoid the code below kicking in build a
   * static library of libpng then link the DLL against that.
   */
  #ifndef PNG_BUILD_DLL
  #  ifdef DLL_EXPORT
        /* This is set by libtool when files are compiled for a DLL; libtool
         * always compiles twice, even on systems where it isn't necessary.  Set
         * PNG_BUILD_DLL in case it is necessary:
         */
  #     define PNG_BUILD_DLL
  #  else
  #     ifdef _WINDLL
           /* This is set by the Microsoft Visual Studio IDE in projects that
            * build a DLL.  It can't easily be removed from those projects (it
            * isn't visible in the Visual Studio UI) so it is a fairly reliable
            * indication that PNG_IMPEXP needs to be set to the DLL export
            * attributes.
            */
  #        define PNG_BUILD_DLL
  #     else
  #        ifdef __DLL__
              /* This is set by the Borland C system when compiling for a DLL
               * (as above.)
               */
  #           define PNG_BUILD_DLL
  #        else
              /* Add additional compiler cases here. */
  #        endif
  #     endif
  #  endif
  #endif /* Setting PNG_BUILD_DLL if required */
  
  /* See pngconf.h for more details: the builder of the library may set this on
   * the command line to the right thing for the specific compilation system or it
   * may be automagically set above (at present we know of no system where it does
   * need to be set on the command line.)
   *
   * PNG_IMPEXP must be set here when building the library to prevent pngconf.h
   * setting it to the "import" setting for a DLL build.
   */
  #ifndef PNG_IMPEXP
  #  ifdef PNG_BUILD_DLL
  #     define PNG_IMPEXP PNG_DLL_EXPORT
  #  else
        /* Not building a DLL, or the DLL doesn't require specific export
         * definitions.
         */
  #     define PNG_IMPEXP
  #  endif
  #endif
  
  /* No warnings for private or deprecated functions in the build: */
  #ifndef PNG_DEPRECATED
  #  define PNG_DEPRECATED
  #endif
  #ifndef PNG_PRIVATE
  #  define PNG_PRIVATE
  #endif
  
  /* Symbol preprocessing support.
   *
   * To enable listing global, but internal, symbols the following macros should
   * always be used to declare an extern data or function object in this file.
   */
  #ifndef PNG_INTERNAL_DATA
  #  define PNG_INTERNAL_DATA(type, name, array) extern type name array
  #endif
  
  #ifndef PNG_INTERNAL_FUNCTION
  #  define PNG_INTERNAL_FUNCTION(type, name, args, attributes)\
        extern PNG_FUNCTION(type, name, args, PNG_EMPTY attributes)
  #endif
  
  #ifndef PNG_INTERNAL_CALLBACK
  #  define PNG_INTERNAL_CALLBACK(type, name, args, attributes)\
        extern PNG_FUNCTION(type, (PNGCBAPI name), args, PNG_EMPTY attributes)
  #endif
  
  /* If floating or fixed point APIs are disabled they may still be compiled
   * internally.  To handle this make sure they are declared as the appropriate
   * internal extern function (otherwise the symbol prefixing stuff won't work and
   * the functions will be used without definitions.)
   *
   * NOTE: although all the API functions are declared here they are not all
   * actually built!  Because the declarations are still made it is necessary to
   * fake out types that they depend on.
   */
  #ifndef PNG_FP_EXPORT
  #  ifndef PNG_FLOATING_POINT_SUPPORTED
  #     define PNG_FP_EXPORT(ordinal, type, name, args)\
           PNG_INTERNAL_FUNCTION(type, name, args, PNG_EMPTY);
  #     ifndef PNG_VERSION_INFO_ONLY
           typedef struct png_incomplete png_double;
           typedef png_double*           png_doublep;
           typedef const png_double*     png_const_doublep;
           typedef png_double**          png_doublepp;
  #     endif
  #  endif
  #endif
  #ifndef PNG_FIXED_EXPORT
  #  ifndef PNG_FIXED_POINT_SUPPORTED
  #     define PNG_FIXED_EXPORT(ordinal, type, name, args)\
           PNG_INTERNAL_FUNCTION(type, name, args, PNG_EMPTY);
  #  endif
  #endif
  
  #include "png.h"
  
  /* pngconf.h does not set PNG_DLL_EXPORT unless it is required, so: */
  #ifndef PNG_DLL_EXPORT
  #  define PNG_DLL_EXPORT
  #endif
  
  /* SECURITY and SAFETY:
   *
   * By default libpng is built without any internal limits on image size,
   * individual heap (png_malloc) allocations or the total amount of memory used.
   * If PNG_SAFE_LIMITS_SUPPORTED is defined, however, the limits below are used
   * (unless individually overridden).  These limits are believed to be fairly
   * safe, but builders of secure systems should verify the values against the
   * real system capabilities.
   */
  #ifdef PNG_SAFE_LIMITS_SUPPORTED
     /* 'safe' limits */
  #  ifndef PNG_USER_WIDTH_MAX
  #     define PNG_USER_WIDTH_MAX 1000000
  #  endif
  #  ifndef PNG_USER_HEIGHT_MAX
  #     define PNG_USER_HEIGHT_MAX 1000000
  #  endif
  #  ifndef PNG_USER_CHUNK_CACHE_MAX
  #     define PNG_USER_CHUNK_CACHE_MAX 128
  #  endif
  #  ifndef PNG_USER_CHUNK_MALLOC_MAX
  #     define PNG_USER_CHUNK_MALLOC_MAX 8000000
  #  endif
  #else
     /* values for no limits */
  #  ifndef PNG_USER_WIDTH_MAX
  #     define PNG_USER_WIDTH_MAX 0x7fffffff
  #  endif
  #  ifndef PNG_USER_HEIGHT_MAX
  #     define PNG_USER_HEIGHT_MAX 0x7fffffff
  #  endif
  #  ifndef PNG_USER_CHUNK_CACHE_MAX
  #     define PNG_USER_CHUNK_CACHE_MAX 0
  #  endif
  #  ifndef PNG_USER_CHUNK_MALLOC_MAX
  #     define PNG_USER_CHUNK_MALLOC_MAX 0
  #  endif
  #endif
  
  /* Moved to pngpriv.h at libpng-1.5.0 */
  /* NOTE: some of these may have been used in external applications as
   * these definitions were exposed in pngconf.h prior to 1.5.
   */
  
  /* If you are running on a machine where you cannot allocate more
   * than 64K of memory at once, uncomment this.  While libpng will not
   * normally need that much memory in a chunk (unless you load up a very
   * large file), zlib needs to know how big of a chunk it can use, and
   * libpng thus makes sure to check any memory allocation to verify it
   * will fit into memory.
   *
   * zlib provides 'MAXSEG_64K' which, if defined, indicates the
   * same limit and pngconf.h (already included) sets the limit
   * if certain operating systems are detected.
   */
  #if defined(MAXSEG_64K) && !defined(PNG_MAX_MALLOC_64K)
  #  define PNG_MAX_MALLOC_64K
  #endif
  
  #ifndef PNG_UNUSED
  /* Unused formal parameter warnings are silenced using the following macro
   * which is expected to have no bad effects on performance (optimizing
   * compilers will probably remove it entirely).  Note that if you replace
   * it with something other than whitespace, you must include the terminating
   * semicolon.
   */
  #  define PNG_UNUSED(param) (void)param;
  #endif
  
  /* Just a little check that someone hasn't tried to define something
   * contradictory.
   */
  #if (PNG_ZBUF_SIZE > 65536L) && defined(PNG_MAX_MALLOC_64K)
  #  undef PNG_ZBUF_SIZE
  #  define PNG_ZBUF_SIZE 65536L
  #endif
  
  /* If warnings or errors are turned off the code is disabled or redirected here.
   * From 1.5.4 functions have been added to allow very limited formatting of
   * error and warning messages - this code will also be disabled here.
   */
  #ifdef PNG_WARNINGS_SUPPORTED
  #  define PNG_WARNING_PARAMETERS(p) png_warning_parameters p;
  #else
  #  define png_warning_parameter(p,number,string) ((void)0)
  #  define png_warning_parameter_unsigned(p,number,format,value) ((void)0)
  #  define png_warning_parameter_signed(p,number,format,value) ((void)0)
  #  define png_formatted_warning(pp,p,message) ((void)(pp))
  #  define PNG_WARNING_PARAMETERS(p)
  #endif
  #ifndef PNG_ERROR_TEXT_SUPPORTED
  #  define png_fixed_error(s1,s2) png_err(s1)
  #endif
  
  /* C allows up-casts from (void*) to any pointer and (const void*) to any
   * pointer to a const object.  C++ regards this as a type error and requires an
   * explicit, static, cast and provides the static_cast<> rune to ensure that
   * const is not cast away.
   */
  #ifdef __cplusplus
  #  define png_voidcast(type, value) static_cast<type>(value)
  #  define png_constcast(type, value) const_cast<type>(value)
  #  define png_aligncast(type, value) \
     static_cast<type>(static_cast<void*>(value))
  #  define png_aligncastconst(type, value) \
     static_cast<type>(static_cast<const void*>(value))
  #else
  #  define png_voidcast(type, value) (value)
  #  define png_constcast(type, value) ((type)(value))
  #  define png_aligncast(type, value) ((void*)(value))
  #  define png_aligncastconst(type, value) ((const void*)(value))
  #endif /* __cplusplus */
  
  /* Some fixed point APIs are still required even if not exported because
   * they get used by the corresponding floating point APIs.  This magic
   * deals with this:
   */
  #ifdef PNG_FIXED_POINT_SUPPORTED
  #  define PNGFAPI PNGAPI
  #else
  #  define PNGFAPI /* PRIVATE */
  #endif
  
  #ifndef PNG_VERSION_INFO_ONLY
  /* Other defines specific to compilers can go here.  Try to keep
   * them inside an appropriate ifdef/endif pair for portability.
   */
  #if defined(PNG_FLOATING_POINT_SUPPORTED) ||\
      defined(PNG_FLOATING_ARITHMETIC_SUPPORTED)
     /* png.c requires the following ANSI-C constants if the conversion of
      * floating point to ASCII is implemented therein:
      *
      *  DBL_DIG  Maximum number of decimal digits (can be set to any constant)
      *  DBL_MIN  Smallest normalized fp number (can be set to an arbitrary value)
      *  DBL_MAX  Maximum floating point number (can be set to an arbitrary value)
      */
  #  include <float.h>
  
  #  if (defined(__MWERKS__) && defined(macintosh)) || defined(applec) || \
      defined(THINK_C) || defined(__SC__) || defined(TARGET_OS_MAC)
       /* We need to check that <math.h> hasn't already been included earlier
        * as it seems it doesn't agree with <fp.h>, yet we should really use
        * <fp.h> if possible.
        */
  #    if !defined(__MATH_H__) && !defined(__MATH_H) && !defined(__cmath__)
  #      include <fp.h>
  #    endif
  #  else
  #    include <math.h>
  #  endif
  #  if defined(_AMIGA) && defined(__SASC) && defined(_M68881)
       /* Amiga SAS/C: We must include builtin FPU functions when compiling using
        * MATH=68881
        */
  #    include <m68881.h>
  #  endif
  #endif
  
  /* This provides the non-ANSI (far) memory allocation routines. */
  #if defined(__TURBOC__) && defined(__MSDOS__)
  #  include <mem.h>
  #  include <alloc.h>
  #endif
  
  #if defined(WIN32) || defined(_Windows) || defined(_WINDOWS) || \
      defined(_WIN32) || defined(__WIN32__)
  #  include <windows.h>  /* defines _WINDOWS_ macro */
  #endif
  #endif /* PNG_VERSION_INFO_ONLY */
  
  /* Moved here around 1.5.0beta36 from pngconf.h */
  /* Users may want to use these so they are not private.  Any library
   * functions that are passed far data must be model-independent.
   */
  
  /* Memory model/platform independent fns */
  #ifndef PNG_ABORT
  #  ifdef _WINDOWS_
  #    define PNG_ABORT() ExitProcess(0)
  #  else
  #    define PNG_ABORT() abort()
  #  endif
  #endif
  
  /* These macros may need to be architecture dependent. */
  #define PNG_ALIGN_NONE   0 /* do not use data alignment */
  #define PNG_ALIGN_ALWAYS 1 /* assume unaligned accesses are OK */
  #ifdef offsetof
  #  define PNG_ALIGN_OFFSET 2 /* use offsetof to determine alignment */
  #else
  #  define PNG_ALIGN_OFFSET -1 /* prevent the use of this */
  #endif
  #define PNG_ALIGN_SIZE   3 /* use sizeof to determine alignment */
  
  #ifndef PNG_ALIGN_TYPE
     /* Default to using aligned access optimizations and requiring alignment to a
      * multiple of the data type size.  Override in a compiler specific fashion
      * if necessary by inserting tests here:
      */
  #  define PNG_ALIGN_TYPE PNG_ALIGN_SIZE
  #endif
  
  #if PNG_ALIGN_TYPE == PNG_ALIGN_SIZE
     /* This is used because in some compiler implementations non-aligned
      * structure members are supported, so the offsetof approach below fails.
      * Set PNG_ALIGN_SIZE=0 for compiler combinations where unaligned access
      * is good for performance.  Do not do this unless you have tested the result
      * and understand it.
      */
  #  define png_alignof(type) (sizeof (type))
  #else
  #  if PNG_ALIGN_TYPE == PNG_ALIGN_OFFSET
  #     define png_alignof(type) offsetof(struct{char c; type t;}, t)
  #  else
  #     if PNG_ALIGN_TYPE == PNG_ALIGN_ALWAYS
  #        define png_alignof(type) (1)
  #     endif
        /* Else leave png_alignof undefined to prevent use thereof */
  #  endif
  #endif
  
  /* This implicitly assumes alignment is always to a power of 2. */
  #ifdef png_alignof
  #  define png_isaligned(ptr, type)\
     ((((const char*)ptr-(const char*)0) & (png_alignof(type)-1)) == 0)
  #else
  #  define png_isaligned(ptr, type) 0
  #endif
  
  /* End of memory model/platform independent support */
  /* End of 1.5.0beta36 move from pngconf.h */
  
  /* CONSTANTS and UTILITY MACROS
   * These are used internally by libpng and not exposed in the API
   */
  
  /* Various modes of operation.  Note that after an init, mode is set to
   * zero automatically when the structure is created.  Three of these
   * are defined in png.h because they need to be visible to applications
   * that call png_set_unknown_chunk().
   */
  /* #define PNG_HAVE_IHDR            0x01 (defined in png.h) */
  /* #define PNG_HAVE_PLTE            0x02 (defined in png.h) */
  #define PNG_HAVE_IDAT               0x04
  /* #define PNG_AFTER_IDAT           0x08 (defined in png.h) */
  #define PNG_HAVE_IEND               0x10
                     /*               0x20 (unused) */
                     /*               0x40 (unused) */
                     /*               0x80 (unused) */
  #define PNG_HAVE_CHUNK_HEADER      0x100
  #define PNG_WROTE_tIME             0x200
  #define PNG_WROTE_INFO_BEFORE_PLTE 0x400
  #define PNG_BACKGROUND_IS_GRAY     0x800
  #define PNG_HAVE_PNG_SIGNATURE    0x1000
  #define PNG_HAVE_CHUNK_AFTER_IDAT 0x2000 /* Have another chunk after IDAT */
                     /*             0x4000 (unused) */
  #define PNG_IS_READ_STRUCT        0x8000 /* Else is a write struct */
  
  /* Flags for the transformations the PNG library does on the image data */
  #define PNG_BGR                 0x0001
  #define PNG_INTERLACE           0x0002
  #define PNG_PACK                0x0004
  #define PNG_SHIFT               0x0008
  #define PNG_SWAP_BYTES          0x0010
  #define PNG_INVERT_MONO         0x0020
  #define PNG_QUANTIZE            0x0040
  #define PNG_COMPOSE             0x0080     /* Was PNG_BACKGROUND */
  #define PNG_BACKGROUND_EXPAND   0x0100
  #define PNG_EXPAND_16           0x0200     /* Added to libpng 1.5.2 */
  #define PNG_16_TO_8             0x0400     /* Becomes 'chop' in 1.5.4 */
  #define PNG_RGBA                0x0800
  #define PNG_EXPAND              0x1000
  #define PNG_GAMMA               0x2000
  #define PNG_GRAY_TO_RGB         0x4000
  #define PNG_FILLER              0x8000
  #define PNG_PACKSWAP           0x10000
  #define PNG_SWAP_ALPHA         0x20000
  #define PNG_STRIP_ALPHA        0x40000
  #define PNG_INVERT_ALPHA       0x80000
  #define PNG_USER_TRANSFORM    0x100000
  #define PNG_RGB_TO_GRAY_ERR   0x200000
  #define PNG_RGB_TO_GRAY_WARN  0x400000
  #define PNG_RGB_TO_GRAY       0x600000 /* two bits, RGB_TO_GRAY_ERR|WARN */
  #define PNG_ENCODE_ALPHA      0x800000 /* Added to libpng-1.5.4 */
  #define PNG_ADD_ALPHA         0x1000000 /* Added to libpng-1.2.7 */
  #define PNG_EXPAND_tRNS       0x2000000 /* Added to libpng-1.2.9 */
  #define PNG_SCALE_16_TO_8     0x4000000 /* Added to libpng-1.5.4 */
                         /*   0x8000000 unused */
                         /*  0x10000000 unused */
                         /*  0x20000000 unused */
                         /*  0x40000000 unused */
  /* Flags for png_create_struct */
  #define PNG_STRUCT_PNG   0x0001
  #define PNG_STRUCT_INFO  0x0002
  
  /* Scaling factor for filter heuristic weighting calculations */
  #define PNG_WEIGHT_FACTOR (1<<(PNG_WEIGHT_SHIFT))
  #define PNG_COST_FACTOR (1<<(PNG_COST_SHIFT))
  
  /* Flags for the png_ptr->flags rather than declaring a byte for each one */
  #define PNG_FLAG_ZLIB_CUSTOM_STRATEGY     0x0001
  #define PNG_FLAG_ZSTREAM_INITIALIZED      0x0002 /* Added to libpng-1.6.0 */
                                    /*      0x0004    unused */
  #define PNG_FLAG_ZSTREAM_ENDED            0x0008 /* Added to libpng-1.6.0 */
                                    /*      0x0010    unused */
                                    /*      0x0020    unused */
  #define PNG_FLAG_ROW_INIT                 0x0040
  #define PNG_FLAG_FILLER_AFTER             0x0080
  #define PNG_FLAG_CRC_ANCILLARY_USE        0x0100
  #define PNG_FLAG_CRC_ANCILLARY_NOWARN     0x0200
  #define PNG_FLAG_CRC_CRITICAL_USE         0x0400
  #define PNG_FLAG_CRC_CRITICAL_IGNORE      0x0800
  #define PNG_FLAG_ASSUME_sRGB              0x1000 /* Added to libpng-1.5.4 */
  #define PNG_FLAG_OPTIMIZE_ALPHA           0x2000 /* Added to libpng-1.5.4 */
  #define PNG_FLAG_DETECT_UNINITIALIZED     0x4000 /* Added to libpng-1.5.4 */
  /* #define PNG_FLAG_KEEP_UNKNOWN_CHUNKS      0x8000 */
  /* #define PNG_FLAG_KEEP_UNSAFE_CHUNKS      0x10000 */
  #define PNG_FLAG_LIBRARY_MISMATCH        0x20000
  #define PNG_FLAG_STRIP_ERROR_NUMBERS     0x40000
  #define PNG_FLAG_STRIP_ERROR_TEXT        0x80000
  #define PNG_FLAG_BENIGN_ERRORS_WARN     0x100000 /* Added to libpng-1.4.0 */
  #define PNG_FLAG_APP_WARNINGS_WARN      0x200000 /* Added to libpng-1.6.0 */
  #define PNG_FLAG_APP_ERRORS_WARN        0x400000 /* Added to libpng-1.6.0 */
                                    /*    0x800000    unused */
                                    /*   0x1000000    unused */
                                    /*   0x2000000    unused */
                                    /*   0x4000000    unused */
                                    /*   0x8000000    unused */
                                    /*  0x10000000    unused */
                                    /*  0x20000000    unused */
                                    /*  0x40000000    unused */
  
  #define PNG_FLAG_CRC_ANCILLARY_MASK (PNG_FLAG_CRC_ANCILLARY_USE | \
                                       PNG_FLAG_CRC_ANCILLARY_NOWARN)
  
  #define PNG_FLAG_CRC_CRITICAL_MASK  (PNG_FLAG_CRC_CRITICAL_USE | \
                                       PNG_FLAG_CRC_CRITICAL_IGNORE)
  
  #define PNG_FLAG_CRC_MASK           (PNG_FLAG_CRC_ANCILLARY_MASK | \
                                       PNG_FLAG_CRC_CRITICAL_MASK)
  
  /* Save typing and make code easier to understand */
  
  #define PNG_COLOR_DIST(c1, c2) (abs((int)((c1).red) - (int)((c2).red)) + \
     abs((int)((c1).green) - (int)((c2).green)) + \
     abs((int)((c1).blue) - (int)((c2).blue)))
  
  /* Added to libpng-1.6.0: scale a 16-bit value in the range 0..65535 to 0..255
   * by dividing by 257 *with rounding*.  This macro is exact for the given range.
   * See the discourse in pngrtran.c png_do_scale_16_to_8.  The values in the
   * macro were established by experiment (modifying the added value).  The macro
   * has a second variant that takes a value already scaled by 255 and divides by
   * 65535 - this has a maximum error of .502.  Over the range 0..65535*65535 it
   * only gives off-by-one errors and only for 0.5% (1 in 200) of the values.
   */
  #define PNG_DIV65535(v24) (((v24) + 32895) >> 16)
  #define PNG_DIV257(v16) PNG_DIV65535((png_uint_32)(v16) * 255)
  
  /* Added to libpng-1.2.6 JB */
  #define PNG_ROWBYTES(pixel_bits, width) \
      ((pixel_bits) >= 8 ? \
      ((png_size_t)(width) * (((png_size_t)(pixel_bits)) >> 3)) : \
      (( ((png_size_t)(width) * ((png_size_t)(pixel_bits))) + 7) >> 3) )
  
  /* PNG_OUT_OF_RANGE returns true if value is outside the range
   * ideal-delta..ideal+delta.  Each argument is evaluated twice.
   * "ideal" and "delta" should be constants, normally simple
   * integers, "value" a variable. Added to libpng-1.2.6 JB
   */
  #define PNG_OUT_OF_RANGE(value, ideal, delta) \
     ( (value) < (ideal)-(delta) || (value) > (ideal)+(delta) )
  
  /* Conversions between fixed and floating point, only defined if
   * required (to make sure the code doesn't accidentally use float
   * when it is supposedly disabled.)
   */
  #ifdef PNG_FLOATING_POINT_SUPPORTED
  /* The floating point conversion can't overflow, though it can and
   * does lose accuracy relative to the original fixed point value.
   * In practice this doesn't matter because png_fixed_point only
   * stores numbers with very low precision.  The png_ptr and s
   * arguments are unused by default but are there in case error
   * checking becomes a requirement.
   */
  #define png_float(png_ptr, fixed, s) (.00001 * (fixed))
  
  /* The fixed point conversion performs range checking and evaluates
   * its argument multiple times, so must be used with care.  The
   * range checking uses the PNG specification values for a signed
   * 32 bit fixed point value except that the values are deliberately
   * rounded-to-zero to an integral value - 21474 (21474.83 is roughly
   * (2^31-1) * 100000). 's' is a string that describes the value being
   * converted.
   *
   * NOTE: this macro will raise a png_error if the range check fails,
   * therefore it is normally only appropriate to use this on values
   * that come from API calls or other sources where an out of range
   * error indicates a programming error, not a data error!
   *
   * NOTE: by default this is off - the macro is not used - because the
   * function call saves a lot of code.
   */
  #ifdef PNG_FIXED_POINT_MACRO_SUPPORTED
  #define png_fixed(png_ptr, fp, s) ((fp) <= 21474 && (fp) >= -21474 ?\
      ((png_fixed_point)(100000 * (fp))) : (png_fixed_error(png_ptr, s),0))
  #endif
  /* else the corresponding function is defined below, inside the scope of the
   * cplusplus test.
   */
  #endif
  
  /* Constants for known chunk types.  If you need to add a chunk, define the name
   * here.  For historical reasons these constants have the form png_<name>; i.e.
   * the prefix is lower case.  Please use decimal values as the parameters to
   * match the ISO PNG specification and to avoid relying on the C locale
   * interpretation of character values.
   *
   * Prior to 1.5.6 these constants were strings, as of 1.5.6 png_uint_32 values
   * are computed and a new macro (PNG_STRING_FROM_CHUNK) added to allow a string
   * to be generated if required.
   *
   * PNG_32b correctly produces a value shifted by up to 24 bits, even on
   * architectures where (int) is only 16 bits.
   */
  #define PNG_32b(b,s) ((png_uint_32)(b) << (s))
  #define PNG_U32(b1,b2,b3,b4) \
     (PNG_32b(b1,24) | PNG_32b(b2,16) | PNG_32b(b3,8) | PNG_32b(b4,0))
  
  /* Constants for known chunk types.
   *
   * MAINTAINERS: If you need to add a chunk, define the name here.
   * For historical reasons these constants have the form png_<name>; i.e.
   * the prefix is lower case.  Please use decimal values as the parameters to
   * match the ISO PNG specification and to avoid relying on the C locale
   * interpretation of character values.  Please keep the list sorted.
   *
   * Notice that PNG_U32 is used to define a 32-bit value for the 4 byte chunk
   * type.  In fact the specification does not express chunk types this way,
   * however using a 32-bit value means that the chunk type can be read from the
   * stream using exactly the same code as used for a 32-bit unsigned value and
   * can be examined far more efficiently (using one arithmetic compare).
   *
   * Prior to 1.5.6 the chunk type constants were expressed as C strings.  The
   * libpng API still uses strings for 'unknown' chunks and a macro,
   * PNG_STRING_FROM_CHUNK, allows a string to be generated if required.  Notice
   * that for portable code numeric values must still be used; the string "IHDR"
   * is not portable and neither is PNG_U32('I', 'H', 'D', 'R').
   *
   * In 1.7.0 the definitions will be made public in png.h to avoid having to
   * duplicate the same definitions in application code.
   */
  #define png_IDAT PNG_U32( 73,  68,  65,  84)
  #define png_IEND PNG_U32( 73,  69,  78,  68)
  #define png_IHDR PNG_U32( 73,  72,  68,  82)
  #define png_PLTE PNG_U32( 80,  76,  84,  69)
  #define png_bKGD PNG_U32( 98,  75,  71,  68)
  #define png_cHRM PNG_U32( 99,  72,  82,  77)
  #define png_fRAc PNG_U32(102,  82,  65,  99) /* registered, not defined */
  #define png_gAMA PNG_U32(103,  65,  77,  65)
  #define png_gIFg PNG_U32(103,  73,  70, 103)
  #define png_gIFt PNG_U32(103,  73,  70, 116) /* deprecated */
  #define png_gIFx PNG_U32(103,  73,  70, 120)
  #define png_hIST PNG_U32(104,  73,  83,  84)
  #define png_iCCP PNG_U32(105,  67,  67,  80)
  #define png_iTXt PNG_U32(105,  84,  88, 116)
  #define png_oFFs PNG_U32(111,  70,  70, 115)
  #define png_pCAL PNG_U32(112,  67,  65,  76)
  #define png_pHYs PNG_U32(112,  72,  89, 115)
  #define png_sBIT PNG_U32(115,  66,  73,  84)
  #define png_sCAL PNG_U32(115,  67,  65,  76)
  #define png_sPLT PNG_U32(115,  80,  76,  84)
  #define png_sRGB PNG_U32(115,  82,  71,  66)
  #define png_sTER PNG_U32(115,  84,  69,  82)
  #define png_tEXt PNG_U32(116,  69,  88, 116)
  #define png_tIME PNG_U32(116,  73,  77,  69)
  #define png_tRNS PNG_U32(116,  82,  78,  83)
  #define png_zTXt PNG_U32(122,  84,  88, 116)
  
  /* The following will work on (signed char*) strings, whereas the get_uint_32
   * macro will fail on top-bit-set values because of the sign extension.
   */
  #define PNG_CHUNK_FROM_STRING(s)\
     PNG_U32(0xff&(s)[0], 0xff&(s)[1], 0xff&(s)[2], 0xff&(s)[3])
  
  /* This uses (char), not (png_byte) to avoid warnings on systems where (char) is
   * signed and the argument is a (char[])  This macro will fail miserably on
   * systems where (char) is more than 8 bits.
   */
  #define PNG_STRING_FROM_CHUNK(s,c)\
     (void)(((char*)(s))[0]=(char)((c)>>24), ((char*)(s))[1]=(char)((c)>>16),\
     ((char*)(s))[2]=(char)((c)>>8), ((char*)(s))[3]=(char)((c)))
  
  /* Do the same but terminate with a null character. */
  #define PNG_CSTRING_FROM_CHUNK(s,c)\
     (void)(PNG_STRING_FROM_CHUNK(s,c), ((char*)(s))[4] = 0)
  
  /* Test on flag values as defined in the spec (section 5.4): */
  #define PNG_CHUNK_ANCILLARY(c)   (1 & ((c) >> 29))
  #define PNG_CHUNK_CRITICAL(c)     (!PNG_CHUNK_ANCILLARY(c))
  #define PNG_CHUNK_PRIVATE(c)      (1 & ((c) >> 21))
  #define PNG_CHUNK_RESERVED(c)     (1 & ((c) >> 13))
  #define PNG_CHUNK_SAFE_TO_COPY(c) (1 & ((c) >>  5))
  
  /* Gamma values (new at libpng-1.5.4): */
  #define PNG_GAMMA_MAC_OLD 151724  /* Assume '1.8' is really 2.2/1.45! */
  #define PNG_GAMMA_MAC_INVERSE 65909
  #define PNG_GAMMA_sRGB_INVERSE 45455
  
  /* Almost everything below is C specific; the #defines above can be used in
   * non-C code (so long as it is C-preprocessed) the rest of this stuff cannot.
   */
  #ifndef PNG_VERSION_INFO_ONLY
  
  #include "pngstruct.h"
  #include "pnginfo.h"
  
  /* Validate the include paths - the include path used to generate pnglibconf.h
   * must match that used in the build, or we must be using pnglibconf.h.prebuilt:
   */
  #if PNG_ZLIB_VERNUM != 0 && PNG_ZLIB_VERNUM != ZLIB_VERNUM
  #  error ZLIB_VERNUM != PNG_ZLIB_VERNUM \
        "-I (include path) error: see the notes in pngpriv.h"
     /* This means that when pnglibconf.h was built the copy of zlib.h that it
      * used is not the same as the one being used here.  Because the build of
      * libpng makes decisions to use inflateInit2 and inflateReset2 based on the
      * zlib version number and because this affects handling of certain broken
      * PNG files the -I directives must match.
      *
      * The most likely explanation is that you passed a -I in CFLAGS. This will
      * not work; all the preprocessor directories and in particular all the -I
      * directives must be in CPPFLAGS.
      */
  #endif
  
  /* This is used for 16 bit gamma tables -- only the top level pointers are
   * const; this could be changed:
   */
  typedef const png_uint_16p * png_const_uint_16pp;
  
  /* Added to libpng-1.5.7: sRGB conversion tables */
  #if defined(PNG_SIMPLIFIED_READ_SUPPORTED) ||\
     defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)
  #ifdef PNG_SIMPLIFIED_READ_SUPPORTED
  PNG_INTERNAL_DATA(const png_uint_16, png_sRGB_table, [256]);
     /* Convert from an sRGB encoded value 0..255 to a 16-bit linear value,
      * 0..65535.  This table gives the closest 16-bit answers (no errors).
      */
  #endif
  
  PNG_INTERNAL_DATA(const png_uint_16, png_sRGB_base, [512]);
  PNG_INTERNAL_DATA(const png_byte, png_sRGB_delta, [512]);
  
  #define PNG_sRGB_FROM_LINEAR(linear) ((png_byte)((png_sRGB_base[(linear)>>15] +\
     ((((linear)&0x7fff)*png_sRGB_delta[(linear)>>15])>>12)) >> 8))
     /* Given a value 'linear' in the range 0..255*65535 calculate the 8-bit sRGB
      * encoded value with maximum error 0.646365.  Note that the input is not a
      * 16-bit value; it has been multiplied by 255! */
  #endif /* SIMPLIFIED_READ/WRITE */
  
  
  /* Inhibit C++ name-mangling for libpng functions but not for system calls. */
  #ifdef __cplusplus
  extern "C" {
  #endif /* __cplusplus */
  
  /* Internal functions; these are not exported from a DLL however because they
   * are used within several of the C source files they have to be C extern.
   *
   * All of these functions must be declared with PNG_INTERNAL_FUNCTION.
   */
  
  /* Zlib support */
  #define PNG_UNEXPECTED_ZLIB_RETURN (-7)
  PNG_INTERNAL_FUNCTION(void, png_zstream_error,(png_structrp png_ptr, int ret),
     PNG_EMPTY);
     /* Used by the zlib handling functions to ensure that z_stream::msg is always
      * set before they return.
      */
  
  #ifdef PNG_WRITE_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_free_buffer_list,(png_structrp png_ptr,
     png_compression_bufferp *list),PNG_EMPTY);
     /* Free the buffer list used by the compressed write code. */
  #endif
  
  #if defined(PNG_FLOATING_POINT_SUPPORTED) && \
     !defined(PNG_FIXED_POINT_MACRO_SUPPORTED) && \
     (defined(PNG_gAMA_SUPPORTED) || defined(PNG_cHRM_SUPPORTED) || \
     defined(PNG_sCAL_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED) || \
     defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)) || \
     (defined(PNG_sCAL_SUPPORTED) && \
     defined(PNG_FLOATING_ARITHMETIC_SUPPORTED))
  PNG_INTERNAL_FUNCTION(png_fixed_point,png_fixed,(png_const_structrp png_ptr,
     double fp, png_const_charp text),PNG_EMPTY);
  #endif
  
  /* Check the user version string for compatibility, returns false if the version
   * numbers aren't compatible.
   */
  PNG_INTERNAL_FUNCTION(int,png_user_version_check,(png_structrp png_ptr,
     png_const_charp user_png_ver),PNG_EMPTY);
  
  /* Internal base allocator - no messages, NULL on failure to allocate.  This
   * does, however, call the application provided allocator and that could call
   * png_error (although that would be a bug in the application implementation.)
   */
  PNG_INTERNAL_FUNCTION(png_voidp,png_malloc_base,(png_const_structrp png_ptr,
     png_alloc_size_t size),PNG_ALLOCATED);
  
  #if defined(PNG_TEXT_SUPPORTED) || defined(PNG_sPLT_SUPPORTED) ||\
     defined(PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED)
  /* Internal array allocator, outputs no error or warning messages on failure,
   * just returns NULL.  
   */
  PNG_INTERNAL_FUNCTION(png_voidp,png_malloc_array,(png_const_structrp png_ptr,
     int nelements, size_t element_size),PNG_ALLOCATED);
  
  /* The same but an existing array is extended by add_elements.  This function
   * also memsets the new elements to 0 and copies the old elements.  The old
   * array is not freed or altered.
   */
  PNG_INTERNAL_FUNCTION(png_voidp,png_realloc_array,(png_const_structrp png_ptr,
     png_const_voidp array, int old_elements, int add_elements,
     size_t element_size),PNG_ALLOCATED);
  #endif /* text, sPLT or unknown chunks */
  
  /* Magic to create a struct when there is no struct to call the user supplied
   * memory allocators.  Because error handling has not been set up the memory
   * handlers can't safely call png_error, but this is an obscure and undocumented
   * restriction so libpng has to assume that the 'free' handler, at least, might
   * call png_error.
   */
  PNG_INTERNAL_FUNCTION(png_structp,png_create_png_struct,
     (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_ALLOCATED);
  
  /* Free memory from internal libpng struct */
  PNG_INTERNAL_FUNCTION(void,png_destroy_png_struct,(png_structrp png_ptr),
     PNG_EMPTY);
  
  /* Free an allocated jmp_buf (always succeeds) */
  PNG_INTERNAL_FUNCTION(void,png_free_jmpbuf,(png_structrp png_ptr),PNG_EMPTY);
  
  /* Function to allocate memory for zlib.  PNGAPI is disallowed. */
  PNG_INTERNAL_FUNCTION(voidpf,png_zalloc,(voidpf png_ptr, uInt items, uInt size),
     PNG_ALLOCATED);
  
  /* Function to free memory for zlib.  PNGAPI is disallowed. */
  PNG_INTERNAL_FUNCTION(void,png_zfree,(voidpf png_ptr, voidpf ptr),PNG_EMPTY);
  
  /* Next four functions are used internally as callbacks.  PNGCBAPI is required
   * but not PNG_EXPORT.  PNGAPI added at libpng version 1.2.3, changed to
   * PNGCBAPI at 1.5.0
   */
  
  PNG_INTERNAL_FUNCTION(void PNGCBAPI,png_default_read_data,(png_structp png_ptr,
      png_bytep data, png_size_t length),PNG_EMPTY);
  
  #ifdef PNG_PROGRESSIVE_READ_SUPPORTED
  PNG_INTERNAL_FUNCTION(void PNGCBAPI,png_push_fill_buffer,(png_structp png_ptr,
      png_bytep buffer, png_size_t length),PNG_EMPTY);
  #endif
  
  PNG_INTERNAL_FUNCTION(void PNGCBAPI,png_default_write_data,(png_structp png_ptr,
      png_bytep data, png_size_t length),PNG_EMPTY);
  
  #ifdef PNG_WRITE_FLUSH_SUPPORTED
  #  ifdef PNG_STDIO_SUPPORTED
  PNG_INTERNAL_FUNCTION(void PNGCBAPI,png_default_flush,(png_structp png_ptr),
     PNG_EMPTY);
  #  endif
  #endif
  
  /* Reset the CRC variable */
  PNG_INTERNAL_FUNCTION(void,png_reset_crc,(png_structrp png_ptr),PNG_EMPTY);
  
  /* Write the "data" buffer to whatever output you are using */
  PNG_INTERNAL_FUNCTION(void,png_write_data,(png_structrp png_ptr,
      png_const_bytep data, png_size_t length),PNG_EMPTY);
  
  /* Read and check the PNG file signature */
  PNG_INTERNAL_FUNCTION(void,png_read_sig,(png_structrp png_ptr,
     png_inforp info_ptr),PNG_EMPTY);
  
  /* Read the chunk header (length + type name) */
  PNG_INTERNAL_FUNCTION(png_uint_32,png_read_chunk_header,(png_structrp png_ptr),
     PNG_EMPTY);
  
  /* Read data from whatever input you are using into the "data" buffer */
  PNG_INTERNAL_FUNCTION(void,png_read_data,(png_structrp png_ptr, png_bytep data,
      png_size_t length),PNG_EMPTY);
  
  /* Read bytes into buf, and update png_ptr->crc */
  PNG_INTERNAL_FUNCTION(void,png_crc_read,(png_structrp png_ptr, png_bytep buf,
      png_uint_32 length),PNG_EMPTY);
  
  /* Read "skip" bytes, read the file crc, and (optionally) verify png_ptr->crc */
  PNG_INTERNAL_FUNCTION(int,png_crc_finish,(png_structrp png_ptr,
     png_uint_32 skip),PNG_EMPTY);
  
  /* Read the CRC from the file and compare it to the libpng calculated CRC */
  PNG_INTERNAL_FUNCTION(int,png_crc_error,(png_structrp png_ptr),PNG_EMPTY);
  
  /* Calculate the CRC over a section of data.  Note that we are only
   * passing a maximum of 64K on systems that have this as a memory limit,
   * since this is the maximum buffer size we can specify.
   */
  PNG_INTERNAL_FUNCTION(void,png_calculate_crc,(png_structrp png_ptr,
     png_const_bytep ptr, png_size_t length),PNG_EMPTY);
  
  #ifdef PNG_WRITE_FLUSH_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_flush,(png_structrp png_ptr),PNG_EMPTY);
  #endif
  
  /* Write various chunks */
  
  /* Write the IHDR chunk, and update the png_struct with the necessary
   * information.
   */
  PNG_INTERNAL_FUNCTION(void,png_write_IHDR,(png_structrp png_ptr,
     png_uint_32 width, png_uint_32 height, int bit_depth, int color_type,
     int compression_method, int filter_method, int interlace_method),PNG_EMPTY);
  
  PNG_INTERNAL_FUNCTION(void,png_write_PLTE,(png_structrp png_ptr,
     png_const_colorp palette, png_uint_32 num_pal),PNG_EMPTY);
  
  PNG_INTERNAL_FUNCTION(void,png_compress_IDAT,(png_structrp png_ptr,
     png_const_bytep row_data, png_alloc_size_t row_data_length, int flush),
     PNG_EMPTY);
  
  PNG_INTERNAL_FUNCTION(void,png_write_IEND,(png_structrp png_ptr),PNG_EMPTY);
  
  #ifdef PNG_WRITE_gAMA_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_write_gAMA_fixed,(png_structrp png_ptr,
      png_fixed_point file_gamma),PNG_EMPTY);
  #endif
  
  #ifdef PNG_WRITE_sBIT_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_write_sBIT,(png_structrp png_ptr,
      png_const_color_8p sbit, int color_type),PNG_EMPTY);
  #endif
  
  #ifdef PNG_WRITE_cHRM_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_write_cHRM_fixed,(png_structrp png_ptr,
      const png_xy *xy), PNG_EMPTY);
      /* The xy value must have been previously validated */
  #endif
  
  #ifdef PNG_WRITE_sRGB_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_write_sRGB,(png_structrp png_ptr,
      int intent),PNG_EMPTY);
  #endif
  
  #ifdef PNG_WRITE_iCCP_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_write_iCCP,(png_structrp png_ptr,
     png_const_charp name, png_const_bytep profile), PNG_EMPTY);
     /* The profile must have been previously validated for correctness, the
      * length comes from the first four bytes.  Only the base, deflate,
      * compression is supported.
      */
  #endif
  
  #ifdef PNG_WRITE_sPLT_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_write_sPLT,(png_structrp png_ptr,
      png_const_sPLT_tp palette),PNG_EMPTY);
  #endif
  
  #ifdef PNG_WRITE_tRNS_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_write_tRNS,(png_structrp png_ptr,
      png_const_bytep trans, png_const_color_16p values, int number,
      int color_type),PNG_EMPTY);
  #endif
  
  #ifdef PNG_WRITE_bKGD_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_write_bKGD,(png_structrp png_ptr,
      png_const_color_16p values, int color_type),PNG_EMPTY);
  #endif
  
  #ifdef PNG_WRITE_hIST_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_write_hIST,(png_structrp png_ptr,
      png_const_uint_16p hist, int num_hist),PNG_EMPTY);
  #endif
  
  /* Chunks that have keywords */
  #ifdef PNG_WRITE_tEXt_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_write_tEXt,(png_structrp png_ptr,
     png_const_charp key, png_const_charp text, png_size_t text_len),PNG_EMPTY);
  #endif
  
  #ifdef PNG_WRITE_zTXt_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_write_zTXt,(png_structrp png_ptr, png_const_charp
      key, png_const_charp text, int compression),PNG_EMPTY);
  #endif
  
  #ifdef PNG_WRITE_iTXt_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_write_iTXt,(png_structrp png_ptr,
      int compression, png_const_charp key, png_const_charp lang,
      png_const_charp lang_key, png_const_charp text),PNG_EMPTY);
  #endif
  
  #ifdef PNG_TEXT_SUPPORTED  /* Added at version 1.0.14 and 1.2.4 */
  PNG_INTERNAL_FUNCTION(int,png_set_text_2,(png_const_structrp png_ptr,
      png_inforp info_ptr, png_const_textp text_ptr, int num_text),PNG_EMPTY);
  #endif
  
  #ifdef PNG_WRITE_oFFs_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_write_oFFs,(png_structrp png_ptr,
      png_int_32 x_offset, png_int_32 y_offset, int unit_type),PNG_EMPTY);
  #endif
  
  #ifdef PNG_WRITE_pCAL_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_write_pCAL,(png_structrp png_ptr,
      png_charp purpose, png_int_32 X0, png_int_32 X1, int type, int nparams,
      png_const_charp units, png_charpp params),PNG_EMPTY);
  #endif
  
  #ifdef PNG_WRITE_pHYs_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_write_pHYs,(png_structrp png_ptr,
      png_uint_32 x_pixels_per_unit, png_uint_32 y_pixels_per_unit,
      int unit_type),PNG_EMPTY);
  #endif
  
  #ifdef PNG_WRITE_tIME_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_write_tIME,(png_structrp png_ptr,
      png_const_timep mod_time),PNG_EMPTY);
  #endif
  
  #ifdef PNG_WRITE_sCAL_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_write_sCAL_s,(png_structrp png_ptr,
      int unit, png_const_charp width, png_const_charp height),PNG_EMPTY);
  #endif
  
  /* Called when finished processing a row of data */
  PNG_INTERNAL_FUNCTION(void,png_write_finish_row,(png_structrp png_ptr),
      PNG_EMPTY);
  
  /* Internal use only.   Called before first row of data */
  PNG_INTERNAL_FUNCTION(void,png_write_start_row,(png_structrp png_ptr),
      PNG_EMPTY);
  
  /* Combine a row of data, dealing with alpha, etc. if requested.  'row' is an
   * array of png_ptr->width pixels.  If the image is not interlaced or this
   * is the final pass this just does a memcpy, otherwise the "display" flag
   * is used to determine whether to copy pixels that are not in the current pass.
   *
   * Because 'png_do_read_interlace' (below) replicates pixels this allows this
   * function to achieve the documented 'blocky' appearance during interlaced read
   * if display is 1 and the 'sparkle' appearance, where existing pixels in 'row'
   * are not changed if they are not in the current pass, when display is 0.
   *
   * 'display' must be 0 or 1, otherwise the memcpy will be done regardless.
   *
   * The API always reads from the png_struct row buffer and always assumes that
   * it is full width (png_do_read_interlace has already been called.)
   *
   * This function is only ever used to write to row buffers provided by the
   * caller of the relevant libpng API and the row must have already been
   * transformed by the read transformations.
   *
   * The PNG_USE_COMPILE_TIME_MASKS option causes generation of pre-computed
   * bitmasks for use within the code, otherwise runtime generated masks are used.
   * The default is compile time masks.
   */
  #ifndef PNG_USE_COMPILE_TIME_MASKS
  #  define PNG_USE_COMPILE_TIME_MASKS 1
  #endif
  PNG_INTERNAL_FUNCTION(void,png_combine_row,(png_const_structrp png_ptr,
      png_bytep row, int display),PNG_EMPTY);
  
  #ifdef PNG_READ_INTERLACING_SUPPORTED
  /* Expand an interlaced row: the 'row_info' describes the pass data that has
   * been read in and must correspond to the pixels in 'row', the pixels are
   * expanded (moved apart) in 'row' to match the final layout, when doing this
   * the pixels are *replicated* to the intervening space.  This is essential for
   * the correct operation of png_combine_row, above.
   */
  PNG_INTERNAL_FUNCTION(void,png_do_read_interlace,(png_row_infop row_info,
      png_bytep row, int pass, png_uint_32 transformations),PNG_EMPTY);
  #endif
  
  /* GRR TO DO (2.0 or whenever):  simplify other internal calling interfaces */
  
  #ifdef PNG_WRITE_INTERLACING_SUPPORTED
  /* Grab pixels out of a row for an interlaced pass */
  PNG_INTERNAL_FUNCTION(void,png_do_write_interlace,(png_row_infop row_info,
      png_bytep row, int pass),PNG_EMPTY);
  #endif
  
  /* Unfilter a row: check the filter value before calling this, there is no point
   * calling it for PNG_FILTER_VALUE_NONE.
   */
  PNG_INTERNAL_FUNCTION(void,png_read_filter_row,(png_structrp pp, png_row_infop
      row_info, png_bytep row, png_const_bytep prev_row, int filter),PNG_EMPTY);
  
  PNG_INTERNAL_FUNCTION(void,png_read_filter_row_up_neon,(png_row_infop row_info,
      png_bytep row, png_const_bytep prev_row),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_read_filter_row_sub3_neon,(png_row_infop
      row_info, png_bytep row, png_const_bytep prev_row),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_read_filter_row_sub4_neon,(png_row_infop
      row_info, png_bytep row, png_const_bytep prev_row),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_read_filter_row_avg3_neon,(png_row_infop
      row_info, png_bytep row, png_const_bytep prev_row),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_read_filter_row_avg4_neon,(png_row_infop
      row_info, png_bytep row, png_const_bytep prev_row),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_read_filter_row_paeth3_neon,(png_row_infop
      row_info, png_bytep row, png_const_bytep prev_row),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_read_filter_row_paeth4_neon,(png_row_infop
      row_info, png_bytep row, png_const_bytep prev_row),PNG_EMPTY);
  
  /* Choose the best filter to use and filter the row data */
  PNG_INTERNAL_FUNCTION(void,png_write_find_filter,(png_structrp png_ptr,
      png_row_infop row_info),PNG_EMPTY);
  
  #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_read_IDAT_data,(png_structrp png_ptr,
     png_bytep output, png_alloc_size_t avail_out),PNG_EMPTY);
     /* Read 'avail_out' bytes of data from the IDAT stream.  If the output buffer
      * is NULL the function checks, instead, for the end of the stream.  In this
      * case a benign error will be issued if the stream end is not found or if
      * extra data has to be consumed.
      */
  PNG_INTERNAL_FUNCTION(void,png_read_finish_IDAT,(png_structrp png_ptr),
     PNG_EMPTY);
     /* This cleans up when the IDAT LZ stream does not end when the last image
      * byte is read; there is still some pending input.
      */
  
  PNG_INTERNAL_FUNCTION(void,png_read_finish_row,(png_structrp png_ptr),
     PNG_EMPTY);
     /* Finish a row while reading, dealing with interlacing passes, etc. */
  #endif /* SEQUENTIAL_READ */
  
  /* Initialize the row buffers, etc. */
  PNG_INTERNAL_FUNCTION(void,png_read_start_row,(png_structrp png_ptr),PNG_EMPTY);
  
  #ifdef PNG_READ_TRANSFORMS_SUPPORTED
  /* Optional call to update the users info structure */
  PNG_INTERNAL_FUNCTION(void,png_read_transform_info,(png_structrp png_ptr,
      png_inforp info_ptr),PNG_EMPTY);
  #endif
  
  /* Shared transform functions, defined in pngtran.c */
  #if defined(PNG_WRITE_FILLER_SUPPORTED) || \
      defined(PNG_READ_STRIP_ALPHA_SUPPORTED)
  PNG_INTERNAL_FUNCTION(void,png_do_strip_channel,(png_row_infop row_info,
      png_bytep row, int at_start),PNG_EMPTY);
  #endif
  
  #ifdef PNG_16BIT_SUPPORTED
  #if defined(PNG_READ_SWAP_SUPPORTED) || defined(PNG_WRITE_SWAP_SUPPORTED)
  PNG_INTERNAL_FUNCTION(void,png_do_swap,(png_row_infop row_info,
      png_bytep row),PNG_EMPTY);
  #endif
  #endif
  
  #if defined(PNG_READ_PACKSWAP_SUPPORTED) || \
      defined(PNG_WRITE_PACKSWAP_SUPPORTED)
  PNG_INTERNAL_FUNCTION(void,png_do_packswap,(png_row_infop row_info,
      png_bytep row),PNG_EMPTY);
  #endif
  
  #if defined(PNG_READ_INVERT_SUPPORTED) || defined(PNG_WRITE_INVERT_SUPPORTED)
  PNG_INTERNAL_FUNCTION(void,png_do_invert,(png_row_infop row_info,
      png_bytep row),PNG_EMPTY);
  #endif
  
  #if defined(PNG_READ_BGR_SUPPORTED) || defined(PNG_WRITE_BGR_SUPPORTED)
  PNG_INTERNAL_FUNCTION(void,png_do_bgr,(png_row_infop row_info,
      png_bytep row),PNG_EMPTY);
  #endif
  
  /* The following decodes the appropriate chunks, and does error correction,
   * then calls the appropriate callback for the chunk if it is valid.
   */
  
  /* Decode the IHDR chunk */
  PNG_INTERNAL_FUNCTION(void,png_handle_IHDR,(png_structrp png_ptr,
      png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_handle_PLTE,(png_structrp png_ptr,
      png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_handle_IEND,(png_structrp png_ptr,
      png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
  
  #ifdef PNG_READ_bKGD_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_handle_bKGD,(png_structrp png_ptr,
      png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
  #endif
  
  #ifdef PNG_READ_cHRM_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_handle_cHRM,(png_structrp png_ptr,
      png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
  #endif
  
  #ifdef PNG_READ_gAMA_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_handle_gAMA,(png_structrp png_ptr,
      png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
  #endif
  
  #ifdef PNG_READ_hIST_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_handle_hIST,(png_structrp png_ptr,
      png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
  #endif
  
  #ifdef PNG_READ_iCCP_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_handle_iCCP,(png_structrp png_ptr,
      png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
  #endif /* READ_iCCP */
  
  #ifdef PNG_READ_iTXt_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_handle_iTXt,(png_structrp png_ptr,
      png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
  #endif
  
  #ifdef PNG_READ_oFFs_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_handle_oFFs,(png_structrp png_ptr,
      png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
  #endif
  
  #ifdef PNG_READ_pCAL_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_handle_pCAL,(png_structrp png_ptr,
      png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
  #endif
  
  #ifdef PNG_READ_pHYs_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_handle_pHYs,(png_structrp png_ptr,
      png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
  #endif
  
  #ifdef PNG_READ_sBIT_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_handle_sBIT,(png_structrp png_ptr,
      png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
  #endif
  
  #ifdef PNG_READ_sCAL_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_handle_sCAL,(png_structrp png_ptr,
      png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
  #endif
  
  #ifdef PNG_READ_sPLT_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_handle_sPLT,(png_structrp png_ptr,
      png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
  #endif /* READ_sPLT */
  
  #ifdef PNG_READ_sRGB_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_handle_sRGB,(png_structrp png_ptr,
      png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
  #endif
  
  #ifdef PNG_READ_tEXt_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_handle_tEXt,(png_structrp png_ptr,
      png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
  #endif
  
  #ifdef PNG_READ_tIME_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_handle_tIME,(png_structrp png_ptr,
      png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
  #endif
  
  #ifdef PNG_READ_tRNS_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_handle_tRNS,(png_structrp png_ptr,
      png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
  #endif
  
  #ifdef PNG_READ_zTXt_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_handle_zTXt,(png_structrp png_ptr,
      png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
  #endif
  
  PNG_INTERNAL_FUNCTION(void,png_check_chunk_name,(png_structrp png_ptr,
      png_uint_32 chunk_name),PNG_EMPTY);
  
  PNG_INTERNAL_FUNCTION(void,png_handle_unknown,(png_structrp png_ptr,
      png_inforp info_ptr, png_uint_32 length, int keep),PNG_EMPTY);
     /* This is the function that gets called for unknown chunks.  The 'keep'
      * argument is either non-zero for a known chunk that has been set to be
      * handled as unknown or zero for an unknown chunk.  By default the function
      * just skips the chunk or errors out if it is critical.
      */
  
  #if defined(PNG_READ_UNKNOWN_CHUNKS_SUPPORTED) ||\
      defined(PNG_HANDLE_AS_UNKNOWN_SUPPORTED)
  PNG_INTERNAL_FUNCTION(int,png_chunk_unknown_handling,
      (png_const_structrp png_ptr, png_uint_32 chunk_name),PNG_EMPTY);
     /* Exactly as the API png_handle_as_unknown() except that the argument is a
      * 32-bit chunk name, not a string.
      */
  #endif /* READ_UNKNOWN_CHUNKS || HANDLE_AS_UNKNOWN */
  
  /* Handle the transformations for reading and writing */
  #ifdef PNG_READ_TRANSFORMS_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_do_read_transformations,(png_structrp png_ptr,
     png_row_infop row_info),PNG_EMPTY);
  #endif
  #ifdef PNG_WRITE_TRANSFORMS_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_do_write_transformations,(png_structrp png_ptr,
     png_row_infop row_info),PNG_EMPTY);
  #endif
  
  #ifdef PNG_READ_TRANSFORMS_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_init_read_transformations,(png_structrp png_ptr),
      PNG_EMPTY);
  #endif
  
  #ifdef PNG_PROGRESSIVE_READ_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_push_read_chunk,(png_structrp png_ptr,
      png_inforp info_ptr),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_push_read_sig,(png_structrp png_ptr,
      png_inforp info_ptr),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_push_check_crc,(png_structrp png_ptr),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_push_crc_skip,(png_structrp png_ptr,
      png_uint_32 length),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_push_crc_finish,(png_structrp png_ptr),
      PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_push_save_buffer,(png_structrp png_ptr),
      PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_push_restore_buffer,(png_structrp png_ptr,
      png_bytep buffer, png_size_t buffer_length),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_push_read_IDAT,(png_structrp png_ptr),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_process_IDAT_data,(png_structrp png_ptr,
      png_bytep buffer, png_size_t buffer_length),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_push_process_row,(png_structrp png_ptr),
      PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_push_handle_unknown,(png_structrp png_ptr,
     png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_push_have_info,(png_structrp png_ptr,
     png_inforp info_ptr),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_push_have_end,(png_structrp png_ptr,
     png_inforp info_ptr),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_push_have_row,(png_structrp png_ptr,
       png_bytep row),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_push_read_end,(png_structrp png_ptr,
      png_inforp info_ptr),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_process_some_data,(png_structrp png_ptr,
      png_inforp info_ptr),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_read_push_finish_row,(png_structrp png_ptr),
      PNG_EMPTY);
  #  ifdef PNG_READ_tEXt_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_push_handle_tEXt,(png_structrp png_ptr,
      png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_push_read_tEXt,(png_structrp png_ptr,
      png_inforp info_ptr),PNG_EMPTY);
  #  endif
  #  ifdef PNG_READ_zTXt_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_push_handle_zTXt,(png_structrp png_ptr,
      png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_push_read_zTXt,(png_structrp png_ptr,
      png_inforp info_ptr),PNG_EMPTY);
  #  endif
  #  ifdef PNG_READ_iTXt_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_push_handle_iTXt,(png_structrp png_ptr,
      png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_push_read_iTXt,(png_structrp png_ptr,
      png_inforp info_ptr),PNG_EMPTY);
  #  endif
  
  #endif /* PROGRESSIVE_READ */
  
  /* Added at libpng version 1.6.0 */
  #ifdef PNG_GAMMA_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_colorspace_set_gamma,(png_const_structrp png_ptr,
      png_colorspacerp colorspace, png_fixed_point gAMA), PNG_EMPTY);
     /* Set the colorspace gamma with a value provided by the application or by
      * the gAMA chunk on read.  The value will override anything set by an ICC
      * profile.
      */
  
  PNG_INTERNAL_FUNCTION(void,png_colorspace_sync_info,(png_const_structrp png_ptr,
      png_inforp info_ptr), PNG_EMPTY);
      /* Synchronize the info 'valid' flags with the colorspace */
  
  PNG_INTERNAL_FUNCTION(void,png_colorspace_sync,(png_const_structrp png_ptr,
      png_inforp info_ptr), PNG_EMPTY);
      /* Copy the png_struct colorspace to the info_struct and call the above to
       * synchronize the flags.  Checks for NULL info_ptr and does nothing.
       */
  #endif
  
  /* Added at libpng version 1.4.0 */
  #ifdef PNG_COLORSPACE_SUPPORTED
  /* These internal functions are for maintaining the colorspace structure within
   * a png_info or png_struct (or, indeed, both).
   */
  PNG_INTERNAL_FUNCTION(int,png_colorspace_set_chromaticities,
     (png_const_structrp png_ptr, png_colorspacerp colorspace, const png_xy *xy,
      int preferred), PNG_EMPTY);
  
  PNG_INTERNAL_FUNCTION(int,png_colorspace_set_endpoints,
     (png_const_structrp png_ptr, png_colorspacerp colorspace, const png_XYZ *XYZ,
      int preferred), PNG_EMPTY);
  
  #ifdef PNG_sRGB_SUPPORTED
  PNG_INTERNAL_FUNCTION(int,png_colorspace_set_sRGB,(png_const_structrp png_ptr,
     png_colorspacerp colorspace, int intent), PNG_EMPTY);
     /* This does set the colorspace gAMA and cHRM values too, but doesn't set the
      * flags to write them, if it returns false there was a problem and an error
      * message has already been output (but the colorspace may still need to be
      * synced to record the invalid flag).
      */
  #endif /* sRGB */
  
  #ifdef PNG_iCCP_SUPPORTED
  PNG_INTERNAL_FUNCTION(int,png_colorspace_set_ICC,(png_const_structrp png_ptr,
     png_colorspacerp colorspace, png_const_charp name,
     png_uint_32 profile_length, png_const_bytep profile, int color_type),
     PNG_EMPTY);
     /* The 'name' is used for information only */
  
  /* Routines for checking parts of an ICC profile. */
  PNG_INTERNAL_FUNCTION(int,png_icc_check_length,(png_const_structrp png_ptr,
     png_colorspacerp colorspace, png_const_charp name,
     png_uint_32 profile_length), PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(int,png_icc_check_header,(png_const_structrp png_ptr,
     png_colorspacerp colorspace, png_const_charp name,
     png_uint_32 profile_length,
     png_const_bytep profile /* first 132 bytes only */, int color_type),
     PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(int,png_icc_check_tag_table,(png_const_structrp png_ptr,
     png_colorspacerp colorspace, png_const_charp name,
     png_uint_32 profile_length,
     png_const_bytep profile /* header plus whole tag table */), PNG_EMPTY);
  #ifdef PNG_sRGB_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_icc_set_sRGB,(
     png_const_structrp png_ptr, png_colorspacerp colorspace,
     png_const_bytep profile, uLong adler), PNG_EMPTY);
     /* 'adler' is the Adler32 checksum of the uncompressed profile data. It may
      * be zero to indicate that it is not available.  It is used, if provided,
      * as a fast check on the profile when checking to see if it is sRGB.
      */
  #endif
  #endif /* iCCP */
  
  #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_colorspace_set_rgb_coefficients,
     (png_structrp png_ptr), PNG_EMPTY);
     /* Set the rgb_to_gray coefficients from the colorspace Y values */
  #endif /* READ_RGB_TO_GRAY */
  #endif /* COLORSPACE */
  
  /* Added at libpng version 1.4.0 */
  PNG_INTERNAL_FUNCTION(void,png_check_IHDR,(png_const_structrp png_ptr,
      png_uint_32 width, png_uint_32 height, int bit_depth,
      int color_type, int interlace_type, int compression_type,
      int filter_type),PNG_EMPTY);
  
  /* Added at libpng version 1.5.10 */
  #if defined(PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED) || \
      defined(PNG_WRITE_CHECK_FOR_INVALID_INDEX_SUPPORTED)
  PNG_INTERNAL_FUNCTION(void,png_do_check_palette_indexes,
     (png_structrp png_ptr, png_row_infop row_info),PNG_EMPTY);
  #endif
  
  #if defined(PNG_FLOATING_POINT_SUPPORTED) && defined(PNG_ERROR_TEXT_SUPPORTED)
  PNG_INTERNAL_FUNCTION(void,png_fixed_error,(png_const_structrp png_ptr,
     png_const_charp name),PNG_NORETURN);
  #endif
  
  /* Puts 'string' into 'buffer' at buffer[pos], taking care never to overwrite
   * the end.  Always leaves the buffer nul terminated.  Never errors out (and
   * there is no error code.)
   */
  PNG_INTERNAL_FUNCTION(size_t,png_safecat,(png_charp buffer, size_t bufsize,
     size_t pos, png_const_charp string),PNG_EMPTY);
  
  /* Various internal functions to handle formatted warning messages, currently
   * only implemented for warnings.
   */
  #if defined(PNG_WARNINGS_SUPPORTED) || defined(PNG_TIME_RFC1123_SUPPORTED)
  /* Utility to dump an unsigned value into a buffer, given a start pointer and
   * and end pointer (which should point just *beyond* the end of the buffer!)
   * Returns the pointer to the start of the formatted string.  This utility only
   * does unsigned values.
   */
  PNG_INTERNAL_FUNCTION(png_charp,png_format_number,(png_const_charp start,
     png_charp end, int format, png_alloc_size_t number),PNG_EMPTY);
  
  /* Convenience macro that takes an array: */
  #define PNG_FORMAT_NUMBER(buffer,format,number) \
     png_format_number(buffer, buffer + (sizeof buffer), format, number)
  
  /* Suggested size for a number buffer (enough for 64 bits and a sign!) */
  #define PNG_NUMBER_BUFFER_SIZE 24
  
  /* These are the integer formats currently supported, the name is formed from
   * the standard printf(3) format string.
   */
  #define PNG_NUMBER_FORMAT_u     1 /* chose unsigned API! */
  #define PNG_NUMBER_FORMAT_02u   2
  #define PNG_NUMBER_FORMAT_d     1 /* chose signed API! */
  #define PNG_NUMBER_FORMAT_02d   2
  #define PNG_NUMBER_FORMAT_x     3
  #define PNG_NUMBER_FORMAT_02x   4
  #define PNG_NUMBER_FORMAT_fixed 5 /* choose the signed API */
  #endif
  
  #ifdef PNG_WARNINGS_SUPPORTED
  /* New defines and members adding in libpng-1.5.4 */
  #  define PNG_WARNING_PARAMETER_SIZE 32
  #  define PNG_WARNING_PARAMETER_COUNT 8 /* Maximum 9; see pngerror.c */
  
  /* An l-value of this type has to be passed to the APIs below to cache the
   * values of the parameters to a formatted warning message.
   */
  typedef char png_warning_parameters[PNG_WARNING_PARAMETER_COUNT][
     PNG_WARNING_PARAMETER_SIZE];
  
  PNG_INTERNAL_FUNCTION(void,png_warning_parameter,(png_warning_parameters p,
     int number, png_const_charp string),PNG_EMPTY);
     /* Parameters are limited in size to PNG_WARNING_PARAMETER_SIZE characters,
      * including the trailing '\0'.
      */
  PNG_INTERNAL_FUNCTION(void,png_warning_parameter_unsigned,
     (png_warning_parameters p, int number, int format, png_alloc_size_t value),
     PNG_EMPTY);
     /* Use png_alloc_size_t because it is an unsigned type as big as any we
      * need to output.  Use the following for a signed value.
      */
  PNG_INTERNAL_FUNCTION(void,png_warning_parameter_signed,
     (png_warning_parameters p, int number, int format, png_int_32 value),
     PNG_EMPTY);
  
  PNG_INTERNAL_FUNCTION(void,png_formatted_warning,(png_const_structrp png_ptr,
     png_warning_parameters p, png_const_charp message),PNG_EMPTY);
     /* 'message' follows the X/Open approach of using @1, @2 to insert
      * parameters previously supplied using the above functions.  Errors in
      * specifying the parameters will simply result in garbage substitutions.
      */
  #endif
  
  #ifdef PNG_BENIGN_ERRORS_SUPPORTED
  /* Application errors (new in 1.6); use these functions (declared below) for
   * errors in the parameters or order of API function calls on read.  The
   * 'warning' should be used for an error that can be handled completely; the
   * 'error' for one which can be handled safely but which may lose application
   * information or settings.
   *
   * By default these both result in a png_error call prior to release, while in a
   * released version the 'warning' is just a warning.  However if the application
   * explicitly disables benign errors (explicitly permitting the code to lose
   * information) they both turn into warnings.
   *
   * If benign errors aren't supported they end up as the corresponding base call
   * (png_warning or png_error.)
   */
  PNG_INTERNAL_FUNCTION(void,png_app_warning,(png_const_structrp png_ptr,
     png_const_charp message),PNG_EMPTY);
     /* The application provided invalid parameters to an API function or called
      * an API function at the wrong time, libpng can completely recover.
      */
  
  PNG_INTERNAL_FUNCTION(void,png_app_error,(png_const_structrp png_ptr,
     png_const_charp message),PNG_EMPTY);
     /* As above but libpng will ignore the call, or attempt some other partial
      * recovery from the error.
      */
  #else
  #  define png_app_warning(pp,s) png_warning(pp,s)
  #  define png_app_error(pp,s) png_error(pp,s)
  #endif
  
  PNG_INTERNAL_FUNCTION(void,png_chunk_report,(png_const_structrp png_ptr,
     png_const_charp message, int error),PNG_EMPTY);
     /* Report a recoverable issue in chunk data.  On read this is used to report
      * a problem found while reading a particular chunk and the
      * png_chunk_benign_error or png_chunk_warning function is used as
      * appropriate.  On write this is used to report an error that comes from
      * data set via an application call to a png_set_ API and png_app_error or
      * png_app_warning is used as appropriate.
      *
      * The 'error' parameter must have one of the following values:
      */
  #define PNG_CHUNK_WARNING     0 /* never an error */
  #define PNG_CHUNK_WRITE_ERROR 1 /* an error only on write */
  #define PNG_CHUNK_ERROR       2 /* always an error */
  
  /* ASCII to FP interfaces, currently only implemented if sCAL
   * support is required.
   */
  #if defined(PNG_sCAL_SUPPORTED)
  /* MAX_DIGITS is actually the maximum number of characters in an sCAL
   * width or height, derived from the precision (number of significant
   * digits - a build time settable option) and assumptions about the
   * maximum ridiculous exponent.
   */
  #define PNG_sCAL_MAX_DIGITS (PNG_sCAL_PRECISION+1/*.*/+1/*E*/+10/*exponent*/)
  
  #ifdef PNG_FLOATING_POINT_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_ascii_from_fp,(png_const_structrp png_ptr,
     png_charp ascii, png_size_t size, double fp, unsigned int precision),
     PNG_EMPTY);
  #endif /* FLOATING_POINT */
  
  #ifdef PNG_FIXED_POINT_SUPPORTED
  PNG_INTERNAL_FUNCTION(void,png_ascii_from_fixed,(png_const_structrp png_ptr,
     png_charp ascii, png_size_t size, png_fixed_point fp),PNG_EMPTY);
  #endif /* FIXED_POINT */
  #endif /* sCAL */
  
  #if defined(PNG_sCAL_SUPPORTED) || defined(PNG_pCAL_SUPPORTED)
  /* An internal API to validate the format of a floating point number.
   * The result is the index of the next character.  If the number is
   * not valid it will be the index of a character in the supposed number.
   *
   * The format of a number is defined in the PNG extensions specification
   * and this API is strictly conformant to that spec, not anyone elses!
   *
   * The format as a regular expression is:
   *
   * [+-]?[0-9]+.?([Ee][+-]?[0-9]+)?
   *
   * or:
   *
   * [+-]?.[0-9]+(.[0-9]+)?([Ee][+-]?[0-9]+)?
   *
   * The complexity is that either integer or fraction must be present and the
   * fraction is permitted to have no digits only if the integer is present.
   *
   * NOTE: The dangling E problem.
   *   There is a PNG valid floating point number in the following:
   *
   *       PNG floating point numbers are not greedy.
   *
   *   Working this out requires *TWO* character lookahead (because of the
   *   sign), the parser does not do this - it will fail at the 'r' - this
   *   doesn't matter for PNG sCAL chunk values, but it requires more care
   *   if the value were ever to be embedded in something more complex.  Use
   *   ANSI-C strtod if you need the lookahead.
   */
  /* State table for the parser. */
  #define PNG_FP_INTEGER    0  /* before or in integer */
  #define PNG_FP_FRACTION   1  /* before or in fraction */
  #define PNG_FP_EXPONENT   2  /* before or in exponent */
  #define PNG_FP_STATE      3  /* mask for the above */
  #define PNG_FP_SAW_SIGN   4  /* Saw +/- in current state */
  #define PNG_FP_SAW_DIGIT  8  /* Saw a digit in current state */
  #define PNG_FP_SAW_DOT   16  /* Saw a dot in current state */
  #define PNG_FP_SAW_E     32  /* Saw an E (or e) in current state */
  #define PNG_FP_SAW_ANY   60  /* Saw any of the above 4 */
  
  /* These three values don't affect the parser.  They are set but not used.
   */
  #define PNG_FP_WAS_VALID 64  /* Preceding substring is a valid fp number */
  #define PNG_FP_NEGATIVE 128  /* A negative number, including "-0" */
  #define PNG_FP_NONZERO  256  /* A non-zero value */
  #define PNG_FP_STICKY   448  /* The above three flags */
  
  /* This is available for the caller to store in 'state' if required.  Do not
   * call the parser after setting it (the parser sometimes clears it.)
   */
  #define PNG_FP_INVALID  512  /* Available for callers as a distinct value */
  
  /* Result codes for the parser (boolean - true meants ok, false means
   * not ok yet.)
   */
  #define PNG_FP_MAYBE      0  /* The number may be valid in the future */
  #define PNG_FP_OK         1  /* The number is valid */
  
  /* Tests on the sticky non-zero and negative flags.  To pass these checks
   * the state must also indicate that the whole number is valid - this is
   * achieved by testing PNG_FP_SAW_DIGIT (see the implementation for why this
   * is equivalent to PNG_FP_OK above.)
   */
  #define PNG_FP_NZ_MASK (PNG_FP_SAW_DIGIT | PNG_FP_NEGATIVE | PNG_FP_NONZERO)
     /* NZ_MASK: the string is valid and a non-zero negative value */
  #define PNG_FP_Z_MASK (PNG_FP_SAW_DIGIT | PNG_FP_NONZERO)
     /* Z MASK: the string is valid and a non-zero value. */
     /* PNG_FP_SAW_DIGIT: the string is valid. */
  #define PNG_FP_IS_ZERO(state) (((state) & PNG_FP_Z_MASK) == PNG_FP_SAW_DIGIT)
  #define PNG_FP_IS_POSITIVE(state) (((state) & PNG_FP_NZ_MASK) == PNG_FP_Z_MASK)
  #define PNG_FP_IS_NEGATIVE(state) (((state) & PNG_FP_NZ_MASK) == PNG_FP_NZ_MASK)
  
  /* The actual parser.  This can be called repeatedly. It updates
   * the index into the string and the state variable (which must
   * be initialized to 0).  It returns a result code, as above.  There
   * is no point calling the parser any more if it fails to advance to
   * the end of the string - it is stuck on an invalid character (or
   * terminated by '\0').
   *
   * Note that the pointer will consume an E or even an E+ and then leave
   * a 'maybe' state even though a preceding integer.fraction is valid.
   * The PNG_FP_WAS_VALID flag indicates that a preceding substring was
   * a valid number.  It's possible to recover from this by calling
   * the parser again (from the start, with state 0) but with a string
   * that omits the last character (i.e. set the size to the index of
   * the problem character.)  This has not been tested within libpng.
   */
  PNG_INTERNAL_FUNCTION(int,png_check_fp_number,(png_const_charp string,
     png_size_t size, int *statep, png_size_tp whereami),PNG_EMPTY);
  
  /* This is the same but it checks a complete string and returns true
   * only if it just contains a floating point number.  As of 1.5.4 this
   * function also returns the state at the end of parsing the number if
   * it was valid (otherwise it returns 0.)  This can be used for testing
   * for negative or zero values using the sticky flag.
   */
  PNG_INTERNAL_FUNCTION(int,png_check_fp_string,(png_const_charp string,
     png_size_t size),PNG_EMPTY);
  #endif /* pCAL || sCAL */
  
  #if defined(PNG_GAMMA_SUPPORTED) ||\
      defined(PNG_INCH_CONVERSIONS_SUPPORTED) || defined(PNG_READ_pHYs_SUPPORTED)
  /* Added at libpng version 1.5.0 */
  /* This is a utility to provide a*times/div (rounded) and indicate
   * if there is an overflow.  The result is a boolean - false (0)
   * for overflow, true (1) if no overflow, in which case *res
   * holds the result.
   */
  PNG_INTERNAL_FUNCTION(int,png_muldiv,(png_fixed_point_p res, png_fixed_point a,
     png_int_32 multiplied_by, png_int_32 divided_by),PNG_EMPTY);
  #endif
  
  #if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_INCH_CONVERSIONS_SUPPORTED)
  /* Same deal, but issue a warning on overflow and return 0. */
  PNG_INTERNAL_FUNCTION(png_fixed_point,png_muldiv_warn,
     (png_const_structrp png_ptr, png_fixed_point a, png_int_32 multiplied_by,
     png_int_32 divided_by),PNG_EMPTY);
  #endif
  
  #ifdef PNG_GAMMA_SUPPORTED
  /* Calculate a reciprocal - used for gamma values.  This returns
   * 0 if the argument is 0 in order to maintain an undefined value;
   * there are no warnings.
   */
  PNG_INTERNAL_FUNCTION(png_fixed_point,png_reciprocal,(png_fixed_point a),
     PNG_EMPTY);
  
  #ifdef PNG_READ_GAMMA_SUPPORTED
  /* The same but gives a reciprocal of the product of two fixed point
   * values.  Accuracy is suitable for gamma calculations but this is
   * not exact - use png_muldiv for that.  Only required at present on read.
   */
  PNG_INTERNAL_FUNCTION(png_fixed_point,png_reciprocal2,(png_fixed_point a,
     png_fixed_point b),PNG_EMPTY);
  #endif
  
  /* Return true if the gamma value is significantly different from 1.0 */
  PNG_INTERNAL_FUNCTION(int,png_gamma_significant,(png_fixed_point gamma_value),
     PNG_EMPTY);
  #endif
  
  #ifdef PNG_READ_GAMMA_SUPPORTED
  /* Internal fixed point gamma correction.  These APIs are called as
   * required to convert single values - they don't need to be fast,
   * they are not used when processing image pixel values.
   *
   * While the input is an 'unsigned' value it must actually be the
   * correct bit value - 0..255 or 0..65535 as required.
   */
  PNG_INTERNAL_FUNCTION(png_uint_16,png_gamma_correct,(png_structrp png_ptr,
     unsigned int value, png_fixed_point gamma_value),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(png_uint_16,png_gamma_16bit_correct,(unsigned int value,
     png_fixed_point gamma_value),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(png_byte,png_gamma_8bit_correct,(unsigned int value,
     png_fixed_point gamma_value),PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_destroy_gamma_table,(png_structrp png_ptr),
     PNG_EMPTY);
  PNG_INTERNAL_FUNCTION(void,png_build_gamma_table,(png_structrp png_ptr,
     int bit_depth),PNG_EMPTY);
  #endif
  
  /* SIMPLIFIED READ/WRITE SUPPORT */
  #if defined(PNG_SIMPLIFIED_READ_SUPPORTED) ||\
     defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)
  /* The internal structure that png_image::opaque points to. */
  typedef struct png_control
  {
     png_structp png_ptr;
     png_infop   info_ptr;
     png_voidp   error_buf;           /* Always a jmp_buf at present. */
  
     png_const_bytep memory;          /* Memory buffer. */
     png_size_t      size;            /* Size of the memory buffer. */
  
     unsigned int for_write       :1; /* Otherwise it is a read structure */
     unsigned int owned_file      :1; /* We own the file in io_ptr */
  } png_control;
  
  /* Return the pointer to the jmp_buf from a png_control: necessary because C
   * does not reveal the type of the elements of jmp_buf.
   */
  #ifdef __cplusplus
  #  define png_control_jmp_buf(pc) (((jmp_buf*)((pc)->error_buf))[0])
  #else
  #  define png_control_jmp_buf(pc) ((pc)->error_buf)
  #endif
  
  /* Utility to safely execute a piece of libpng code catching and logging any
   * errors that might occur.  Returns true on success, false on failure (either
   * of the function or as a result of a png_error.)
   */
  PNG_INTERNAL_CALLBACK(void,png_safe_error,(png_structp png_ptr,
     png_const_charp error_message),PNG_NORETURN);
  
  #ifdef PNG_WARNINGS_SUPPORTED
  PNG_INTERNAL_CALLBACK(void,png_safe_warning,(png_structp png_ptr,
     png_const_charp warning_message),PNG_EMPTY);
  #else
  #  define png_safe_warning 0/*dummy argument*/
  #endif
  
  PNG_INTERNAL_FUNCTION(int,png_safe_execute,(png_imagep image,
     int (*function)(png_voidp), png_voidp arg),PNG_EMPTY);
  
  /* Utility to log an error; this also cleans up the png_image; the function
   * always returns 0 (false).
   */
  PNG_INTERNAL_FUNCTION(int,png_image_error,(png_imagep image,
     png_const_charp error_message),PNG_EMPTY);
  
  #ifndef PNG_SIMPLIFIED_READ_SUPPORTED
  /* png_image_free is used by the write code but not exported */
  PNG_INTERNAL_FUNCTION(void, png_image_free, (png_imagep image), PNG_EMPTY);
  #endif /* !SIMPLIFIED_READ */
  
  #endif /* SIMPLIFIED READ/WRITE */
  
  /* These are initialization functions for hardware specific PNG filter
   * optimizations; list these here then select the appropriate one at compile
   * time using the macro PNG_FILTER_OPTIMIZATIONS.  If the macro is not defined
   * the generic code is used.
   */
  #ifdef PNG_FILTER_OPTIMIZATIONS
  PNG_INTERNAL_FUNCTION(void, PNG_FILTER_OPTIMIZATIONS, (png_structp png_ptr,
     unsigned int bpp), PNG_EMPTY);
     /* Just declare the optimization that will be used */
  #else
     /* List *all* the possible optimizations here - this branch is required if
      * the builder of libpng passes the definition of PNG_FILTER_OPTIMIZATIONS in
      * CFLAGS in place of CPPFLAGS *and* uses symbol prefixing.
      */
  PNG_INTERNAL_FUNCTION(void, png_init_filter_functions_neon,
     (png_structp png_ptr, unsigned int bpp), PNG_EMPTY);
  #endif
  
  /* Maintainer: Put new private prototypes here ^ */
  
  #include "pngdebug.h"
  
  #ifdef __cplusplus
  }
  #endif
  
  #endif /* PNG_VERSION_INFO_ONLY */
  #endif /* PNGPRIV_H */
  