XFA: Upgrade libpng to 1.6.20.

R=tsepez@chromium.org

Review URL: https://codereview.chromium.org/1591483003 .

1 files changed, 0 insertions, 4297 deletions

diff --git a/third_party/lpng_v163/png.c b/third_party/lpng_v163/png.c
deleted file mode 100644
index 93c675b085..0000000000
--- a/third_party/lpng_v163/png.c
+++ /dev/null
@@ -1,4297 +0,0 @@
-/* png.c - location for general purpose libpng functions

- *

- * Last changed in libpng 1.6.2 [April 25, 2013]

- * Copyright (c) 1998-2013 Glenn Randers-Pehrson

- * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)

- * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)

- *

- * This code is released under the libpng license.

- * For conditions of distribution and use, see the disclaimer

- * and license in png.h

- */

-

-#include "pngpriv.h"

-

-/* Generate a compiler error if there is an old png.h in the search path. */

-typedef png_libpng_version_1_6_3 Your_png_h_is_not_version_1_6_3;

-

-/* Tells libpng that we have already handled the first "num_bytes" bytes

- * of the PNG file signature.  If the PNG data is embedded into another

- * stream we can set num_bytes = 8 so that libpng will not attempt to read

- * or write any of the magic bytes before it starts on the IHDR.

- */

-

-#ifdef PNG_READ_SUPPORTED

-void PNGAPI

-png_set_sig_bytes(png_structrp png_ptr, int num_bytes)

-{

-   png_debug(1, "in png_set_sig_bytes");

-

-   if (png_ptr == NULL)

-      return;

-

-   if (num_bytes > 8)

-      png_error(png_ptr, "Too many bytes for PNG signature");

-

-   png_ptr->sig_bytes = (png_byte)(num_bytes < 0 ? 0 : num_bytes);

-}

-

-/* Checks whether the supplied bytes match the PNG signature.  We allow

- * checking less than the full 8-byte signature so that those apps that

- * already read the first few bytes of a file to determine the file type

- * can simply check the remaining bytes for extra assurance.  Returns

- * an integer less than, equal to, or greater than zero if sig is found,

- * respectively, to be less than, to match, or be greater than the correct

- * PNG signature (this is the same behavior as strcmp, memcmp, etc).

- */

-int PNGAPI

-png_sig_cmp(png_const_bytep sig, png_size_t start, png_size_t num_to_check)

-{

-   png_byte png_signature[8] = {137, 80, 78, 71, 13, 10, 26, 10};

-

-   if (num_to_check > 8)

-      num_to_check = 8;

-

-   else if (num_to_check < 1)

-      return (-1);

-

-   if (start > 7)

-      return (-1);

-

-   if (start + num_to_check > 8)

-      num_to_check = 8 - start;

-

-   return ((int)(memcmp(&sig[start], &png_signature[start], num_to_check)));

-}

-

-#endif /* PNG_READ_SUPPORTED */

-

-#if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)

-/* Function to allocate memory for zlib */

-PNG_FUNCTION(voidpf /* PRIVATE */,

-png_zalloc,(voidpf png_ptr, uInt items, uInt size),PNG_ALLOCATED)

-{

-   png_alloc_size_t num_bytes = size;

-

-   if (png_ptr == NULL)

-      return NULL;

-

-   if (items >= (~(png_alloc_size_t)0)/size)

-   {

-      png_warning (png_voidcast(png_structrp, png_ptr),

-         "Potential overflow in png_zalloc()");

-      return NULL;

-   }

-

-   num_bytes *= items;

-   return png_malloc_warn(png_voidcast(png_structrp, png_ptr), num_bytes);

-}

-

-/* Function to free memory for zlib */

-void /* PRIVATE */

-png_zfree(voidpf png_ptr, voidpf ptr)

-{

-   png_free(png_voidcast(png_const_structrp,png_ptr), ptr);

-}

-

-/* Reset the CRC variable to 32 bits of 1's.  Care must be taken

- * in case CRC is > 32 bits to leave the top bits 0.

- */

-void /* PRIVATE */

-png_reset_crc(png_structrp png_ptr)

-{

-   /* The cast is safe because the crc is a 32 bit value. */

-   png_ptr->crc = (png_uint_32)crc32(0, Z_NULL, 0);

-}

-

-/* Calculate the CRC over a section of data.  We can only pass as

- * much data to this routine as the largest single buffer size.  We

- * also check that this data will actually be used before going to the

- * trouble of calculating it.

- */

-void /* PRIVATE */

-png_calculate_crc(png_structrp png_ptr, png_const_bytep ptr, png_size_t length)

-{

-   int need_crc = 1;

-

-   if (PNG_CHUNK_ANCILLARY(png_ptr->chunk_name))

-   {

-      if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_MASK) ==

-          (PNG_FLAG_CRC_ANCILLARY_USE | PNG_FLAG_CRC_ANCILLARY_NOWARN))

-         need_crc = 0;

-   }

-

-   else /* critical */

-   {

-      if (png_ptr->flags & PNG_FLAG_CRC_CRITICAL_IGNORE)

-         need_crc = 0;

-   }

-

-   /* 'uLong' is defined in zlib.h as unsigned long; this means that on some

-    * systems it is a 64 bit value.  crc32, however, returns 32 bits so the

-    * following cast is safe.  'uInt' may be no more than 16 bits, so it is

-    * necessary to perform a loop here.

-    */

-   if (need_crc && length > 0)

-   {

-      uLong crc = png_ptr->crc; /* Should never issue a warning */

-

-      do

-      {

-         uInt safe_length = (uInt)length;

-         if (safe_length == 0)

-            safe_length = (uInt)-1; /* evil, but safe */

-

-         crc = crc32(crc, ptr, safe_length);

-

-         /* The following should never issue compiler warnings; if they do the

-          * target system has characteristics that will probably violate other

-          * assumptions within the libpng code.

-          */

-         ptr += safe_length;

-         length -= safe_length;

-      }

-      while (length > 0);

-

-      /* And the following is always safe because the crc is only 32 bits. */

-      png_ptr->crc = (png_uint_32)crc;

-   }

-}

-

-/* Check a user supplied version number, called from both read and write

- * functions that create a png_struct.

- */

-int

-png_user_version_check(png_structrp png_ptr, png_const_charp user_png_ver)

-{

-   if (user_png_ver)

-   {

-      int i = 0;

-

-      do

-      {

-         if (user_png_ver[i] != png_libpng_ver[i])

-            png_ptr->flags |= PNG_FLAG_LIBRARY_MISMATCH;

-      } while (png_libpng_ver[i++]);

-   }

-

-   else

-      png_ptr->flags |= PNG_FLAG_LIBRARY_MISMATCH;

-

-   if (png_ptr->flags & PNG_FLAG_LIBRARY_MISMATCH)

-   {

-     /* Libpng 0.90 and later are binary incompatible with libpng 0.89, so

-      * we must recompile any applications that use any older library version.

-      * For versions after libpng 1.0, we will be compatible, so we need

-      * only check the first and third digits (note that when we reach version

-      * 1.10 we will need to check the fourth symbol, namely user_png_ver[3]).

-      */

-      if (user_png_ver == NULL || user_png_ver[0] != png_libpng_ver[0] ||

-          (user_png_ver[0] == '1' && (user_png_ver[2] != png_libpng_ver[2] ||

-          user_png_ver[3] != png_libpng_ver[3])) ||

-          (user_png_ver[0] == '0' && user_png_ver[2] < '9'))

-      {

-#ifdef PNG_WARNINGS_SUPPORTED

-         size_t pos = 0;

-         char m[128];

-

-         pos = png_safecat(m, (sizeof m), pos,

-             "Application built with libpng-");

-         pos = png_safecat(m, (sizeof m), pos, user_png_ver);

-         pos = png_safecat(m, (sizeof m), pos, " but running with ");

-         pos = png_safecat(m, (sizeof m), pos, png_libpng_ver);

-

-         png_warning(png_ptr, m);

-#endif

-

-#ifdef PNG_ERROR_NUMBERS_SUPPORTED

-         png_ptr->flags = 0;

-#endif

-

-         return 0;

-      }

-   }

-

-   /* Success return. */

-   return 1;

-}

-

-/* Generic function to create a png_struct for either read or write - this

- * contains the common initialization.

- */

-PNG_FUNCTION(png_structp /* PRIVATE */,

-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)

-{

-   png_struct create_struct;

-#  ifdef PNG_SETJMP_SUPPORTED

-      jmp_buf create_jmp_buf;

-#  endif

-

-   /* This temporary stack-allocated structure is used to provide a place to

-    * build enough context to allow the user provided memory allocator (if any)

-    * to be called.

-    */

-   memset(&create_struct, 0, (sizeof create_struct));

-

-   /* Added at libpng-1.2.6 */

-#  ifdef PNG_USER_LIMITS_SUPPORTED

-      create_struct.user_width_max = PNG_USER_WIDTH_MAX;

-      create_struct.user_height_max = PNG_USER_HEIGHT_MAX;

-

-#     ifdef PNG_USER_CHUNK_CACHE_MAX

-         /* Added at libpng-1.2.43 and 1.4.0 */

-         create_struct.user_chunk_cache_max = PNG_USER_CHUNK_CACHE_MAX;

-#     endif

-

-#     ifdef PNG_USER_CHUNK_MALLOC_MAX

-         /* Added at libpng-1.2.43 and 1.4.1, required only for read but exists

-          * in png_struct regardless.

-          */

-         create_struct.user_chunk_malloc_max = PNG_USER_CHUNK_MALLOC_MAX;

-#     endif

-#  endif

-

-   /* The following two API calls simply set fields in png_struct, so it is safe

-    * to do them now even though error handling is not yet set up.

-    */

-#  ifdef PNG_USER_MEM_SUPPORTED

-      png_set_mem_fn(&create_struct, mem_ptr, malloc_fn, free_fn);

-#  endif

-

-   /* (*error_fn) can return control to the caller after the error_ptr is set,

-    * this will result in a memory leak unless the error_fn does something

-    * extremely sophisticated.  The design lacks merit but is implicit in the

-    * API.

-    */

-   png_set_error_fn(&create_struct, error_ptr, error_fn, warn_fn);

-

-#  ifdef PNG_SETJMP_SUPPORTED

-      if (!setjmp(create_jmp_buf))

-      {

-         /* Temporarily fake out the longjmp information until we have

-          * successfully completed this function.  This only works if we have

-          * setjmp() support compiled in, but it is safe - this stuff should

-          * never happen.

-          */

-         create_struct.jmp_buf_ptr = &create_jmp_buf;

-         create_struct.jmp_buf_size = 0; /*stack allocation*/

-         create_struct.longjmp_fn = longjmp;

-#  else

-      {

-#  endif

-         /* Call the general version checker (shared with read and write code):

-          */

-         if (png_user_version_check(&create_struct, user_png_ver))

-         {

-            png_structrp png_ptr = png_voidcast(png_structrp,

-               png_malloc_warn(&create_struct, (sizeof *png_ptr)));

-

-            if (png_ptr != NULL)

-            {

-               /* png_ptr->zstream holds a back-pointer to the png_struct, so

-                * this can only be done now:

-                */

-               create_struct.zstream.zalloc = png_zalloc;

-               create_struct.zstream.zfree = png_zfree;

-               create_struct.zstream.opaque = png_ptr;

-

-#              ifdef PNG_SETJMP_SUPPORTED

-                  /* Eliminate the local error handling: */

-                  create_struct.jmp_buf_ptr = NULL;

-                  create_struct.jmp_buf_size = 0;

-                  create_struct.longjmp_fn = 0;

-#              endif

-

-               *png_ptr = create_struct;

-

-               /* This is the successful return point */

-               return png_ptr;

-            }

-         }

-      }

-

-   /* A longjmp because of a bug in the application storage allocator or a

-    * simple failure to allocate the png_struct.

-    */

-   return NULL;

-}

-

-/* Allocate the memory for an info_struct for the application. */

-PNG_FUNCTION(png_infop,PNGAPI

-png_create_info_struct,(png_const_structrp png_ptr),PNG_ALLOCATED)

-{

-   png_inforp info_ptr;

-

-   png_debug(1, "in png_create_info_struct");

-

-   if (png_ptr == NULL)

-      return NULL;

-

-   /* Use the internal API that does not (or at least should not) error out, so

-    * that this call always returns ok.  The application typically sets up the

-    * error handling *after* creating the info_struct because this is the way it

-    * has always been done in 'example.c'.

-    */

-   info_ptr = png_voidcast(png_inforp, png_malloc_base(png_ptr,

-      (sizeof *info_ptr)));

-

-   if (info_ptr != NULL)

-      memset(info_ptr, 0, (sizeof *info_ptr));

-

-   return info_ptr;

-}

-

-/* This function frees the memory associated with a single info struct.

- * Normally, one would use either png_destroy_read_struct() or

- * png_destroy_write_struct() to free an info struct, but this may be

- * useful for some applications.  From libpng 1.6.0 this function is also used

- * internally to implement the png_info release part of the 'struct' destroy

- * APIs.  This ensures that all possible approaches free the same data (all of

- * it).

- */

-void PNGAPI

-png_destroy_info_struct(png_const_structrp png_ptr, png_infopp info_ptr_ptr)

-{

-   png_inforp info_ptr = NULL;

-

-   png_debug(1, "in png_destroy_info_struct");

-

-   if (png_ptr == NULL)

-      return;

-

-   if (info_ptr_ptr != NULL)

-      info_ptr = *info_ptr_ptr;

-

-   if (info_ptr != NULL)

-   {

-      /* Do this first in case of an error below; if the app implements its own

-       * memory management this can lead to png_free calling png_error, which

-       * will abort this routine and return control to the app error handler.

-       * An infinite loop may result if it then tries to free the same info

-       * ptr.

-       */

-      *info_ptr_ptr = NULL;

-

-      png_free_data(png_ptr, info_ptr, PNG_FREE_ALL, -1);

-      memset(info_ptr, 0, (sizeof *info_ptr));

-      png_free(png_ptr, info_ptr);

-   }

-}

-

-/* Initialize the info structure.  This is now an internal function (0.89)

- * and applications using it are urged to use png_create_info_struct()

- * instead.  Use deprecated in 1.6.0, internal use removed (used internally it

- * is just a memset).

- *

- * NOTE: it is almost inconceivable that this API is used because it bypasses

- * the user-memory mechanism and the user error handling/warning mechanisms in

- * those cases where it does anything other than a memset.

- */

-PNG_FUNCTION(void,PNGAPI

-png_info_init_3,(png_infopp ptr_ptr, png_size_t png_info_struct_size),

-   PNG_DEPRECATED)

-{

-   png_inforp info_ptr = *ptr_ptr;

-

-   png_debug(1, "in png_info_init_3");

-

-   if (info_ptr == NULL)

-      return;

-

-   if ((sizeof (png_info)) > png_info_struct_size)

-   {

-      *ptr_ptr = NULL;

-      /* The following line is why this API should not be used: */

-      free(info_ptr);

-      info_ptr = png_voidcast(png_inforp, png_malloc_base(NULL,

-         (sizeof *info_ptr)));

-      *ptr_ptr = info_ptr;

-   }

-

-   /* Set everything to 0 */

-   memset(info_ptr, 0, (sizeof *info_ptr));

-}

-

-/* The following API is not called internally */

-void PNGAPI

-png_data_freer(png_const_structrp png_ptr, png_inforp info_ptr,

-   int freer, png_uint_32 mask)

-{

-   png_debug(1, "in png_data_freer");

-

-   if (png_ptr == NULL || info_ptr == NULL)

-      return;

-

-   if (freer == PNG_DESTROY_WILL_FREE_DATA)

-      info_ptr->free_me |= mask;

-

-   else if (freer == PNG_USER_WILL_FREE_DATA)

-      info_ptr->free_me &= ~mask;

-

-   else

-      png_error(png_ptr, "Unknown freer parameter in png_data_freer");

-}

-

-void PNGAPI

-png_free_data(png_const_structrp png_ptr, png_inforp info_ptr, png_uint_32 mask,

-   int num)

-{

-   png_debug(1, "in png_free_data");

-

-   if (png_ptr == NULL || info_ptr == NULL)

-      return;

-

-#ifdef PNG_TEXT_SUPPORTED

-   /* Free text item num or (if num == -1) all text items */

-   if ((mask & PNG_FREE_TEXT) & info_ptr->free_me)

-   {

-      if (num != -1)

-      {

-         if (info_ptr->text && info_ptr->text[num].key)

-         {

-            png_free(png_ptr, info_ptr->text[num].key);

-            info_ptr->text[num].key = NULL;

-         }

-      }

-

-      else

-      {

-         int i;

-         for (i = 0; i < info_ptr->num_text; i++)

-             png_free_data(png_ptr, info_ptr, PNG_FREE_TEXT, i);

-         png_free(png_ptr, info_ptr->text);

-         info_ptr->text = NULL;

-         info_ptr->num_text=0;

-      }

-   }

-#endif

-

-#ifdef PNG_tRNS_SUPPORTED

-   /* Free any tRNS entry */

-   if ((mask & PNG_FREE_TRNS) & info_ptr->free_me)

-   {

-      png_free(png_ptr, info_ptr->trans_alpha);

-      info_ptr->trans_alpha = NULL;

-      info_ptr->valid &= ~PNG_INFO_tRNS;

-   }

-#endif

-

-#ifdef PNG_sCAL_SUPPORTED

-   /* Free any sCAL entry */

-   if ((mask & PNG_FREE_SCAL) & info_ptr->free_me)

-   {

-      png_free(png_ptr, info_ptr->scal_s_width);

-      png_free(png_ptr, info_ptr->scal_s_height);

-      info_ptr->scal_s_width = NULL;

-      info_ptr->scal_s_height = NULL;

-      info_ptr->valid &= ~PNG_INFO_sCAL;

-   }

-#endif

-

-#ifdef PNG_pCAL_SUPPORTED

-   /* Free any pCAL entry */

-   if ((mask & PNG_FREE_PCAL) & info_ptr->free_me)

-   {

-      png_free(png_ptr, info_ptr->pcal_purpose);

-      png_free(png_ptr, info_ptr->pcal_units);

-      info_ptr->pcal_purpose = NULL;

-      info_ptr->pcal_units = NULL;

-      if (info_ptr->pcal_params != NULL)

-         {

-            unsigned int i;

-            for (i = 0; i < info_ptr->pcal_nparams; i++)

-            {

-               png_free(png_ptr, info_ptr->pcal_params[i]);

-               info_ptr->pcal_params[i] = NULL;

-            }

-            png_free(png_ptr, info_ptr->pcal_params);

-            info_ptr->pcal_params = NULL;

-         }

-      info_ptr->valid &= ~PNG_INFO_pCAL;

-   }

-#endif

-

-#ifdef PNG_iCCP_SUPPORTED

-   /* Free any profile entry */

-   if ((mask & PNG_FREE_ICCP) & info_ptr->free_me)

-   {

-      png_free(png_ptr, info_ptr->iccp_name);

-      png_free(png_ptr, info_ptr->iccp_profile);

-      info_ptr->iccp_name = NULL;

-      info_ptr->iccp_profile = NULL;

-      info_ptr->valid &= ~PNG_INFO_iCCP;

-   }

-#endif

-

-#ifdef PNG_sPLT_SUPPORTED

-   /* Free a given sPLT entry, or (if num == -1) all sPLT entries */

-   if ((mask & PNG_FREE_SPLT) & info_ptr->free_me)

-   {

-      if (num != -1)

-      {

-         if (info_ptr->splt_palettes)

-         {

-            png_free(png_ptr, info_ptr->splt_palettes[num].name);

-            png_free(png_ptr, info_ptr->splt_palettes[num].entries);

-            info_ptr->splt_palettes[num].name = NULL;

-            info_ptr->splt_palettes[num].entries = NULL;

-         }

-      }

-

-      else

-      {

-         if (info_ptr->splt_palettes_num)

-         {

-            int i;

-            for (i = 0; i < info_ptr->splt_palettes_num; i++)

-               png_free_data(png_ptr, info_ptr, PNG_FREE_SPLT, (int)i);

-

-            png_free(png_ptr, info_ptr->splt_palettes);

-            info_ptr->splt_palettes = NULL;

-            info_ptr->splt_palettes_num = 0;

-         }

-         info_ptr->valid &= ~PNG_INFO_sPLT;

-      }

-   }

-#endif

-

-#ifdef PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED

-   if ((mask & PNG_FREE_UNKN) & info_ptr->free_me)

-   {

-      if (num != -1)

-      {

-          if (info_ptr->unknown_chunks)

-          {

-             png_free(png_ptr, info_ptr->unknown_chunks[num].data);

-             info_ptr->unknown_chunks[num].data = NULL;

-          }

-      }

-

-      else

-      {

-         int i;

-

-         if (info_ptr->unknown_chunks_num)

-         {

-            for (i = 0; i < info_ptr->unknown_chunks_num; i++)

-               png_free_data(png_ptr, info_ptr, PNG_FREE_UNKN, (int)i);

-

-            png_free(png_ptr, info_ptr->unknown_chunks);

-            info_ptr->unknown_chunks = NULL;

-            info_ptr->unknown_chunks_num = 0;

-         }

-      }

-   }

-#endif

-

-#ifdef PNG_hIST_SUPPORTED

-   /* Free any hIST entry */

-   if ((mask & PNG_FREE_HIST)  & info_ptr->free_me)

-   {

-      png_free(png_ptr, info_ptr->hist);

-      info_ptr->hist = NULL;

-      info_ptr->valid &= ~PNG_INFO_hIST;

-   }

-#endif

-

-   /* Free any PLTE entry that was internally allocated */

-   if ((mask & PNG_FREE_PLTE) & info_ptr->free_me)

-   {

-      png_free(png_ptr, info_ptr->palette);

-      info_ptr->palette = NULL;

-      info_ptr->valid &= ~PNG_INFO_PLTE;

-      info_ptr->num_palette = 0;

-   }

-

-#ifdef PNG_INFO_IMAGE_SUPPORTED

-   /* Free any image bits attached to the info structure */

-   if ((mask & PNG_FREE_ROWS) & info_ptr->free_me)

-   {

-      if (info_ptr->row_pointers)

-      {

-         png_uint_32 row;

-         for (row = 0; row < info_ptr->height; row++)

-         {

-            png_free(png_ptr, info_ptr->row_pointers[row]);

-            info_ptr->row_pointers[row] = NULL;

-         }

-         png_free(png_ptr, info_ptr->row_pointers);

-         info_ptr->row_pointers = NULL;

-      }

-      info_ptr->valid &= ~PNG_INFO_IDAT;

-   }

-#endif

-

-   if (num != -1)

-      mask &= ~PNG_FREE_MUL;

-

-   info_ptr->free_me &= ~mask;

-}

-#endif /* defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) */

-

-/* This function returns a pointer to the io_ptr associated with the user

- * functions.  The application should free any memory associated with this

- * pointer before png_write_destroy() or png_read_destroy() are called.

- */

-png_voidp PNGAPI

-png_get_io_ptr(png_const_structrp png_ptr)

-{

-   if (png_ptr == NULL)

-      return (NULL);

-

-   return (png_ptr->io_ptr);

-}

-

-#if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)

-#  ifdef PNG_STDIO_SUPPORTED

-/* Initialize the default input/output functions for the PNG file.  If you

- * use your own read or write routines, you can call either png_set_read_fn()

- * or png_set_write_fn() instead of png_init_io().  If you have defined

- * PNG_NO_STDIO or otherwise disabled PNG_STDIO_SUPPORTED, you must use a

- * function of your own because "FILE *" isn't necessarily available.

- */

-void PNGAPI

-png_init_io(png_structrp png_ptr, png_FILE_p fp)

-{

-   png_debug(1, "in png_init_io");

-

-   if (png_ptr == NULL)

-      return;

-

-   png_ptr->io_ptr = (png_voidp)fp;

-}

-#  endif

-

-#ifdef PNG_SAVE_INT_32_SUPPORTED

-/* The png_save_int_32 function assumes integers are stored in two's

- * complement format.  If this isn't the case, then this routine needs to

- * be modified to write data in two's complement format.  Note that,

- * the following works correctly even if png_int_32 has more than 32 bits

- * (compare the more complex code required on read for sign extension.)

- */

-void PNGAPI

-png_save_int_32(png_bytep buf, png_int_32 i)

-{

-   buf[0] = (png_byte)((i >> 24) & 0xff);

-   buf[1] = (png_byte)((i >> 16) & 0xff);

-   buf[2] = (png_byte)((i >> 8) & 0xff);

-   buf[3] = (png_byte)(i & 0xff);

-}

-#endif

-

-#  ifdef PNG_TIME_RFC1123_SUPPORTED

-/* Convert the supplied time into an RFC 1123 string suitable for use in

- * a "Creation Time" or other text-based time string.

- */

-int PNGAPI

-png_convert_to_rfc1123_buffer(char out[29], png_const_timep ptime)

-{

-   static PNG_CONST char short_months[12][4] =

-        {"Jan", "Feb", "Mar", "Apr", "May", "Jun",

-         "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};

-

-   if (out == NULL)

-      return 0;

-

-   if (ptime->year > 9999 /* RFC1123 limitation */ ||

-       ptime->month == 0    ||  ptime->month > 12  ||

-       ptime->day   == 0    ||  ptime->day   > 31  ||

-       ptime->hour  > 23    ||  ptime->minute > 59 ||

-       ptime->second > 60)

-      return 0;

-

-   {

-      size_t pos = 0;

-      char number_buf[5]; /* enough for a four-digit year */

-

-#     define APPEND_STRING(string) pos = png_safecat(out, 29, pos, (string))

-#     define APPEND_NUMBER(format, value)\

-         APPEND_STRING(PNG_FORMAT_NUMBER(number_buf, format, (value)))

-#     define APPEND(ch) if (pos < 28) out[pos++] = (ch)

-

-      APPEND_NUMBER(PNG_NUMBER_FORMAT_u, (unsigned)ptime->day);

-      APPEND(' ');

-      APPEND_STRING(short_months[(ptime->month - 1)]);

-      APPEND(' ');

-      APPEND_NUMBER(PNG_NUMBER_FORMAT_u, ptime->year);

-      APPEND(' ');

-      APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->hour);

-      APPEND(':');

-      APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->minute);

-      APPEND(':');

-      APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->second);

-      APPEND_STRING(" +0000"); /* This reliably terminates the buffer */

-

-#     undef APPEND

-#     undef APPEND_NUMBER

-#     undef APPEND_STRING

-   }

-

-   return 1;

-}

-

-#     if PNG_LIBPNG_VER < 10700

-/* To do: remove the following from libpng-1.7 */

-/* Original API that uses a private buffer in png_struct.

- * Deprecated because it causes png_struct to carry a spurious temporary

- * buffer (png_struct::time_buffer), better to have the caller pass this in.

- */

-png_const_charp PNGAPI

-png_convert_to_rfc1123(png_structrp png_ptr, png_const_timep ptime)

-{

-   if (png_ptr != NULL)

-   {

-      /* The only failure above if png_ptr != NULL is from an invalid ptime */

-      if (!png_convert_to_rfc1123_buffer(png_ptr->time_buffer, ptime))

-         png_warning(png_ptr, "Ignoring invalid time value");

-

-      else

-         return png_ptr->time_buffer;

-   }

-

-   return NULL;

-}

-#     endif

-#  endif /* PNG_TIME_RFC1123_SUPPORTED */

-

-#endif /* defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) */

-

-png_const_charp PNGAPI

-png_get_copyright(png_const_structrp png_ptr)

-{

-   PNG_UNUSED(png_ptr)  /* Silence compiler warning about unused png_ptr */

-#ifdef PNG_STRING_COPYRIGHT

-   return PNG_STRING_COPYRIGHT

-#else

-#  ifdef __STDC__

-   return PNG_STRING_NEWLINE \

-     "libpng version 1.6.3 - July 18, 2013" PNG_STRING_NEWLINE \

-     "Copyright (c) 1998-2013 Glenn Randers-Pehrson" PNG_STRING_NEWLINE \

-     "Copyright (c) 1996-1997 Andreas Dilger" PNG_STRING_NEWLINE \

-     "Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc." \

-     PNG_STRING_NEWLINE;

-#  else

-      return "libpng version 1.6.3 - July 18, 2013\

-      Copyright (c) 1998-2013 Glenn Randers-Pehrson\

-      Copyright (c) 1996-1997 Andreas Dilger\

-      Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.";

-#  endif

-#endif

-}

-

-/* The following return the library version as a short string in the

- * format 1.0.0 through 99.99.99zz.  To get the version of *.h files

- * used with your application, print out PNG_LIBPNG_VER_STRING, which

- * is defined in png.h.

- * Note: now there is no difference between png_get_libpng_ver() and

- * png_get_header_ver().  Due to the version_nn_nn_nn typedef guard,

- * it is guaranteed that png.c uses the correct version of png.h.

- */

-png_const_charp PNGAPI

-png_get_libpng_ver(png_const_structrp png_ptr)

-{

-   /* Version of *.c files used when building libpng */

-   return png_get_header_ver(png_ptr);

-}

-

-png_const_charp PNGAPI

-png_get_header_ver(png_const_structrp png_ptr)

-{

-   /* Version of *.h files used when building libpng */

-   PNG_UNUSED(png_ptr)  /* Silence compiler warning about unused png_ptr */

-   return PNG_LIBPNG_VER_STRING;

-}

-

-png_const_charp PNGAPI

-png_get_header_version(png_const_structrp png_ptr)

-{

-   /* Returns longer string containing both version and date */

-   PNG_UNUSED(png_ptr)  /* Silence compiler warning about unused png_ptr */

-#ifdef __STDC__

-   return PNG_HEADER_VERSION_STRING

-#  ifndef PNG_READ_SUPPORTED

-   "     (NO READ SUPPORT)"

-#  endif

-   PNG_STRING_NEWLINE;

-#else

-   return PNG_HEADER_VERSION_STRING;

-#endif

-}

-

-#ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED

-int PNGAPI

-png_handle_as_unknown(png_const_structrp png_ptr, png_const_bytep chunk_name)

-{

-   /* Check chunk_name and return "keep" value if it's on the list, else 0 */

-   png_const_bytep p, p_end;

-

-   if (png_ptr == NULL || chunk_name == NULL || png_ptr->num_chunk_list == 0)

-      return PNG_HANDLE_CHUNK_AS_DEFAULT;

-

-   p_end = png_ptr->chunk_list;

-   p = p_end + png_ptr->num_chunk_list*5; /* beyond end */

-

-   /* The code is the fifth byte after each four byte string.  Historically this

-    * code was always searched from the end of the list, this is no longer

-    * necessary because the 'set' routine handles duplicate entries correcty.

-    */

-   do /* num_chunk_list > 0, so at least one */

-   {

-      p -= 5;

-

-      if (!memcmp(chunk_name, p, 4))

-         return p[4];

-   }

-   while (p > p_end);

-

-   /* This means that known chunks should be processed and unknown chunks should

-    * be handled according to the value of png_ptr->unknown_default; this can be

-    * confusing because, as a result, there are two levels of defaulting for

-    * unknown chunks.

-    */

-   return PNG_HANDLE_CHUNK_AS_DEFAULT;

-}

-

-#ifdef PNG_READ_UNKNOWN_CHUNKS_SUPPORTED

-int /* PRIVATE */

-png_chunk_unknown_handling(png_const_structrp png_ptr, png_uint_32 chunk_name)

-{

-   png_byte chunk_string[5];

-

-   PNG_CSTRING_FROM_CHUNK(chunk_string, chunk_name);

-   return png_handle_as_unknown(png_ptr, chunk_string);

-}

-#endif /* READ_UNKNOWN_CHUNKS */

-#endif /* SET_UNKNOWN_CHUNKS */

-

-#ifdef PNG_READ_SUPPORTED

-/* This function, added to libpng-1.0.6g, is untested. */

-int PNGAPI

-png_reset_zstream(png_structrp png_ptr)

-{

-   if (png_ptr == NULL)

-      return Z_STREAM_ERROR;

-

-   /* WARNING: this resets the window bits to the maximum! */

-   return (inflateReset(&png_ptr->zstream));

-}

-#endif /* PNG_READ_SUPPORTED */

-

-/* This function was added to libpng-1.0.7 */

-png_uint_32 PNGAPI

-png_access_version_number(void)

-{

-   /* Version of *.c files used when building libpng */

-   return((png_uint_32)PNG_LIBPNG_VER);

-}

-

-

-

-#if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)

-/* Ensure that png_ptr->zstream.msg holds some appropriate error message string.

- * If it doesn't 'ret' is used to set it to something appropriate, even in cases

- * like Z_OK or Z_STREAM_END where the error code is apparently a success code.

- */

-void /* PRIVATE */

-png_zstream_error(png_structrp png_ptr, int ret)

-{

-   /* Translate 'ret' into an appropriate error string, priority is given to the

-    * one in zstream if set.  This always returns a string, even in cases like

-    * Z_OK or Z_STREAM_END where the error code is a success code.

-    */

-   if (png_ptr->zstream.msg == NULL) switch (ret)

-   {

-      default:

-      case Z_OK:

-         png_ptr->zstream.msg = PNGZ_MSG_CAST("unexpected zlib return code");

-         break;

-

-      case Z_STREAM_END:

-         /* Normal exit */

-         png_ptr->zstream.msg = PNGZ_MSG_CAST("unexpected end of LZ stream");

-         break;

-

-      case Z_NEED_DICT:

-         /* This means the deflate stream did not have a dictionary; this

-          * indicates a bogus PNG.

-          */

-         png_ptr->zstream.msg = PNGZ_MSG_CAST("missing LZ dictionary");

-         break;

-

-      case Z_ERRNO:

-         /* gz APIs only: should not happen */

-         png_ptr->zstream.msg = PNGZ_MSG_CAST("zlib IO error");

-         break;

-

-      case Z_STREAM_ERROR:

-         /* internal libpng error */

-         png_ptr->zstream.msg = PNGZ_MSG_CAST("bad parameters to zlib");

-         break;

-

-      case Z_DATA_ERROR:

-         png_ptr->zstream.msg = PNGZ_MSG_CAST("damaged LZ stream");

-         break;

-

-      case Z_MEM_ERROR:

-         png_ptr->zstream.msg = PNGZ_MSG_CAST("insufficient memory");

-         break;

-

-      case Z_BUF_ERROR:

-         /* End of input or output; not a problem if the caller is doing

-          * incremental read or write.

-          */

-         png_ptr->zstream.msg = PNGZ_MSG_CAST("truncated");

-         break;

-

-      case Z_VERSION_ERROR:

-         png_ptr->zstream.msg = PNGZ_MSG_CAST("unsupported zlib version");

-         break;

-

-      case PNG_UNEXPECTED_ZLIB_RETURN:

-         /* Compile errors here mean that zlib now uses the value co-opted in

-          * pngpriv.h for PNG_UNEXPECTED_ZLIB_RETURN; update the switch above

-          * and change pngpriv.h.  Note that this message is "... return",

-          * whereas the default/Z_OK one is "... return code".

-          */

-         png_ptr->zstream.msg = PNGZ_MSG_CAST("unexpected zlib return");

-         break;

-   }

-}

-

-/* png_convert_size: a PNGAPI but no longer in png.h, so deleted

- * at libpng 1.5.5!

- */

-

-/* Added at libpng version 1.2.34 and 1.4.0 (moved from pngset.c) */

-#ifdef PNG_GAMMA_SUPPORTED /* always set if COLORSPACE */

-static int

-png_colorspace_check_gamma(png_const_structrp png_ptr,

-   png_colorspacerp colorspace, png_fixed_point gAMA, int from)

-   /* This is called to check a new gamma value against an existing one.  The

-    * routine returns false if the new gamma value should not be written.

-    *

-    * 'from' says where the new gamma value comes from:

-    *

-    *    0: the new gamma value is the libpng estimate for an ICC profile

-    *    1: the new gamma value comes from a gAMA chunk

-    *    2: the new gamma value comes from an sRGB chunk

-    */

-{

-   png_fixed_point gtest;

-

-   if ((colorspace->flags & PNG_COLORSPACE_HAVE_GAMMA) != 0 &&

-      (!png_muldiv(&gtest, colorspace->gamma, PNG_FP_1, gAMA) ||

-      png_gamma_significant(gtest)))

-   {

-      /* Either this is an sRGB image, in which case the calculated gamma

-       * approximation should match, or this is an image with a profile and the

-       * value libpng calculates for the gamma of the profile does not match the

-       * value recorded in the file.  The former, sRGB, case is an error, the

-       * latter is just a warning.

-       */

-      if ((colorspace->flags & PNG_COLORSPACE_FROM_sRGB) != 0 || from == 2)

-      {

-         png_chunk_report(png_ptr, "gamma value does not match sRGB",

-            PNG_CHUNK_ERROR);

-         /* Do not overwrite an sRGB value */

-         return from == 2;

-      }

-

-      else /* sRGB tag not involved */

-      {

-         png_chunk_report(png_ptr, "gamma value does not match libpng estimate",

-            PNG_CHUNK_WARNING);

-         return from == 1;

-      }

-   }

-

-   return 1;

-}

-

-void /* PRIVATE */

-png_colorspace_set_gamma(png_const_structrp png_ptr,

-   png_colorspacerp colorspace, png_fixed_point gAMA)

-{

-   /* Changed in libpng-1.5.4 to limit the values to ensure overflow can't

-    * occur.  Since the fixed point representation is assymetrical it is

-    * possible for 1/gamma to overflow the limit of 21474 and this means the

-    * gamma value must be at least 5/100000 and hence at most 20000.0.  For

-    * safety the limits here are a little narrower.  The values are 0.00016 to

-    * 6250.0, which are truly ridiculous gamma values (and will produce

-    * displays that are all black or all white.)

-    *

-    * In 1.6.0 this test replaces the ones in pngrutil.c, in the gAMA chunk

-    * handling code, which only required the value to be >0.

-    */

-   png_const_charp errmsg;

-

-   if (gAMA < 16 || gAMA > 625000000)

-      errmsg = "gamma value out of range";

-

-#  ifdef PNG_READ_gAMA_SUPPORTED

-      /* Allow the application to set the gamma value more than once */

-      else if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0 &&

-         (colorspace->flags & PNG_COLORSPACE_FROM_gAMA) != 0)

-         errmsg = "duplicate";

-#  endif

-

-   /* Do nothing if the colorspace is already invalid */

-   else if (colorspace->flags & PNG_COLORSPACE_INVALID)

-      return;

-

-   else

-   {

-      if (png_colorspace_check_gamma(png_ptr, colorspace, gAMA, 1/*from gAMA*/))

-      {

-         /* Store this gamma value. */

-         colorspace->gamma = gAMA;

-         colorspace->flags |=

-            (PNG_COLORSPACE_HAVE_GAMMA | PNG_COLORSPACE_FROM_gAMA);

-      }

-

-      /* At present if the check_gamma test fails the gamma of the colorspace is

-       * not updated however the colorspace is not invalidated.  This

-       * corresponds to the case where the existing gamma comes from an sRGB

-       * chunk or profile.  An error message has already been output.

-       */

-      return;

-   }

-

-   /* Error exit - errmsg has been set. */

-   colorspace->flags |= PNG_COLORSPACE_INVALID;

-   png_chunk_report(png_ptr, errmsg, PNG_CHUNK_WRITE_ERROR);

-}

-

-void /* PRIVATE */

-png_colorspace_sync_info(png_const_structrp png_ptr, png_inforp info_ptr)

-{

-   if (info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID)

-   {

-      /* Everything is invalid */

-      info_ptr->valid &= ~(PNG_INFO_gAMA|PNG_INFO_cHRM|PNG_INFO_sRGB|

-         PNG_INFO_iCCP);

-

-#     ifdef PNG_COLORSPACE_SUPPORTED

-         /* Clean up the iCCP profile now if it won't be used. */

-         png_free_data(png_ptr, info_ptr, PNG_FREE_ICCP, -1/*not used*/);

-#     else

-         PNG_UNUSED(png_ptr)

-#     endif

-   }

-

-   else

-   {

-#     ifdef PNG_COLORSPACE_SUPPORTED

-         /* Leave the INFO_iCCP flag set if the pngset.c code has already set

-          * it; this allows a PNG to contain a profile which matches sRGB and

-          * yet still have that profile retrievable by the application.

-          */

-         if (info_ptr->colorspace.flags & PNG_COLORSPACE_MATCHES_sRGB)

-            info_ptr->valid |= PNG_INFO_sRGB;

-

-         else

-            info_ptr->valid &= ~PNG_INFO_sRGB;

-

-         if (info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS)

-            info_ptr->valid |= PNG_INFO_cHRM;

-

-         else

-            info_ptr->valid &= ~PNG_INFO_cHRM;

-#     endif

-

-      if (info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA)

-         info_ptr->valid |= PNG_INFO_gAMA;

-

-      else

-         info_ptr->valid &= ~PNG_INFO_gAMA;

-   }

-}

-

-#ifdef PNG_READ_SUPPORTED

-void /* PRIVATE */

-png_colorspace_sync(png_const_structrp png_ptr, png_inforp info_ptr)

-{

-   if (info_ptr == NULL) /* reduce code size; check here not in the caller */

-      return;

-

-   info_ptr->colorspace = png_ptr->colorspace;

-   png_colorspace_sync_info(png_ptr, info_ptr);

-}

-#endif

-#endif

-

-#ifdef PNG_COLORSPACE_SUPPORTED

-/* Added at libpng-1.5.5 to support read and write of true CIEXYZ values for

- * cHRM, as opposed to using chromaticities.  These internal APIs return

- * non-zero on a parameter error.  The X, Y and Z values are required to be

- * positive and less than 1.0.

- */

-static int

-png_xy_from_XYZ(png_xy *xy, const png_XYZ *XYZ)

-{

-   png_int_32 d, dwhite, whiteX, whiteY;

-

-   d = XYZ->red_X + XYZ->red_Y + XYZ->red_Z;

-   if (!png_muldiv(&xy->redx, XYZ->red_X, PNG_FP_1, d)) return 1;

-   if (!png_muldiv(&xy->redy, XYZ->red_Y, PNG_FP_1, d)) return 1;

-   dwhite = d;

-   whiteX = XYZ->red_X;

-   whiteY = XYZ->red_Y;

-

-   d = XYZ->green_X + XYZ->green_Y + XYZ->green_Z;

-   if (!png_muldiv(&xy->greenx, XYZ->green_X, PNG_FP_1, d)) return 1;

-   if (!png_muldiv(&xy->greeny, XYZ->green_Y, PNG_FP_1, d)) return 1;

-   dwhite += d;

-   whiteX += XYZ->green_X;

-   whiteY += XYZ->green_Y;

-

-   d = XYZ->blue_X + XYZ->blue_Y + XYZ->blue_Z;

-   if (!png_muldiv(&xy->bluex, XYZ->blue_X, PNG_FP_1, d)) return 1;

-   if (!png_muldiv(&xy->bluey, XYZ->blue_Y, PNG_FP_1, d)) return 1;

-   dwhite += d;

-   whiteX += XYZ->blue_X;

-   whiteY += XYZ->blue_Y;

-

-   /* The reference white is simply the sum of the end-point (X,Y,Z) vectors,

-    * thus:

-    */

-   if (!png_muldiv(&xy->whitex, whiteX, PNG_FP_1, dwhite)) return 1;

-   if (!png_muldiv(&xy->whitey, whiteY, PNG_FP_1, dwhite)) return 1;

-

-   return 0;

-}

-

-static int

-png_XYZ_from_xy(png_XYZ *XYZ, const png_xy *xy)

-{

-   png_fixed_point red_inverse, green_inverse, blue_scale;

-   png_fixed_point left, right, denominator;

-

-   /* Check xy and, implicitly, z.  Note that wide gamut color spaces typically

-    * have end points with 0 tristimulus values (these are impossible end

-    * points, but they are used to cover the possible colors.)

-    */

-   if (xy->redx < 0 || xy->redx > PNG_FP_1) return 1;

-   if (xy->redy < 0 || xy->redy > PNG_FP_1-xy->redx) return 1;

-   if (xy->greenx < 0 || xy->greenx > PNG_FP_1) return 1;

-   if (xy->greeny < 0 || xy->greeny > PNG_FP_1-xy->greenx) return 1;

-   if (xy->bluex < 0 || xy->bluex > PNG_FP_1) return 1;

-   if (xy->bluey < 0 || xy->bluey > PNG_FP_1-xy->bluex) return 1;

-   if (xy->whitex < 0 || xy->whitex > PNG_FP_1) return 1;

-   if (xy->whitey < 0 || xy->whitey > PNG_FP_1-xy->whitex) return 1;

-

-   /* The reverse calculation is more difficult because the original tristimulus

-    * value had 9 independent values (red,green,blue)x(X,Y,Z) however only 8

-    * derived values were recorded in the cHRM chunk;

-    * (red,green,blue,white)x(x,y).  This loses one degree of freedom and

-    * therefore an arbitrary ninth value has to be introduced to undo the

-    * original transformations.

-    *

-    * Think of the original end-points as points in (X,Y,Z) space.  The

-    * chromaticity values (c) have the property:

-    *

-    *           C

-    *   c = ---------

-    *       X + Y + Z

-    *

-    * For each c (x,y,z) from the corresponding original C (X,Y,Z).  Thus the

-    * three chromaticity values (x,y,z) for each end-point obey the

-    * relationship:

-    *

-    *   x + y + z = 1

-    *

-    * This describes the plane in (X,Y,Z) space that intersects each axis at the

-    * value 1.0; call this the chromaticity plane.  Thus the chromaticity

-    * calculation has scaled each end-point so that it is on the x+y+z=1 plane

-    * and chromaticity is the intersection of the vector from the origin to the

-    * (X,Y,Z) value with the chromaticity plane.

-    *

-    * To fully invert the chromaticity calculation we would need the three

-    * end-point scale factors, (red-scale, green-scale, blue-scale), but these

-    * were not recorded.  Instead we calculated the reference white (X,Y,Z) and

-    * recorded the chromaticity of this.  The reference white (X,Y,Z) would have

-    * given all three of the scale factors since:

-    *

-    *    color-C = color-c * color-scale

-    *    white-C = red-C + green-C + blue-C

-    *            = red-c*red-scale + green-c*green-scale + blue-c*blue-scale

-    *

-    * But cHRM records only white-x and white-y, so we have lost the white scale

-    * factor:

-    *

-    *    white-C = white-c*white-scale

-    *

-    * To handle this the inverse transformation makes an arbitrary assumption

-    * about white-scale:

-    *

-    *    Assume: white-Y = 1.0

-    *    Hence:  white-scale = 1/white-y

-    *    Or:     red-Y + green-Y + blue-Y = 1.0

-    *

-    * Notice the last statement of the assumption gives an equation in three of

-    * the nine values we want to calculate.  8 more equations come from the

-    * above routine as summarised at the top above (the chromaticity

-    * calculation):

-    *

-    *    Given: color-x = color-X / (color-X + color-Y + color-Z)

-    *    Hence: (color-x - 1)*color-X + color.x*color-Y + color.x*color-Z = 0

-    *

-    * This is 9 simultaneous equations in the 9 variables "color-C" and can be

-    * solved by Cramer's rule.  Cramer's rule requires calculating 10 9x9 matrix

-    * determinants, however this is not as bad as it seems because only 28 of

-    * the total of 90 terms in the various matrices are non-zero.  Nevertheless

-    * Cramer's rule is notoriously numerically unstable because the determinant

-    * calculation involves the difference of large, but similar, numbers.  It is

-    * difficult to be sure that the calculation is stable for real world values

-    * and it is certain that it becomes unstable where the end points are close

-    * together.

-    *

-    * So this code uses the perhaps slightly less optimal but more

-    * understandable and totally obvious approach of calculating color-scale.

-    *

-    * This algorithm depends on the precision in white-scale and that is

-    * (1/white-y), so we can immediately see that as white-y approaches 0 the

-    * accuracy inherent in the cHRM chunk drops off substantially.

-    *

-    * libpng arithmetic: a simple invertion of the above equations

-    * ------------------------------------------------------------

-    *

-    *    white_scale = 1/white-y

-    *    white-X = white-x * white-scale

-    *    white-Y = 1.0

-    *    white-Z = (1 - white-x - white-y) * white_scale

-    *

-    *    white-C = red-C + green-C + blue-C

-    *            = red-c*red-scale + green-c*green-scale + blue-c*blue-scale

-    *

-    * This gives us three equations in (red-scale,green-scale,blue-scale) where

-    * all the coefficients are now known:

-    *

-    *    red-x*red-scale + green-x*green-scale + blue-x*blue-scale

-    *       = white-x/white-y

-    *    red-y*red-scale + green-y*green-scale + blue-y*blue-scale = 1

-    *    red-z*red-scale + green-z*green-scale + blue-z*blue-scale

-    *       = (1 - white-x - white-y)/white-y

-    *

-    * In the last equation color-z is (1 - color-x - color-y) so we can add all

-    * three equations together to get an alternative third:

-    *

-    *    red-scale + green-scale + blue-scale = 1/white-y = white-scale

-    *

-    * So now we have a Cramer's rule solution where the determinants are just

-    * 3x3 - far more tractible.  Unfortunately 3x3 determinants still involve

-    * multiplication of three coefficients so we can't guarantee to avoid

-    * overflow in the libpng fixed point representation.  Using Cramer's rule in

-    * floating point is probably a good choice here, but it's not an option for

-    * fixed point.  Instead proceed to simplify the first two equations by

-    * eliminating what is likely to be the largest value, blue-scale:

-    *

-    *    blue-scale = white-scale - red-scale - green-scale

-    *

-    * Hence:

-    *

-    *    (red-x - blue-x)*red-scale + (green-x - blue-x)*green-scale =

-    *                (white-x - blue-x)*white-scale

-    *

-    *    (red-y - blue-y)*red-scale + (green-y - blue-y)*green-scale =

-    *                1 - blue-y*white-scale

-    *

-    * And now we can trivially solve for (red-scale,green-scale):

-    *

-    *    green-scale =

-    *                (white-x - blue-x)*white-scale - (red-x - blue-x)*red-scale

-    *                -----------------------------------------------------------

-    *                                  green-x - blue-x

-    *

-    *    red-scale =

-    *                1 - blue-y*white-scale - (green-y - blue-y) * green-scale

-    *                ---------------------------------------------------------

-    *                                  red-y - blue-y

-    *

-    * Hence:

-    *

-    *    red-scale =

-    *          ( (green-x - blue-x) * (white-y - blue-y) -

-    *            (green-y - blue-y) * (white-x - blue-x) ) / white-y

-    * -------------------------------------------------------------------------

-    *  (green-x - blue-x)*(red-y - blue-y)-(green-y - blue-y)*(red-x - blue-x)

-    *

-    *    green-scale =

-    *          ( (red-y - blue-y) * (white-x - blue-x) -

-    *            (red-x - blue-x) * (white-y - blue-y) ) / white-y

-    * -------------------------------------------------------------------------

-    *  (green-x - blue-x)*(red-y - blue-y)-(green-y - blue-y)*(red-x - blue-x)

-    *

-    * Accuracy:

-    * The input values have 5 decimal digits of accuracy.  The values are all in

-    * the range 0 < value < 1, so simple products are in the same range but may

-    * need up to 10 decimal digits to preserve the original precision and avoid

-    * underflow.  Because we are using a 32-bit signed representation we cannot

-    * match this; the best is a little over 9 decimal digits, less than 10.

-    *

-    * The approach used here is to preserve the maximum precision within the

-    * signed representation.  Because the red-scale calculation above uses the

-    * difference between two products of values that must be in the range -1..+1

-    * it is sufficient to divide the product by 7; ceil(100,000/32767*2).  The

-    * factor is irrelevant in the calculation because it is applied to both

-    * numerator and denominator.

-    *

-    * Note that the values of the differences of the products of the

-    * chromaticities in the above equations tend to be small, for example for

-    * the sRGB chromaticities they are:

-    *

-    * red numerator:    -0.04751

-    * green numerator:  -0.08788

-    * denominator:      -0.2241 (without white-y multiplication)

-    *

-    *  The resultant Y coefficients from the chromaticities of some widely used

-    *  color space definitions are (to 15 decimal places):

-    *

-    *  sRGB

-    *    0.212639005871510 0.715168678767756 0.072192315360734

-    *  Kodak ProPhoto

-    *    0.288071128229293 0.711843217810102 0.000085653960605

-    *  Adobe RGB

-    *    0.297344975250536 0.627363566255466 0.075291458493998

-    *  Adobe Wide Gamut RGB

-    *    0.258728243040113 0.724682314948566 0.016589442011321

-    */

-   /* By the argument, above overflow should be impossible here. The return

-    * value of 2 indicates an internal error to the caller.

-    */

-   if (!png_muldiv(&left, xy->greenx-xy->bluex, xy->redy - xy->bluey, 7))

-      return 2;

-   if (!png_muldiv(&right, xy->greeny-xy->bluey, xy->redx - xy->bluex, 7))

-      return 2;

-   denominator = left - right;

-

-   /* Now find the red numerator. */

-   if (!png_muldiv(&left, xy->greenx-xy->bluex, xy->whitey-xy->bluey, 7))

-      return 2;

-   if (!png_muldiv(&right, xy->greeny-xy->bluey, xy->whitex-xy->bluex, 7))

-      return 2;

-

-   /* Overflow is possible here and it indicates an extreme set of PNG cHRM

-    * chunk values.  This calculation actually returns the reciprocal of the

-    * scale value because this allows us to delay the multiplication of white-y

-    * into the denominator, which tends to produce a small number.

-    */

-   if (!png_muldiv(&red_inverse, xy->whitey, denominator, left-right) ||

-       red_inverse <= xy->whitey /* r+g+b scales = white scale */)

-      return 1;

-

-   /* Similarly for green_inverse: */

-   if (!png_muldiv(&left, xy->redy-xy->bluey, xy->whitex-xy->bluex, 7))

-      return 2;

-   if (!png_muldiv(&right, xy->redx-xy->bluex, xy->whitey-xy->bluey, 7))

-      return 2;

-   if (!png_muldiv(&green_inverse, xy->whitey, denominator, left-right) ||

-       green_inverse <= xy->whitey)

-      return 1;

-

-   /* And the blue scale, the checks above guarantee this can't overflow but it

-    * can still produce 0 for extreme cHRM values.

-    */

-   blue_scale = png_reciprocal(xy->whitey) - png_reciprocal(red_inverse) -

-      png_reciprocal(green_inverse);

-   if (blue_scale <= 0) return 1;

-

-

-   /* And fill in the png_XYZ: */

-   if (!png_muldiv(&XYZ->red_X, xy->redx, PNG_FP_1, red_inverse)) return 1;

-   if (!png_muldiv(&XYZ->red_Y, xy->redy, PNG_FP_1, red_inverse)) return 1;

-   if (!png_muldiv(&XYZ->red_Z, PNG_FP_1 - xy->redx - xy->redy, PNG_FP_1,

-      red_inverse))

-      return 1;

-

-   if (!png_muldiv(&XYZ->green_X, xy->greenx, PNG_FP_1, green_inverse))

-      return 1;

-   if (!png_muldiv(&XYZ->green_Y, xy->greeny, PNG_FP_1, green_inverse))

-      return 1;

-   if (!png_muldiv(&XYZ->green_Z, PNG_FP_1 - xy->greenx - xy->greeny, PNG_FP_1,

-      green_inverse))

-      return 1;

-

-   if (!png_muldiv(&XYZ->blue_X, xy->bluex, blue_scale, PNG_FP_1)) return 1;

-   if (!png_muldiv(&XYZ->blue_Y, xy->bluey, blue_scale, PNG_FP_1)) return 1;

-   if (!png_muldiv(&XYZ->blue_Z, PNG_FP_1 - xy->bluex - xy->bluey, blue_scale,

-      PNG_FP_1))

-      return 1;

-

-   return 0; /*success*/

-}

-

-static int

-png_XYZ_normalize(png_XYZ *XYZ)

-{

-   png_int_32 Y;

-

-   if (XYZ->red_Y < 0 || XYZ->green_Y < 0 || XYZ->blue_Y < 0 ||

-      XYZ->red_X < 0 || XYZ->green_X < 0 || XYZ->blue_X < 0 ||

-      XYZ->red_Z < 0 || XYZ->green_Z < 0 || XYZ->blue_Z < 0)

-      return 1;

-

-   /* Normalize by scaling so the sum of the end-point Y values is PNG_FP_1.

-    * IMPLEMENTATION NOTE: ANSI requires signed overflow not to occur, therefore

-    * relying on addition of two positive values producing a negative one is not

-    * safe.

-    */

-   Y = XYZ->red_Y;

-   if (0x7fffffff - Y < XYZ->green_X) return 1;

-   Y += XYZ->green_Y;

-   if (0x7fffffff - Y < XYZ->blue_X) return 1;

-   Y += XYZ->blue_Y;

-

-   if (Y != PNG_FP_1)

-   {

-      if (!png_muldiv(&XYZ->red_X, XYZ->red_X, PNG_FP_1, Y)) return 1;

-      if (!png_muldiv(&XYZ->red_Y, XYZ->red_Y, PNG_FP_1, Y)) return 1;

-      if (!png_muldiv(&XYZ->red_Z, XYZ->red_Z, PNG_FP_1, Y)) return 1;

-

-      if (!png_muldiv(&XYZ->green_X, XYZ->green_X, PNG_FP_1, Y)) return 1;

-      if (!png_muldiv(&XYZ->green_Y, XYZ->green_Y, PNG_FP_1, Y)) return 1;

-      if (!png_muldiv(&XYZ->green_Z, XYZ->green_Z, PNG_FP_1, Y)) return 1;

-

-      if (!png_muldiv(&XYZ->blue_X, XYZ->blue_X, PNG_FP_1, Y)) return 1;

-      if (!png_muldiv(&XYZ->blue_Y, XYZ->blue_Y, PNG_FP_1, Y)) return 1;

-      if (!png_muldiv(&XYZ->blue_Z, XYZ->blue_Z, PNG_FP_1, Y)) return 1;

-   }

-

-   return 0;

-}

-

-static int

-png_colorspace_endpoints_match(const png_xy *xy1, const png_xy *xy2, int delta)

-{

-   /* Allow an error of +/-0.01 (absolute value) on each chromaticity */

-   return !(PNG_OUT_OF_RANGE(xy1->whitex, xy2->whitex,delta) ||

-      PNG_OUT_OF_RANGE(xy1->whitey, xy2->whitey,delta) ||

-      PNG_OUT_OF_RANGE(xy1->redx,   xy2->redx,  delta) ||

-      PNG_OUT_OF_RANGE(xy1->redy,   xy2->redy,  delta) ||

-      PNG_OUT_OF_RANGE(xy1->greenx, xy2->greenx,delta) ||

-      PNG_OUT_OF_RANGE(xy1->greeny, xy2->greeny,delta) ||

-      PNG_OUT_OF_RANGE(xy1->bluex,  xy2->bluex, delta) ||

-      PNG_OUT_OF_RANGE(xy1->bluey,  xy2->bluey, delta));

-}

-

-/* Added in libpng-1.6.0, a different check for the validity of a set of cHRM

- * chunk chromaticities.  Earlier checks used to simply look for the overflow

- * condition (where the determinant of the matrix to solve for XYZ ends up zero

- * because the chromaticity values are not all distinct.)  Despite this it is

- * theoretically possible to produce chromaticities that are apparently valid

- * but that rapidly degrade to invalid, potentially crashing, sets because of

- * arithmetic inaccuracies when calculations are performed on them.  The new

- * check is to round-trip xy -> XYZ -> xy and then check that the result is

- * within a small percentage of the original.

- */

-static int

-png_colorspace_check_xy(png_XYZ *XYZ, const png_xy *xy)

-{

-   int result;

-   png_xy xy_test;

-

-   /* As a side-effect this routine also returns the XYZ endpoints. */

-   result = png_XYZ_from_xy(XYZ, xy);

-   if (result) return result;

-

-   result = png_xy_from_XYZ(&xy_test, XYZ);

-   if (result) return result;

-

-   if (png_colorspace_endpoints_match(xy, &xy_test,

-      5/*actually, the math is pretty accurate*/))

-      return 0;

-

-   /* Too much slip */

-   return 1;

-}

-

-/* This is the check going the other way.  The XYZ is modified to normalize it

- * (another side-effect) and the xy chromaticities are returned.

- */

-static int

-png_colorspace_check_XYZ(png_xy *xy, png_XYZ *XYZ)

-{

-   int result;

-   png_XYZ XYZtemp;

-

-   result = png_XYZ_normalize(XYZ);

-   if (result) return result;

-

-   result = png_xy_from_XYZ(xy, XYZ);

-   if (result) return result;

-

-   XYZtemp = *XYZ;

-   return png_colorspace_check_xy(&XYZtemp, xy);

-}

-

-/* Used to check for an endpoint match against sRGB */

-static const png_xy sRGB_xy = /* From ITU-R BT.709-3 */

-{

-   /* color      x       y */

-   /* red   */ 64000, 33000,

-   /* green */ 30000, 60000,

-   /* blue  */ 15000,  6000,

-   /* white */ 31270, 32900

-};

-

-static int

-png_colorspace_set_xy_and_XYZ(png_const_structrp png_ptr,

-   png_colorspacerp colorspace, const png_xy *xy, const png_XYZ *XYZ,

-   int preferred)

-{

-   if (colorspace->flags & PNG_COLORSPACE_INVALID)

-      return 0;

-

-   /* The consistency check is performed on the chromaticities; this factors out

-    * variations because of the normalization (or not) of the end point Y

-    * values.

-    */

-   if (preferred < 2 && (colorspace->flags & PNG_COLORSPACE_HAVE_ENDPOINTS))

-   {

-      /* The end points must be reasonably close to any we already have.  The

-       * following allows an error of up to +/-.001

-       */

-      if (!png_colorspace_endpoints_match(xy, &colorspace->end_points_xy, 100))

-      {

-         colorspace->flags |= PNG_COLORSPACE_INVALID;

-         png_benign_error(png_ptr, "inconsistent chromaticities");

-         return 0; /* failed */

-      }

-

-      /* Only overwrite with preferred values */

-      if (!preferred)

-         return 1; /* ok, but no change */

-   }

-

-   colorspace->end_points_xy = *xy;

-   colorspace->end_points_XYZ = *XYZ;

-   colorspace->flags |= PNG_COLORSPACE_HAVE_ENDPOINTS;

-

-   /* The end points are normally quoted to two decimal digits, so allow +/-0.01

-    * on this test.

-    */

-   if (png_colorspace_endpoints_match(xy, &sRGB_xy, 1000))

-      colorspace->flags |= PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB;

-

-   else

-      colorspace->flags &= PNG_COLORSPACE_CANCEL(

-         PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB);

-

-   return 2; /* ok and changed */

-}

-

-int /* PRIVATE */

-png_colorspace_set_chromaticities(png_const_structrp png_ptr,

-   png_colorspacerp colorspace, const png_xy *xy, int preferred)

-{

-   /* We must check the end points to ensure they are reasonable - in the past

-    * color management systems have crashed as a result of getting bogus

-    * colorant values, while this isn't the fault of libpng it is the

-    * responsibility of libpng because PNG carries the bomb and libpng is in a

-    * position to protect against it.

-    */

-   png_XYZ XYZ;

-

-   switch (png_colorspace_check_xy(&XYZ, xy))

-   {

-      case 0: /* success */

-         return png_colorspace_set_xy_and_XYZ(png_ptr, colorspace, xy, &XYZ,

-            preferred);

-

-      case 1:

-         /* We can't invert the chromaticities so we can't produce value XYZ

-          * values.  Likely as not a color management system will fail too.

-          */

-         colorspace->flags |= PNG_COLORSPACE_INVALID;

-         png_benign_error(png_ptr, "invalid chromaticities");

-         break;

-

-      default:

-         /* libpng is broken; this should be a warning but if it happens we

-          * want error reports so for the moment it is an error.

-          */

-         colorspace->flags |= PNG_COLORSPACE_INVALID;

-         png_error(png_ptr, "internal error checking chromaticities");

-         break;

-   }

-

-   return 0; /* failed */

-}

-

-int /* PRIVATE */

-png_colorspace_set_endpoints(png_const_structrp png_ptr,

-   png_colorspacerp colorspace, const png_XYZ *XYZ_in, int preferred)

-{

-   png_XYZ XYZ = *XYZ_in;

-   png_xy xy;

-

-   switch (png_colorspace_check_XYZ(&xy, &XYZ))

-   {

-      case 0:

-         return png_colorspace_set_xy_and_XYZ(png_ptr, colorspace, &xy, &XYZ,

-            preferred);

-

-      case 1:

-         /* End points are invalid. */

-         colorspace->flags |= PNG_COLORSPACE_INVALID;

-         png_benign_error(png_ptr, "invalid end points");

-         break;

-

-      default:

-         colorspace->flags |= PNG_COLORSPACE_INVALID;

-         png_error(png_ptr, "internal error checking chromaticities");

-         break;

-   }

-

-   return 0; /* failed */

-}

-

-#if defined(PNG_sRGB_SUPPORTED) || defined(PNG_iCCP_SUPPORTED)

-/* Error message generation */

-static char

-png_icc_tag_char(png_uint_32 byte)

-{

-   byte &= 0xff;

-   if (byte >= 32 && byte <= 126)

-      return (char)byte;

-   else

-      return '?';

-}

-

-static void

-png_icc_tag_name(char *name, png_uint_32 tag)

-{

-   name[0] = '\'';

-   name[1] = png_icc_tag_char(tag >> 24);

-   name[2] = png_icc_tag_char(tag >> 16);

-   name[3] = png_icc_tag_char(tag >>  8);

-   name[4] = png_icc_tag_char(tag      );

-   name[5] = '\'';

-}

-

-static int

-is_ICC_signature_char(png_alloc_size_t it)

-{

-   return it == 32 || (it >= 48 && it <= 57) || (it >= 65 && it <= 90) ||

-      (it >= 97 && it <= 122);

-}

-

-static int is_ICC_signature(png_alloc_size_t it)

-{

-   return is_ICC_signature_char(it >> 24) /* checks all the top bits */ &&

-      is_ICC_signature_char((it >> 16) & 0xff) &&

-      is_ICC_signature_char((it >> 8) & 0xff) &&

-      is_ICC_signature_char(it & 0xff);

-}

-

-static int

-png_icc_profile_error(png_const_structrp png_ptr, png_colorspacerp colorspace,

-   png_const_charp name, png_alloc_size_t value, png_const_charp reason)

-{

-   size_t pos;

-   char message[196]; /* see below for calculation */

-

-   if (colorspace != NULL)

-      colorspace->flags |= PNG_COLORSPACE_INVALID;

-

-   pos = png_safecat(message, (sizeof message), 0, "profile '"); /* 9 chars */

-   pos = png_safecat(message, pos+79, pos, name); /* Truncate to 79 chars */

-   pos = png_safecat(message, (sizeof message), pos, "': "); /* +2 = 90 */

-   if (is_ICC_signature(value))

-   {

-      /* So 'value' is at most 4 bytes and the following cast is safe */

-      png_icc_tag_name(message+pos, (png_uint_32)value);

-      pos += 6; /* total +8; less than the else clause */

-      message[pos++] = ':';

-      message[pos++] = ' ';

-   }

-#  ifdef PNG_WARNINGS_SUPPORTED

-   else

-      {

-         char number[PNG_NUMBER_BUFFER_SIZE]; /* +24 = 114*/

-

-         pos = png_safecat(message, (sizeof message), pos,

-            png_format_number(number, number+(sizeof number),

-               PNG_NUMBER_FORMAT_x, value));

-         pos = png_safecat(message, (sizeof message), pos, "h: "); /*+2 = 116*/

-      }

-#  endif

-   /* The 'reason' is an arbitrary message, allow +79 maximum 195 */

-   pos = png_safecat(message, (sizeof message), pos, reason);

-

-   /* This is recoverable, but make it unconditionally an app_error on write to

-    * avoid writing invalid ICC profiles into PNG files.  (I.e.  we handle them

-    * on read, with a warning, but on write unless the app turns off

-    * application errors the PNG won't be written.)

-    */

-   png_chunk_report(png_ptr, message,

-      (colorspace != NULL) ? PNG_CHUNK_ERROR : PNG_CHUNK_WRITE_ERROR);

-

-   return 0;

-}

-#endif /* sRGB || iCCP */

-

-#ifdef PNG_sRGB_SUPPORTED

-int /* PRIVATE */

-png_colorspace_set_sRGB(png_const_structrp png_ptr, png_colorspacerp colorspace,

-   int intent)

-{

-   /* sRGB sets known gamma, end points and (from the chunk) intent. */

-   /* IMPORTANT: these are not necessarily the values found in an ICC profile

-    * because ICC profiles store values adapted to a D50 environment; it is

-    * expected that the ICC profile mediaWhitePointTag will be D50, see the

-    * checks and code elsewhere to understand this better.

-    *

-    * These XYZ values, which are accurate to 5dp, produce rgb to gray

-    * coefficients of (6968,23435,2366), which are reduced (because they add up

-    * to 32769 not 32768) to (6968,23434,2366).  These are the values that

-    * libpng has traditionally used (and are the best values given the 15bit

-    * algorithm used by the rgb to gray code.)

-    */

-   static const png_XYZ sRGB_XYZ = /* D65 XYZ (*not* the D50 adapted values!) */

-   {

-      /* color      X      Y      Z */

-      /* red   */ 41239, 21264,  1933,

-      /* green */ 35758, 71517, 11919,

-      /* blue  */ 18048,  7219, 95053

-   };

-

-   /* Do nothing if the colorspace is already invalidated. */

-   if (colorspace->flags & PNG_COLORSPACE_INVALID)

-      return 0;

-

-   /* Check the intent, then check for existing settings.  It is valid for the

-    * PNG file to have cHRM or gAMA chunks along with sRGB, but the values must

-    * be consistent with the correct values.  If, however, this function is

-    * called below because an iCCP chunk matches sRGB then it is quite

-    * conceivable that an older app recorded incorrect gAMA and cHRM because of

-    * an incorrect calculation based on the values in the profile - this does

-    * *not* invalidate the profile (though it still produces an error, which can

-    * be ignored.)

-    */

-   if (intent < 0 || intent >= PNG_sRGB_INTENT_LAST)

-      return png_icc_profile_error(png_ptr, colorspace, "sRGB",

-         (unsigned)intent, "invalid sRGB rendering intent");

-

-   if ((colorspace->flags & PNG_COLORSPACE_HAVE_INTENT) != 0 &&

-      colorspace->rendering_intent != intent)

-      return png_icc_profile_error(png_ptr, colorspace, "sRGB",

-         (unsigned)intent, "inconsistent rendering intents");

-

-   if ((colorspace->flags & PNG_COLORSPACE_FROM_sRGB) != 0)

-   {

-      png_benign_error(png_ptr, "duplicate sRGB information ignored");

-      return 0;

-   }

-

-   /* If the standard sRGB cHRM chunk does not match the one from the PNG file

-    * warn but overwrite the value with the correct one.

-    */

-   if ((colorspace->flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0 &&

-      !png_colorspace_endpoints_match(&sRGB_xy, &colorspace->end_points_xy,

-         100))

-      png_chunk_report(png_ptr, "cHRM chunk does not match sRGB",

-         PNG_CHUNK_ERROR);

-

-   /* This check is just done for the error reporting - the routine always

-    * returns true when the 'from' argument corresponds to sRGB (2).

-    */

-   (void)png_colorspace_check_gamma(png_ptr, colorspace, PNG_GAMMA_sRGB_INVERSE,

-      2/*from sRGB*/);

-

-   /* intent: bugs in GCC force 'int' to be used as the parameter type. */

-   colorspace->rendering_intent = (png_uint_16)intent;

-   colorspace->flags |= PNG_COLORSPACE_HAVE_INTENT;

-

-   /* endpoints */

-   colorspace->end_points_xy = sRGB_xy;

-   colorspace->end_points_XYZ = sRGB_XYZ;

-   colorspace->flags |=

-      (PNG_COLORSPACE_HAVE_ENDPOINTS|PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB);

-

-   /* gamma */

-   colorspace->gamma = PNG_GAMMA_sRGB_INVERSE;

-   colorspace->flags |= PNG_COLORSPACE_HAVE_GAMMA;

-

-   /* Finally record that we have an sRGB profile */

-   colorspace->flags |=

-      (PNG_COLORSPACE_MATCHES_sRGB|PNG_COLORSPACE_FROM_sRGB);

-

-   return 1; /* set */

-}

-#endif /* sRGB */

-

-#ifdef PNG_iCCP_SUPPORTED

-/* Encoded value of D50 as an ICC XYZNumber.  From the ICC 2010 spec the value

- * is XYZ(0.9642,1.0,0.8249), which scales to:

- *

- *    (63189.8112, 65536, 54060.6464)

- */

-static const png_byte D50_nCIEXYZ[12] =

-   { 0x00, 0x00, 0xf6, 0xd6, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0xd3, 0x2d };

-

-int /* PRIVATE */

-png_icc_check_length(png_const_structrp png_ptr, png_colorspacerp colorspace,

-   png_const_charp name, png_uint_32 profile_length)

-{

-   if (profile_length < 132)

-      return png_icc_profile_error(png_ptr, colorspace, name, profile_length,

-         "too short");

-

-   if (profile_length & 3)

-      return png_icc_profile_error(png_ptr, colorspace, name, profile_length,

-         "invalid length");

-

-   return 1;

-}

-

-int /* PRIVATE */

-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_uint_32 temp;

-

-   /* Length check; this cannot be ignored in this code because profile_length

-    * is used later to check the tag table, so even if the profile seems over

-    * long profile_length from the caller must be correct.  The caller can fix

-    * this up on read or write by just passing in the profile header length.

-    */

-   temp = png_get_uint_32(profile);

-   if (temp != profile_length)

-      return png_icc_profile_error(png_ptr, colorspace, name, temp,

-         "length does not match profile");

-

-   temp = png_get_uint_32(profile+128); /* tag count: 12 bytes/tag */

-   if (temp > 357913930 || /* (2^32-4-132)/12: maximum possible tag count */

-      profile_length < 132+12*temp) /* truncated tag table */

-      return png_icc_profile_error(png_ptr, colorspace, name, temp,

-         "tag count too large");

-

-   /* The 'intent' must be valid or we can't store it, ICC limits the intent to

-    * 16 bits.

-    */

-   temp = png_get_uint_32(profile+64);

-   if (temp >= 0xffff) /* The ICC limit */

-      return png_icc_profile_error(png_ptr, colorspace, name, temp,

-         "invalid rendering intent");

-

-   /* This is just a warning because the profile may be valid in future

-    * versions.

-    */

-   if (temp >= PNG_sRGB_INTENT_LAST)

-      (void)png_icc_profile_error(png_ptr, NULL, name, temp,

-         "intent outside defined range");

-

-   /* At this point the tag table can't be checked because it hasn't necessarily

-    * been loaded; however, various header fields can be checked.  These checks

-    * are for values permitted by the PNG spec in an ICC profile; the PNG spec

-    * restricts the profiles that can be passed in an iCCP chunk (they must be

-    * appropriate to processing PNG data!)

-    */

-

-   /* Data checks (could be skipped).  These checks must be independent of the

-    * version number; however, the version number doesn't accomodate changes in

-    * the header fields (just the known tags and the interpretation of the

-    * data.)

-    */

-   temp = png_get_uint_32(profile+36); /* signature 'ascp' */

-   if (temp != 0x61637370)

-      return png_icc_profile_error(png_ptr, colorspace, name, temp,

-         "invalid signature");

-

-   /* Currently the PCS illuminant/adopted white point (the computational

-    * white point) are required to be D50,

-    * however the profile contains a record of the illuminant so perhaps ICC

-    * expects to be able to change this in the future (despite the rationale in

-    * the introduction for using a fixed PCS adopted white.)  Consequently the

-    * following is just a warning.

-    */

-   if (memcmp(profile+68, D50_nCIEXYZ, 12) != 0)

-      (void)png_icc_profile_error(png_ptr, NULL, name, 0/*no tag value*/,

-         "PCS illuminant is not D50");

-

-   /* The PNG spec requires this:

-    * "If the iCCP chunk is present, the image samples conform to the colour

-    * space represented by the embedded ICC profile as defined by the

-    * International Color Consortium [ICC]. The colour space of the ICC profile

-    * shall be an RGB colour space for colour images (PNG colour types 2, 3, and

-    * 6), or a greyscale colour space for greyscale images (PNG colour types 0

-    * and 4)."

-    *

-    * This checking code ensures the embedded profile (on either read or write)

-    * conforms to the specification requirements.  Notice that an ICC 'gray'

-    * color-space profile contains the information to transform the monochrome

-    * data to XYZ or L*a*b (according to which PCS the profile uses) and this

-    * should be used in preference to the standard libpng K channel replication

-    * into R, G and B channels.

-    *

-    * Previously it was suggested that an RGB profile on grayscale data could be

-    * handled.  However it it is clear that using an RGB profile in this context

-    * must be an error - there is no specification of what it means.  Thus it is

-    * almost certainly more correct to ignore the profile.

-    */

-   temp = png_get_uint_32(profile+16); /* data colour space field */

-   switch (temp)

-   {

-      case 0x52474220: /* 'RGB ' */

-         if (!(color_type & PNG_COLOR_MASK_COLOR))

-            return png_icc_profile_error(png_ptr, colorspace, name, temp,

-               "RGB color space not permitted on grayscale PNG");

-         break;

-

-      case 0x47524159: /* 'GRAY' */

-         if (color_type & PNG_COLOR_MASK_COLOR)

-            return png_icc_profile_error(png_ptr, colorspace, name, temp,

-               "Gray color space not permitted on RGB PNG");

-         break;

-

-      default:

-         return png_icc_profile_error(png_ptr, colorspace, name, temp,

-            "invalid ICC profile color space");

-   }

-

-   /* It is up to the application to check that the profile class matches the

-    * application requirements; the spec provides no guidance, but it's pretty

-    * weird if the profile is not scanner ('scnr'), monitor ('mntr'), printer

-    * ('prtr') or 'spac' (for generic color spaces).  Issue a warning in these

-    * cases.  Issue an error for device link or abstract profiles - these don't

-    * contain the records necessary to transform the color-space to anything

-    * other than the target device (and not even that for an abstract profile).

-    * Profiles of these classes may not be embedded in images.

-    */

-   temp = png_get_uint_32(profile+12); /* profile/device class */

-   switch (temp)

-   {

-      case 0x73636E72: /* 'scnr' */

-      case 0x6D6E7472: /* 'mntr' */

-      case 0x70727472: /* 'prtr' */

-      case 0x73706163: /* 'spac' */

-         /* All supported */

-         break;

-

-      case 0x61627374: /* 'abst' */

-         /* May not be embedded in an image */

-         return png_icc_profile_error(png_ptr, colorspace, name, temp,

-            "invalid embedded Abstract ICC profile");

-

-      case 0x6C696E6B: /* 'link' */

-         /* DeviceLink profiles cannnot be interpreted in a non-device specific

-          * fashion, if an app uses the AToB0Tag in the profile the results are

-          * undefined unless the result is sent to the intended device,

-          * therefore a DeviceLink profile should not be found embedded in a

-          * PNG.

-          */

-         return png_icc_profile_error(png_ptr, colorspace, name, temp,

-            "unexpected DeviceLink ICC profile class");

-

-      case 0x6E6D636C: /* 'nmcl' */

-         /* A NamedColor profile is also device specific, however it doesn't

-          * contain an AToB0 tag that is open to misintrepretation.  Almost

-          * certainly it will fail the tests below.

-          */

-         (void)png_icc_profile_error(png_ptr, NULL, name, temp,

-            "unexpected NamedColor ICC profile class");

-         break;

-

-      default:

-         /* To allow for future enhancements to the profile accept unrecognized

-          * profile classes with a warning, these then hit the test below on the

-          * tag content to ensure they are backward compatible with one of the

-          * understood profiles.

-          */

-         (void)png_icc_profile_error(png_ptr, NULL, name, temp,

-            "unrecognized ICC profile class");

-         break;

-   }

-

-   /* For any profile other than a device link one the PCS must be encoded

-    * either in XYZ or Lab.

-    */

-   temp = png_get_uint_32(profile+20);

-   switch (temp)

-   {

-      case 0x58595A20: /* 'XYZ ' */

-      case 0x4C616220: /* 'Lab ' */

-         break;

-

-      default:

-         return png_icc_profile_error(png_ptr, colorspace, name, temp,

-            "unexpected ICC PCS encoding");

-   }

-

-   return 1;

-}

-

-int /* PRIVATE */

-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_uint_32 tag_count = png_get_uint_32(profile+128);

-   png_uint_32 itag;

-   png_const_bytep tag = profile+132; /* The first tag */

-

-   /* First scan all the tags in the table and add bits to the icc_info value

-    * (temporarily in 'tags').

-    */

-   for (itag=0; itag < tag_count; ++itag, tag += 12)

-   {

-      png_uint_32 tag_id = png_get_uint_32(tag+0);

-      png_uint_32 tag_start = png_get_uint_32(tag+4); /* must be aligned */

-      png_uint_32 tag_length = png_get_uint_32(tag+8);/* not padded */

-

-      /* The ICC specification does not exclude zero length tags, therefore the

-       * start might actually be anywhere if there is no data, but this would be

-       * a clear abuse of the intent of the standard so the start is checked for

-       * being in range.  All defined tag types have an 8 byte header - a 4 byte

-       * type signature then 0.

-       */

-      if ((tag_start & 3) != 0)

-      {

-         /* CNHP730S.icc shipped with Microsoft Windows 64 violates this, it is

-          * only a warning here because libpng does not care about the

-          * alignment.

-          */

-         (void)png_icc_profile_error(png_ptr, NULL, name, tag_id,

-            "ICC profile tag start not a multiple of 4");

-      }

-

-      /* This is a hard error; potentially it can cause read outside the

-       * profile.

-       */

-      if (tag_start > profile_length || tag_length > profile_length - tag_start)

-         return png_icc_profile_error(png_ptr, colorspace, name, tag_id,

-            "ICC profile tag outside profile");

-   }

-

-   return 1; /* success, maybe with warnings */

-}

-

-#ifdef PNG_sRGB_SUPPORTED

-/* Information about the known ICC sRGB profiles */

-static const struct

-{

-   png_uint_32 adler, crc, length;

-   png_uint_32 md5[4];

-   png_byte    have_md5;

-   png_byte    is_broken;

-   png_uint_16 intent;

-

-#  define PNG_MD5(a,b,c,d) { a, b, c, d }, (a!=0)||(b!=0)||(c!=0)||(d!=0)

-#  define PNG_ICC_CHECKSUM(adler, crc, md5, intent, broke, date, length, fname)\

-      { adler, crc, length, md5, broke, intent },

-

-} png_sRGB_checks[] =

-{

-   /* This data comes from contrib/tools/checksum-icc run on downloads of

-    * all four ICC sRGB profiles from www.color.org.

-    */

-   /* adler32, crc32, MD5[4], intent, date, length, file-name */

-   PNG_ICC_CHECKSUM(0x0a3fd9f6, 0x3b8772b9,

-      PNG_MD5(0x29f83dde, 0xaff255ae, 0x7842fae4, 0xca83390d), 0, 0,

-      "2009/03/27 21:36:31", 3048, "sRGB_IEC61966-2-1_black_scaled.icc")

-

-   /* ICC sRGB v2 perceptual no black-compensation: */

-   PNG_ICC_CHECKSUM(0x4909e5e1, 0x427ebb21,

-      PNG_MD5(0xc95bd637, 0xe95d8a3b, 0x0df38f99, 0xc1320389), 1, 0,

-      "2009/03/27 21:37:45", 3052, "sRGB_IEC61966-2-1_no_black_scaling.icc")

-

-   PNG_ICC_CHECKSUM(0xfd2144a1, 0x306fd8ae,

-      PNG_MD5(0xfc663378, 0x37e2886b, 0xfd72e983, 0x8228f1b8), 0, 0,

-      "2009/08/10 17:28:01", 60988, "sRGB_v4_ICC_preference_displayclass.icc")

-

-   /* ICC sRGB v4 perceptual */

-   PNG_ICC_CHECKSUM(0x209c35d2, 0xbbef7812,

-      PNG_MD5(0x34562abf, 0x994ccd06, 0x6d2c5721, 0xd0d68c5d), 0, 0,

-      "2007/07/25 00:05:37", 60960, "sRGB_v4_ICC_preference.icc")

-

-   /* The following profiles have no known MD5 checksum. If there is a match

-    * on the (empty) MD5 the other fields are used to attempt a match and

-    * a warning is produced.  The first two of these profiles have a 'cprt' tag

-    * which suggests that they were also made by Hewlett Packard.

-    */

-   PNG_ICC_CHECKSUM(0xa054d762, 0x5d5129ce,

-      PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 1, 0,

-      "2004/07/21 18:57:42", 3024, "sRGB_IEC61966-2-1_noBPC.icc")

-

-   /* This is a 'mntr' (display) profile with a mediaWhitePointTag that does not

-    * match the D50 PCS illuminant in the header (it is in fact the D65 values,

-    * so the white point is recorded as the un-adapted value.)  The profiles

-    * below only differ in one byte - the intent - and are basically the same as

-    * the previous profile except for the mediaWhitePointTag error and a missing

-    * chromaticAdaptationTag.

-    */

-   PNG_ICC_CHECKSUM(0xf784f3fb, 0x182ea552,

-      PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 0, 1/*broken*/,

-      "1998/02/09 06:49:00", 3144, "HP-Microsoft sRGB v2 perceptual")

-

-   PNG_ICC_CHECKSUM(0x0398f3fc, 0xf29e526d,

-      PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 1, 1/*broken*/,

-      "1998/02/09 06:49:00", 3144, "HP-Microsoft sRGB v2 media-relative")

-};

-

-static int

-png_compare_ICC_profile_with_sRGB(png_const_structrp png_ptr,

-   png_const_bytep profile, uLong adler)

-{

-   /* The quick check is to verify just the MD5 signature and trust the

-    * rest of the data.  Because the profile has already been verified for

-    * correctness this is safe.  png_colorspace_set_sRGB will check the 'intent'

-    * field too, so if the profile has been edited with an intent not defined

-    * by sRGB (but maybe defined by a later ICC specification) the read of

-    * the profile will fail at that point.

-    */

-   png_uint_32 length = 0;

-   png_uint_32 intent = 0x10000; /* invalid */

-#if PNG_sRGB_PROFILE_CHECKS > 1

-   uLong crc = 0; /* the value for 0 length data */

-#endif

-   unsigned int i;

-

-   for (i=0; i < (sizeof png_sRGB_checks) / (sizeof png_sRGB_checks[0]); ++i)

-   {

-      if (png_get_uint_32(profile+84) == png_sRGB_checks[i].md5[0] &&

-         png_get_uint_32(profile+88) == png_sRGB_checks[i].md5[1] &&

-         png_get_uint_32(profile+92) == png_sRGB_checks[i].md5[2] &&

-         png_get_uint_32(profile+96) == png_sRGB_checks[i].md5[3])

-      {

-         /* This may be one of the old HP profiles without an MD5, in that

-          * case we can only use the length and Adler32 (note that these

-          * are not used by default if there is an MD5!)

-          */

-#        if PNG_sRGB_PROFILE_CHECKS == 0

-            if (png_sRGB_checks[i].have_md5)

-               return 1+png_sRGB_checks[i].is_broken;

-#        endif

-

-         /* Profile is unsigned or more checks have been configured in. */

-         if (length == 0)

-         {

-            length = png_get_uint_32(profile);

-            intent = png_get_uint_32(profile+64);

-         }

-

-         /* Length *and* intent must match */

-         if (length == png_sRGB_checks[i].length &&

-            intent == png_sRGB_checks[i].intent)

-         {

-            /* Now calculate the adler32 if not done already. */

-            if (adler == 0)

-            {

-               adler = adler32(0, NULL, 0);

-               adler = adler32(adler, profile, length);

-            }

-

-            if (adler == png_sRGB_checks[i].adler)

-            {

-               /* These basic checks suggest that the data has not been

-                * modified, but if the check level is more than 1 perform

-                * our own crc32 checksum on the data.

-                */

-#              if PNG_sRGB_PROFILE_CHECKS > 1

-                  if (crc == 0)

-                  {

-                     crc = crc32(0, NULL, 0);

-                     crc = crc32(crc, profile, length);

-                  }

-

-                  /* So this check must pass for the 'return' below to happen.

-                   */

-                  if (crc == png_sRGB_checks[i].crc)

-#              endif

-               {

-                  if (png_sRGB_checks[i].is_broken)

-                  {

-                     /* These profiles are known to have bad data that may cause

-                      * problems if they are used, therefore attempt to

-                      * discourage their use, skip the 'have_md5' warning below,

-                      * which is made irrelevant by this error.

-                      */

-                     png_chunk_report(png_ptr, "known incorrect sRGB profile",

-                        PNG_CHUNK_ERROR);

-                  }

-

-                  /* Warn that this being done; this isn't even an error since

-                   * the profile is perfectly valid, but it would be nice if

-                   * people used the up-to-date ones.

-                   */

-                  else if (!png_sRGB_checks[i].have_md5)

-                  {

-                     png_chunk_report(png_ptr,

-                        "out-of-date sRGB profile with no signature",

-                        PNG_CHUNK_WARNING);

-                  }

-

-                  return 1+png_sRGB_checks[i].is_broken;

-               }

-            }

-         }

-

-#        if PNG_sRGB_PROFILE_CHECKS > 0

-            /* The signature matched, but the profile had been changed in some

-             * way.  This is an apparent violation of the ICC terms of use and,

-             * anyway, probably indicates a data error or uninformed hacking.

-             */

-            if (png_sRGB_checks[i].have_md5)

-               png_benign_error(png_ptr,

-                  "copyright violation: edited ICC profile ignored");

-#        endif

-      }

-   }

-

-   return 0; /* no match */

-}

-#endif

-

-#ifdef PNG_sRGB_SUPPORTED

-void /* PRIVATE */

-png_icc_set_sRGB(png_const_structrp png_ptr,

-   png_colorspacerp colorspace, png_const_bytep profile, uLong adler)

-{

-   /* Is this profile one of the known ICC sRGB profiles?  If it is, just set

-    * the sRGB information.

-    */

-   if (png_compare_ICC_profile_with_sRGB(png_ptr, profile, adler))

-      (void)png_colorspace_set_sRGB(png_ptr, colorspace,

-         (int)/*already checked*/png_get_uint_32(profile+64));

-}

-#endif /* PNG_READ_sRGB_SUPPORTED */

-

-int /* PRIVATE */

-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)

-{

-   if (colorspace->flags & PNG_COLORSPACE_INVALID)

-      return 0;

-

-   if (png_icc_check_length(png_ptr, colorspace, name, profile_length) &&

-      png_icc_check_header(png_ptr, colorspace, name, profile_length, profile,

-         color_type) &&

-      png_icc_check_tag_table(png_ptr, colorspace, name, profile_length,

-         profile))

-   {

-#     ifdef PNG_sRGB_SUPPORTED

-         /* If no sRGB support, don't try storing sRGB information */

-         png_icc_set_sRGB(png_ptr, colorspace, profile, 0);

-#     endif

-      return 1;

-   }

-

-   /* Failure case */

-   return 0;

-}

-#endif /* iCCP */

-

-#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED

-void /* PRIVATE */

-png_colorspace_set_rgb_coefficients(png_structrp png_ptr)

-{

-   /* Set the rgb_to_gray coefficients from the colorspace. */

-   if (!png_ptr->rgb_to_gray_coefficients_set &&

-      (png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0)

-   {

-      /* png_set_background has not been called, get the coefficients from the Y

-       * values of the colorspace colorants.

-       */

-      png_fixed_point r = png_ptr->colorspace.end_points_XYZ.red_Y;

-      png_fixed_point g = png_ptr->colorspace.end_points_XYZ.green_Y;

-      png_fixed_point b = png_ptr->colorspace.end_points_XYZ.blue_Y;

-      png_fixed_point total = r+g+b;

-

-      if (total > 0 &&

-         r >= 0 && png_muldiv(&r, r, 32768, total) && r >= 0 && r <= 32768 &&

-         g >= 0 && png_muldiv(&g, g, 32768, total) && g >= 0 && g <= 32768 &&

-         b >= 0 && png_muldiv(&b, b, 32768, total) && b >= 0 && b <= 32768 &&

-         r+g+b <= 32769)

-      {

-         /* We allow 0 coefficients here.  r+g+b may be 32769 if two or

-          * all of the coefficients were rounded up.  Handle this by

-          * reducing the *largest* coefficient by 1; this matches the

-          * approach used for the default coefficients in pngrtran.c

-          */

-         int add = 0;

-

-         if (r+g+b > 32768)

-            add = -1;

-         else if (r+g+b < 32768)

-            add = 1;

-

-         if (add != 0)

-         {

-            if (g >= r && g >= b)

-               g += add;

-            else if (r >= g && r >= b)

-               r += add;

-            else

-               b += add;

-         }

-

-         /* Check for an internal error. */

-         if (r+g+b != 32768)

-            png_error(png_ptr,

-               "internal error handling cHRM coefficients");

-

-         else

-         {

-            png_ptr->rgb_to_gray_red_coeff   = (png_uint_16)r;

-            png_ptr->rgb_to_gray_green_coeff = (png_uint_16)g;

-         }

-      }

-

-      /* This is a png_error at present even though it could be ignored -

-       * it should never happen, but it is important that if it does, the

-       * bug is fixed.

-       */

-      else

-         png_error(png_ptr, "internal error handling cHRM->XYZ");

-   }

-}

-#endif

-

-#endif /* COLORSPACE */

-

-void /* PRIVATE */

-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)

-{

-   int error = 0;

-

-   /* Check for width and height valid values */

-   if (width == 0)

-   {

-      png_warning(png_ptr, "Image width is zero in IHDR");

-      error = 1;

-   }

-

-   if (height == 0)

-   {

-      png_warning(png_ptr, "Image height is zero in IHDR");

-      error = 1;

-   }

-

-#  ifdef PNG_SET_USER_LIMITS_SUPPORTED

-   if (width > png_ptr->user_width_max)

-

-#  else

-   if (width > PNG_USER_WIDTH_MAX)

-#  endif

-   {

-      png_warning(png_ptr, "Image width exceeds user limit in IHDR");

-      error = 1;

-   }

-

-#  ifdef PNG_SET_USER_LIMITS_SUPPORTED

-   if (height > png_ptr->user_height_max)

-#  else

-   if (height > PNG_USER_HEIGHT_MAX)

-#  endif

-   {

-      png_warning(png_ptr, "Image height exceeds user limit in IHDR");

-      error = 1;

-   }

-

-   if (width > PNG_UINT_31_MAX)

-   {

-      png_warning(png_ptr, "Invalid image width in IHDR");

-      error = 1;

-   }

-

-   if (height > PNG_UINT_31_MAX)

-   {

-      png_warning(png_ptr, "Invalid image height in IHDR");

-      error = 1;

-   }

-

-   if (width > (PNG_UINT_32_MAX

-                 >> 3)      /* 8-byte RGBA pixels */

-                 - 48       /* bigrowbuf hack */

-                 - 1        /* filter byte */

-                 - 7*8      /* rounding of width to multiple of 8 pixels */

-                 - 8)       /* extra max_pixel_depth pad */

-      png_warning(png_ptr, "Width is too large for libpng to process pixels");

-

-   /* Check other values */

-   if (bit_depth != 1 && bit_depth != 2 && bit_depth != 4 &&

-       bit_depth != 8 && bit_depth != 16)

-   {

-      png_warning(png_ptr, "Invalid bit depth in IHDR");

-      error = 1;

-   }

-

-   if (color_type < 0 || color_type == 1 ||

-       color_type == 5 || color_type > 6)

-   {

-      png_warning(png_ptr, "Invalid color type in IHDR");

-      error = 1;

-   }

-

-   if (((color_type == PNG_COLOR_TYPE_PALETTE) && bit_depth > 8) ||

-       ((color_type == PNG_COLOR_TYPE_RGB ||

-         color_type == PNG_COLOR_TYPE_GRAY_ALPHA ||

-         color_type == PNG_COLOR_TYPE_RGB_ALPHA) && bit_depth < 8))

-   {

-      png_warning(png_ptr, "Invalid color type/bit depth combination in IHDR");

-      error = 1;

-   }

-

-   if (interlace_type >= PNG_INTERLACE_LAST)

-   {

-      png_warning(png_ptr, "Unknown interlace method in IHDR");

-      error = 1;

-   }

-

-   if (compression_type != PNG_COMPRESSION_TYPE_BASE)

-   {

-      png_warning(png_ptr, "Unknown compression method in IHDR");

-      error = 1;

-   }

-

-#  ifdef PNG_MNG_FEATURES_SUPPORTED

-   /* Accept filter_method 64 (intrapixel differencing) only if

-    * 1. Libpng was compiled with PNG_MNG_FEATURES_SUPPORTED and

-    * 2. Libpng did not read a PNG signature (this filter_method is only

-    *    used in PNG datastreams that are embedded in MNG datastreams) and

-    * 3. The application called png_permit_mng_features with a mask that

-    *    included PNG_FLAG_MNG_FILTER_64 and

-    * 4. The filter_method is 64 and

-    * 5. The color_type is RGB or RGBA

-    */

-   if ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) &&

-       png_ptr->mng_features_permitted)

-      png_warning(png_ptr, "MNG features are not allowed in a PNG datastream");

-

-   if (filter_type != PNG_FILTER_TYPE_BASE)

-   {

-      if (!((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) &&

-          (filter_type == PNG_INTRAPIXEL_DIFFERENCING) &&

-          ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) == 0) &&

-          (color_type == PNG_COLOR_TYPE_RGB ||

-          color_type == PNG_COLOR_TYPE_RGB_ALPHA)))

-      {

-         png_warning(png_ptr, "Unknown filter method in IHDR");

-         error = 1;

-      }

-

-      if (png_ptr->mode & PNG_HAVE_PNG_SIGNATURE)

-      {

-         png_warning(png_ptr, "Invalid filter method in IHDR");

-         error = 1;

-      }

-   }

-

-#  else

-   if (filter_type != PNG_FILTER_TYPE_BASE)

-   {

-      png_warning(png_ptr, "Unknown filter method in IHDR");

-      error = 1;

-   }

-#  endif

-

-   if (error == 1)

-      png_error(png_ptr, "Invalid IHDR data");

-}

-

-#if defined(PNG_sCAL_SUPPORTED) || defined(PNG_pCAL_SUPPORTED)

-/* ASCII to fp functions */

-/* Check an ASCII formated floating point value, see the more detailed

- * comments in pngpriv.h

- */

-/* The following is used internally to preserve the sticky flags */

-#define png_fp_add(state, flags) ((state) |= (flags))

-#define png_fp_set(state, value) ((state) = (value) | ((state) & PNG_FP_STICKY))

-

-int /* PRIVATE */

-png_check_fp_number(png_const_charp string, png_size_t size, int *statep,

-   png_size_tp whereami)

-{

-   int state = *statep;

-   png_size_t i = *whereami;

-

-   while (i < size)

-   {

-      int type;

-      /* First find the type of the next character */

-      switch (string[i])

-      {

-      case 43:  type = PNG_FP_SAW_SIGN;                   break;

-      case 45:  type = PNG_FP_SAW_SIGN + PNG_FP_NEGATIVE; break;

-      case 46:  type = PNG_FP_SAW_DOT;                    break;

-      case 48:  type = PNG_FP_SAW_DIGIT;                  break;

-      case 49: case 50: case 51: case 52:

-      case 53: case 54: case 55: case 56:

-      case 57:  type = PNG_FP_SAW_DIGIT + PNG_FP_NONZERO; break;

-      case 69:

-      case 101: type = PNG_FP_SAW_E;                      break;

-      default:  goto PNG_FP_End;

-      }

-

-      /* Now deal with this type according to the current

-       * state, the type is arranged to not overlap the

-       * bits of the PNG_FP_STATE.

-       */

-      switch ((state & PNG_FP_STATE) + (type & PNG_FP_SAW_ANY))

-      {

-      case PNG_FP_INTEGER + PNG_FP_SAW_SIGN:

-         if (state & PNG_FP_SAW_ANY)

-            goto PNG_FP_End; /* not a part of the number */

-

-         png_fp_add(state, type);

-         break;

-

-      case PNG_FP_INTEGER + PNG_FP_SAW_DOT:

-         /* Ok as trailer, ok as lead of fraction. */

-         if (state & PNG_FP_SAW_DOT) /* two dots */

-            goto PNG_FP_End;

-

-         else if (state & PNG_FP_SAW_DIGIT) /* trailing dot? */

-            png_fp_add(state, type);

-

-         else

-            png_fp_set(state, PNG_FP_FRACTION | type);

-

-         break;

-

-      case PNG_FP_INTEGER + PNG_FP_SAW_DIGIT:

-         if (state & PNG_FP_SAW_DOT) /* delayed fraction */

-            png_fp_set(state, PNG_FP_FRACTION | PNG_FP_SAW_DOT);

-

-         png_fp_add(state, type | PNG_FP_WAS_VALID);

-

-         break;

-

-      case PNG_FP_INTEGER + PNG_FP_SAW_E:

-         if ((state & PNG_FP_SAW_DIGIT) == 0)

-            goto PNG_FP_End;

-

-         png_fp_set(state, PNG_FP_EXPONENT);

-

-         break;

-

-   /* case PNG_FP_FRACTION + PNG_FP_SAW_SIGN:

-         goto PNG_FP_End; ** no sign in fraction */

-

-   /* case PNG_FP_FRACTION + PNG_FP_SAW_DOT:

-         goto PNG_FP_End; ** Because SAW_DOT is always set */

-

-      case PNG_FP_FRACTION + PNG_FP_SAW_DIGIT:

-         png_fp_add(state, type | PNG_FP_WAS_VALID);

-         break;

-

-      case PNG_FP_FRACTION + PNG_FP_SAW_E:

-         /* This is correct because the trailing '.' on an

-          * integer is handled above - so we can only get here

-          * with the sequence ".E" (with no preceding digits).

-          */

-         if ((state & PNG_FP_SAW_DIGIT) == 0)

-            goto PNG_FP_End;

-

-         png_fp_set(state, PNG_FP_EXPONENT);

-

-         break;

-

-      case PNG_FP_EXPONENT + PNG_FP_SAW_SIGN:

-         if (state & PNG_FP_SAW_ANY)

-            goto PNG_FP_End; /* not a part of the number */

-

-         png_fp_add(state, PNG_FP_SAW_SIGN);

-

-         break;

-

-   /* case PNG_FP_EXPONENT + PNG_FP_SAW_DOT:

-         goto PNG_FP_End; */

-

-      case PNG_FP_EXPONENT + PNG_FP_SAW_DIGIT:

-         png_fp_add(state, PNG_FP_SAW_DIGIT | PNG_FP_WAS_VALID);

-

-         break;

-

-   /* case PNG_FP_EXPONEXT + PNG_FP_SAW_E:

-         goto PNG_FP_End; */

-

-      default: goto PNG_FP_End; /* I.e. break 2 */

-      }

-

-      /* The character seems ok, continue. */

-      ++i;

-   }

-

-PNG_FP_End:

-   /* Here at the end, update the state and return the correct

-    * return code.

-    */

-   *statep = state;

-   *whereami = i;

-

-   return (state & PNG_FP_SAW_DIGIT) != 0;

-}

-

-

-/* The same but for a complete string. */

-int

-png_check_fp_string(png_const_charp string, png_size_t size)

-{

-   int        state=0;

-   png_size_t char_index=0;

-

-   if (png_check_fp_number(string, size, &state, &char_index) &&

-      (char_index == size || string[char_index] == 0))

-      return state /* must be non-zero - see above */;

-

-   return 0; /* i.e. fail */

-}

-#endif /* pCAL or sCAL */

-

-#ifdef PNG_sCAL_SUPPORTED

-#  ifdef PNG_FLOATING_POINT_SUPPORTED

-/* Utility used below - a simple accurate power of ten from an integral

- * exponent.

- */

-static double

-png_pow10(int power)

-{

-   int recip = 0;

-   double d = 1;

-

-   /* Handle negative exponent with a reciprocal at the end because

-    * 10 is exact whereas .1 is inexact in base 2

-    */

-   if (power < 0)

-   {

-      if (power < DBL_MIN_10_EXP) return 0;

-      recip = 1, power = -power;

-   }

-

-   if (power > 0)

-   {

-      /* Decompose power bitwise. */

-      double mult = 10;

-      do

-      {

-         if (power & 1) d *= mult;

-         mult *= mult;

-         power >>= 1;

-      }

-      while (power > 0);

-

-      if (recip) d = 1/d;

-   }

-   /* else power is 0 and d is 1 */

-

-   return d;

-}

-

-/* Function to format a floating point value in ASCII with a given

- * precision.

- */

-void /* PRIVATE */

-png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, png_size_t size,

-    double fp, unsigned int precision)

-{

-   /* We use standard functions from math.h, but not printf because

-    * that would require stdio.  The caller must supply a buffer of

-    * sufficient size or we will png_error.  The tests on size and

-    * the space in ascii[] consumed are indicated below.

-    */

-   if (precision < 1)

-      precision = DBL_DIG;

-

-   /* Enforce the limit of the implementation precision too. */

-   if (precision > DBL_DIG+1)

-      precision = DBL_DIG+1;

-

-   /* Basic sanity checks */

-   if (size >= precision+5) /* See the requirements below. */

-   {

-      if (fp < 0)

-      {

-         fp = -fp;

-         *ascii++ = 45; /* '-'  PLUS 1 TOTAL 1 */

-         --size;

-      }

-

-      if (fp >= DBL_MIN && fp <= DBL_MAX)

-      {

-         int exp_b10;       /* A base 10 exponent */

-         double base;   /* 10^exp_b10 */

-

-         /* First extract a base 10 exponent of the number,

-          * the calculation below rounds down when converting

-          * from base 2 to base 10 (multiply by log10(2) -

-          * 0.3010, but 77/256 is 0.3008, so exp_b10 needs to

-          * be increased.  Note that the arithmetic shift

-          * performs a floor() unlike C arithmetic - using a

-          * C multiply would break the following for negative

-          * exponents.

-          */

-         (void)frexp(fp, &exp_b10); /* exponent to base 2 */

-

-         exp_b10 = (exp_b10 * 77) >> 8; /* <= exponent to base 10 */

-

-         /* Avoid underflow here. */

-         base = png_pow10(exp_b10); /* May underflow */

-

-         while (base < DBL_MIN || base < fp)

-         {

-            /* And this may overflow. */

-            double test = png_pow10(exp_b10+1);

-

-            if (test <= DBL_MAX)

-               ++exp_b10, base = test;

-

-            else

-               break;

-         }

-

-         /* Normalize fp and correct exp_b10, after this fp is in the

-          * range [.1,1) and exp_b10 is both the exponent and the digit

-          * *before* which the decimal point should be inserted

-          * (starting with 0 for the first digit).  Note that this

-          * works even if 10^exp_b10 is out of range because of the

-          * test on DBL_MAX above.

-          */

-         fp /= base;

-         while (fp >= 1) fp /= 10, ++exp_b10;

-

-         /* Because of the code above fp may, at this point, be

-          * less than .1, this is ok because the code below can

-          * handle the leading zeros this generates, so no attempt

-          * is made to correct that here.

-          */

-

-         {

-            int czero, clead, cdigits;

-            char exponent[10];

-

-            /* Allow up to two leading zeros - this will not lengthen

-             * the number compared to using E-n.

-             */

-            if (exp_b10 < 0 && exp_b10 > -3) /* PLUS 3 TOTAL 4 */

-            {

-               czero = -exp_b10; /* PLUS 2 digits: TOTAL 3 */

-               exp_b10 = 0;      /* Dot added below before first output. */

-            }

-            else

-               czero = 0;    /* No zeros to add */

-

-            /* Generate the digit list, stripping trailing zeros and

-             * inserting a '.' before a digit if the exponent is 0.

-             */

-            clead = czero; /* Count of leading zeros */

-            cdigits = 0;   /* Count of digits in list. */

-

-            do

-            {

-               double d;

-

-               fp *= 10;

-               /* Use modf here, not floor and subtract, so that

-                * the separation is done in one step.  At the end

-                * of the loop don't break the number into parts so

-                * that the final digit is rounded.

-                */

-               if (cdigits+czero-clead+1 < (int)precision)

-                  fp = modf(fp, &d);

-

-               else

-               {

-                  d = floor(fp + .5);

-

-                  if (d > 9)

-                  {

-                     /* Rounding up to 10, handle that here. */

-                     if (czero > 0)

-                     {

-                        --czero, d = 1;

-                        if (cdigits == 0) --clead;

-                     }

-                     else

-                     {

-                        while (cdigits > 0 && d > 9)

-                        {

-                           int ch = *--ascii;

-

-                           if (exp_b10 != (-1))

-                              ++exp_b10;

-

-                           else if (ch == 46)

-                           {

-                              ch = *--ascii, ++size;

-                              /* Advance exp_b10 to '1', so that the

-                               * decimal point happens after the

-                               * previous digit.

-                               */

-                              exp_b10 = 1;

-                           }

-

-                           --cdigits;

-                           d = ch - 47;  /* I.e. 1+(ch-48) */

-                        }

-

-                        /* Did we reach the beginning? If so adjust the

-                         * exponent but take into account the leading

-                         * decimal point.

-                         */

-                        if (d > 9)  /* cdigits == 0 */

-                        {

-                           if (exp_b10 == (-1))

-                           {

-                              /* Leading decimal point (plus zeros?), if

-                               * we lose the decimal point here it must

-                               * be reentered below.

-                               */

-                              int ch = *--ascii;

-

-                              if (ch == 46)

-                                 ++size, exp_b10 = 1;

-

-                              /* Else lost a leading zero, so 'exp_b10' is

-                               * still ok at (-1)

-                               */

-                           }

-                           else

-                              ++exp_b10;

-

-                           /* In all cases we output a '1' */

-                           d = 1;

-                        }

-                     }

-                  }

-                  fp = 0; /* Guarantees termination below. */

-               }

-

-               if (d == 0)

-               {

-                  ++czero;

-                  if (cdigits == 0) ++clead;

-               }

-               else

-               {

-                  /* Included embedded zeros in the digit count. */

-                  cdigits += czero - clead;

-                  clead = 0;

-

-                  while (czero > 0)

-                  {

-                     /* exp_b10 == (-1) means we just output the decimal

-                      * place - after the DP don't adjust 'exp_b10' any

-                      * more!

-                      */

-                     if (exp_b10 != (-1))

-                     {

-                        if (exp_b10 == 0) *ascii++ = 46, --size;

-                        /* PLUS 1: TOTAL 4 */

-                        --exp_b10;

-                     }

-                     *ascii++ = 48, --czero;

-                  }

-

-                  if (exp_b10 != (-1))

-                  {

-                     if (exp_b10 == 0) *ascii++ = 46, --size; /* counted

-                                                                 above */

-                     --exp_b10;

-                  }

-                  *ascii++ = (char)(48 + (int)d), ++cdigits;

-               }

-            }

-            while (cdigits+czero-clead < (int)precision && fp > DBL_MIN);

-

-            /* The total output count (max) is now 4+precision */

-

-            /* Check for an exponent, if we don't need one we are

-             * done and just need to terminate the string.  At

-             * this point exp_b10==(-1) is effectively if flag - it got

-             * to '-1' because of the decrement after outputing

-             * the decimal point above (the exponent required is

-             * *not* -1!)

-             */

-            if (exp_b10 >= (-1) && exp_b10 <= 2)

-            {

-               /* The following only happens if we didn't output the

-                * leading zeros above for negative exponent, so this

-                * doest add to the digit requirement.  Note that the

-                * two zeros here can only be output if the two leading

-                * zeros were *not* output, so this doesn't increase

-                * the output count.

-                */

-               while (--exp_b10 >= 0) *ascii++ = 48;

-

-               *ascii = 0;

-

-               /* Total buffer requirement (including the '\0') is

-                * 5+precision - see check at the start.

-                */

-               return;

-            }

-

-            /* Here if an exponent is required, adjust size for

-             * the digits we output but did not count.  The total

-             * digit output here so far is at most 1+precision - no

-             * decimal point and no leading or trailing zeros have

-             * been output.

-             */

-            size -= cdigits;

-

-            *ascii++ = 69, --size;    /* 'E': PLUS 1 TOTAL 2+precision */

-

-            /* The following use of an unsigned temporary avoids ambiguities in

-             * the signed arithmetic on exp_b10 and permits GCC at least to do

-             * better optimization.

-             */

-            {

-               unsigned int uexp_b10;

-

-               if (exp_b10 < 0)

-               {

-                  *ascii++ = 45, --size; /* '-': PLUS 1 TOTAL 3+precision */

-                  uexp_b10 = -exp_b10;

-               }

-

-               else

-                  uexp_b10 = exp_b10;

-

-               cdigits = 0;

-

-               while (uexp_b10 > 0)

-               {

-                  exponent[cdigits++] = (char)(48 + uexp_b10 % 10);

-                  uexp_b10 /= 10;

-               }

-            }

-

-            /* Need another size check here for the exponent digits, so

-             * this need not be considered above.

-             */

-            if ((int)size > cdigits)

-            {

-               while (cdigits > 0) *ascii++ = exponent[--cdigits];

-

-               *ascii = 0;

-

-               return;

-            }

-         }

-      }

-      else if (!(fp >= DBL_MIN))

-      {

-         *ascii++ = 48; /* '0' */

-         *ascii = 0;

-         return;

-      }

-      else

-      {

-         *ascii++ = 105; /* 'i' */

-         *ascii++ = 110; /* 'n' */

-         *ascii++ = 102; /* 'f' */

-         *ascii = 0;

-         return;

-      }

-   }

-

-   /* Here on buffer too small. */

-   png_error(png_ptr, "ASCII conversion buffer too small");

-}

-

-#  endif /* FLOATING_POINT */

-

-#  ifdef PNG_FIXED_POINT_SUPPORTED

-/* Function to format a fixed point value in ASCII.

- */

-void /* PRIVATE */

-png_ascii_from_fixed(png_const_structrp png_ptr, png_charp ascii,

-    png_size_t size, png_fixed_point fp)

-{

-   /* Require space for 10 decimal digits, a decimal point, a minus sign and a

-    * trailing \0, 13 characters:

-    */

-   if (size > 12)

-   {

-      png_uint_32 num;

-

-      /* Avoid overflow here on the minimum integer. */

-      if (fp < 0)

-         *ascii++ = 45, --size, num = -fp;

-      else

-         num = fp;

-

-      if (num <= 0x80000000) /* else overflowed */

-      {

-         unsigned int ndigits = 0, first = 16 /* flag value */;

-         char digits[10];

-

-         while (num)

-         {

-            /* Split the low digit off num: */

-            unsigned int tmp = num/10;

-            num -= tmp*10;

-            digits[ndigits++] = (char)(48 + num);

-            /* Record the first non-zero digit, note that this is a number

-             * starting at 1, it's not actually the array index.

-             */

-            if (first == 16 && num > 0)

-               first = ndigits;

-            num = tmp;

-         }

-

-         if (ndigits > 0)

-         {

-            while (ndigits > 5) *ascii++ = digits[--ndigits];

-            /* The remaining digits are fractional digits, ndigits is '5' or

-             * smaller at this point.  It is certainly not zero.  Check for a

-             * non-zero fractional digit:

-             */

-            if (first <= 5)

-            {

-               unsigned int i;

-               *ascii++ = 46; /* decimal point */

-               /* ndigits may be <5 for small numbers, output leading zeros

-                * then ndigits digits to first:

-                */

-               i = 5;

-               while (ndigits < i) *ascii++ = 48, --i;

-               while (ndigits >= first) *ascii++ = digits[--ndigits];

-               /* Don't output the trailing zeros! */

-            }

-         }

-         else

-            *ascii++ = 48;

-

-         /* And null terminate the string: */

-         *ascii = 0;

-         return;

-      }

-   }

-

-   /* Here on buffer too small. */

-   png_error(png_ptr, "ASCII conversion buffer too small");

-}

-#   endif /* FIXED_POINT */

-#endif /* READ_SCAL */

-

-#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_fixed_point

-png_fixed(png_const_structrp png_ptr, double fp, png_const_charp text)

-{

-   double r = floor(100000 * fp + .5);

-

-   if (r > 2147483647. || r < -2147483648.)

-      png_fixed_error(png_ptr, text);

-

-   return (png_fixed_point)r;

-}

-#endif

-

-#if defined(PNG_READ_GAMMA_SUPPORTED) || \

-    defined(PNG_INCH_CONVERSIONS_SUPPORTED) || defined(PNG_READ_pHYs_SUPPORTED)

-/* muldiv functions */

-/* This API takes signed arguments and rounds the result to the nearest

- * integer (or, for a fixed point number - the standard argument - to

- * the nearest .00001).  Overflow and divide by zero are signalled in

- * the result, a boolean - true on success, false on overflow.

- */

-int

-png_muldiv(png_fixed_point_p res, png_fixed_point a, png_int_32 times,

-    png_int_32 divisor)

-{

-   /* Return a * times / divisor, rounded. */

-   if (divisor != 0)

-   {

-      if (a == 0 || times == 0)

-      {

-         *res = 0;

-         return 1;

-      }

-      else

-      {

-#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED

-         double r = a;

-         r *= times;

-         r /= divisor;

-         r = floor(r+.5);

-

-         /* A png_fixed_point is a 32-bit integer. */

-         if (r <= 2147483647. && r >= -2147483648.)

-         {

-            *res = (png_fixed_point)r;

-            return 1;

-         }

-#else

-         int negative = 0;

-         png_uint_32 A, T, D;

-         png_uint_32 s16, s32, s00;

-

-         if (a < 0)

-            negative = 1, A = -a;

-         else

-            A = a;

-

-         if (times < 0)

-            negative = !negative, T = -times;

-         else

-            T = times;

-

-         if (divisor < 0)

-            negative = !negative, D = -divisor;

-         else

-            D = divisor;

-

-         /* Following can't overflow because the arguments only

-          * have 31 bits each, however the result may be 32 bits.

-          */

-         s16 = (A >> 16) * (T & 0xffff) +

-                           (A & 0xffff) * (T >> 16);

-         /* Can't overflow because the a*times bit is only 30

-          * bits at most.

-          */

-         s32 = (A >> 16) * (T >> 16) + (s16 >> 16);

-         s00 = (A & 0xffff) * (T & 0xffff);

-

-         s16 = (s16 & 0xffff) << 16;

-         s00 += s16;

-

-         if (s00 < s16)

-            ++s32; /* carry */

-

-         if (s32 < D) /* else overflow */

-         {

-            /* s32.s00 is now the 64-bit product, do a standard

-             * division, we know that s32 < D, so the maximum

-             * required shift is 31.

-             */

-            int bitshift = 32;

-            png_fixed_point result = 0; /* NOTE: signed */

-

-            while (--bitshift >= 0)

-            {

-               png_uint_32 d32, d00;

-

-               if (bitshift > 0)

-                  d32 = D >> (32-bitshift), d00 = D << bitshift;

-

-               else

-                  d32 = 0, d00 = D;

-

-               if (s32 > d32)

-               {

-                  if (s00 < d00) --s32; /* carry */

-                  s32 -= d32, s00 -= d00, result += 1<<bitshift;

-               }

-

-               else

-                  if (s32 == d32 && s00 >= d00)

-                     s32 = 0, s00 -= d00, result += 1<<bitshift;

-            }

-

-            /* Handle the rounding. */

-            if (s00 >= (D >> 1))

-               ++result;

-

-            if (negative)

-               result = -result;

-

-            /* Check for overflow. */

-            if ((negative && result <= 0) || (!negative && result >= 0))

-            {

-               *res = result;

-               return 1;

-            }

-         }

-#endif

-      }

-   }

-

-   return 0;

-}

-#endif /* READ_GAMMA || INCH_CONVERSIONS */

-

-#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_INCH_CONVERSIONS_SUPPORTED)

-/* The following is for when the caller doesn't much care about the

- * result.

- */

-png_fixed_point

-png_muldiv_warn(png_const_structrp png_ptr, png_fixed_point a, png_int_32 times,

-    png_int_32 divisor)

-{

-   png_fixed_point result;

-

-   if (png_muldiv(&result, a, times, divisor))

-      return result;

-

-   png_warning(png_ptr, "fixed point overflow ignored");

-   return 0;

-}

-#endif

-

-#ifdef PNG_GAMMA_SUPPORTED /* more fixed point functions for gamma */

-/* Calculate a reciprocal, return 0 on div-by-zero or overflow. */

-png_fixed_point

-png_reciprocal(png_fixed_point a)

-{

-#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED

-   double r = floor(1E10/a+.5);

-

-   if (r <= 2147483647. && r >= -2147483648.)

-      return (png_fixed_point)r;

-#else

-   png_fixed_point res;

-

-   if (png_muldiv(&res, 100000, 100000, a))

-      return res;

-#endif

-

-   return 0; /* error/overflow */

-}

-

-/* This is the shared test on whether a gamma value is 'significant' - whether

- * it is worth doing gamma correction.

- */

-int /* PRIVATE */

-png_gamma_significant(png_fixed_point gamma_val)

-{

-   return gamma_val < PNG_FP_1 - PNG_GAMMA_THRESHOLD_FIXED ||

-       gamma_val > PNG_FP_1 + PNG_GAMMA_THRESHOLD_FIXED;

-}

-#endif

-

-#ifdef PNG_READ_GAMMA_SUPPORTED

-/* A local convenience routine. */

-static png_fixed_point

-png_product2(png_fixed_point a, png_fixed_point b)

-{

-   /* The required result is 1/a * 1/b; the following preserves accuracy. */

-#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED

-   double r = a * 1E-5;

-   r *= b;

-   r = floor(r+.5);

-

-   if (r <= 2147483647. && r >= -2147483648.)

-      return (png_fixed_point)r;

-#else

-   png_fixed_point res;

-

-   if (png_muldiv(&res, a, b, 100000))

-      return res;

-#endif

-

-   return 0; /* overflow */

-}

-

-/* The inverse of the above. */

-png_fixed_point

-png_reciprocal2(png_fixed_point a, png_fixed_point b)

-{

-   /* The required result is 1/a * 1/b; the following preserves accuracy. */

-#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED

-   double r = 1E15/a;

-   r /= b;

-   r = floor(r+.5);

-

-   if (r <= 2147483647. && r >= -2147483648.)

-      return (png_fixed_point)r;

-#else

-   /* This may overflow because the range of png_fixed_point isn't symmetric,

-    * but this API is only used for the product of file and screen gamma so it

-    * doesn't matter that the smallest number it can produce is 1/21474, not

-    * 1/100000

-    */

-   png_fixed_point res = png_product2(a, b);

-

-   if (res != 0)

-      return png_reciprocal(res);

-#endif

-

-   return 0; /* overflow */

-}

-#endif /* READ_GAMMA */

-

-#ifdef PNG_READ_GAMMA_SUPPORTED /* gamma table code */

-#ifndef PNG_FLOATING_ARITHMETIC_SUPPORTED

-/* Fixed point gamma.

- *

- * The code to calculate the tables used below can be found in the shell script

- * contrib/tools/intgamma.sh

- *

- * To calculate gamma this code implements fast log() and exp() calls using only

- * fixed point arithmetic.  This code has sufficient precision for either 8-bit

- * or 16-bit sample values.

- *

- * The tables used here were calculated using simple 'bc' programs, but C double

- * precision floating point arithmetic would work fine.

- *

- * 8-bit log table

- *   This is a table of -log(value/255)/log(2) for 'value' in the range 128 to

- *   255, so it's the base 2 logarithm of a normalized 8-bit floating point

- *   mantissa.  The numbers are 32-bit fractions.

- */

-static const png_uint_32

-png_8bit_l2[128] =

-{

-   4270715492U, 4222494797U, 4174646467U, 4127164793U, 4080044201U, 4033279239U,

-   3986864580U, 3940795015U, 3895065449U, 3849670902U, 3804606499U, 3759867474U,

-   3715449162U, 3671346997U, 3627556511U, 3584073329U, 3540893168U, 3498011834U,

-   3455425220U, 3413129301U, 3371120137U, 3329393864U, 3287946700U, 3246774933U,

-   3205874930U, 3165243125U, 3124876025U, 3084770202U, 3044922296U, 3005329011U,

-   2965987113U, 2926893432U, 2888044853U, 2849438323U, 2811070844U, 2772939474U,

-   2735041326U, 2697373562U, 2659933400U, 2622718104U, 2585724991U, 2548951424U,

-   2512394810U, 2476052606U, 2439922311U, 2404001468U, 2368287663U, 2332778523U,

-   2297471715U, 2262364947U, 2227455964U, 2192742551U, 2158222529U, 2123893754U,

-   2089754119U, 2055801552U, 2022034013U, 1988449497U, 1955046031U, 1921821672U,

-   1888774511U, 1855902668U, 1823204291U, 1790677560U, 1758320682U, 1726131893U,

-   1694109454U, 1662251657U, 1630556815U, 1599023271U, 1567649391U, 1536433567U,

-   1505374214U, 1474469770U, 1443718700U, 1413119487U, 1382670639U, 1352370686U,

-   1322218179U, 1292211689U, 1262349810U, 1232631153U, 1203054352U, 1173618059U,

-   1144320946U, 1115161701U, 1086139034U, 1057251672U, 1028498358U, 999877854U,

-   971388940U, 943030410U, 914801076U, 886699767U, 858725327U, 830876614U,

-   803152505U, 775551890U, 748073672U, 720716771U, 693480120U, 666362667U,

-   639363374U, 612481215U, 585715177U, 559064263U, 532527486U, 506103872U,

-   479792461U, 453592303U, 427502463U, 401522014U, 375650043U, 349885648U,

-   324227938U, 298676034U, 273229066U, 247886176U, 222646516U, 197509248U,

-   172473545U, 147538590U, 122703574U, 97967701U, 73330182U, 48790236U,

-   24347096U, 0U

-

-#if 0

-   /* The following are the values for 16-bit tables - these work fine for the

-    * 8-bit conversions but produce very slightly larger errors in the 16-bit

-    * log (about 1.2 as opposed to 0.7 absolute error in the final value).  To

-    * use these all the shifts below must be adjusted appropriately.

-    */

-   65166, 64430, 63700, 62976, 62257, 61543, 60835, 60132, 59434, 58741, 58054,

-   57371, 56693, 56020, 55352, 54689, 54030, 53375, 52726, 52080, 51439, 50803,

-   50170, 49542, 48918, 48298, 47682, 47070, 46462, 45858, 45257, 44661, 44068,

-   43479, 42894, 42312, 41733, 41159, 40587, 40020, 39455, 38894, 38336, 37782,

-   37230, 36682, 36137, 35595, 35057, 34521, 33988, 33459, 32932, 32408, 31887,

-   31369, 30854, 30341, 29832, 29325, 28820, 28319, 27820, 27324, 26830, 26339,

-   25850, 25364, 24880, 24399, 23920, 23444, 22970, 22499, 22029, 21562, 21098,

-   20636, 20175, 19718, 19262, 18808, 18357, 17908, 17461, 17016, 16573, 16132,

-   15694, 15257, 14822, 14390, 13959, 13530, 13103, 12678, 12255, 11834, 11415,

-   10997, 10582, 10168, 9756, 9346, 8937, 8531, 8126, 7723, 7321, 6921, 6523,

-   6127, 5732, 5339, 4947, 4557, 4169, 3782, 3397, 3014, 2632, 2251, 1872, 1495,

-   1119, 744, 372

-#endif

-};

-

-static png_int_32

-png_log8bit(unsigned int x)

-{

-   unsigned int lg2 = 0;

-   /* Each time 'x' is multiplied by 2, 1 must be subtracted off the final log,

-    * because the log is actually negate that means adding 1.  The final

-    * returned value thus has the range 0 (for 255 input) to 7.994 (for 1

-    * input), return -1 for the overflow (log 0) case, - so the result is

-    * always at most 19 bits.

-    */

-   if ((x &= 0xff) == 0)

-      return -1;

-

-   if ((x & 0xf0) == 0)

-      lg2  = 4, x <<= 4;

-

-   if ((x & 0xc0) == 0)

-      lg2 += 2, x <<= 2;

-

-   if ((x & 0x80) == 0)

-      lg2 += 1, x <<= 1;

-

-   /* result is at most 19 bits, so this cast is safe: */

-   return (png_int_32)((lg2 << 16) + ((png_8bit_l2[x-128]+32768)>>16));

-}

-

-/* The above gives exact (to 16 binary places) log2 values for 8-bit images,

- * for 16-bit images we use the most significant 8 bits of the 16-bit value to

- * get an approximation then multiply the approximation by a correction factor

- * determined by the remaining up to 8 bits.  This requires an additional step

- * in the 16-bit case.

- *

- * We want log2(value/65535), we have log2(v'/255), where:

- *

- *    value = v' * 256 + v''

- *          = v' * f

- *

- * So f is value/v', which is equal to (256+v''/v') since v' is in the range 128

- * to 255 and v'' is in the range 0 to 255 f will be in the range 256 to less

- * than 258.  The final factor also needs to correct for the fact that our 8-bit

- * value is scaled by 255, whereas the 16-bit values must be scaled by 65535.

- *

- * This gives a final formula using a calculated value 'x' which is value/v' and

- * scaling by 65536 to match the above table:

- *

- *   log2(x/257) * 65536

- *

- * Since these numbers are so close to '1' we can use simple linear

- * interpolation between the two end values 256/257 (result -368.61) and 258/257

- * (result 367.179).  The values used below are scaled by a further 64 to give

- * 16-bit precision in the interpolation:

- *

- * Start (256): -23591

- * Zero  (257):      0

- * End   (258):  23499

- */

-static png_int_32

-png_log16bit(png_uint_32 x)

-{

-   unsigned int lg2 = 0;

-

-   /* As above, but now the input has 16 bits. */

-   if ((x &= 0xffff) == 0)

-      return -1;

-

-   if ((x & 0xff00) == 0)

-      lg2  = 8, x <<= 8;

-

-   if ((x & 0xf000) == 0)

-      lg2 += 4, x <<= 4;

-

-   if ((x & 0xc000) == 0)

-      lg2 += 2, x <<= 2;

-

-   if ((x & 0x8000) == 0)

-      lg2 += 1, x <<= 1;

-

-   /* Calculate the base logarithm from the top 8 bits as a 28-bit fractional

-    * value.

-    */

-   lg2 <<= 28;

-   lg2 += (png_8bit_l2[(x>>8)-128]+8) >> 4;

-

-   /* Now we need to interpolate the factor, this requires a division by the top

-    * 8 bits.  Do this with maximum precision.

-    */

-   x = ((x << 16) + (x >> 9)) / (x >> 8);

-

-   /* Since we divided by the top 8 bits of 'x' there will be a '1' at 1<<24,

-    * the value at 1<<16 (ignoring this) will be 0 or 1; this gives us exactly

-    * 16 bits to interpolate to get the low bits of the result.  Round the

-    * answer.  Note that the end point values are scaled by 64 to retain overall

-    * precision and that 'lg2' is current scaled by an extra 12 bits, so adjust

-    * the overall scaling by 6-12.  Round at every step.

-    */

-   x -= 1U << 24;

-

-   if (x <= 65536U) /* <= '257' */

-      lg2 += ((23591U * (65536U-x)) + (1U << (16+6-12-1))) >> (16+6-12);

-

-   else

-      lg2 -= ((23499U * (x-65536U)) + (1U << (16+6-12-1))) >> (16+6-12);

-

-   /* Safe, because the result can't have more than 20 bits: */

-   return (png_int_32)((lg2 + 2048) >> 12);

-}

-

-/* The 'exp()' case must invert the above, taking a 20-bit fixed point

- * logarithmic value and returning a 16 or 8-bit number as appropriate.  In

- * each case only the low 16 bits are relevant - the fraction - since the

- * integer bits (the top 4) simply determine a shift.

- *

- * The worst case is the 16-bit distinction between 65535 and 65534, this

- * requires perhaps spurious accuracty in the decoding of the logarithm to

- * distinguish log2(65535/65534.5) - 10^-5 or 17 bits.  There is little chance

- * of getting this accuracy in practice.

- *

- * To deal with this the following exp() function works out the exponent of the

- * frational part of the logarithm by using an accurate 32-bit value from the

- * top four fractional bits then multiplying in the remaining bits.

- */

-static const png_uint_32

-png_32bit_exp[16] =

-{

-   /* NOTE: the first entry is deliberately set to the maximum 32-bit value. */

-   4294967295U, 4112874773U, 3938502376U, 3771522796U, 3611622603U, 3458501653U,

-   3311872529U, 3171459999U, 3037000500U, 2908241642U, 2784941738U, 2666869345U,

-   2553802834U, 2445529972U, 2341847524U, 2242560872U

-};

-

-/* Adjustment table; provided to explain the numbers in the code below. */

-#if 0

-for (i=11;i>=0;--i){ print i, " ", (1 - e(-(2^i)/65536*l(2))) * 2^(32-i), "\n"}

-   11 44937.64284865548751208448

-   10 45180.98734845585101160448

-    9 45303.31936980687359311872

-    8 45364.65110595323018870784

-    7 45395.35850361789624614912

-    6 45410.72259715102037508096

-    5 45418.40724413220722311168

-    4 45422.25021786898173001728

-    3 45424.17186732298419044352

-    2 45425.13273269940811464704

-    1 45425.61317555035558641664

-    0 45425.85339951654943850496

-#endif

-

-static png_uint_32

-png_exp(png_fixed_point x)

-{

-   if (x > 0 && x <= 0xfffff) /* Else overflow or zero (underflow) */

-   {

-      /* Obtain a 4-bit approximation */

-      png_uint_32 e = png_32bit_exp[(x >> 12) & 0xf];

-

-      /* Incorporate the low 12 bits - these decrease the returned value by

-       * multiplying by a number less than 1 if the bit is set.  The multiplier

-       * is determined by the above table and the shift. Notice that the values

-       * converge on 45426 and this is used to allow linear interpolation of the

-       * low bits.

-       */

-      if (x & 0x800)

-         e -= (((e >> 16) * 44938U) +  16U) >> 5;

-

-      if (x & 0x400)

-         e -= (((e >> 16) * 45181U) +  32U) >> 6;

-

-      if (x & 0x200)

-         e -= (((e >> 16) * 45303U) +  64U) >> 7;

-

-      if (x & 0x100)

-         e -= (((e >> 16) * 45365U) + 128U) >> 8;

-

-      if (x & 0x080)

-         e -= (((e >> 16) * 45395U) + 256U) >> 9;

-

-      if (x & 0x040)

-         e -= (((e >> 16) * 45410U) + 512U) >> 10;

-

-      /* And handle the low 6 bits in a single block. */

-      e -= (((e >> 16) * 355U * (x & 0x3fU)) + 256U) >> 9;

-

-      /* Handle the upper bits of x. */

-      e >>= x >> 16;

-      return e;

-   }

-

-   /* Check for overflow */

-   if (x <= 0)

-      return png_32bit_exp[0];

-

-   /* Else underflow */

-   return 0;

-}

-

-static png_byte

-png_exp8bit(png_fixed_point lg2)

-{

-   /* Get a 32-bit value: */

-   png_uint_32 x = png_exp(lg2);

-

-   /* Convert the 32-bit value to 0..255 by multiplying by 256-1, note that the

-    * second, rounding, step can't overflow because of the first, subtraction,

-    * step.

-    */

-   x -= x >> 8;

-   return (png_byte)((x + 0x7fffffU) >> 24);

-}

-

-static png_uint_16

-png_exp16bit(png_fixed_point lg2)

-{

-   /* Get a 32-bit value: */

-   png_uint_32 x = png_exp(lg2);

-

-   /* Convert the 32-bit value to 0..65535 by multiplying by 65536-1: */

-   x -= x >> 16;

-   return (png_uint_16)((x + 32767U) >> 16);

-}

-#endif /* FLOATING_ARITHMETIC */

-

-png_byte

-png_gamma_8bit_correct(unsigned int value, png_fixed_point gamma_val)

-{

-   if (value > 0 && value < 255)

-   {

-#     ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED

-         double r = floor(255*pow(value/255.,gamma_val*.00001)+.5);

-         return (png_byte)r;

-#     else

-         png_int_32 lg2 = png_log8bit(value);

-         png_fixed_point res;

-

-         if (png_muldiv(&res, gamma_val, lg2, PNG_FP_1))

-            return png_exp8bit(res);

-

-         /* Overflow. */

-         value = 0;

-#     endif

-   }

-

-   return (png_byte)value;

-}

-

-png_uint_16

-png_gamma_16bit_correct(unsigned int value, png_fixed_point gamma_val)

-{

-   if (value > 0 && value < 65535)

-   {

-#     ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED

-         double r = floor(65535*pow(value/65535.,gamma_val*.00001)+.5);

-         return (png_uint_16)r;

-#     else

-         png_int_32 lg2 = png_log16bit(value);

-         png_fixed_point res;

-

-         if (png_muldiv(&res, gamma_val, lg2, PNG_FP_1))

-            return png_exp16bit(res);

-

-         /* Overflow. */

-         value = 0;

-#     endif

-   }

-

-   return (png_uint_16)value;

-}

-

-/* This does the right thing based on the bit_depth field of the

- * png_struct, interpreting values as 8-bit or 16-bit.  While the result

- * is nominally a 16-bit value if bit depth is 8 then the result is

- * 8-bit (as are the arguments.)

- */

-png_uint_16 /* PRIVATE */

-png_gamma_correct(png_structrp png_ptr, unsigned int value,

-    png_fixed_point gamma_val)

-{

-   if (png_ptr->bit_depth == 8)

-      return png_gamma_8bit_correct(value, gamma_val);

-

-   else

-      return png_gamma_16bit_correct(value, gamma_val);

-}

-

-/* Internal function to build a single 16-bit table - the table consists of

- * 'num' 256 entry subtables, where 'num' is determined by 'shift' - the amount

- * to shift the input values right (or 16-number_of_signifiant_bits).

- *

- * The caller is responsible for ensuring that the table gets cleaned up on

- * png_error (i.e. if one of the mallocs below fails) - i.e. the *table argument

- * should be somewhere that will be cleaned.

- */

-static void

-png_build_16bit_table(png_structrp png_ptr, png_uint_16pp *ptable,

-   PNG_CONST unsigned int shift, PNG_CONST png_fixed_point gamma_val)

-{

-   /* Various values derived from 'shift': */

-   PNG_CONST unsigned int num = 1U << (8U - shift);

-   PNG_CONST unsigned int max = (1U << (16U - shift))-1U;

-   PNG_CONST unsigned int max_by_2 = 1U << (15U-shift);

-   unsigned int i;

-

-   png_uint_16pp table = *ptable =

-       (png_uint_16pp)png_calloc(png_ptr, num * (sizeof (png_uint_16p)));

-

-   for (i = 0; i < num; i++)

-   {

-      png_uint_16p sub_table = table[i] =

-          (png_uint_16p)png_malloc(png_ptr, 256 * (sizeof (png_uint_16)));

-

-      /* The 'threshold' test is repeated here because it can arise for one of

-       * the 16-bit tables even if the others don't hit it.

-       */

-      if (png_gamma_significant(gamma_val))

-      {

-         /* The old code would overflow at the end and this would cause the

-          * 'pow' function to return a result >1, resulting in an

-          * arithmetic error.  This code follows the spec exactly; ig is

-          * the recovered input sample, it always has 8-16 bits.

-          *

-          * We want input * 65535/max, rounded, the arithmetic fits in 32

-          * bits (unsigned) so long as max <= 32767.

-          */

-         unsigned int j;

-         for (j = 0; j < 256; j++)

-         {

-            png_uint_32 ig = (j << (8-shift)) + i;

-#           ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED

-               /* Inline the 'max' scaling operation: */

-               double d = floor(65535*pow(ig/(double)max, gamma_val*.00001)+.5);

-               sub_table[j] = (png_uint_16)d;

-#           else

-               if (shift)

-                  ig = (ig * 65535U + max_by_2)/max;

-

-               sub_table[j] = png_gamma_16bit_correct(ig, gamma_val);

-#           endif

-         }

-      }

-      else

-      {

-         /* We must still build a table, but do it the fast way. */

-         unsigned int j;

-

-         for (j = 0; j < 256; j++)

-         {

-            png_uint_32 ig = (j << (8-shift)) + i;

-

-            if (shift)

-               ig = (ig * 65535U + max_by_2)/max;

-

-            sub_table[j] = (png_uint_16)ig;

-         }

-      }

-   }

-}

-

-/* NOTE: this function expects the *inverse* of the overall gamma transformation

- * required.

- */

-static void

-png_build_16to8_table(png_structrp png_ptr, png_uint_16pp *ptable,

-   PNG_CONST unsigned int shift, PNG_CONST png_fixed_point gamma_val)

-{

-   PNG_CONST unsigned int num = 1U << (8U - shift);

-   PNG_CONST unsigned int max = (1U << (16U - shift))-1U;

-   unsigned int i;

-   png_uint_32 last;

-

-   png_uint_16pp table = *ptable =

-       (png_uint_16pp)png_calloc(png_ptr, num * (sizeof (png_uint_16p)));

-

-   /* 'num' is the number of tables and also the number of low bits of low

-    * bits of the input 16-bit value used to select a table.  Each table is

-    * itself index by the high 8 bits of the value.

-    */

-   for (i = 0; i < num; i++)

-      table[i] = (png_uint_16p)png_malloc(png_ptr,

-          256 * (sizeof (png_uint_16)));

-

-   /* 'gamma_val' is set to the reciprocal of the value calculated above, so

-    * pow(out,g) is an *input* value.  'last' is the last input value set.

-    *

-    * In the loop 'i' is used to find output values.  Since the output is

-    * 8-bit there are only 256 possible values.  The tables are set up to

-    * select the closest possible output value for each input by finding

-    * the input value at the boundary between each pair of output values

-    * and filling the table up to that boundary with the lower output

-    * value.

-    *

-    * The boundary values are 0.5,1.5..253.5,254.5.  Since these are 9-bit

-    * values the code below uses a 16-bit value in i; the values start at

-    * 128.5 (for 0.5) and step by 257, for a total of 254 values (the last

-    * entries are filled with 255).  Start i at 128 and fill all 'last'

-    * table entries <= 'max'

-    */

-   last = 0;

-   for (i = 0; i < 255; ++i) /* 8-bit output value */

-   {

-      /* Find the corresponding maximum input value */

-      png_uint_16 out = (png_uint_16)(i * 257U); /* 16-bit output value */

-

-      /* Find the boundary value in 16 bits: */

-      png_uint_32 bound = png_gamma_16bit_correct(out+128U, gamma_val);

-

-      /* Adjust (round) to (16-shift) bits: */

-      bound = (bound * max + 32768U)/65535U + 1U;

-

-      while (last < bound)

-      {

-         table[last & (0xffU >> shift)][last >> (8U - shift)] = out;

-         last++;

-      }

-   }

-

-   /* And fill in the final entries. */

-   while (last < (num << 8))

-   {

-      table[last & (0xff >> shift)][last >> (8U - shift)] = 65535U;

-      last++;

-   }

-}

-

-/* Build a single 8-bit table: same as the 16-bit case but much simpler (and

- * typically much faster).  Note that libpng currently does no sBIT processing

- * (apparently contrary to the spec) so a 256 entry table is always generated.

- */

-static void

-png_build_8bit_table(png_structrp png_ptr, png_bytepp ptable,

-   PNG_CONST png_fixed_point gamma_val)

-{

-   unsigned int i;

-   png_bytep table = *ptable = (png_bytep)png_malloc(png_ptr, 256);

-

-   if (png_gamma_significant(gamma_val)) for (i=0; i<256; i++)

-      table[i] = png_gamma_8bit_correct(i, gamma_val);

-

-   else for (i=0; i<256; ++i)

-      table[i] = (png_byte)i;

-}

-

-/* Used from png_read_destroy and below to release the memory used by the gamma

- * tables.

- */

-void /* PRIVATE */

-png_destroy_gamma_table(png_structrp png_ptr)

-{

-   png_free(png_ptr, png_ptr->gamma_table);

-   png_ptr->gamma_table = NULL;

-

-   if (png_ptr->gamma_16_table != NULL)

-   {

-      int i;

-      int istop = (1 << (8 - png_ptr->gamma_shift));

-      for (i = 0; i < istop; i++)

-      {

-         png_free(png_ptr, png_ptr->gamma_16_table[i]);

-      }

-   png_free(png_ptr, png_ptr->gamma_16_table);

-   png_ptr->gamma_16_table = NULL;

-   }

-

-#if defined(PNG_READ_BACKGROUND_SUPPORTED) || \

-   defined(PNG_READ_ALPHA_MODE_SUPPORTED) || \

-   defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)

-   png_free(png_ptr, png_ptr->gamma_from_1);

-   png_ptr->gamma_from_1 = NULL;

-   png_free(png_ptr, png_ptr->gamma_to_1);

-   png_ptr->gamma_to_1 = NULL;

-

-   if (png_ptr->gamma_16_from_1 != NULL)

-   {

-      int i;

-      int istop = (1 << (8 - png_ptr->gamma_shift));

-      for (i = 0; i < istop; i++)

-      {

-         png_free(png_ptr, png_ptr->gamma_16_from_1[i]);

-      }

-   png_free(png_ptr, png_ptr->gamma_16_from_1);

-   png_ptr->gamma_16_from_1 = NULL;

-   }

-   if (png_ptr->gamma_16_to_1 != NULL)

-   {

-      int i;

-      int istop = (1 << (8 - png_ptr->gamma_shift));

-      for (i = 0; i < istop; i++)

-      {

-         png_free(png_ptr, png_ptr->gamma_16_to_1[i]);

-      }

-   png_free(png_ptr, png_ptr->gamma_16_to_1);

-   png_ptr->gamma_16_to_1 = NULL;

-   }

-#endif /* READ_BACKGROUND || READ_ALPHA_MODE || RGB_TO_GRAY */

-}

-

-/* We build the 8- or 16-bit gamma tables here.  Note that for 16-bit

- * tables, we don't make a full table if we are reducing to 8-bit in

- * the future.  Note also how the gamma_16 tables are segmented so that

- * we don't need to allocate > 64K chunks for a full 16-bit table.

- */

-void /* PRIVATE */

-png_build_gamma_table(png_structrp png_ptr, int bit_depth)

-{

-  png_debug(1, "in png_build_gamma_table");

-

-  /* Remove any existing table; this copes with multiple calls to

-   * png_read_update_info.  The warning is because building the gamma tables

-   * multiple times is a performance hit - it's harmless but the ability to call

-   * png_read_update_info() multiple times is new in 1.5.6 so it seems sensible

-   * to warn if the app introduces such a hit.

-   */

-  if (png_ptr->gamma_table != NULL || png_ptr->gamma_16_table != NULL)

-  {

-    png_warning(png_ptr, "gamma table being rebuilt");

-    png_destroy_gamma_table(png_ptr);

-  }

-

-  if (bit_depth <= 8)

-  {

-     png_build_8bit_table(png_ptr, &png_ptr->gamma_table,

-         png_ptr->screen_gamma > 0 ?  png_reciprocal2(png_ptr->colorspace.gamma,

-         png_ptr->screen_gamma) : PNG_FP_1);

-

-#if defined(PNG_READ_BACKGROUND_SUPPORTED) || \

-   defined(PNG_READ_ALPHA_MODE_SUPPORTED) || \

-   defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)

-     if (png_ptr->transformations & (PNG_COMPOSE | PNG_RGB_TO_GRAY))

-     {

-        png_build_8bit_table(png_ptr, &png_ptr->gamma_to_1,

-            png_reciprocal(png_ptr->colorspace.gamma));

-

-        png_build_8bit_table(png_ptr, &png_ptr->gamma_from_1,

-            png_ptr->screen_gamma > 0 ?  png_reciprocal(png_ptr->screen_gamma) :

-            png_ptr->colorspace.gamma/* Probably doing rgb_to_gray */);

-     }

-#endif /* READ_BACKGROUND || READ_ALPHA_MODE || RGB_TO_GRAY */

-  }

-  else

-  {

-     png_byte shift, sig_bit;

-

-     if (png_ptr->color_type & PNG_COLOR_MASK_COLOR)

-     {

-        sig_bit = png_ptr->sig_bit.red;

-

-        if (png_ptr->sig_bit.green > sig_bit)

-           sig_bit = png_ptr->sig_bit.green;

-

-        if (png_ptr->sig_bit.blue > sig_bit)

-           sig_bit = png_ptr->sig_bit.blue;

-     }

-     else

-        sig_bit = png_ptr->sig_bit.gray;

-

-     /* 16-bit gamma code uses this equation:

-      *

-      *   ov = table[(iv & 0xff) >> gamma_shift][iv >> 8]

-      *

-      * Where 'iv' is the input color value and 'ov' is the output value -

-      * pow(iv, gamma).

-      *

-      * Thus the gamma table consists of up to 256 256 entry tables.  The table

-      * is selected by the (8-gamma_shift) most significant of the low 8 bits of

-      * the color value then indexed by the upper 8 bits:

-      *

-      *   table[low bits][high 8 bits]

-      *

-      * So the table 'n' corresponds to all those 'iv' of:

-      *

-      *   <all high 8-bit values><n << gamma_shift>..<(n+1 << gamma_shift)-1>

-      *

-      */

-     if (sig_bit > 0 && sig_bit < 16U)

-        shift = (png_byte)(16U - sig_bit); /* shift == insignificant bits */

-

-     else

-        shift = 0; /* keep all 16 bits */

-

-     if (png_ptr->transformations & (PNG_16_TO_8 | PNG_SCALE_16_TO_8))

-     {

-        /* PNG_MAX_GAMMA_8 is the number of bits to keep - effectively

-         * the significant bits in the *input* when the output will

-         * eventually be 8 bits.  By default it is 11.

-         */

-        if (shift < (16U - PNG_MAX_GAMMA_8))

-           shift = (16U - PNG_MAX_GAMMA_8);

-     }

-

-     if (shift > 8U)

-        shift = 8U; /* Guarantees at least one table! */

-

-     png_ptr->gamma_shift = shift;

-

-#ifdef PNG_16BIT_SUPPORTED

-     /* NOTE: prior to 1.5.4 this test used to include PNG_BACKGROUND (now

-      * PNG_COMPOSE).  This effectively smashed the background calculation for

-      * 16-bit output because the 8-bit table assumes the result will be reduced

-      * to 8 bits.

-      */

-     if (png_ptr->transformations & (PNG_16_TO_8 | PNG_SCALE_16_TO_8))

-#endif

-         png_build_16to8_table(png_ptr, &png_ptr->gamma_16_table, shift,

-         png_ptr->screen_gamma > 0 ? png_product2(png_ptr->colorspace.gamma,

-         png_ptr->screen_gamma) : PNG_FP_1);

-

-#ifdef PNG_16BIT_SUPPORTED

-     else

-         png_build_16bit_table(png_ptr, &png_ptr->gamma_16_table, shift,

-         png_ptr->screen_gamma > 0 ? png_reciprocal2(png_ptr->colorspace.gamma,

-         png_ptr->screen_gamma) : PNG_FP_1);

-#endif

-

-#if defined(PNG_READ_BACKGROUND_SUPPORTED) || \

-   defined(PNG_READ_ALPHA_MODE_SUPPORTED) || \

-   defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)

-     if (png_ptr->transformations & (PNG_COMPOSE | PNG_RGB_TO_GRAY))

-     {

-        png_build_16bit_table(png_ptr, &png_ptr->gamma_16_to_1, shift,

-            png_reciprocal(png_ptr->colorspace.gamma));

-

-        /* Notice that the '16 from 1' table should be full precision, however

-         * the lookup on this table still uses gamma_shift, so it can't be.

-         * TODO: fix this.

-         */

-        png_build_16bit_table(png_ptr, &png_ptr->gamma_16_from_1, shift,

-            png_ptr->screen_gamma > 0 ? png_reciprocal(png_ptr->screen_gamma) :

-            png_ptr->colorspace.gamma/* Probably doing rgb_to_gray */);

-     }

-#endif /* READ_BACKGROUND || READ_ALPHA_MODE || RGB_TO_GRAY */

-  }

-}

-#endif /* READ_GAMMA */

-

-/* HARDWARE OPTION SUPPORT */

-#ifdef PNG_SET_OPTION_SUPPORTED

-int PNGAPI

-png_set_option(png_structrp png_ptr, int option, int onoff)

-{

-   if (png_ptr != NULL && option >= 0 && option < PNG_OPTION_NEXT &&

-      (option & 1) == 0)

-   {

-      int mask = 3 << option;

-      int setting = (2 + (onoff != 0)) << option;

-      int current = png_ptr->options;

-

-      png_ptr->options = (png_byte)((current & ~mask) | setting);

-

-      return (current & mask) >> option;

-   }

-

-   return PNG_OPTION_INVALID;

-}

-#endif

-

-/* sRGB support */

-#if defined(PNG_SIMPLIFIED_READ_SUPPORTED) ||\

-   defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)

-/* sRGB conversion tables; these are machine generated with the code in

- * contrib/tools/makesRGB.c.  The actual sRGB transfer curve defined in the

- * specification (see the article at http://en.wikipedia.org/wiki/SRGB)

- * is used, not the gamma=1/2.2 approximation use elsewhere in libpng.

- * The sRGB to linear table is exact (to the nearest 16 bit linear fraction).

- * The inverse (linear to sRGB) table has accuracies as follows:

- *

- * For all possible (255*65535+1) input values:

- *

- *    error: -0.515566 - 0.625971, 79441 (0.475369%) of readings inexact

- *

- * For the input values corresponding to the 65536 16-bit values:

- *

- *    error: -0.513727 - 0.607759, 308 (0.469978%) of readings inexact

- *

- * In all cases the inexact readings are off by one.

- */

-

-#ifdef PNG_SIMPLIFIED_READ_SUPPORTED

-/* The convert-to-sRGB table is only currently required for read. */

-const png_uint_16 png_sRGB_table[256] =

-{

-   0,20,40,60,80,99,119,139,

-   159,179,199,219,241,264,288,313,

-   340,367,396,427,458,491,526,562,

-   599,637,677,718,761,805,851,898,

-   947,997,1048,1101,1156,1212,1270,1330,

-   1391,1453,1517,1583,1651,1720,1790,1863,

-   1937,2013,2090,2170,2250,2333,2418,2504,

-   2592,2681,2773,2866,2961,3058,3157,3258,

-   3360,3464,3570,3678,3788,3900,4014,4129,

-   4247,4366,4488,4611,4736,4864,4993,5124,

-   5257,5392,5530,5669,5810,5953,6099,6246,

-   6395,6547,6700,6856,7014,7174,7335,7500,

-   7666,7834,8004,8177,8352,8528,8708,8889,

-   9072,9258,9445,9635,9828,10022,10219,10417,

-   10619,10822,11028,11235,11446,11658,11873,12090,

-   12309,12530,12754,12980,13209,13440,13673,13909,

-   14146,14387,14629,14874,15122,15371,15623,15878,

-   16135,16394,16656,16920,17187,17456,17727,18001,

-   18277,18556,18837,19121,19407,19696,19987,20281,

-   20577,20876,21177,21481,21787,22096,22407,22721,

-   23038,23357,23678,24002,24329,24658,24990,25325,

-   25662,26001,26344,26688,27036,27386,27739,28094,

-   28452,28813,29176,29542,29911,30282,30656,31033,

-   31412,31794,32179,32567,32957,33350,33745,34143,

-   34544,34948,35355,35764,36176,36591,37008,37429,

-   37852,38278,38706,39138,39572,40009,40449,40891,

-   41337,41785,42236,42690,43147,43606,44069,44534,

-   45002,45473,45947,46423,46903,47385,47871,48359,

-   48850,49344,49841,50341,50844,51349,51858,52369,

-   52884,53401,53921,54445,54971,55500,56032,56567,

-   57105,57646,58190,58737,59287,59840,60396,60955,

-   61517,62082,62650,63221,63795,64372,64952,65535

-};

-

-#endif /* simplified read only */

-

-/* The base/delta tables are required for both read and write (but currently

- * only the simplified versions.)

- */

-const png_uint_16 png_sRGB_base[512] =

-{

-   128,1782,3383,4644,5675,6564,7357,8074,

-   8732,9346,9921,10463,10977,11466,11935,12384,

-   12816,13233,13634,14024,14402,14769,15125,15473,

-   15812,16142,16466,16781,17090,17393,17690,17981,

-   18266,18546,18822,19093,19359,19621,19879,20133,

-   20383,20630,20873,21113,21349,21583,21813,22041,

-   22265,22487,22707,22923,23138,23350,23559,23767,

-   23972,24175,24376,24575,24772,24967,25160,25352,

-   25542,25730,25916,26101,26284,26465,26645,26823,

-   27000,27176,27350,27523,27695,27865,28034,28201,

-   28368,28533,28697,28860,29021,29182,29341,29500,

-   29657,29813,29969,30123,30276,30429,30580,30730,

-   30880,31028,31176,31323,31469,31614,31758,31902,

-   32045,32186,32327,32468,32607,32746,32884,33021,

-   33158,33294,33429,33564,33697,33831,33963,34095,

-   34226,34357,34486,34616,34744,34873,35000,35127,

-   35253,35379,35504,35629,35753,35876,35999,36122,

-   36244,36365,36486,36606,36726,36845,36964,37083,

-   37201,37318,37435,37551,37668,37783,37898,38013,

-   38127,38241,38354,38467,38580,38692,38803,38915,

-   39026,39136,39246,39356,39465,39574,39682,39790,

-   39898,40005,40112,40219,40325,40431,40537,40642,

-   40747,40851,40955,41059,41163,41266,41369,41471,

-   41573,41675,41777,41878,41979,42079,42179,42279,

-   42379,42478,42577,42676,42775,42873,42971,43068,

-   43165,43262,43359,43456,43552,43648,43743,43839,

-   43934,44028,44123,44217,44311,44405,44499,44592,

-   44685,44778,44870,44962,45054,45146,45238,45329,

-   45420,45511,45601,45692,45782,45872,45961,46051,

-   46140,46229,46318,46406,46494,46583,46670,46758,

-   46846,46933,47020,47107,47193,47280,47366,47452,

-   47538,47623,47709,47794,47879,47964,48048,48133,

-   48217,48301,48385,48468,48552,48635,48718,48801,

-   48884,48966,49048,49131,49213,49294,49376,49458,

-   49539,49620,49701,49782,49862,49943,50023,50103,

-   50183,50263,50342,50422,50501,50580,50659,50738,

-   50816,50895,50973,51051,51129,51207,51285,51362,

-   51439,51517,51594,51671,51747,51824,51900,51977,

-   52053,52129,52205,52280,52356,52432,52507,52582,

-   52657,52732,52807,52881,52956,53030,53104,53178,

-   53252,53326,53400,53473,53546,53620,53693,53766,

-   53839,53911,53984,54056,54129,54201,54273,54345,

-   54417,54489,54560,54632,54703,54774,54845,54916,

-   54987,55058,55129,55199,55269,55340,55410,55480,

-   55550,55620,55689,55759,55828,55898,55967,56036,

-   56105,56174,56243,56311,56380,56448,56517,56585,

-   56653,56721,56789,56857,56924,56992,57059,57127,

-   57194,57261,57328,57395,57462,57529,57595,57662,

-   57728,57795,57861,57927,57993,58059,58125,58191,

-   58256,58322,58387,58453,58518,58583,58648,58713,

-   58778,58843,58908,58972,59037,59101,59165,59230,

-   59294,59358,59422,59486,59549,59613,59677,59740,

-   59804,59867,59930,59993,60056,60119,60182,60245,

-   60308,60370,60433,60495,60558,60620,60682,60744,

-   60806,60868,60930,60992,61054,61115,61177,61238,

-   61300,61361,61422,61483,61544,61605,61666,61727,

-   61788,61848,61909,61969,62030,62090,62150,62211,

-   62271,62331,62391,62450,62510,62570,62630,62689,

-   62749,62808,62867,62927,62986,63045,63104,63163,

-   63222,63281,63340,63398,63457,63515,63574,63632,

-   63691,63749,63807,63865,63923,63981,64039,64097,

-   64155,64212,64270,64328,64385,64443,64500,64557,

-   64614,64672,64729,64786,64843,64900,64956,65013,

-   65070,65126,65183,65239,65296,65352,65409,65465

-};

-

-const png_byte png_sRGB_delta[512] =

-{

-   207,201,158,129,113,100,90,82,77,72,68,64,61,59,56,54,

-   52,50,49,47,46,45,43,42,41,40,39,39,38,37,36,36,

-   35,34,34,33,33,32,32,31,31,30,30,30,29,29,28,28,

-   28,27,27,27,27,26,26,26,25,25,25,25,24,24,24,24,

-   23,23,23,23,23,22,22,22,22,22,22,21,21,21,21,21,

-   21,20,20,20,20,20,20,20,20,19,19,19,19,19,19,19,

-   19,18,18,18,18,18,18,18,18,18,18,17,17,17,17,17,

-   17,17,17,17,17,17,16,16,16,16,16,16,16,16,16,16,

-   16,16,16,16,15,15,15,15,15,15,15,15,15,15,15,15,

-   15,15,15,15,14,14,14,14,14,14,14,14,14,14,14,14,

-   14,14,14,14,14,14,14,13,13,13,13,13,13,13,13,13,

-   13,13,13,13,13,13,13,13,13,13,13,13,13,13,12,12,

-   12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,

-   12,12,12,12,12,12,12,12,12,12,12,12,11,11,11,11,

-   11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,

-   11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,

-   11,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,

-   10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,

-   10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,

-   10,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,

-   9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,

-   9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,

-   9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,

-   9,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,

-   8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,

-   8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,

-   8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,

-   8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,

-   8,8,8,8,8,8,8,8,8,7,7,7,7,7,7,7,

-   7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,

-   7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,

-   7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7

-};

-#endif /* SIMPLIFIED READ/WRITE sRGB support */

-

-/* SIMPLIFIED READ/WRITE SUPPORT */

-#if defined(PNG_SIMPLIFIED_READ_SUPPORTED) ||\

-   defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)

-static int

-png_image_free_function(png_voidp argument)

-{

-   png_imagep image = png_voidcast(png_imagep, argument);

-   png_controlp cp = image->opaque;

-   png_control c;

-

-   /* Double check that we have a png_ptr - it should be impossible to get here

-    * without one.

-    */

-   if (cp->png_ptr == NULL)

-      return 0;

-

-   /* First free any data held in the control structure. */

-#  ifdef PNG_STDIO_SUPPORTED

-      if (cp->owned_file)

-      {

-         FILE *fp = png_voidcast(FILE*, cp->png_ptr->io_ptr);

-         cp->owned_file = 0;

-

-         /* Ignore errors here. */

-         if (fp != NULL)

-         {

-            cp->png_ptr->io_ptr = NULL;

-            (void)fclose(fp);

-         }

-      }

-#  endif

-

-   /* Copy the control structure so that the original, allocated, version can be

-    * safely freed.  Notice that a png_error here stops the remainder of the

-    * cleanup, but this is probably fine because that would indicate bad memory

-    * problems anyway.

-    */

-   c = *cp;

-   image->opaque = &c;

-   png_free(c.png_ptr, cp);

-

-   /* Then the structures, calling the correct API. */

-   if (c.for_write)

-   {

-#     ifdef PNG_SIMPLIFIED_WRITE_SUPPORTED

-         png_destroy_write_struct(&c.png_ptr, &c.info_ptr);

-#     else

-         png_error(c.png_ptr, "simplified write not supported");

-#     endif

-   }

-   else

-   {

-#     ifdef PNG_SIMPLIFIED_READ_SUPPORTED

-         png_destroy_read_struct(&c.png_ptr, &c.info_ptr, NULL);

-#     else

-         png_error(c.png_ptr, "simplified read not supported");

-#     endif

-   }

-

-   /* Success. */

-   return 1;

-}

-

-void PNGAPI

-png_image_free(png_imagep image)

-{

-   /* Safely call the real function, but only if doing so is safe at this point

-    * (if not inside an error handling context).  Otherwise assume

-    * png_safe_execute will call this API after the return.

-    */

-   if (image != NULL && image->opaque != NULL &&

-      image->opaque->error_buf == NULL)

-   {

-      /* Ignore errors here: */

-      (void)png_safe_execute(image, png_image_free_function, image);

-      image->opaque = NULL;

-   }

-}

-

-int /* PRIVATE */

-png_image_error(png_imagep image, png_const_charp error_message)

-{

-   /* Utility to log an error. */

-   png_safecat(image->message, (sizeof image->message), 0, error_message);

-   image->warning_or_error |= PNG_IMAGE_ERROR;

-   png_image_free(image);

-   return 0;

-}

-

-#endif /* SIMPLIFIED READ/WRITE */

-#endif /* defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) */