X-Git-Url: https://git.saurik.com/wxWidgets.git/blobdiff_plain/b61cc19c06d9795c73fc6fbe893e92898938c70e..ba49d2acf95d53517719c4fd9ac2ad5aaa13540b:/src/png/pngrutil.c?ds=sidebyside

diff --git a/src/png/pngrutil.c b/src/png/pngrutil.c
index 11e412b729..52a73cfc39 100644
--- a/src/png/pngrutil.c
+++ b/src/png/pngrutil.c
@@ -1,8 +1,8 @@
 
 /* pngrutil.c - utilities to read a PNG file
  *
- * Last changed in libpng 1.4.4 [August 26, 2010]
- * Copyright (c) 1998-2010 Glenn Randers-Pehrson
+ * Last changed in libpng 1.5.7 [December 15, 2011]
+ * Copyright (c) 1998-2011 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.)
  *
@@ -14,32 +14,68 @@
  * libpng itself during the course of reading an image.
  */
 
-#define PNG_NO_PEDANTIC_WARNINGS
-#include "png.h"
-#ifdef PNG_READ_SUPPORTED
 #include "pngpriv.h"
 
-#    define png_strtod(p,a,b) strtod(a,b)
+#ifdef PNG_READ_SUPPORTED
+
+#define png_strtod(p,a,b) strtod(a,b)
+
 png_uint_32 PNGAPI
-png_get_uint_31(png_structp png_ptr, png_bytep buf)
+png_get_uint_31(png_structp png_ptr, png_const_bytep buf)
+{
+   png_uint_32 uval = png_get_uint_32(buf);
+
+   if (uval > PNG_UINT_31_MAX)
+      png_error(png_ptr, "PNG unsigned integer out of range");
+
+   return (uval);
+}
+
+#if defined(PNG_READ_gAMA_SUPPORTED) || defined(PNG_READ_cHRM_SUPPORTED)
+/* The following is a variation on the above for use with the fixed
+ * point values used for gAMA and cHRM.  Instead of png_error it
+ * issues a warning and returns (-1) - an invalid value because both
+ * gAMA and cHRM use *unsigned* integers for fixed point values.
+ */
+#define PNG_FIXED_ERROR (-1)
+
+static png_fixed_point /* PRIVATE */
+png_get_fixed_point(png_structp png_ptr, png_const_bytep buf)
 {
-   png_uint_32 i = png_get_uint_32(buf);
-   if (i > PNG_UINT_31_MAX)
-     png_error(png_ptr, "PNG unsigned integer out of range");
-   return (i);
+   png_uint_32 uval = png_get_uint_32(buf);
+
+   if (uval <= PNG_UINT_31_MAX)
+      return (png_fixed_point)uval; /* known to be in range */
+
+   /* The caller can turn off the warning by passing NULL. */
+   if (png_ptr != NULL)
+      png_warning(png_ptr, "PNG fixed point integer out of range");
+
+   return PNG_FIXED_ERROR;
 }
-#ifndef PNG_USE_READ_MACROS
+#endif
+
+#ifdef PNG_READ_INT_FUNCTIONS_SUPPORTED
+/* NOTE: the read macros will obscure these definitions, so that if
+ * PNG_USE_READ_MACROS is set the library will not use them internally,
+ * but the APIs will still be available externally.
+ *
+ * The parentheses around "PNGAPI function_name" in the following three
+ * functions are necessary because they allow the macros to co-exist with
+ * these (unused but exported) functions.
+ */
+
 /* Grab an unsigned 32-bit integer from a buffer in big-endian format. */
 png_uint_32 (PNGAPI
-png_get_uint_32)(png_bytep buf)
+png_get_uint_32)(png_const_bytep buf)
 {
-   png_uint_32 i =
+   png_uint_32 uval =
        ((png_uint_32)(*(buf    )) << 24) +
        ((png_uint_32)(*(buf + 1)) << 16) +
        ((png_uint_32)(*(buf + 2)) <<  8) +
        ((png_uint_32)(*(buf + 3))      ) ;
 
-   return (i);
+   return uval;
 }
 
 /* Grab a signed 32-bit integer from a buffer in big-endian format.  The
@@ -48,27 +84,66 @@ png_get_uint_32)(png_bytep buf)
  * the following code does a two's complement to native conversion.
  */
 png_int_32 (PNGAPI
-png_get_int_32)(png_bytep buf)
+png_get_int_32)(png_const_bytep buf)
 {
-   png_uint_32 u = png_get_uint_32(buf);
-   if ((u & 0x80000000) == 0) /* non-negative */
-      return u;
+   png_uint_32 uval = png_get_uint_32(buf);
+   if ((uval & 0x80000000) == 0) /* non-negative */
+      return uval;
 
-   u = (u ^ 0xffffffff) + 1;  /* 2's complement: -x = ~x+1 */
-   return -(png_int_32)u;
+   uval = (uval ^ 0xffffffff) + 1;  /* 2's complement: -x = ~x+1 */
+   return -(png_int_32)uval;
 }
 
 /* Grab an unsigned 16-bit integer from a buffer in big-endian format. */
 png_uint_16 (PNGAPI
-png_get_uint_16)(png_bytep buf)
+png_get_uint_16)(png_const_bytep buf)
+{
+   /* ANSI-C requires an int value to accomodate at least 16 bits so this
+    * works and allows the compiler not to worry about possible narrowing
+    * on 32 bit systems.  (Pre-ANSI systems did not make integers smaller
+    * than 16 bits either.)
+    */
+   unsigned int val =
+       ((unsigned int)(*buf) << 8) +
+       ((unsigned int)(*(buf + 1)));
+
+   return (png_uint_16)val;
+}
+
+#endif /* PNG_READ_INT_FUNCTIONS_SUPPORTED */
+
+/* Read and check the PNG file signature */
+void /* PRIVATE */
+png_read_sig(png_structp png_ptr, png_infop info_ptr)
 {
-   png_uint_16 i =
-       ((png_uint_32)(*buf) << 8) +
-       ((png_uint_32)(*(buf + 1)));
+   png_size_t num_checked, num_to_check;
+
+   /* Exit if the user application does not expect a signature. */
+   if (png_ptr->sig_bytes >= 8)
+      return;
+
+   num_checked = png_ptr->sig_bytes;
+   num_to_check = 8 - num_checked;
+
+#ifdef PNG_IO_STATE_SUPPORTED
+   png_ptr->io_state = PNG_IO_READING | PNG_IO_SIGNATURE;
+#endif
 
-   return (i);
+   /* The signature must be serialized in a single I/O call. */
+   png_read_data(png_ptr, &(info_ptr->signature[num_checked]), num_to_check);
+   png_ptr->sig_bytes = 8;
+
+   if (png_sig_cmp(info_ptr->signature, num_checked, num_to_check))
+   {
+      if (num_checked < 4 &&
+          png_sig_cmp(info_ptr->signature, num_checked, num_to_check - 4))
+         png_error(png_ptr, "Not a PNG file");
+      else
+         png_error(png_ptr, "PNG file corrupted by ASCII conversion");
+   }
+   if (num_checked < 3)
+      png_ptr->mode |= PNG_HAVE_PNG_SIGNATURE;
 }
-#endif /* PNG_USE_READ_MACROS */
 
 /* Read the chunk header (length + type name).
  * Put the type name into png_ptr->chunk_name, and return the length.
@@ -80,33 +155,29 @@ png_read_chunk_header(png_structp png_ptr)
    png_uint_32 length;
 
 #ifdef PNG_IO_STATE_SUPPORTED
-   /* Inform the I/O callback that the chunk header is being read.
-    * PNG_IO_CHUNK_HDR requires a single I/O call.
-    */
    png_ptr->io_state = PNG_IO_READING | PNG_IO_CHUNK_HDR;
 #endif
 
-   /* Read the length and the chunk name */
+   /* Read the length and the chunk name.
+    * This must be performed in a single I/O call.
+    */
    png_read_data(png_ptr, buf, 8);
    length = png_get_uint_31(png_ptr, buf);
 
-   /* Put the chunk name into png_ptr->chunk_name */
-   png_memcpy(png_ptr->chunk_name, buf + 4, 4);
+   /* Put the chunk name into png_ptr->chunk_name. */
+   png_ptr->chunk_name = PNG_CHUNK_FROM_STRING(buf+4);
 
-   png_debug2(0, "Reading %s chunk, length = %lu",
-      png_ptr->chunk_name, length);
+   png_debug2(0, "Reading %lx chunk, length = %lu",
+       (unsigned long)png_ptr->chunk_name, (unsigned long)length);
 
-   /* Reset the crc and run it over the chunk name */
+   /* Reset the crc and run it over the chunk name. */
    png_reset_crc(png_ptr);
-   png_calculate_crc(png_ptr, png_ptr->chunk_name, 4);
+   png_calculate_crc(png_ptr, buf + 4, 4);
 
-   /* Check to see if chunk name is valid */
+   /* Check to see if chunk name is valid. */
    png_check_chunk_name(png_ptr, png_ptr->chunk_name);
 
 #ifdef PNG_IO_STATE_SUPPORTED
-   /* Inform the I/O callback that chunk data will (possibly) be read.
-    * PNG_IO_CHUNK_DATA does NOT require a specific number of I/O calls.
-    */
    png_ptr->io_state = PNG_IO_READING | PNG_IO_CHUNK_DATA;
 #endif
 
@@ -119,6 +190,7 @@ png_crc_read(png_structp png_ptr, png_bytep buf, png_size_t length)
 {
    if (png_ptr == NULL)
       return;
+
    png_read_data(png_ptr, buf, length);
    png_calculate_crc(png_ptr, buf, length);
 }
@@ -138,6 +210,7 @@ png_crc_finish(png_structp png_ptr, png_uint_32 skip)
    {
       png_crc_read(png_ptr, png_ptr->zbuf, png_ptr->zbuf_size);
    }
+
    if (i)
    {
       png_crc_read(png_ptr, png_ptr->zbuf, i);
@@ -145,18 +218,19 @@ png_crc_finish(png_structp png_ptr, png_uint_32 skip)
 
    if (png_crc_error(png_ptr))
    {
-      if (((png_ptr->chunk_name[0] & 0x20) &&                /* Ancillary */
-          !(png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_NOWARN)) ||
-          (!(png_ptr->chunk_name[0] & 0x20) &&             /* Critical  */
-          (png_ptr->flags & PNG_FLAG_CRC_CRITICAL_USE)))
+      if (PNG_CHUNK_ANCILLIARY(png_ptr->chunk_name) ?
+          !(png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_NOWARN) :
+          (png_ptr->flags & PNG_FLAG_CRC_CRITICAL_USE))
       {
          png_chunk_warning(png_ptr, "CRC error");
       }
+
       else
       {
          png_chunk_benign_error(png_ptr, "CRC error");
          return (0);
       }
+
       return (1);
    }
 
@@ -173,24 +247,24 @@ png_crc_error(png_structp png_ptr)
    png_uint_32 crc;
    int need_crc = 1;
 
-   if (png_ptr->chunk_name[0] & 0x20)                     /* ancillary */
+   if (PNG_CHUNK_ANCILLIARY(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 */
+
+   else /* critical */
    {
       if (png_ptr->flags & PNG_FLAG_CRC_CRITICAL_IGNORE)
          need_crc = 0;
    }
 
 #ifdef PNG_IO_STATE_SUPPORTED
-   /* Inform the I/O callback that the chunk CRC is being read */
-   /* PNG_IO_CHUNK_CRC requires the I/O to be done at once */
    png_ptr->io_state = PNG_IO_READING | PNG_IO_CHUNK_CRC;
 #endif
 
+   /* The chunk CRC must be serialized in a single I/O call. */
    png_read_data(png_ptr, crc_bytes, 4);
 
    if (need_crc)
@@ -198,25 +272,58 @@ png_crc_error(png_structp png_ptr)
       crc = png_get_uint_32(crc_bytes);
       return ((int)(crc != png_ptr->crc));
    }
+
    else
       return (0);
 }
 
-#if defined(PNG_READ_zTXt_SUPPORTED) || defined(PNG_READ_iTXt_SUPPORTED) || \
-    defined(PNG_READ_iCCP_SUPPORTED)
+#ifdef PNG_READ_COMPRESSED_TEXT_SUPPORTED
 static png_size_t
-png_inflate(png_structp png_ptr, const png_byte *data, png_size_t size,
-        png_bytep output, png_size_t output_size)
+png_inflate(png_structp png_ptr, png_bytep data, png_size_t size,
+    png_bytep output, png_size_t output_size)
 {
    png_size_t count = 0;
 
-   png_ptr->zstream.next_in = (png_bytep)data; /* const_cast: VALID */
-   png_ptr->zstream.avail_in = size;
+   /* zlib can't necessarily handle more than 65535 bytes at once (i.e. it can't
+    * even necessarily handle 65536 bytes) because the type uInt is "16 bits or
+    * more".  Consequently it is necessary to chunk the input to zlib.  This
+    * code uses ZLIB_IO_MAX, from pngpriv.h, as the maximum (the maximum value
+    * that can be stored in a uInt.)  It is possible to set ZLIB_IO_MAX to a
+    * lower value in pngpriv.h and this may sometimes have a performance
+    * advantage, because it forces access of the input data to be separated from
+    * at least some of the use by some period of time.
+    */
+   png_ptr->zstream.next_in = data;
+   /* avail_in is set below from 'size' */
+   png_ptr->zstream.avail_in = 0;
 
    while (1)
    {
       int ret, avail;
 
+      /* The setting of 'avail_in' used to be outside the loop; by setting it
+       * inside it is possible to chunk the input to zlib and simply rely on
+       * zlib to advance the 'next_in' pointer.  This allows arbitrary amounts o
+       * data to be passed through zlib at the unavoidable cost of requiring a
+       * window save (memcpy of up to 32768 output bytes) every ZLIB_IO_MAX
+       * input bytes.
+       */
+      if (png_ptr->zstream.avail_in == 0 && size > 0)
+      {
+         if (size <= ZLIB_IO_MAX)
+         {
+            /* The value is less than ZLIB_IO_MAX so the cast is safe: */
+            png_ptr->zstream.avail_in = (uInt)size;
+            size = 0;
+         }
+
+         else
+         {
+            png_ptr->zstream.avail_in = ZLIB_IO_MAX;
+            size -= ZLIB_IO_MAX;
+         }
+      }
+
       /* Reset the output buffer each time round - we empty it
        * after every inflate call.
        */
@@ -231,13 +338,18 @@ png_inflate(png_structp png_ptr, const png_byte *data, png_size_t size,
        */
       if ((ret == Z_OK || ret == Z_STREAM_END) && avail > 0)
       {
+         png_size_t space = avail; /* > 0, see above */
+
          if (output != 0 && output_size > count)
          {
-            int copy = output_size - count;
-            if (avail < copy) copy = avail;
+            png_size_t copy = output_size - count;
+
+            if (space < copy)
+               copy = space;
+
             png_memcpy(output + count, png_ptr->zbuf, copy);
          }
-         count += avail;
+         count += space;
       }
 
       if (ret == Z_OK)
@@ -256,39 +368,33 @@ png_inflate(png_structp png_ptr, const png_byte *data, png_size_t size,
        * and the error message is dumped into the uncompressed
        * buffer if available.
        */
+#     ifdef PNG_WARNINGS_SUPPORTED
       {
-         PNG_CONST char *msg;
+         png_const_charp msg;
+
          if (png_ptr->zstream.msg != 0)
             msg = png_ptr->zstream.msg;
-         else
+
+         else switch (ret)
          {
-#ifdef PNG_STDIO_SUPPORTED
-            char umsg[52];
+            case Z_BUF_ERROR:
+               msg = "Buffer error in compressed datastream";
+               break;
 
-            switch (ret)
-            {
-               case Z_BUF_ERROR:
-                  msg = "Buffer error in compressed datastream in %s chunk";
-                  break;
-               case Z_DATA_ERROR:
-                  msg = "Data error in compressed datastream in %s chunk";
-                  break;
-               default:
-                  msg = "Incomplete compressed datastream in %s chunk";
-                  break;
-            }
+            case Z_DATA_ERROR:
+               msg = "Data error in compressed datastream";
+               break;
 
-            png_snprintf(umsg, sizeof umsg, msg, png_ptr->chunk_name);
-            msg = umsg;
-#else
-            msg = "Damaged compressed datastream in chunk other than IDAT";
-#endif
+            default:
+               msg = "Incomplete compressed datastream";
+               break;
          }
 
-         png_warning(png_ptr, msg);
+         png_chunk_warning(png_ptr, msg);
       }
+#     endif
 
-      /* 0 means an error - notice that this code simple ignores
+      /* 0 means an error - notice that this code simply ignores
        * zero length compressed chunks as a result.
        */
       return 0;
@@ -318,9 +424,10 @@ png_decompress_chunk(png_structp png_ptr, int comp_type,
    else if (comp_type == PNG_COMPRESSION_TYPE_BASE)
    {
       png_size_t expanded_size = png_inflate(png_ptr,
-                (png_bytep)(png_ptr->chunkdata + prefix_size),
-                chunklength - prefix_size,
-                0/*output*/, 0/*output size*/);
+          (png_bytep)(png_ptr->chunkdata + prefix_size),
+          chunklength - prefix_size,
+          0,            /* output */
+          0);           /* output size */
 
       /* Now check the limits on this chunk - if the limit fails the
        * compressed data will be removed, the prefix will remain.
@@ -343,14 +450,15 @@ png_decompress_chunk(png_structp png_ptr, int comp_type,
        */
 #if defined(PNG_SET_CHUNK_MALLOC_LIMIT_SUPPORTED) || \
     defined(PNG_USER_CHUNK_MALLOC_MAX)
-      else
-#endif
+      else if (expanded_size > 0)
+#else
       if (expanded_size > 0)
+#endif
       {
          /* Success (maybe) - really uncompress the chunk. */
          png_size_t new_size = 0;
-         png_charp text = png_malloc_warn(png_ptr,
-                        prefix_size + expanded_size + 1);
+         png_charp text = (png_charp)png_malloc_warn(png_ptr,
+             prefix_size + expanded_size + 1);
 
          if (text != NULL)
          {
@@ -372,22 +480,17 @@ png_decompress_chunk(png_structp png_ptr, int comp_type,
             png_warning(png_ptr, "png_inflate logic error");
             png_free(png_ptr, text);
          }
+
          else
-          png_warning(png_ptr, "Not enough memory to decompress chunk");
+            png_warning(png_ptr, "Not enough memory to decompress chunk");
       }
    }
 
    else /* if (comp_type != PNG_COMPRESSION_TYPE_BASE) */
    {
-#ifdef PNG_STDIO_SUPPORTED
-      char umsg[50];
-
-      png_snprintf(umsg, sizeof umsg, "Unknown zTXt compression type %d",
-          comp_type);
-      png_warning(png_ptr, umsg);
-#else
-      png_warning(png_ptr, "Unknown zTXt compression type");
-#endif
+      PNG_WARNING_PARAMETERS(p)
+      png_warning_parameter_signed(p, 1, PNG_NUMBER_FORMAT_d, comp_type);
+      png_formatted_warning(png_ptr, p, "Unknown compression type @1");
 
       /* The recovery is to simply drop the data. */
    }
@@ -397,11 +500,13 @@ png_decompress_chunk(png_structp png_ptr, int comp_type,
     * amount of compressed data.
     */
    {
-      png_charp text = png_malloc_warn(png_ptr, prefix_size + 1);
+      png_charp text = (png_charp)png_malloc_warn(png_ptr, prefix_size + 1);
+
       if (text != NULL)
       {
          if (prefix_size > 0)
             png_memcpy(text, png_ptr->chunkdata, prefix_size);
+
          png_free(png_ptr, png_ptr->chunkdata);
          png_ptr->chunkdata = text;
 
@@ -413,7 +518,7 @@ png_decompress_chunk(png_structp png_ptr, int comp_type,
 
    *newlength = prefix_size;
 }
-#endif
+#endif /* PNG_READ_COMPRESSED_TEXT_SUPPORTED */
 
 /* Read and check the IDHR chunk */
 void /* PRIVATE */
@@ -460,6 +565,7 @@ png_handle_IHDR(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    /* Find number of channels */
    switch (png_ptr->color_type)
    {
+      default: /* invalid, png_set_IHDR calls png_error */
       case PNG_COLOR_TYPE_GRAY:
       case PNG_COLOR_TYPE_PALETTE:
          png_ptr->channels = 1;
@@ -484,9 +590,9 @@ png_handle_IHDR(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    png_ptr->rowbytes = PNG_ROWBYTES(png_ptr->pixel_depth, png_ptr->width);
    png_debug1(3, "bit_depth = %d", png_ptr->bit_depth);
    png_debug1(3, "channels = %d", png_ptr->channels);
-   png_debug1(3, "rowbytes = %lu", png_ptr->rowbytes);
+   png_debug1(3, "rowbytes = %lu", (unsigned long)png_ptr->rowbytes);
    png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth,
-      color_type, interlace_type, compression_type, filter_type);
+       color_type, interlace_type, compression_type, filter_type);
 }
 
 /* Read and check the palette */
@@ -519,10 +625,11 @@ png_handle_PLTE(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    if (!(png_ptr->color_type&PNG_COLOR_MASK_COLOR))
    {
       png_warning(png_ptr,
-        "Ignoring PLTE chunk in grayscale PNG");
+          "Ignoring PLTE chunk in grayscale PNG");
       png_crc_finish(png_ptr, length);
       return;
    }
+
 #ifndef PNG_READ_OPT_PLTE_SUPPORTED
    if (png_ptr->color_type != PNG_COLOR_TYPE_PALETTE)
    {
@@ -571,7 +678,7 @@ png_handle_PLTE(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    }
 #endif
 
-   /* If we actually NEED the PLTE chunk (ie for a paletted image), we do
+   /* If we actually need the PLTE chunk (ie for a paletted image), we do
     * whatever the normal CRC configuration tells us.  However, if we
     * have an RGB image, the PLTE can be considered ancillary, so
     * we will act as though it is.
@@ -582,25 +689,29 @@ png_handle_PLTE(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    {
       png_crc_finish(png_ptr, 0);
    }
+
 #ifndef PNG_READ_OPT_PLTE_SUPPORTED
    else if (png_crc_error(png_ptr))  /* Only if we have a CRC error */
    {
       /* If we don't want to use the data from an ancillary chunk,
-         we have two options: an error abort, or a warning and we
-         ignore the data in this chunk (which should be OK, since
-         it's considered ancillary for a RGB or RGBA image). */
+       * we have two options: an error abort, or a warning and we
+       * ignore the data in this chunk (which should be OK, since
+       * it's considered ancillary for a RGB or RGBA image).
+       */
       if (!(png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_USE))
       {
          if (png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_NOWARN)
          {
             png_chunk_benign_error(png_ptr, "CRC error");
          }
+
          else
          {
             png_chunk_warning(png_ptr, "CRC error");
             return;
          }
       }
+
       /* Otherwise, we (optionally) emit a warning and use the chunk. */
       else if (!(png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_NOWARN))
       {
@@ -621,6 +732,7 @@ png_handle_PLTE(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
             png_warning(png_ptr, "Truncating incorrect tRNS chunk length");
             png_ptr->num_trans = (png_uint_16)num;
          }
+
          if (info_ptr->num_trans > (png_uint_16)num)
          {
             png_warning(png_ptr, "Truncating incorrect info tRNS chunk length");
@@ -648,9 +760,10 @@ png_handle_IEND(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    {
       png_warning(png_ptr, "Incorrect IEND chunk length");
    }
+
    png_crc_finish(png_ptr, length);
 
-   info_ptr = info_ptr; /* Quiet compiler warnings about unused info_ptr */
+   PNG_UNUSED(info_ptr) /* Quiet compiler warnings about unused info_ptr */
 }
 
 #ifdef PNG_READ_gAMA_SUPPORTED
@@ -658,30 +771,29 @@ void /* PRIVATE */
 png_handle_gAMA(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 {
    png_fixed_point igamma;
-#ifdef PNG_FLOATING_POINT_SUPPORTED
-   float file_gamma;
-#endif
    png_byte buf[4];
 
    png_debug(1, "in png_handle_gAMA");
 
    if (!(png_ptr->mode & PNG_HAVE_IHDR))
       png_error(png_ptr, "Missing IHDR before gAMA");
+
    else if (png_ptr->mode & PNG_HAVE_IDAT)
    {
       png_warning(png_ptr, "Invalid gAMA after IDAT");
       png_crc_finish(png_ptr, length);
       return;
    }
+
    else if (png_ptr->mode & PNG_HAVE_PLTE)
       /* Should be an error, but we can cope with it */
       png_warning(png_ptr, "Out of place gAMA chunk");
 
    if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_gAMA)
 #ifdef PNG_READ_sRGB_SUPPORTED
-      && !(info_ptr->valid & PNG_INFO_sRGB)
+       && !(info_ptr->valid & PNG_INFO_sRGB)
 #endif
-      )
+       )
    {
       png_warning(png_ptr, "Duplicate gAMA chunk");
       png_crc_finish(png_ptr, length);
@@ -696,41 +808,41 @@ png_handle_gAMA(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    }
 
    png_crc_read(png_ptr, buf, 4);
+
    if (png_crc_finish(png_ptr, 0))
       return;
 
-   igamma = (png_fixed_point)png_get_uint_32(buf);
-   /* Check for zero gamma */
-   if (igamma == 0)
-      {
-         png_warning(png_ptr,
-           "Ignoring gAMA chunk with gamma=0");
-         return;
-      }
+   igamma = png_get_fixed_point(NULL, buf);
 
-#ifdef PNG_READ_sRGB_SUPPORTED
+   /* Check for zero gamma or an error. */
+   if (igamma <= 0)
+   {
+      png_warning(png_ptr,
+          "Ignoring gAMA chunk with out of range gamma");
+
+      return;
+   }
+
+#  ifdef PNG_READ_sRGB_SUPPORTED
    if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_sRGB))
-      if (PNG_OUT_OF_RANGE(igamma, 45500L, 500))
+   {
+      if (PNG_OUT_OF_RANGE(igamma, 45500, 500))
       {
-         png_warning(png_ptr,
-           "Ignoring incorrect gAMA value when sRGB is also present");
-#ifdef PNG_CONSOLE_IO_SUPPORTED
-         fprintf(stderr, "gamma = (%d/100000)", (int)igamma);
-#endif
+         PNG_WARNING_PARAMETERS(p)
+         png_warning_parameter_signed(p, 1, PNG_NUMBER_FORMAT_fixed, igamma);
+         png_formatted_warning(png_ptr, p,
+             "Ignoring incorrect gAMA value @1 when sRGB is also present");
          return;
       }
-#endif /* PNG_READ_sRGB_SUPPORTED */
+   }
+#  endif /* PNG_READ_sRGB_SUPPORTED */
 
-#ifdef PNG_FLOATING_POINT_SUPPORTED
-   file_gamma = (float)igamma / (float)100000.0;
 #  ifdef PNG_READ_GAMMA_SUPPORTED
-     png_ptr->gamma = file_gamma;
+   /* Gamma correction on read is supported. */
+   png_ptr->gamma = igamma;
 #  endif
-     png_set_gAMA(png_ptr, info_ptr, file_gamma);
-#endif
-#ifdef PNG_FIXED_POINT_SUPPORTED
+   /* And set the 'info' structure members. */
    png_set_gAMA_fixed(png_ptr, info_ptr, igamma);
-#endif
 }
 #endif
 
@@ -747,17 +859,20 @@ png_handle_sBIT(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 
    if (!(png_ptr->mode & PNG_HAVE_IHDR))
       png_error(png_ptr, "Missing IHDR before sBIT");
+
    else if (png_ptr->mode & PNG_HAVE_IDAT)
    {
       png_warning(png_ptr, "Invalid sBIT after IDAT");
       png_crc_finish(png_ptr, length);
       return;
    }
+
    else if (png_ptr->mode & PNG_HAVE_PLTE)
    {
       /* Should be an error, but we can cope with it */
       png_warning(png_ptr, "Out of place sBIT chunk");
    }
+
    if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_sBIT))
    {
       png_warning(png_ptr, "Duplicate sBIT chunk");
@@ -767,6 +882,7 @@ png_handle_sBIT(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 
    if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
       truelen = 3;
+
    else
       truelen = (png_size_t)png_ptr->channels;
 
@@ -778,6 +894,7 @@ png_handle_sBIT(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    }
 
    png_crc_read(png_ptr, buf, truelen);
+
    if (png_crc_finish(png_ptr, 0))
       return;
 
@@ -788,6 +905,7 @@ png_handle_sBIT(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
       png_ptr->sig_bit.blue = buf[2];
       png_ptr->sig_bit.alpha = buf[3];
    }
+
    else
    {
       png_ptr->sig_bit.gray = buf[0];
@@ -796,6 +914,7 @@ png_handle_sBIT(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
       png_ptr->sig_bit.blue = buf[0];
       png_ptr->sig_bit.alpha = buf[1];
    }
+
    png_set_sBIT(png_ptr, info_ptr, &(png_ptr->sig_bit));
 }
 #endif
@@ -805,32 +924,29 @@ void /* PRIVATE */
 png_handle_cHRM(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 {
    png_byte buf[32];
-#ifdef PNG_FLOATING_POINT_SUPPORTED
-   float white_x, white_y, red_x, red_y, green_x, green_y, blue_x, blue_y;
-#endif
-   png_fixed_point int_x_white, int_y_white, int_x_red, int_y_red, int_x_green,
-      int_y_green, int_x_blue, int_y_blue;
-
-   png_uint_32 uint_x, uint_y;
+   png_fixed_point x_white, y_white, x_red, y_red, x_green, y_green, x_blue,
+      y_blue;
 
    png_debug(1, "in png_handle_cHRM");
 
    if (!(png_ptr->mode & PNG_HAVE_IHDR))
       png_error(png_ptr, "Missing IHDR before cHRM");
+
    else if (png_ptr->mode & PNG_HAVE_IDAT)
    {
       png_warning(png_ptr, "Invalid cHRM after IDAT");
       png_crc_finish(png_ptr, length);
       return;
    }
+
    else if (png_ptr->mode & PNG_HAVE_PLTE)
       /* Should be an error, but we can cope with it */
-      png_warning(png_ptr, "Missing PLTE before cHRM");
+      png_warning(png_ptr, "Out of place cHRM chunk");
 
    if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_cHRM)
-#ifdef PNG_READ_sRGB_SUPPORTED
-      && !(info_ptr->valid & PNG_INFO_sRGB)
-#endif
+#  ifdef PNG_READ_sRGB_SUPPORTED
+       && !(info_ptr->valid & PNG_INFO_sRGB)
+#  endif
       )
    {
       png_warning(png_ptr, "Duplicate cHRM chunk");
@@ -846,83 +962,145 @@ png_handle_cHRM(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    }
 
    png_crc_read(png_ptr, buf, 32);
+
    if (png_crc_finish(png_ptr, 0))
       return;
 
-   uint_x = png_get_uint_32(buf);
-   uint_y = png_get_uint_32(buf + 4);
-   int_x_white = (png_fixed_point)uint_x;
-   int_y_white = (png_fixed_point)uint_y;
-
-   uint_x = png_get_uint_32(buf + 8);
-   uint_y = png_get_uint_32(buf + 12);
-   int_x_red = (png_fixed_point)uint_x;
-   int_y_red = (png_fixed_point)uint_y;
-
-   uint_x = png_get_uint_32(buf + 16);
-   uint_y = png_get_uint_32(buf + 20);
-   int_x_green = (png_fixed_point)uint_x;
-   int_y_green = (png_fixed_point)uint_y;
-
-   uint_x = png_get_uint_32(buf + 24);
-   uint_y = png_get_uint_32(buf + 28);
-   int_x_blue = (png_fixed_point)uint_x;
-   int_y_blue = (png_fixed_point)uint_y;
-
-#ifdef PNG_FLOATING_POINT_SUPPORTED
-   white_x = (float)int_x_white / (float)100000.0;
-   white_y = (float)int_y_white / (float)100000.0;
-   red_x   = (float)int_x_red   / (float)100000.0;
-   red_y   = (float)int_y_red   / (float)100000.0;
-   green_x = (float)int_x_green / (float)100000.0;
-   green_y = (float)int_y_green / (float)100000.0;
-   blue_x  = (float)int_x_blue  / (float)100000.0;
-   blue_y  = (float)int_y_blue  / (float)100000.0;
-#endif
+   x_white = png_get_fixed_point(NULL, buf);
+   y_white = png_get_fixed_point(NULL, buf + 4);
+   x_red   = png_get_fixed_point(NULL, buf + 8);
+   y_red   = png_get_fixed_point(NULL, buf + 12);
+   x_green = png_get_fixed_point(NULL, buf + 16);
+   y_green = png_get_fixed_point(NULL, buf + 20);
+   x_blue  = png_get_fixed_point(NULL, buf + 24);
+   y_blue  = png_get_fixed_point(NULL, buf + 28);
+
+   if (x_white == PNG_FIXED_ERROR ||
+       y_white == PNG_FIXED_ERROR ||
+       x_red   == PNG_FIXED_ERROR ||
+       y_red   == PNG_FIXED_ERROR ||
+       x_green == PNG_FIXED_ERROR ||
+       y_green == PNG_FIXED_ERROR ||
+       x_blue  == PNG_FIXED_ERROR ||
+       y_blue  == PNG_FIXED_ERROR)
+   {
+      png_warning(png_ptr, "Ignoring cHRM chunk with negative chromaticities");
+      return;
+   }
 
 #ifdef PNG_READ_sRGB_SUPPORTED
    if ((info_ptr != NULL) && (info_ptr->valid & PNG_INFO_sRGB))
+   {
+      if (PNG_OUT_OF_RANGE(x_white, 31270,  1000) ||
+          PNG_OUT_OF_RANGE(y_white, 32900,  1000) ||
+          PNG_OUT_OF_RANGE(x_red,   64000,  1000) ||
+          PNG_OUT_OF_RANGE(y_red,   33000,  1000) ||
+          PNG_OUT_OF_RANGE(x_green, 30000,  1000) ||
+          PNG_OUT_OF_RANGE(y_green, 60000,  1000) ||
+          PNG_OUT_OF_RANGE(x_blue,  15000,  1000) ||
+          PNG_OUT_OF_RANGE(y_blue,   6000,  1000))
       {
-      if (PNG_OUT_OF_RANGE(int_x_white, 31270,  1000) ||
-          PNG_OUT_OF_RANGE(int_y_white, 32900,  1000) ||
-          PNG_OUT_OF_RANGE(int_x_red,   64000L, 1000) ||
-          PNG_OUT_OF_RANGE(int_y_red,   33000,  1000) ||
-          PNG_OUT_OF_RANGE(int_x_green, 30000,  1000) ||
-          PNG_OUT_OF_RANGE(int_y_green, 60000L, 1000) ||
-          PNG_OUT_OF_RANGE(int_x_blue,  15000,  1000) ||
-          PNG_OUT_OF_RANGE(int_y_blue,   6000,  1000))
-         {
-            png_warning(png_ptr,
-              "Ignoring incorrect cHRM value when sRGB is also present");
-#ifdef PNG_CONSOLE_IO_SUPPORTED
-#ifdef PNG_FLOATING_POINT_SUPPORTED
-            fprintf(stderr, "wx=%f, wy=%f, rx=%f, ry=%f\n",
-               white_x, white_y, red_x, red_y);
-            fprintf(stderr, "gx=%f, gy=%f, bx=%f, by=%f\n",
-               green_x, green_y, blue_x, blue_y);
-#else
-            fprintf(stderr, "wx=%ld, wy=%ld, rx=%ld, ry=%ld\n",
-               (long)int_x_white, (long)int_y_white,
-               (long)int_x_red, (long)int_y_red);
-            fprintf(stderr, "gx=%ld, gy=%ld, bx=%ld, by=%ld\n",
-               (long)int_x_green, (long)int_y_green,
-               (long)int_x_blue, (long)int_y_blue);
-#endif
-#endif /* PNG_CONSOLE_IO_SUPPORTED */
-         }
-         return;
+         PNG_WARNING_PARAMETERS(p)
+
+         png_warning_parameter_signed(p, 1, PNG_NUMBER_FORMAT_fixed, x_white);
+         png_warning_parameter_signed(p, 2, PNG_NUMBER_FORMAT_fixed, y_white);
+         png_warning_parameter_signed(p, 3, PNG_NUMBER_FORMAT_fixed, x_red);
+         png_warning_parameter_signed(p, 4, PNG_NUMBER_FORMAT_fixed, y_red);
+         png_warning_parameter_signed(p, 5, PNG_NUMBER_FORMAT_fixed, x_green);
+         png_warning_parameter_signed(p, 6, PNG_NUMBER_FORMAT_fixed, y_green);
+         png_warning_parameter_signed(p, 7, PNG_NUMBER_FORMAT_fixed, x_blue);
+         png_warning_parameter_signed(p, 8, PNG_NUMBER_FORMAT_fixed, y_blue);
+
+         png_formatted_warning(png_ptr, p,
+             "Ignoring incorrect cHRM white(@1,@2) r(@3,@4)g(@5,@6)b(@7,@8) "
+             "when sRGB is also present");
       }
+      return;
+   }
 #endif /* PNG_READ_sRGB_SUPPORTED */
 
-#ifdef PNG_FLOATING_POINT_SUPPORTED
-   png_set_cHRM(png_ptr, info_ptr,
-      white_x, white_y, red_x, red_y, green_x, green_y, blue_x, blue_y);
-#endif
-#ifdef PNG_FIXED_POINT_SUPPORTED
-   png_set_cHRM_fixed(png_ptr, info_ptr,
-      int_x_white, int_y_white, int_x_red, int_y_red, int_x_green,
-      int_y_green, int_x_blue, int_y_blue);
+#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
+   /* Store the _white values as default coefficients for the rgb to gray
+    * operation if it is supported.  Check if the transform is already set to
+    * avoid destroying the transform values.
+    */
+   if (!png_ptr->rgb_to_gray_coefficients_set)
+   {
+      /* png_set_background has not been called and we haven't seen an sRGB
+       * chunk yet.  Find the XYZ of the three end points.
+       */
+      png_XYZ XYZ;
+      png_xy xy;
+
+      xy.redx = x_red;
+      xy.redy = y_red;
+      xy.greenx = x_green;
+      xy.greeny = y_green;
+      xy.bluex = x_blue;
+      xy.bluey = y_blue;
+      xy.whitex = x_white;
+      xy.whitey = y_white;
+
+      if (png_XYZ_from_xy_checked(png_ptr, &XYZ, xy))
+      {
+         /* The success case, because XYZ_from_xy normalises to a reference
+          * white Y of 1.0 we just need to scale the numbers.  This should
+          * always work just fine. It is an internal error if this overflows.
+          */
+         {
+            png_fixed_point r, g, b;
+            if (png_muldiv(&r, XYZ.redY, 32768, PNG_FP_1) &&
+               r >= 0 && r <= 32768 &&
+               png_muldiv(&g, XYZ.greenY, 32768, PNG_FP_1) &&
+               g >= 0 && g <= 32768 &&
+               png_muldiv(&b, XYZ.blueY, 32768, PNG_FP_1) &&
+               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");
+
+               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
+
+   png_set_cHRM_fixed(png_ptr, info_ptr, x_white, y_white, x_red, y_red,
+      x_green, y_green, x_blue, y_blue);
 }
 #endif
 
@@ -937,12 +1115,14 @@ png_handle_sRGB(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 
    if (!(png_ptr->mode & PNG_HAVE_IHDR))
       png_error(png_ptr, "Missing IHDR before sRGB");
+
    else if (png_ptr->mode & PNG_HAVE_IDAT)
    {
       png_warning(png_ptr, "Invalid sRGB after IDAT");
       png_crc_finish(png_ptr, length);
       return;
    }
+
    else if (png_ptr->mode & PNG_HAVE_PLTE)
       /* Should be an error, but we can cope with it */
       png_warning(png_ptr, "Out of place sRGB chunk");
@@ -962,10 +1142,12 @@ png_handle_sRGB(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    }
 
    png_crc_read(png_ptr, buf, 1);
+
    if (png_crc_finish(png_ptr, 0))
       return;
 
    intent = buf[0];
+
    /* Check for bad intent */
    if (intent >= PNG_sRGB_INTENT_LAST)
    {
@@ -976,50 +1158,76 @@ png_handle_sRGB(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 #if defined(PNG_READ_gAMA_SUPPORTED) && defined(PNG_READ_GAMMA_SUPPORTED)
    if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_gAMA))
    {
-   png_fixed_point igamma;
-#ifdef PNG_FIXED_POINT_SUPPORTED
-      igamma=info_ptr->int_gamma;
-#else
-#  ifdef PNG_FLOATING_POINT_SUPPORTED
-      igamma=(png_fixed_point)(info_ptr->gamma * 100000.);
-#  endif
-#endif
-      if (PNG_OUT_OF_RANGE(igamma, 45500L, 500))
+      if (PNG_OUT_OF_RANGE(info_ptr->gamma, 45500, 500))
       {
-         png_warning(png_ptr,
-           "Ignoring incorrect gAMA value when sRGB is also present");
-#ifdef PNG_CONSOLE_IO_SUPPORTED
-#  ifdef PNG_FIXED_POINT_SUPPORTED
-         fprintf(stderr, "incorrect gamma=(%d/100000)\n",
-            (int)png_ptr->int_gamma);
-#  else
-#    ifdef PNG_FLOATING_POINT_SUPPORTED
-         fprintf(stderr, "incorrect gamma=%f\n", png_ptr->gamma);
-#    endif
-#  endif
-#endif
+         PNG_WARNING_PARAMETERS(p)
+
+         png_warning_parameter_signed(p, 1, PNG_NUMBER_FORMAT_fixed,
+            info_ptr->gamma);
+
+         png_formatted_warning(png_ptr, p,
+             "Ignoring incorrect gAMA value @1 when sRGB is also present");
       }
    }
 #endif /* PNG_READ_gAMA_SUPPORTED */
 
 #ifdef PNG_READ_cHRM_SUPPORTED
-#ifdef PNG_FIXED_POINT_SUPPORTED
    if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_cHRM))
-      if (PNG_OUT_OF_RANGE(info_ptr->int_x_white, 31270,  1000) ||
-          PNG_OUT_OF_RANGE(info_ptr->int_y_white, 32900,  1000) ||
-          PNG_OUT_OF_RANGE(info_ptr->int_x_red,   64000L, 1000) ||
-          PNG_OUT_OF_RANGE(info_ptr->int_y_red,   33000,  1000) ||
-          PNG_OUT_OF_RANGE(info_ptr->int_x_green, 30000,  1000) ||
-          PNG_OUT_OF_RANGE(info_ptr->int_y_green, 60000L, 1000) ||
-          PNG_OUT_OF_RANGE(info_ptr->int_x_blue,  15000,  1000) ||
-          PNG_OUT_OF_RANGE(info_ptr->int_y_blue,   6000,  1000))
-         {
-            png_warning(png_ptr,
-              "Ignoring incorrect cHRM value when sRGB is also present");
-         }
-#endif /* PNG_FIXED_POINT_SUPPORTED */
+      if (PNG_OUT_OF_RANGE(info_ptr->x_white, 31270,  1000) ||
+          PNG_OUT_OF_RANGE(info_ptr->y_white, 32900,  1000) ||
+          PNG_OUT_OF_RANGE(info_ptr->x_red,   64000,  1000) ||
+          PNG_OUT_OF_RANGE(info_ptr->y_red,   33000,  1000) ||
+          PNG_OUT_OF_RANGE(info_ptr->x_green, 30000,  1000) ||
+          PNG_OUT_OF_RANGE(info_ptr->y_green, 60000,  1000) ||
+          PNG_OUT_OF_RANGE(info_ptr->x_blue,  15000,  1000) ||
+          PNG_OUT_OF_RANGE(info_ptr->y_blue,   6000,  1000))
+      {
+         png_warning(png_ptr,
+             "Ignoring incorrect cHRM value when sRGB is also present");
+      }
 #endif /* PNG_READ_cHRM_SUPPORTED */
 
+   /* This is recorded for use when handling the cHRM chunk above.  An sRGB
+    * chunk unconditionally overwrites the coefficients for grayscale conversion
+    * too.
+    */
+   png_ptr->is_sRGB = 1;
+
+#  ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
+      /* Don't overwrite user supplied values: */
+      if (!png_ptr->rgb_to_gray_coefficients_set)
+      {
+         /* These numbers come from the sRGB specification (or, since one has to
+          * pay much money to get a copy, the wikipedia sRGB page) the
+          * chromaticity values quoted have been inverted to get the reverse
+          * transformation from RGB to XYZ and the 'Y' coefficients scaled by
+          * 32768 (then rounded).
+          *
+          * sRGB and ITU Rec-709 both truncate the values for the D65 white
+          * point to four digits and, even though it actually stores five
+          * digits, the PNG spec gives the truncated value.
+          *
+          * This means that when the chromaticities are converted back to XYZ
+          * end points we end up with (6968,23435,2366), which, as described in
+          * pngrtran.c, would overflow.  If the five digit precision and up is
+          * used we get, instead:
+          *
+          *    6968*R + 23435*G + 2365*B
+          *
+          * (Notice that this rounds the blue coefficient down, rather than the
+          * choice used in pngrtran.c which is to round the green one down.)
+          */
+         png_ptr->rgb_to_gray_red_coeff   =  6968; /* 0.212639005871510 */
+         png_ptr->rgb_to_gray_green_coeff = 23434; /* 0.715168678767756 */
+         /* png_ptr->rgb_to_gray_blue_coeff  =  2366; 0.072192315360734	*/
+
+         /* The following keeps the cHRM chunk from destroying the
+          * coefficients again in the event that it follows the sRGB chunk.
+          */
+         png_ptr->rgb_to_gray_coefficients_set = 1;
+      }
+#  endif
+
    png_set_sRGB_gAMA_and_cHRM(png_ptr, info_ptr, intent);
 }
 #endif /* PNG_READ_sRGB_SUPPORTED */
@@ -1033,19 +1241,22 @@ png_handle_iCCP(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    png_bytep pC;
    png_charp profile;
    png_uint_32 skip = 0;
-   png_uint_32 profile_size, profile_length;
+   png_uint_32 profile_size;
+   png_alloc_size_t profile_length;
    png_size_t slength, prefix_length, data_length;
 
    png_debug(1, "in png_handle_iCCP");
 
    if (!(png_ptr->mode & PNG_HAVE_IHDR))
       png_error(png_ptr, "Missing IHDR before iCCP");
+
    else if (png_ptr->mode & PNG_HAVE_IDAT)
    {
       png_warning(png_ptr, "Invalid iCCP after IDAT");
       png_crc_finish(png_ptr, length);
       return;
    }
+
    else if (png_ptr->mode & PNG_HAVE_PLTE)
       /* Should be an error, but we can cope with it */
       png_warning(png_ptr, "Out of place iCCP chunk");
@@ -1088,7 +1299,7 @@ png_handle_iCCP(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    /* There should be at least one zero (the compression type byte)
     * following the separator, and we should be on it
     */
-   if ( profile >= png_ptr->chunkdata + slength - 1)
+   if (profile >= png_ptr->chunkdata + slength - 1)
    {
       png_free(png_ptr, png_ptr->chunkdata);
       png_ptr->chunkdata = NULL;
@@ -1098,6 +1309,7 @@ png_handle_iCCP(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 
    /* Compression_type should always be zero */
    compression_type = *profile++;
+
    if (compression_type)
    {
       png_warning(png_ptr, "Ignoring nonzero compression type in iCCP chunk");
@@ -1107,11 +1319,11 @@ png_handle_iCCP(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 
    prefix_length = profile - png_ptr->chunkdata;
    png_decompress_chunk(png_ptr, compression_type,
-     slength, prefix_length, &data_length);
+       slength, prefix_length, &data_length);
 
    profile_length = data_length - prefix_length;
 
-   if ( prefix_length > data_length || profile_length < 4)
+   if (prefix_length > data_length || profile_length < 4)
    {
       png_free(png_ptr, png_ptr->chunkdata);
       png_ptr->chunkdata = NULL;
@@ -1121,36 +1333,35 @@ png_handle_iCCP(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 
    /* Check the profile_size recorded in the first 32 bits of the ICC profile */
    pC = (png_bytep)(png_ptr->chunkdata + prefix_length);
-   profile_size = ((*(pC    ))<<24) |
-                  ((*(pC + 1))<<16) |
-                  ((*(pC + 2))<< 8) |
-                  ((*(pC + 3))    );
+   profile_size = ((*(pC    )) << 24) |
+                  ((*(pC + 1)) << 16) |
+                  ((*(pC + 2)) <<  8) |
+                  ((*(pC + 3))      );
 
+   /* NOTE: the following guarantees that 'profile_length' fits into 32 bits,
+    * because profile_size is a 32 bit value.
+    */
    if (profile_size < profile_length)
       profile_length = profile_size;
 
+   /* And the following guarantees that profile_size == profile_length. */
    if (profile_size > profile_length)
    {
-#ifdef PNG_STDIO_SUPPORTED
-         char umsg[50];
-#endif
+      PNG_WARNING_PARAMETERS(p)
+
       png_free(png_ptr, png_ptr->chunkdata);
       png_ptr->chunkdata = NULL;
-      png_warning(png_ptr, "Ignoring truncated iCCP profile");
-#ifdef PNG_STDIO_SUPPORTED
 
-      png_snprintf(umsg, 50, "declared profile size = %lu",
-          (unsigned long)profile_size);
-      png_warning(png_ptr, umsg);
-      png_snprintf(umsg, 50, "actual profile length = %lu",
-          (unsigned long)profile_length);
-      png_warning(png_ptr, umsg);
-#endif
+      png_warning_parameter_unsigned(p, 1, PNG_NUMBER_FORMAT_u, profile_size);
+      png_warning_parameter_unsigned(p, 2, PNG_NUMBER_FORMAT_u, profile_length);
+      png_formatted_warning(png_ptr, p,
+         "Ignoring iCCP chunk with declared size = @1 and actual length = @2");
       return;
    }
 
    png_set_iCCP(png_ptr, info_ptr, png_ptr->chunkdata,
-     compression_type, png_ptr->chunkdata + prefix_length, profile_length);
+       compression_type, (png_bytep)png_ptr->chunkdata + prefix_length,
+       profile_size);
    png_free(png_ptr, png_ptr->chunkdata);
    png_ptr->chunkdata = NULL;
 }
@@ -1163,12 +1374,13 @@ png_handle_sPLT(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 {
    png_bytep entry_start;
    png_sPLT_t new_palette;
-#ifdef PNG_POINTER_INDEXING_SUPPORTED
    png_sPLT_entryp pp;
-#endif
-   int data_length, entry_size, i;
+   png_uint_32 data_length;
+   int entry_size, i;
    png_uint_32 skip = 0;
    png_size_t slength;
+   png_uint_32 dl;
+   png_size_t max_dl;
 
    png_debug(1, "in png_handle_sPLT");
 
@@ -1181,6 +1393,7 @@ png_handle_sPLT(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
          png_crc_finish(png_ptr, length);
          return;
       }
+
       if (--png_ptr->user_chunk_cache_max == 1)
       {
          png_warning(png_ptr, "No space in chunk cache for sPLT");
@@ -1192,6 +1405,7 @@ png_handle_sPLT(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 
    if (!(png_ptr->mode & PNG_HAVE_IHDR))
       png_error(png_ptr, "Missing IHDR before sPLT");
+
    else if (png_ptr->mode & PNG_HAVE_IDAT)
    {
       png_warning(png_ptr, "Invalid sPLT after IDAT");
@@ -1210,6 +1424,11 @@ png_handle_sPLT(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 
    png_free(png_ptr, png_ptr->chunkdata);
    png_ptr->chunkdata = (png_charp)png_malloc(png_ptr, length + 1);
+
+   /* WARNING: this may break if size_t is less than 32 bits; it is assumed
+    * that the PNG_MAX_MALLOC_64K test is enabled in this case, but this is a
+    * potential breakage point if the types in pngconf.h aren't exactly right.
+    */
    slength = (png_size_t)length;
    png_crc_read(png_ptr, (png_bytep)png_ptr->chunkdata, slength);
 
@@ -1225,6 +1444,7 @@ png_handle_sPLT(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    for (entry_start = (png_bytep)png_ptr->chunkdata; *entry_start;
        entry_start++)
       /* Empty loop to find end of name */ ;
+
    ++entry_start;
 
    /* A sample depth should follow the separator, and we should be on it  */
@@ -1238,7 +1458,12 @@ png_handle_sPLT(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 
    new_palette.depth = *entry_start++;
    entry_size = (new_palette.depth == 8 ? 6 : 10);
-   data_length = (slength - (entry_start - (png_bytep)png_ptr->chunkdata));
+   /* This must fit in a png_uint_32 because it is derived from the original
+    * chunk data length (and use 'length', not 'slength' here for clarity -
+    * they are guaranteed to be the same, see the tests above.)
+    */
+   data_length = length - (png_uint_32)(entry_start -
+      (png_bytep)png_ptr->chunkdata);
 
    /* Integrity-check the data length */
    if (data_length % entry_size)
@@ -1249,15 +1474,20 @@ png_handle_sPLT(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
       return;
    }
 
-   new_palette.nentries = (png_int_32) ( data_length / entry_size);
-   if ((png_uint_32) new_palette.nentries >
-       (png_uint_32) (PNG_SIZE_MAX / png_sizeof(png_sPLT_entry)))
+   dl = (png_int_32)(data_length / entry_size);
+   max_dl = PNG_SIZE_MAX / png_sizeof(png_sPLT_entry);
+
+   if (dl > max_dl)
    {
        png_warning(png_ptr, "sPLT chunk too long");
        return;
    }
+
+   new_palette.nentries = (png_int_32)(data_length / entry_size);
+
    new_palette.entries = (png_sPLT_entryp)png_malloc_warn(
        png_ptr, new_palette.nentries * png_sizeof(png_sPLT_entry));
+
    if (new_palette.entries == NULL)
    {
        png_warning(png_ptr, "sPLT chunk requires too much memory");
@@ -1271,40 +1501,45 @@ png_handle_sPLT(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 
       if (new_palette.depth == 8)
       {
-          pp->red = *entry_start++;
-          pp->green = *entry_start++;
-          pp->blue = *entry_start++;
-          pp->alpha = *entry_start++;
+         pp->red = *entry_start++;
+         pp->green = *entry_start++;
+         pp->blue = *entry_start++;
+         pp->alpha = *entry_start++;
       }
+
       else
       {
-          pp->red   = png_get_uint_16(entry_start); entry_start += 2;
-          pp->green = png_get_uint_16(entry_start); entry_start += 2;
-          pp->blue  = png_get_uint_16(entry_start); entry_start += 2;
-          pp->alpha = png_get_uint_16(entry_start); entry_start += 2;
+         pp->red   = png_get_uint_16(entry_start); entry_start += 2;
+         pp->green = png_get_uint_16(entry_start); entry_start += 2;
+         pp->blue  = png_get_uint_16(entry_start); entry_start += 2;
+         pp->alpha = png_get_uint_16(entry_start); entry_start += 2;
       }
+
       pp->frequency = png_get_uint_16(entry_start); entry_start += 2;
    }
 #else
    pp = new_palette.entries;
+
    for (i = 0; i < new_palette.nentries; i++)
    {
 
       if (new_palette.depth == 8)
       {
-          pp[i].red   = *entry_start++;
-          pp[i].green = *entry_start++;
-          pp[i].blue  = *entry_start++;
-          pp[i].alpha = *entry_start++;
+         pp[i].red   = *entry_start++;
+         pp[i].green = *entry_start++;
+         pp[i].blue  = *entry_start++;
+         pp[i].alpha = *entry_start++;
       }
+
       else
       {
-          pp[i].red   = png_get_uint_16(entry_start); entry_start += 2;
-          pp[i].green = png_get_uint_16(entry_start); entry_start += 2;
-          pp[i].blue  = png_get_uint_16(entry_start); entry_start += 2;
-          pp[i].alpha = png_get_uint_16(entry_start); entry_start += 2;
+         pp[i].red   = png_get_uint_16(entry_start); entry_start += 2;
+         pp[i].green = png_get_uint_16(entry_start); entry_start += 2;
+         pp[i].blue  = png_get_uint_16(entry_start); entry_start += 2;
+         pp[i].alpha = png_get_uint_16(entry_start); entry_start += 2;
       }
-      pp->frequency = png_get_uint_16(entry_start); entry_start += 2;
+
+      pp[i].frequency = png_get_uint_16(entry_start); entry_start += 2;
    }
 #endif
 
@@ -1329,12 +1564,14 @@ png_handle_tRNS(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 
    if (!(png_ptr->mode & PNG_HAVE_IHDR))
       png_error(png_ptr, "Missing IHDR before tRNS");
+
    else if (png_ptr->mode & PNG_HAVE_IDAT)
    {
       png_warning(png_ptr, "Invalid tRNS after IDAT");
       png_crc_finish(png_ptr, length);
       return;
    }
+
    else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_tRNS))
    {
       png_warning(png_ptr, "Duplicate tRNS chunk");
@@ -1357,6 +1594,7 @@ png_handle_tRNS(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
       png_ptr->num_trans = 1;
       png_ptr->trans_color.gray = png_get_uint_16(buf);
    }
+
    else if (png_ptr->color_type == PNG_COLOR_TYPE_RGB)
    {
       png_byte buf[6];
@@ -1367,12 +1605,14 @@ png_handle_tRNS(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
          png_crc_finish(png_ptr, length);
          return;
       }
+
       png_crc_read(png_ptr, buf, (png_size_t)length);
       png_ptr->num_trans = 1;
       png_ptr->trans_color.red = png_get_uint_16(buf);
       png_ptr->trans_color.green = png_get_uint_16(buf + 2);
       png_ptr->trans_color.blue = png_get_uint_16(buf + 4);
    }
+
    else if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
    {
       if (!(png_ptr->mode & PNG_HAVE_PLTE))
@@ -1380,6 +1620,7 @@ png_handle_tRNS(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
          /* Should be an error, but we can cope with it. */
          png_warning(png_ptr, "Missing PLTE before tRNS");
       }
+
       if (length > (png_uint_32)png_ptr->num_palette ||
           length > PNG_MAX_PALETTE_LENGTH)
       {
@@ -1387,15 +1628,18 @@ png_handle_tRNS(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
          png_crc_finish(png_ptr, length);
          return;
       }
+
       if (length == 0)
       {
          png_warning(png_ptr, "Zero length tRNS chunk");
          png_crc_finish(png_ptr, length);
          return;
       }
+
       png_crc_read(png_ptr, readbuf, (png_size_t)length);
       png_ptr->num_trans = (png_uint_16)length;
    }
+
    else
    {
       png_warning(png_ptr, "tRNS chunk not allowed with alpha channel");
@@ -1410,7 +1654,7 @@ png_handle_tRNS(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    }
 
    png_set_tRNS(png_ptr, info_ptr, readbuf, png_ptr->num_trans,
-      &(png_ptr->trans_color));
+       &(png_ptr->trans_color));
 }
 #endif
 
@@ -1420,24 +1664,28 @@ png_handle_bKGD(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 {
    png_size_t truelen;
    png_byte buf[6];
+   png_color_16 background;
 
    png_debug(1, "in png_handle_bKGD");
 
    if (!(png_ptr->mode & PNG_HAVE_IHDR))
       png_error(png_ptr, "Missing IHDR before bKGD");
+
    else if (png_ptr->mode & PNG_HAVE_IDAT)
    {
       png_warning(png_ptr, "Invalid bKGD after IDAT");
       png_crc_finish(png_ptr, length);
       return;
    }
+
    else if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
-            !(png_ptr->mode & PNG_HAVE_PLTE))
+       !(png_ptr->mode & PNG_HAVE_PLTE))
    {
       png_warning(png_ptr, "Missing PLTE before bKGD");
       png_crc_finish(png_ptr, length);
       return;
    }
+
    else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_bKGD))
    {
       png_warning(png_ptr, "Duplicate bKGD chunk");
@@ -1447,8 +1695,10 @@ png_handle_bKGD(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 
    if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
       truelen = 1;
+
    else if (png_ptr->color_type & PNG_COLOR_MASK_COLOR)
       truelen = 6;
+
    else
       truelen = 2;
 
@@ -1460,46 +1710,57 @@ png_handle_bKGD(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    }
 
    png_crc_read(png_ptr, buf, truelen);
+
    if (png_crc_finish(png_ptr, 0))
       return;
 
    /* We convert the index value into RGB components so that we can allow
     * arbitrary RGB values for background when we have transparency, and
     * so it is easy to determine the RGB values of the background color
-    * from the info_ptr struct. */
+    * from the info_ptr struct.
+    */
    if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
    {
-      png_ptr->background.index = buf[0];
+      background.index = buf[0];
+
       if (info_ptr && info_ptr->num_palette)
       {
-          if (buf[0] >= info_ptr->num_palette)
-          {
-             png_warning(png_ptr, "Incorrect bKGD chunk index value");
-             return;
-          }
-          png_ptr->background.red =
-             (png_uint_16)png_ptr->palette[buf[0]].red;
-          png_ptr->background.green =
-             (png_uint_16)png_ptr->palette[buf[0]].green;
-          png_ptr->background.blue =
-             (png_uint_16)png_ptr->palette[buf[0]].blue;
+         if (buf[0] >= info_ptr->num_palette)
+         {
+            png_warning(png_ptr, "Incorrect bKGD chunk index value");
+            return;
+         }
+
+         background.red = (png_uint_16)png_ptr->palette[buf[0]].red;
+         background.green = (png_uint_16)png_ptr->palette[buf[0]].green;
+         background.blue = (png_uint_16)png_ptr->palette[buf[0]].blue;
       }
+
+      else
+         background.red = background.green = background.blue = 0;
+
+      background.gray = 0;
    }
+
    else if (!(png_ptr->color_type & PNG_COLOR_MASK_COLOR)) /* GRAY */
    {
-      png_ptr->background.red =
-      png_ptr->background.green =
-      png_ptr->background.blue =
-      png_ptr->background.gray = png_get_uint_16(buf);
+      background.index = 0;
+      background.red =
+      background.green =
+      background.blue =
+      background.gray = png_get_uint_16(buf);
    }
+
    else
    {
-      png_ptr->background.red = png_get_uint_16(buf);
-      png_ptr->background.green = png_get_uint_16(buf + 2);
-      png_ptr->background.blue = png_get_uint_16(buf + 4);
+      background.index = 0;
+      background.red = png_get_uint_16(buf);
+      background.green = png_get_uint_16(buf + 2);
+      background.blue = png_get_uint_16(buf + 4);
+      background.gray = 0;
    }
 
-   png_set_bKGD(png_ptr, info_ptr, &(png_ptr->background));
+   png_set_bKGD(png_ptr, info_ptr, &background);
 }
 #endif
 
@@ -1514,18 +1775,21 @@ png_handle_hIST(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 
    if (!(png_ptr->mode & PNG_HAVE_IHDR))
       png_error(png_ptr, "Missing IHDR before hIST");
+
    else if (png_ptr->mode & PNG_HAVE_IDAT)
    {
       png_warning(png_ptr, "Invalid hIST after IDAT");
       png_crc_finish(png_ptr, length);
       return;
    }
+
    else if (!(png_ptr->mode & PNG_HAVE_PLTE))
    {
       png_warning(png_ptr, "Missing PLTE before hIST");
       png_crc_finish(png_ptr, length);
       return;
    }
+
    else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_hIST))
    {
       png_warning(png_ptr, "Duplicate hIST chunk");
@@ -1534,8 +1798,9 @@ png_handle_hIST(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    }
 
    num = length / 2 ;
-   if (num != (unsigned int) png_ptr->num_palette || num >
-      (unsigned int) PNG_MAX_PALETTE_LENGTH)
+
+   if (num != (unsigned int)png_ptr->num_palette || num >
+       (unsigned int)PNG_MAX_PALETTE_LENGTH)
    {
       png_warning(png_ptr, "Incorrect hIST chunk length");
       png_crc_finish(png_ptr, length);
@@ -1569,12 +1834,14 @@ png_handle_pHYs(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 
    if (!(png_ptr->mode & PNG_HAVE_IHDR))
       png_error(png_ptr, "Missing IHDR before pHYs");
+
    else if (png_ptr->mode & PNG_HAVE_IDAT)
    {
       png_warning(png_ptr, "Invalid pHYs after IDAT");
       png_crc_finish(png_ptr, length);
       return;
    }
+
    else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_pHYs))
    {
       png_warning(png_ptr, "Duplicate pHYs chunk");
@@ -1590,6 +1857,7 @@ png_handle_pHYs(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    }
 
    png_crc_read(png_ptr, buf, 9);
+
    if (png_crc_finish(png_ptr, 0))
       return;
 
@@ -1612,12 +1880,14 @@ png_handle_oFFs(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 
    if (!(png_ptr->mode & PNG_HAVE_IHDR))
       png_error(png_ptr, "Missing IHDR before oFFs");
+
    else if (png_ptr->mode & PNG_HAVE_IDAT)
    {
       png_warning(png_ptr, "Invalid oFFs after IDAT");
       png_crc_finish(png_ptr, length);
       return;
    }
+
    else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_oFFs))
    {
       png_warning(png_ptr, "Duplicate oFFs chunk");
@@ -1633,6 +1903,7 @@ png_handle_oFFs(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    }
 
    png_crc_read(png_ptr, buf, 9);
+
    if (png_crc_finish(png_ptr, 0))
       return;
 
@@ -1659,12 +1930,14 @@ png_handle_pCAL(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 
    if (!(png_ptr->mode & PNG_HAVE_IHDR))
       png_error(png_ptr, "Missing IHDR before pCAL");
+
    else if (png_ptr->mode & PNG_HAVE_IDAT)
    {
       png_warning(png_ptr, "Invalid pCAL after IDAT");
       png_crc_finish(png_ptr, length);
       return;
    }
+
    else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_pCAL))
    {
       png_warning(png_ptr, "Duplicate pCAL chunk");
@@ -1672,15 +1945,17 @@ png_handle_pCAL(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
       return;
    }
 
-   png_debug1(2, "Allocating and reading pCAL chunk data (%lu bytes)",
-      length + 1);
+   png_debug1(2, "Allocating and reading pCAL chunk data (%u bytes)",
+       length + 1);
    png_free(png_ptr, png_ptr->chunkdata);
    png_ptr->chunkdata = (png_charp)png_malloc_warn(png_ptr, length + 1);
+
    if (png_ptr->chunkdata == NULL)
-     {
-       png_warning(png_ptr, "No memory for pCAL purpose");
-       return;
-     }
+   {
+      png_warning(png_ptr, "No memory for pCAL purpose");
+      return;
+   }
+
    slength = (png_size_t)length;
    png_crc_read(png_ptr, (png_bytep)png_ptr->chunkdata, slength);
 
@@ -1700,7 +1975,8 @@ png_handle_pCAL(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    endptr = png_ptr->chunkdata + slength;
 
    /* We need to have at least 12 bytes after the purpose string
-      in order to get the parameter information. */
+    * in order to get the parameter information.
+    */
    if (endptr <= buf + 12)
    {
       png_warning(png_ptr, "Invalid pCAL data");
@@ -1718,7 +1994,8 @@ png_handle_pCAL(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 
    png_debug(3, "Checking pCAL equation type and number of parameters");
    /* Check that we have the right number of parameters for known
-      equation types. */
+    * equation types.
+    */
    if ((type == PNG_EQUATION_LINEAR && nparams != 2) ||
        (type == PNG_EQUATION_BASE_E && nparams != 3) ||
        (type == PNG_EQUATION_ARBITRARY && nparams != 3) ||
@@ -1729,6 +2006,7 @@ png_handle_pCAL(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
       png_ptr->chunkdata = NULL;
       return;
    }
+
    else if (type >= PNG_EQUATION_LAST)
    {
       png_warning(png_ptr, "Unrecognized equation type for pCAL chunk");
@@ -1738,15 +2016,17 @@ png_handle_pCAL(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
       /* Empty loop to move past the units string. */ ;
 
    png_debug(3, "Allocating pCAL parameters array");
+
    params = (png_charpp)png_malloc_warn(png_ptr,
-      (png_size_t)(nparams * png_sizeof(png_charp)));
+       (png_size_t)(nparams * png_sizeof(png_charp)));
+
    if (params == NULL)
-     {
-       png_free(png_ptr, png_ptr->chunkdata);
-       png_ptr->chunkdata = NULL;
-       png_warning(png_ptr, "No memory for pCAL params");
-       return;
-     }
+   {
+      png_free(png_ptr, png_ptr->chunkdata);
+      png_ptr->chunkdata = NULL;
+      png_warning(png_ptr, "No memory for pCAL params");
+      return;
+   }
 
    /* Get pointers to the start of each parameter string. */
    for (i = 0; i < (int)nparams; i++)
@@ -1754,6 +2034,7 @@ png_handle_pCAL(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
       buf++; /* Skip the null string terminator from previous parameter. */
 
       png_debug1(3, "Reading pCAL parameter %d", i);
+
       for (params[i] = buf; buf <= endptr && *buf != 0x00; buf++)
          /* Empty loop to move past each parameter string */ ;
 
@@ -1782,27 +2063,21 @@ png_handle_pCAL(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 void /* PRIVATE */
 png_handle_sCAL(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 {
-   png_charp ep;
-#ifdef PNG_FLOATING_POINT_SUPPORTED
-   double width, height;
-   png_charp vp;
-#else
-#ifdef PNG_FIXED_POINT_SUPPORTED
-   png_charp swidth, sheight;
-#endif
-#endif
-   png_size_t slength;
+   png_size_t slength, i;
+   int state;
 
    png_debug(1, "in png_handle_sCAL");
 
    if (!(png_ptr->mode & PNG_HAVE_IHDR))
       png_error(png_ptr, "Missing IHDR before sCAL");
+
    else if (png_ptr->mode & PNG_HAVE_IDAT)
    {
       png_warning(png_ptr, "Invalid sCAL after IDAT");
       png_crc_finish(png_ptr, length);
       return;
    }
+
    else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_sCAL))
    {
       png_warning(png_ptr, "Duplicate sCAL chunk");
@@ -1810,17 +2085,29 @@ png_handle_sCAL(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
       return;
    }
 
-   png_debug1(2, "Allocating and reading sCAL chunk data (%lu bytes)",
+   /* Need unit type, width, \0, height: minimum 4 bytes */
+   else if (length < 4)
+   {
+      png_warning(png_ptr, "sCAL chunk too short");
+      png_crc_finish(png_ptr, length);
+      return;
+   }
+
+   png_debug1(2, "Allocating and reading sCAL chunk data (%u bytes)",
       length + 1);
+
    png_ptr->chunkdata = (png_charp)png_malloc_warn(png_ptr, length + 1);
+
    if (png_ptr->chunkdata == NULL)
    {
       png_warning(png_ptr, "Out of memory while processing sCAL chunk");
       png_crc_finish(png_ptr, length);
       return;
    }
+
    slength = (png_size_t)length;
    png_crc_read(png_ptr, (png_bytep)png_ptr->chunkdata, slength);
+   png_ptr->chunkdata[slength] = 0x00; /* Null terminate the last string */
 
    if (png_crc_finish(png_ptr, 0))
    {
@@ -1829,103 +2116,50 @@ png_handle_sCAL(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
       return;
    }
 
-   png_ptr->chunkdata[slength] = 0x00; /* Null terminate the last string */
-
-   ep = png_ptr->chunkdata + 1;        /* Skip unit byte */
-
-#ifdef PNG_FLOATING_POINT_SUPPORTED
-   width = png_strtod(png_ptr, ep, &vp);
-   if (*vp)
-   {
-      png_warning(png_ptr, "malformed width string in sCAL chunk");
-      png_free(png_ptr, png_ptr->chunkdata);
-      png_ptr->chunkdata = NULL;
-      return;
-   }
-#else
-#ifdef PNG_FIXED_POINT_SUPPORTED
-   swidth = (png_charp)png_malloc_warn(png_ptr, png_strlen(ep) + 1);
-   if (swidth == NULL)
+   /* Validate the unit. */
+   if (png_ptr->chunkdata[0] != 1 && png_ptr->chunkdata[0] != 2)
    {
-      png_warning(png_ptr, "Out of memory while processing sCAL chunk width");
+      png_warning(png_ptr, "Invalid sCAL ignored: invalid unit");
       png_free(png_ptr, png_ptr->chunkdata);
       png_ptr->chunkdata = NULL;
       return;
    }
-   png_memcpy(swidth, ep, png_strlen(ep));
-#endif
-#endif
 
-   for (ep = png_ptr->chunkdata; *ep; ep++)
-      /* Empty loop */ ;
-   ep++;
+   /* Validate the ASCII numbers, need two ASCII numbers separated by
+    * a '\0' and they need to fit exactly in the chunk data.
+    */
+   i = 1;
+   state = 0;
 
-   if (png_ptr->chunkdata + slength < ep)
-   {
-      png_warning(png_ptr, "Truncated sCAL chunk");
-#if defined(PNG_FIXED_POINT_SUPPORTED) && !defined(PNG_FLOATING_POINT_SUPPORTED)
-      png_free(png_ptr, swidth);
-#endif
-      png_free(png_ptr, png_ptr->chunkdata);
-      png_ptr->chunkdata = NULL;
-      return;
-   }
+   if (!png_check_fp_number(png_ptr->chunkdata, slength, &state, &i) ||
+       i >= slength || png_ptr->chunkdata[i++] != 0)
+      png_warning(png_ptr, "Invalid sCAL chunk ignored: bad width format");
 
-#ifdef PNG_FLOATING_POINT_SUPPORTED
-   height = png_strtod(png_ptr, ep, &vp);
-   if (*vp)
-   {
-      png_warning(png_ptr, "malformed height string in sCAL chunk");
-      png_free(png_ptr, png_ptr->chunkdata);
-      png_ptr->chunkdata = NULL;
-      return;
-   }
-#else
-#ifdef PNG_FIXED_POINT_SUPPORTED
-   sheight = (png_charp)png_malloc_warn(png_ptr, png_strlen(ep) + 1);
-   if (sheight == NULL)
-   {
-      png_warning(png_ptr, "Out of memory while processing sCAL chunk height");
-      png_free(png_ptr, png_ptr->chunkdata);
-      png_ptr->chunkdata = NULL;
-      png_free(png_ptr, swidth);
-      return;
-   }
-   png_memcpy(sheight, ep, png_strlen(ep));
-#endif
-#endif
+   else if (!PNG_FP_IS_POSITIVE(state))
+      png_warning(png_ptr, "Invalid sCAL chunk ignored: non-positive width");
 
-   if (png_ptr->chunkdata + slength < ep
-#ifdef PNG_FLOATING_POINT_SUPPORTED
-      || width <= 0. || height <= 0.
-#endif
-      )
+   else
    {
-      png_warning(png_ptr, "Invalid sCAL data");
-      png_free(png_ptr, png_ptr->chunkdata);
-      png_ptr->chunkdata = NULL;
-#if defined(PNG_FIXED_POINT_SUPPORTED) && !defined(PNG_FLOATING_POINT_SUPPORTED)
-      png_free(png_ptr, swidth);
-      png_free(png_ptr, sheight);
-#endif
-      return;
-   }
+      png_size_t heighti = i;
 
+      state = 0;
+      if (!png_check_fp_number(png_ptr->chunkdata, slength, &state, &i) ||
+          i != slength)
+         png_warning(png_ptr, "Invalid sCAL chunk ignored: bad height format");
 
-#ifdef PNG_FLOATING_POINT_SUPPORTED
-   png_set_sCAL(png_ptr, info_ptr, png_ptr->chunkdata[0], width, height);
-#else
-#ifdef PNG_FIXED_POINT_SUPPORTED
-   png_set_sCAL_s(png_ptr, info_ptr, png_ptr->chunkdata[0], swidth, sheight);
-#endif
-#endif
+      else if (!PNG_FP_IS_POSITIVE(state))
+         png_warning(png_ptr,
+            "Invalid sCAL chunk ignored: non-positive height");
 
+      else
+         /* This is the (only) success case. */
+         png_set_sCAL_s(png_ptr, info_ptr, png_ptr->chunkdata[0],
+            png_ptr->chunkdata+1, png_ptr->chunkdata+heighti);
+   }
+
+   /* Clean up - just free the temporarily allocated buffer. */
    png_free(png_ptr, png_ptr->chunkdata);
    png_ptr->chunkdata = NULL;
-#if defined(PNG_FIXED_POINT_SUPPORTED) && !defined(PNG_FLOATING_POINT_SUPPORTED)
-   png_free(png_ptr, swidth);
-   png_free(png_ptr, sheight);
-#endif
 }
 #endif
 
@@ -1940,6 +2174,7 @@ png_handle_tIME(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 
    if (!(png_ptr->mode & PNG_HAVE_IHDR))
       png_error(png_ptr, "Out of place tIME chunk");
+
    else if (info_ptr != NULL && (info_ptr->valid & PNG_INFO_tIME))
    {
       png_warning(png_ptr, "Duplicate tIME chunk");
@@ -1958,6 +2193,7 @@ png_handle_tIME(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    }
 
    png_crc_read(png_ptr, buf, 7);
+
    if (png_crc_finish(png_ptr, 0))
       return;
 
@@ -1994,6 +2230,7 @@ png_handle_tEXt(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
          png_crc_finish(png_ptr, length);
          return;
       }
+
       if (--png_ptr->user_chunk_cache_max == 1)
       {
          png_warning(png_ptr, "No space in chunk cache for tEXt");
@@ -2021,11 +2258,13 @@ png_handle_tEXt(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    png_free(png_ptr, png_ptr->chunkdata);
 
    png_ptr->chunkdata = (png_charp)png_malloc_warn(png_ptr, length + 1);
+
    if (png_ptr->chunkdata == NULL)
    {
      png_warning(png_ptr, "No memory to process text chunk");
      return;
    }
+
    slength = (png_size_t)length;
    png_crc_read(png_ptr, (png_bytep)png_ptr->chunkdata, slength);
 
@@ -2047,21 +2286,21 @@ png_handle_tEXt(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
       text++;
 
    text_ptr = (png_textp)png_malloc_warn(png_ptr,
-      png_sizeof(png_text));
+       png_sizeof(png_text));
+
    if (text_ptr == NULL)
    {
-     png_warning(png_ptr, "Not enough memory to process text chunk");
-     png_free(png_ptr, png_ptr->chunkdata);
-     png_ptr->chunkdata = NULL;
-     return;
+      png_warning(png_ptr, "Not enough memory to process text chunk");
+      png_free(png_ptr, png_ptr->chunkdata);
+      png_ptr->chunkdata = NULL;
+      return;
    }
+
    text_ptr->compression = PNG_TEXT_COMPRESSION_NONE;
    text_ptr->key = key;
-#ifdef PNG_iTXt_SUPPORTED
    text_ptr->lang = NULL;
    text_ptr->lang_key = NULL;
    text_ptr->itxt_length = 0;
-#endif
    text_ptr->text = text;
    text_ptr->text_length = png_strlen(text);
 
@@ -2070,8 +2309,9 @@ png_handle_tEXt(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    png_free(png_ptr, png_ptr->chunkdata);
    png_ptr->chunkdata = NULL;
    png_free(png_ptr, text_ptr);
+
    if (ret)
-     png_warning(png_ptr, "Insufficient memory to process text chunk");
+      png_warning(png_ptr, "Insufficient memory to process text chunk");
 }
 #endif
 
@@ -2096,6 +2336,7 @@ png_handle_zTXt(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
          png_crc_finish(png_ptr, length);
          return;
       }
+
       if (--png_ptr->user_chunk_cache_max == 1)
       {
          png_warning(png_ptr, "No space in chunk cache for zTXt");
@@ -2113,24 +2354,28 @@ png_handle_zTXt(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 
 #ifdef PNG_MAX_MALLOC_64K
    /* We will no doubt have problems with chunks even half this size, but
-      there is no hard and fast rule to tell us where to stop. */
+    * there is no hard and fast rule to tell us where to stop.
+    */
    if (length > (png_uint_32)65535L)
    {
-     png_warning(png_ptr, "zTXt chunk too large to fit in memory");
-     png_crc_finish(png_ptr, length);
-     return;
+      png_warning(png_ptr, "zTXt chunk too large to fit in memory");
+      png_crc_finish(png_ptr, length);
+      return;
    }
 #endif
 
    png_free(png_ptr, png_ptr->chunkdata);
    png_ptr->chunkdata = (png_charp)png_malloc_warn(png_ptr, length + 1);
+
    if (png_ptr->chunkdata == NULL)
    {
-     png_warning(png_ptr, "Out of memory processing zTXt chunk");
-     return;
+      png_warning(png_ptr, "Out of memory processing zTXt chunk");
+      return;
    }
+
    slength = (png_size_t)length;
    png_crc_read(png_ptr, (png_bytep)png_ptr->chunkdata, slength);
+
    if (png_crc_finish(png_ptr, 0))
    {
       png_free(png_ptr, png_ptr->chunkdata);
@@ -2151,37 +2396,41 @@ png_handle_zTXt(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
       png_ptr->chunkdata = NULL;
       return;
    }
+
    else
    {
        comp_type = *(++text);
+
        if (comp_type != PNG_TEXT_COMPRESSION_zTXt)
        {
           png_warning(png_ptr, "Unknown compression type in zTXt chunk");
           comp_type = PNG_TEXT_COMPRESSION_zTXt;
        }
+
        text++;        /* Skip the compression_method byte */
    }
+
    prefix_len = text - png_ptr->chunkdata;
 
    png_decompress_chunk(png_ptr, comp_type,
-     (png_size_t)length, prefix_len, &data_len);
+       (png_size_t)length, prefix_len, &data_len);
 
    text_ptr = (png_textp)png_malloc_warn(png_ptr,
-      png_sizeof(png_text));
+       png_sizeof(png_text));
+
    if (text_ptr == NULL)
    {
-     png_warning(png_ptr, "Not enough memory to process zTXt chunk");
-     png_free(png_ptr, png_ptr->chunkdata);
-     png_ptr->chunkdata = NULL;
-     return;
+      png_warning(png_ptr, "Not enough memory to process zTXt chunk");
+      png_free(png_ptr, png_ptr->chunkdata);
+      png_ptr->chunkdata = NULL;
+      return;
    }
+
    text_ptr->compression = comp_type;
    text_ptr->key = png_ptr->chunkdata;
-#ifdef PNG_iTXt_SUPPORTED
    text_ptr->lang = NULL;
    text_ptr->lang_key = NULL;
    text_ptr->itxt_length = 0;
-#endif
    text_ptr->text = png_ptr->chunkdata + prefix_len;
    text_ptr->text_length = data_len;
 
@@ -2190,8 +2439,9 @@ png_handle_zTXt(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    png_free(png_ptr, text_ptr);
    png_free(png_ptr, png_ptr->chunkdata);
    png_ptr->chunkdata = NULL;
+
    if (ret)
-     png_error(png_ptr, "Insufficient memory to store zTXt chunk");
+      png_error(png_ptr, "Insufficient memory to store zTXt chunk");
 }
 #endif
 
@@ -2217,6 +2467,7 @@ png_handle_iTXt(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
          png_crc_finish(png_ptr, length);
          return;
       }
+
       if (--png_ptr->user_chunk_cache_max == 1)
       {
          png_warning(png_ptr, "No space in chunk cache for iTXt");
@@ -2234,24 +2485,28 @@ png_handle_iTXt(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 
 #ifdef PNG_MAX_MALLOC_64K
    /* We will no doubt have problems with chunks even half this size, but
-      there is no hard and fast rule to tell us where to stop. */
+    * there is no hard and fast rule to tell us where to stop.
+    */
    if (length > (png_uint_32)65535L)
    {
-     png_warning(png_ptr, "iTXt chunk too large to fit in memory");
-     png_crc_finish(png_ptr, length);
-     return;
+      png_warning(png_ptr, "iTXt chunk too large to fit in memory");
+      png_crc_finish(png_ptr, length);
+      return;
    }
 #endif
 
    png_free(png_ptr, png_ptr->chunkdata);
    png_ptr->chunkdata = (png_charp)png_malloc_warn(png_ptr, length + 1);
+
    if (png_ptr->chunkdata == NULL)
    {
-     png_warning(png_ptr, "No memory to process iTXt chunk");
-     return;
+      png_warning(png_ptr, "No memory to process iTXt chunk");
+      return;
    }
+
    slength = (png_size_t)length;
    png_crc_read(png_ptr, (png_bytep)png_ptr->chunkdata, slength);
+
    if (png_crc_finish(png_ptr, 0))
    {
       png_free(png_ptr, png_ptr->chunkdata);
@@ -2263,6 +2518,7 @@ png_handle_iTXt(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 
    for (lang = png_ptr->chunkdata; *lang; lang++)
       /* Empty loop */ ;
+
    lang++;        /* Skip NUL separator */
 
    /* iTXt must have a language tag (possibly empty), two compression bytes,
@@ -2277,14 +2533,24 @@ png_handle_iTXt(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
       png_ptr->chunkdata = NULL;
       return;
    }
+
    else
    {
-       comp_flag = *lang++;
-       comp_type = *lang++;
+      comp_flag = *lang++;
+      comp_type = *lang++;
+   }
+
+   if (comp_type || (comp_flag && comp_flag != PNG_TEXT_COMPRESSION_zTXt))
+   {
+      png_warning(png_ptr, "Unknown iTXt compression type or method");
+      png_free(png_ptr, png_ptr->chunkdata);
+      png_ptr->chunkdata = NULL;
+      return;
    }
 
    for (lang_key = lang; *lang_key; lang_key++)
       /* Empty loop */ ;
+
    lang_key++;        /* Skip NUL separator */
 
    if (lang_key >= png_ptr->chunkdata + slength)
@@ -2297,7 +2563,9 @@ png_handle_iTXt(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 
    for (text = lang_key; *text; text++)
       /* Empty loop */ ;
+
    text++;        /* Skip NUL separator */
+
    if (text >= png_ptr->chunkdata + slength)
    {
       png_warning(png_ptr, "Malformed iTXt chunk");
@@ -2309,20 +2577,25 @@ png_handle_iTXt(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    prefix_len = text - png_ptr->chunkdata;
 
    key=png_ptr->chunkdata;
+
    if (comp_flag)
-       png_decompress_chunk(png_ptr, comp_type,
-         (size_t)length, prefix_len, &data_len);
+      png_decompress_chunk(png_ptr, comp_type,
+          (size_t)length, prefix_len, &data_len);
+
    else
-       data_len = png_strlen(png_ptr->chunkdata + prefix_len);
+      data_len = png_strlen(png_ptr->chunkdata + prefix_len);
+
    text_ptr = (png_textp)png_malloc_warn(png_ptr,
-      png_sizeof(png_text));
+       png_sizeof(png_text));
+
    if (text_ptr == NULL)
    {
-     png_warning(png_ptr, "Not enough memory to process iTXt chunk");
-     png_free(png_ptr, png_ptr->chunkdata);
-     png_ptr->chunkdata = NULL;
-     return;
+      png_warning(png_ptr, "Not enough memory to process iTXt chunk");
+      png_free(png_ptr, png_ptr->chunkdata);
+      png_ptr->chunkdata = NULL;
+      return;
    }
+
    text_ptr->compression = (int)comp_flag + 1;
    text_ptr->lang_key = png_ptr->chunkdata + (lang_key - key);
    text_ptr->lang = png_ptr->chunkdata + (lang - key);
@@ -2336,16 +2609,18 @@ png_handle_iTXt(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    png_free(png_ptr, text_ptr);
    png_free(png_ptr, png_ptr->chunkdata);
    png_ptr->chunkdata = NULL;
+
    if (ret)
-     png_error(png_ptr, "Insufficient memory to store iTXt chunk");
+      png_error(png_ptr, "Insufficient memory to store iTXt chunk");
 }
 #endif
 
 /* This function is called when we haven't found a handler for a
-   chunk.  If there isn't a problem with the chunk itself (ie bad
-   chunk name, CRC, or a critical chunk), the chunk is silently ignored
-   -- unless the PNG_FLAG_UNKNOWN_CHUNKS_SUPPORTED flag is on in which
-   case it will be saved away to be written out later. */
+ * chunk.  If there isn't a problem with the chunk itself (ie bad
+ * chunk name, CRC, or a critical chunk), the chunk is silently ignored
+ * -- unless the PNG_FLAG_UNKNOWN_CHUNKS_SUPPORTED flag is on in which
+ * case it will be saved away to be written out later.
+ */
 void /* PRIVATE */
 png_handle_unknown(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 {
@@ -2361,6 +2636,7 @@ png_handle_unknown(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
          png_crc_finish(png_ptr, length);
          return;
       }
+
       if (--png_ptr->user_chunk_cache_max == 1)
       {
          png_warning(png_ptr, "No space in chunk cache for unknown chunk");
@@ -2372,22 +2648,21 @@ png_handle_unknown(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 
    if (png_ptr->mode & PNG_HAVE_IDAT)
    {
-      PNG_IDAT;
-      if (png_memcmp(png_ptr->chunk_name, png_IDAT, 4))  /* Not an IDAT */
+      if (png_ptr->chunk_name != png_IDAT)
          png_ptr->mode |= PNG_AFTER_IDAT;
    }
 
-   if (!(png_ptr->chunk_name[0] & 0x20))
+   if (PNG_CHUNK_CRITICAL(png_ptr->chunk_name))
    {
 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
-      if (png_handle_as_unknown(png_ptr, png_ptr->chunk_name) !=
-           PNG_HANDLE_CHUNK_ALWAYS
+      if (png_chunk_unknown_handling(png_ptr, png_ptr->chunk_name) !=
+          PNG_HANDLE_CHUNK_ALWAYS
 #ifdef PNG_READ_USER_CHUNKS_SUPPORTED
-           && png_ptr->read_user_chunk_fn == NULL
+          && png_ptr->read_user_chunk_fn == NULL
 #endif
-        )
+          )
 #endif
-          png_chunk_error(png_ptr, "unknown critical chunk");
+         png_chunk_error(png_ptr, "unknown critical chunk");
    }
 
 #ifdef PNG_READ_UNKNOWN_CHUNKS_SUPPORTED
@@ -2395,56 +2670,70 @@ png_handle_unknown(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
 #ifdef PNG_READ_USER_CHUNKS_SUPPORTED
        || (png_ptr->read_user_chunk_fn != NULL)
 #endif
-        )
+       )
    {
 #ifdef PNG_MAX_MALLOC_64K
-       if (length > (png_uint_32)65535L)
-       {
-           png_warning(png_ptr, "unknown chunk too large to fit in memory");
-           skip = length - (png_uint_32)65535L;
-           length = (png_uint_32)65535L;
-       }
+      if (length > 65535)
+      {
+         png_warning(png_ptr, "unknown chunk too large to fit in memory");
+         skip = length - 65535;
+         length = 65535;
+      }
 #endif
-       png_memcpy((png_charp)png_ptr->unknown_chunk.name,
-                  (png_charp)png_ptr->chunk_name,
-                  png_sizeof(png_ptr->unknown_chunk.name));
-       png_ptr->unknown_chunk.name[png_sizeof(png_ptr->unknown_chunk.name)-1]
-           = '\0';
-       png_ptr->unknown_chunk.size = (png_size_t)length;
-       if (length == 0)
+
+      /* TODO: this code is very close to the unknown handling in pngpread.c,
+       * maybe it can be put into a common utility routine?
+       * png_struct::unknown_chunk is just used as a temporary variable, along
+       * with the data into which the chunk is read.  These can be eliminated.
+       */
+      PNG_CSTRING_FROM_CHUNK(png_ptr->unknown_chunk.name, png_ptr->chunk_name);
+      png_ptr->unknown_chunk.size = (png_size_t)length;
+
+      if (length == 0)
          png_ptr->unknown_chunk.data = NULL;
-       else
-       {
+
+      else
+      {
          png_ptr->unknown_chunk.data = (png_bytep)png_malloc(png_ptr, length);
-         png_crc_read(png_ptr, (png_bytep)png_ptr->unknown_chunk.data, length);
-       }
+         png_crc_read(png_ptr, png_ptr->unknown_chunk.data, length);
+      }
+
 #ifdef PNG_READ_USER_CHUNKS_SUPPORTED
-       if (png_ptr->read_user_chunk_fn != NULL)
-       {
-          /* Callback to user unknown chunk handler */
-          int ret;
-          ret = (*(png_ptr->read_user_chunk_fn))
-            (png_ptr, &png_ptr->unknown_chunk);
-          if (ret < 0)
-             png_chunk_error(png_ptr, "error in user chunk");
-          if (ret == 0)
-          {
-             if (!(png_ptr->chunk_name[0] & 0x20))
+      if (png_ptr->read_user_chunk_fn != NULL)
+      {
+         /* Callback to user unknown chunk handler */
+         int ret;
+
+         ret = (*(png_ptr->read_user_chunk_fn))
+             (png_ptr, &png_ptr->unknown_chunk);
+
+         if (ret < 0)
+            png_chunk_error(png_ptr, "error in user chunk");
+
+         if (ret == 0)
+         {
+            if (PNG_CHUNK_CRITICAL(png_ptr->chunk_name))
+            {
 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
-                if (png_handle_as_unknown(png_ptr, png_ptr->chunk_name) !=
-                     PNG_HANDLE_CHUNK_ALWAYS)
+               if (png_chunk_unknown_handling(png_ptr, png_ptr->chunk_name) !=
+                   PNG_HANDLE_CHUNK_ALWAYS)
 #endif
-                   png_chunk_error(png_ptr, "unknown critical chunk");
-             png_set_unknown_chunks(png_ptr, info_ptr,
-               &png_ptr->unknown_chunk, 1);
-          }
-       }
-       else
+                  png_chunk_error(png_ptr, "unknown critical chunk");
+            }
+
+            png_set_unknown_chunks(png_ptr, info_ptr,
+                &png_ptr->unknown_chunk, 1);
+         }
+      }
+
+      else
 #endif
-       png_set_unknown_chunks(png_ptr, info_ptr, &png_ptr->unknown_chunk, 1);
-       png_free(png_ptr, png_ptr->unknown_chunk.data);
-       png_ptr->unknown_chunk.data = NULL;
+         png_set_unknown_chunks(png_ptr, info_ptr, &png_ptr->unknown_chunk, 1);
+
+      png_free(png_ptr, png_ptr->unknown_chunk.data);
+      png_ptr->unknown_chunk.data = NULL;
    }
+
    else
 #endif
       skip = length;
@@ -2452,256 +2741,534 @@ png_handle_unknown(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
    png_crc_finish(png_ptr, skip);
 
 #ifndef PNG_READ_USER_CHUNKS_SUPPORTED
-   info_ptr = info_ptr; /* Quiet compiler warnings about unused info_ptr */
+   PNG_UNUSED(info_ptr) /* Quiet compiler warnings about unused info_ptr */
 #endif
 }
 
 /* This function is called to verify that a chunk name is valid.
-   This function can't have the "critical chunk check" incorporated
-   into it, since in the future we will need to be able to call user
-   functions to handle unknown critical chunks after we check that
-   the chunk name itself is valid. */
+ * This function can't have the "critical chunk check" incorporated
+ * into it, since in the future we will need to be able to call user
+ * functions to handle unknown critical chunks after we check that
+ * the chunk name itself is valid.
+ */
 
-#define isnonalpha(c) ((c) < 65 || (c) > 122 || ((c) > 90 && (c) < 97))
+/* Bit hacking: the test for an invalid byte in the 4 byte chunk name is:
+ *
+ * ((c) < 65 || (c) > 122 || ((c) > 90 && (c) < 97))
+ */
 
 void /* PRIVATE */
-png_check_chunk_name(png_structp png_ptr, png_bytep chunk_name)
+png_check_chunk_name(png_structp png_ptr, png_uint_32 chunk_name)
 {
+   int i;
+
    png_debug(1, "in png_check_chunk_name");
-   if (isnonalpha(chunk_name[0]) || isnonalpha(chunk_name[1]) ||
-       isnonalpha(chunk_name[2]) || isnonalpha(chunk_name[3]))
+
+   for (i=1; i<=4; ++i)
    {
-      png_chunk_error(png_ptr, "invalid chunk type");
+      int c = chunk_name & 0xff;
+
+      if (c < 65 || c > 122 || (c > 90 && c < 97))
+         png_chunk_error(png_ptr, "invalid chunk type");
+
+      chunk_name >>= 8;
    }
 }
 
-/* Combines the row recently read in with the existing pixels in the
-   row.  This routine takes care of alpha and transparency if requested.
-   This routine also handles the two methods of progressive display
-   of interlaced images, depending on the mask value.
-   The mask value describes which pixels are to be combined with
-   the row.  The pattern always repeats every 8 pixels, so just 8
-   bits are needed.  A one indicates the pixel is to be combined,
-   a zero indicates the pixel is to be skipped.  This is in addition
-   to any alpha or transparency value associated with the pixel.  If
-   you want all pixels to be combined, pass 0xff (255) in mask.  */
-
+/* Combines the row recently read in with the existing pixels in the row.  This
+ * routine takes care of alpha and transparency if requested.  This routine also
+ * handles the two methods of progressive display of interlaced images,
+ * depending on the 'display' value; if 'display' is true then the whole row
+ * (dp) is filled from the start by replicating the available pixels.  If
+ * 'display' is false only those pixels present in the pass are filled in.
+ */
 void /* PRIVATE */
-png_combine_row(png_structp png_ptr, png_bytep row, int mask)
+png_combine_row(png_structp png_ptr, png_bytep dp, int display)
 {
+   unsigned int pixel_depth = png_ptr->transformed_pixel_depth;
+   png_const_bytep sp = png_ptr->row_buf + 1;
+   png_uint_32 row_width = png_ptr->width;
+   unsigned int pass = png_ptr->pass;
+   png_bytep end_ptr = 0;
+   png_byte end_byte = 0;
+   unsigned int end_mask;
+
    png_debug(1, "in png_combine_row");
-   if (mask == 0xff)
-   {
-      png_memcpy(row, png_ptr->row_buf + 1,
-         PNG_ROWBYTES(png_ptr->row_info.pixel_depth, png_ptr->width));
-   }
-   else
+
+   /* Added in 1.5.6: it should not be possible to enter this routine until at
+    * least one row has been read from the PNG data and transformed.
+    */
+   if (pixel_depth == 0)
+      png_error(png_ptr, "internal row logic error");
+
+   /* Added in 1.5.4: the pixel depth should match the information returned by
+    * any call to png_read_update_info at this point.  Do not continue if we got
+    * this wrong.
+    */
+   if (png_ptr->info_rowbytes != 0 && png_ptr->info_rowbytes !=
+          PNG_ROWBYTES(pixel_depth, row_width))
+      png_error(png_ptr, "internal row size calculation error");
+
+   /* Don't expect this to ever happen: */
+   if (row_width == 0)
+      png_error(png_ptr, "internal row width error");
+
+   /* Preserve the last byte in cases where only part of it will be overwritten,
+    * the multiply below may overflow, we don't care because ANSI-C guarantees
+    * we get the low bits.
+    */
+   end_mask = (pixel_depth * row_width) & 7;
+   if (end_mask != 0)
+   {
+      /* end_ptr == NULL is a flag to say do nothing */
+      end_ptr = dp + PNG_ROWBYTES(pixel_depth, row_width) - 1;
+      end_byte = *end_ptr;
+#     ifdef PNG_READ_PACKSWAP_SUPPORTED
+         if (png_ptr->transformations & PNG_PACKSWAP) /* little-endian byte */
+            end_mask = 0xff << end_mask;
+
+         else /* big-endian byte */
+#     endif
+         end_mask = 0xff >> end_mask;
+      /* end_mask is now the bits to *keep* from the destination row */
+   }
+
+   /* For non-interlaced images this reduces to a png_memcpy(). A png_memcpy()
+    * will also happen if interlacing isn't supported or if the application
+    * does not call png_set_interlace_handling().  In the latter cases the
+    * caller just gets a sequence of the unexpanded rows from each interlace
+    * pass.
+    */
+#ifdef PNG_READ_INTERLACING_SUPPORTED
+   if (png_ptr->interlaced && (png_ptr->transformations & PNG_INTERLACE) &&
+      pass < 6 && (display == 0 ||
+      /* The following copies everything for 'display' on passes 0, 2 and 4. */
+      (display == 1 && (pass & 1) != 0)))
    {
-      switch (png_ptr->row_info.pixel_depth)
+      /* Narrow images may have no bits in a pass; the caller should handle
+       * this, but this test is cheap:
+       */
+      if (row_width <= PNG_PASS_START_COL(pass))
+         return;
+
+      if (pixel_depth < 8)
       {
-         case 1:
+         /* For pixel depths up to 4 bpp the 8-pixel mask can be expanded to fit
+          * into 32 bits, then a single loop over the bytes using the four byte
+          * values in the 32-bit mask can be used.  For the 'display' option the
+          * expanded mask may also not require any masking within a byte.  To
+          * make this work the PACKSWAP option must be taken into account - it
+          * simply requires the pixels to be reversed in each byte.
+          *
+          * The 'regular' case requires a mask for each of the first 6 passes,
+          * the 'display' case does a copy for the even passes in the range
+          * 0..6.  This has already been handled in the test above.
+          *
+          * The masks are arranged as four bytes with the first byte to use in
+          * the lowest bits (little-endian) regardless of the order (PACKSWAP or
+          * not) of the pixels in each byte.
+          *
+          * NOTE: the whole of this logic depends on the caller of this function
+          * only calling it on rows appropriate to the pass.  This function only
+          * understands the 'x' logic; the 'y' logic is handled by the caller.
+          *
+          * The following defines allow generation of compile time constant bit
+          * masks for each pixel depth and each possibility of swapped or not
+          * swapped bytes.  Pass 'p' is in the range 0..6; 'x', a pixel index,
+          * is in the range 0..7; and the result is 1 if the pixel is to be
+          * copied in the pass, 0 if not.  'S' is for the sparkle method, 'B'
+          * for the block method.
+          *
+          * With some compilers a compile time expression of the general form:
+          *
+          *    (shift >= 32) ? (a >> (shift-32)) : (b >> shift)
+          *
+          * Produces warnings with values of 'shift' in the range 33 to 63
+          * because the right hand side of the ?: expression is evaluated by
+          * the compiler even though it isn't used.  Microsoft Visual C (various
+          * versions) and the Intel C compiler are known to do this.  To avoid
+          * this the following macros are used in 1.5.6.  This is a temporary
+          * solution to avoid destabilizing the code during the release process.
+          */
+#        if PNG_USE_COMPILE_TIME_MASKS
+#           define PNG_LSR(x,s) ((x)>>((s) & 0x1f))
+#           define PNG_LSL(x,s) ((x)<<((s) & 0x1f))
+#        else
+#           define PNG_LSR(x,s) ((x)>>(s))
+#           define PNG_LSL(x,s) ((x)<<(s))
+#        endif
+#        define S_COPY(p,x) (((p)<4 ? PNG_LSR(0x80088822,(3-(p))*8+(7-(x))) :\
+           PNG_LSR(0xaa55ff00,(7-(p))*8+(7-(x)))) & 1)
+#        define B_COPY(p,x) (((p)<4 ? PNG_LSR(0xff0fff33,(3-(p))*8+(7-(x))) :\
+           PNG_LSR(0xff55ff00,(7-(p))*8+(7-(x)))) & 1)
+
+         /* Return a mask for pass 'p' pixel 'x' at depth 'd'.  The mask is
+          * little endian - the first pixel is at bit 0 - however the extra
+          * parameter 's' can be set to cause the mask position to be swapped
+          * within each byte, to match the PNG format.  This is done by XOR of
+          * the shift with 7, 6 or 4 for bit depths 1, 2 and 4.
+          */
+#        define PIXEL_MASK(p,x,d,s) \
+            (PNG_LSL(((PNG_LSL(1U,(d)))-1),(((x)*(d))^((s)?8-(d):0))))
+
+         /* Hence generate the appropriate 'block' or 'sparkle' pixel copy mask.
+          */
+#        define S_MASKx(p,x,d,s) (S_COPY(p,x)?PIXEL_MASK(p,x,d,s):0)
+#        define B_MASKx(p,x,d,s) (B_COPY(p,x)?PIXEL_MASK(p,x,d,s):0)
+
+         /* Combine 8 of these to get the full mask.  For the 1-bpp and 2-bpp
+          * cases the result needs replicating, for the 4-bpp case the above
+          * generates a full 32 bits.
+          */
+#        define MASK_EXPAND(m,d) ((m)*((d)==1?0x01010101:((d)==2?0x00010001:1)))
+
+#        define S_MASK(p,d,s) MASK_EXPAND(S_MASKx(p,0,d,s) + S_MASKx(p,1,d,s) +\
+            S_MASKx(p,2,d,s) + S_MASKx(p,3,d,s) + S_MASKx(p,4,d,s) +\
+            S_MASKx(p,5,d,s) + S_MASKx(p,6,d,s) + S_MASKx(p,7,d,s), d)
+
+#        define B_MASK(p,d,s) MASK_EXPAND(B_MASKx(p,0,d,s) + B_MASKx(p,1,d,s) +\
+            B_MASKx(p,2,d,s) + B_MASKx(p,3,d,s) + B_MASKx(p,4,d,s) +\
+            B_MASKx(p,5,d,s) + B_MASKx(p,6,d,s) + B_MASKx(p,7,d,s), d)
+
+#if PNG_USE_COMPILE_TIME_MASKS
+         /* Utility macros to construct all the masks for a depth/swap
+          * combination.  The 's' parameter says whether the format is PNG
+          * (big endian bytes) or not.  Only the three odd-numbered passes are
+          * required for the display/block algorithm.
+          */
+#        define S_MASKS(d,s) { S_MASK(0,d,s), S_MASK(1,d,s), S_MASK(2,d,s),\
+            S_MASK(3,d,s), S_MASK(4,d,s), S_MASK(5,d,s) }
+
+#        define B_MASKS(d,s) { B_MASK(1,d,s), S_MASK(3,d,s), S_MASK(5,d,s) }
+
+#        define DEPTH_INDEX(d) ((d)==1?0:((d)==2?1:2))
+
+         /* Hence the pre-compiled masks indexed by PACKSWAP (or not), depth and
+          * then pass:
+          */
+         static PNG_CONST png_uint_32 row_mask[2/*PACKSWAP*/][3/*depth*/][6] =
          {
-            png_bytep sp = png_ptr->row_buf + 1;
-            png_bytep dp = row;
-            int s_inc, s_start, s_end;
-            int m = 0x80;
-            int shift;
-            png_uint_32 i;
-            png_uint_32 row_width = png_ptr->width;
-
-#ifdef PNG_READ_PACKSWAP_SUPPORTED
+            /* Little-endian byte masks for PACKSWAP */
+            { S_MASKS(1,0), S_MASKS(2,0), S_MASKS(4,0) },
+            /* Normal (big-endian byte) masks - PNG format */
+            { S_MASKS(1,1), S_MASKS(2,1), S_MASKS(4,1) }
+         };
+
+         /* display_mask has only three entries for the odd passes, so index by
+          * pass>>1.
+          */
+         static PNG_CONST png_uint_32 display_mask[2][3][3] =
+         {
+            /* Little-endian byte masks for PACKSWAP */
+            { B_MASKS(1,0), B_MASKS(2,0), B_MASKS(4,0) },
+            /* Normal (big-endian byte) masks - PNG format */
+            { B_MASKS(1,1), B_MASKS(2,1), B_MASKS(4,1) }
+         };
+
+#        define MASK(pass,depth,display,png)\
+            ((display)?display_mask[png][DEPTH_INDEX(depth)][pass>>1]:\
+               row_mask[png][DEPTH_INDEX(depth)][pass])
+
+#else /* !PNG_USE_COMPILE_TIME_MASKS */
+         /* This is the runtime alternative: it seems unlikely that this will
+          * ever be either smaller or faster than the compile time approach.
+          */
+#        define MASK(pass,depth,display,png)\
+            ((display)?B_MASK(pass,depth,png):S_MASK(pass,depth,png))
+#endif /* !PNG_USE_COMPILE_TIME_MASKS */
+
+         /* Use the appropriate mask to copy the required bits.  In some cases
+          * the byte mask will be 0 or 0xff, optimize these cases.  row_width is
+          * the number of pixels, but the code copies bytes, so it is necessary
+          * to special case the end.
+          */
+         png_uint_32 pixels_per_byte = 8 / pixel_depth;
+         png_uint_32 mask;
+
+#        ifdef PNG_READ_PACKSWAP_SUPPORTED
             if (png_ptr->transformations & PNG_PACKSWAP)
-            {
-                s_start = 0;
-                s_end = 7;
-                s_inc = 1;
-            }
+               mask = MASK(pass, pixel_depth, display, 0);
+
             else
-#endif
+#        endif
+            mask = MASK(pass, pixel_depth, display, 1);
+
+         for (;;)
+         {
+            png_uint_32 m;
+
+            /* It doesn't matter in the following if png_uint_32 has more than
+             * 32 bits because the high bits always match those in m<<24; it is,
+             * however, essential to use OR here, not +, because of this.
+             */
+            m = mask;
+            mask = (m >> 8) | (m << 24); /* rotate right to good compilers */
+            m &= 0xff;
+
+            if (m != 0) /* something to copy */
             {
-                s_start = 7;
-                s_end = 0;
-                s_inc = -1;
+               if (m != 0xff)
+                  *dp = (png_byte)((*dp & ~m) | (*sp & m));
+               else
+                  *dp = *sp;
             }
 
-            shift = s_start;
+            /* NOTE: this may overwrite the last byte with garbage if the image
+             * is not an exact number of bytes wide; libpng has always done
+             * this.
+             */
+            if (row_width <= pixels_per_byte)
+               break; /* May need to restore part of the last byte */
 
-            for (i = 0; i < row_width; i++)
-            {
-               if (m & mask)
+            row_width -= pixels_per_byte;
+            ++dp;
+            ++sp;
+         }
+      }
+
+      else /* pixel_depth >= 8 */
+      {
+         unsigned int bytes_to_copy, bytes_to_jump;
+
+         /* Validate the depth - it must be a multiple of 8 */
+         if (pixel_depth & 7)
+            png_error(png_ptr, "invalid user transform pixel depth");
+
+         pixel_depth >>= 3; /* now in bytes */
+         row_width *= pixel_depth;
+
+         /* Regardless of pass number the Adam 7 interlace always results in a
+          * fixed number of pixels to copy then to skip.  There may be a
+          * different number of pixels to skip at the start though.
+          */
+         {
+            unsigned int offset = PNG_PASS_START_COL(pass) * pixel_depth;
+
+            row_width -= offset;
+            dp += offset;
+            sp += offset;
+         }
+
+         /* Work out the bytes to copy. */
+         if (display)
+         {
+            /* When doing the 'block' algorithm the pixel in the pass gets
+             * replicated to adjacent pixels.  This is why the even (0,2,4,6)
+             * passes are skipped above - the entire expanded row is copied.
+             */
+            bytes_to_copy = (1<<((6-pass)>>1)) * pixel_depth;
+
+            /* But don't allow this number to exceed the actual row width. */
+            if (bytes_to_copy > row_width)
+               bytes_to_copy = row_width;
+         }
+
+         else /* normal row; Adam7 only ever gives us one pixel to copy. */
+            bytes_to_copy = pixel_depth;
+
+         /* In Adam7 there is a constant offset between where the pixels go. */
+         bytes_to_jump = PNG_PASS_COL_OFFSET(pass) * pixel_depth;
+
+         /* And simply copy these bytes.  Some optimization is possible here,
+          * depending on the value of 'bytes_to_copy'.  Special case the low
+          * byte counts, which we know to be frequent.
+          *
+          * Notice that these cases all 'return' rather than 'break' - this
+          * avoids an unnecessary test on whether to restore the last byte
+          * below.
+          */
+         switch (bytes_to_copy)
+         {
+            case 1:
+               for (;;)
                {
-                  int value;
+                  *dp = *sp;
+
+                  if (row_width <= bytes_to_jump)
+                     return;
 
-                  value = (*sp >> shift) & 0x01;
-                  *dp &= (png_byte)((0x7f7f >> (7 - shift)) & 0xff);
-                  *dp |= (png_byte)(value << shift);
+                  dp += bytes_to_jump;
+                  sp += bytes_to_jump;
+                  row_width -= bytes_to_jump;
                }
 
-               if (shift == s_end)
+            case 2:
+               /* There is a possibility of a partial copy at the end here; this
+                * slows the code down somewhat.
+                */
+               do
                {
-                  shift = s_start;
-                  sp++;
-                  dp++;
+                  dp[0] = sp[0], dp[1] = sp[1];
+
+                  if (row_width <= bytes_to_jump)
+                     return;
+
+                  sp += bytes_to_jump;
+                  dp += bytes_to_jump;
+                  row_width -= bytes_to_jump;
                }
-               else
-                  shift += s_inc;
+               while (row_width > 1);
 
-               if (m == 1)
-                  m = 0x80;
-               else
-                  m >>= 1;
-            }
-            break;
-         }
-         case 2:
-         {
-            png_bytep sp = png_ptr->row_buf + 1;
-            png_bytep dp = row;
-            int s_start, s_end, s_inc;
-            int m = 0x80;
-            int shift;
-            png_uint_32 i;
-            png_uint_32 row_width = png_ptr->width;
-            int value;
+               /* And there can only be one byte left at this point: */
+               *dp = *sp;
+               return;
 
-#ifdef PNG_READ_PACKSWAP_SUPPORTED
-            if (png_ptr->transformations & PNG_PACKSWAP)
-            {
-               s_start = 0;
-               s_end = 6;
-               s_inc = 2;
-            }
-            else
-#endif
-            {
-               s_start = 6;
-               s_end = 0;
-               s_inc = -2;
-            }
+            case 3:
+               /* This can only be the RGB case, so each copy is exactly one
+                * pixel and it is not necessary to check for a partial copy.
+                */
+               for(;;)
+               {
+                  dp[0] = sp[0], dp[1] = sp[1], dp[2] = sp[2];
 
-            shift = s_start;
+                  if (row_width <= bytes_to_jump)
+                     return;
 
-            for (i = 0; i < row_width; i++)
-            {
-               if (m & mask)
-               {
-                  value = (*sp >> shift) & 0x03;
-                  *dp &= (png_byte)((0x3f3f >> (6 - shift)) & 0xff);
-                  *dp |= (png_byte)(value << shift);
+                  sp += bytes_to_jump;
+                  dp += bytes_to_jump;
+                  row_width -= bytes_to_jump;
                }
 
-               if (shift == s_end)
+            default:
+#if PNG_ALIGN_TYPE != PNG_ALIGN_NONE
+               /* Check for double byte alignment and, if possible, use a
+                * 16-bit copy.  Don't attempt this for narrow images - ones that
+                * are less than an interlace panel wide.  Don't attempt it for
+                * wide bytes_to_copy either - use the png_memcpy there.
+                */
+               if (bytes_to_copy < 16 /*else use png_memcpy*/ &&
+                  png_isaligned(dp, png_uint_16) &&
+                  png_isaligned(sp, png_uint_16) &&
+                  bytes_to_copy % sizeof (png_uint_16) == 0 &&
+                  bytes_to_jump % sizeof (png_uint_16) == 0)
                {
-                  shift = s_start;
-                  sp++;
-                  dp++;
-               }
-               else
-                  shift += s_inc;
-               if (m == 1)
-                  m = 0x80;
-               else
-                  m >>= 1;
-            }
-            break;
-         }
-         case 4:
-         {
-            png_bytep sp = png_ptr->row_buf + 1;
-            png_bytep dp = row;
-            int s_start, s_end, s_inc;
-            int m = 0x80;
-            int shift;
-            png_uint_32 i;
-            png_uint_32 row_width = png_ptr->width;
-            int value;
-
-#ifdef PNG_READ_PACKSWAP_SUPPORTED
-            if (png_ptr->transformations & PNG_PACKSWAP)
-            {
-               s_start = 0;
-               s_end = 4;
-               s_inc = 4;
-            }
-            else
-#endif
-            {
-               s_start = 4;
-               s_end = 0;
-               s_inc = -4;
-            }
-            shift = s_start;
+                  /* Everything is aligned for png_uint_16 copies, but try for
+                   * png_uint_32 first.
+                   */
+                  if (png_isaligned(dp, png_uint_32) &&
+                     png_isaligned(sp, png_uint_32) &&
+                     bytes_to_copy % sizeof (png_uint_32) == 0 &&
+                     bytes_to_jump % sizeof (png_uint_32) == 0)
+                  {
+                     png_uint_32p dp32 = (png_uint_32p)dp;
+                     png_const_uint_32p sp32 = (png_const_uint_32p)sp;
+                     unsigned int skip = (bytes_to_jump-bytes_to_copy) /
+                        sizeof (png_uint_32);
+
+                     do
+                     {
+                        size_t c = bytes_to_copy;
+                        do
+                        {
+                           *dp32++ = *sp32++;
+                           c -= sizeof (png_uint_32);
+                        }
+                        while (c > 0);
+
+                        if (row_width <= bytes_to_jump)
+                           return;
+
+                        dp32 += skip;
+                        sp32 += skip;
+                        row_width -= bytes_to_jump;
+                     }
+                     while (bytes_to_copy <= row_width);
+
+                     /* Get to here when the row_width truncates the final copy.
+                      * There will be 1-3 bytes left to copy, so don't try the
+                      * 16-bit loop below.
+                      */
+                     dp = (png_bytep)dp32;
+                     sp = (png_const_bytep)sp32;
+                     do
+                        *dp++ = *sp++;
+                     while (--row_width > 0);
+                     return;
+                  }
 
-            for (i = 0; i < row_width; i++)
-            {
-               if (m & mask)
-               {
-                  value = (*sp >> shift) & 0xf;
-                  *dp &= (png_byte)((0xf0f >> (4 - shift)) & 0xff);
-                  *dp |= (png_byte)(value << shift);
+                  /* Else do it in 16-bit quantities, but only if the size is
+                   * not too large.
+                   */
+                  else
+                  {
+                     png_uint_16p dp16 = (png_uint_16p)dp;
+                     png_const_uint_16p sp16 = (png_const_uint_16p)sp;
+                     unsigned int skip = (bytes_to_jump-bytes_to_copy) /
+                        sizeof (png_uint_16);
+
+                     do
+                     {
+                        size_t c = bytes_to_copy;
+                        do
+                        {
+                           *dp16++ = *sp16++;
+                           c -= sizeof (png_uint_16);
+                        }
+                        while (c > 0);
+
+                        if (row_width <= bytes_to_jump)
+                           return;
+
+                        dp16 += skip;
+                        sp16 += skip;
+                        row_width -= bytes_to_jump;
+                     }
+                     while (bytes_to_copy <= row_width);
+
+                     /* End of row - 1 byte left, bytes_to_copy > row_width: */
+                     dp = (png_bytep)dp16;
+                     sp = (png_const_bytep)sp16;
+                     do
+                        *dp++ = *sp++;
+                     while (--row_width > 0);
+                     return;
+                  }
                }
+#endif /* PNG_ALIGN_ code */
 
-               if (shift == s_end)
+               /* The true default - use a png_memcpy: */
+               for (;;)
                {
-                  shift = s_start;
-                  sp++;
-                  dp++;
-               }
-               else
-                  shift += s_inc;
-               if (m == 1)
-                  m = 0x80;
-               else
-                  m >>= 1;
-            }
-            break;
-         }
-         default:
-         {
-            png_bytep sp = png_ptr->row_buf + 1;
-            png_bytep dp = row;
-            png_size_t pixel_bytes = (png_ptr->row_info.pixel_depth >> 3);
-            png_uint_32 i;
-            png_uint_32 row_width = png_ptr->width;
-            png_byte m = 0x80;
+                  png_memcpy(dp, sp, bytes_to_copy);
 
+                  if (row_width <= bytes_to_jump)
+                     return;
 
-            for (i = 0; i < row_width; i++)
-            {
-               if (m & mask)
-               {
-                  png_memcpy(dp, sp, pixel_bytes);
+                  sp += bytes_to_jump;
+                  dp += bytes_to_jump;
+                  row_width -= bytes_to_jump;
+                  if (bytes_to_copy > row_width)
+                     bytes_to_copy = row_width;
                }
+         }
 
-               sp += pixel_bytes;
-               dp += pixel_bytes;
+         /* NOT REACHED*/
+      } /* pixel_depth >= 8 */
 
-               if (m == 1)
-                  m = 0x80;
-               else
-                  m >>= 1;
-            }
-            break;
-         }
-      }
+      /* Here if pixel_depth < 8 to check 'end_ptr' below. */
    }
+   else
+#endif
+
+   /* If here then the switch above wasn't used so just png_memcpy the whole row
+    * from the temporary row buffer (notice that this overwrites the end of the
+    * destination row if it is a partial byte.)
+    */
+   png_memcpy(dp, sp, PNG_ROWBYTES(pixel_depth, row_width));
+
+   /* Restore the overwritten bits from the last byte if necessary. */
+   if (end_ptr != NULL)
+      *end_ptr = (png_byte)((end_byte & end_mask) | (*end_ptr & ~end_mask));
 }
 
 #ifdef PNG_READ_INTERLACING_SUPPORTED
-/* OLD pre-1.0.9 interface:
-void png_do_read_interlace(png_row_infop row_info, png_bytep row, int pass,
-   png_uint_32 transformations)
- */
 void /* PRIVATE */
-png_do_read_interlace(png_structp png_ptr)
+png_do_read_interlace(png_row_infop row_info, png_bytep row, int pass,
+   png_uint_32 transformations /* Because these may affect the byte layout */)
 {
-   png_row_infop row_info = &(png_ptr->row_info);
-   png_bytep row = png_ptr->row_buf + 1;
-   int pass = png_ptr->pass;
-   png_uint_32 transformations = png_ptr->transformations;
    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
    /* Offset to next interlace block */
-   PNG_CONST int png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
+   static PNG_CONST int png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
 
    png_debug(1, "in png_do_read_interlace");
    if (row != NULL && row_info != NULL)
@@ -2732,6 +3299,7 @@ png_do_read_interlace(png_structp png_ptr)
                 s_end = 0;
                 s_inc = -1;
             }
+
             else
 #endif
             {
@@ -2749,24 +3317,29 @@ png_do_read_interlace(png_structp png_ptr)
                {
                   *dp &= (png_byte)((0x7f7f >> (7 - dshift)) & 0xff);
                   *dp |= (png_byte)(v << dshift);
+
                   if (dshift == s_end)
                   {
                      dshift = s_start;
                      dp--;
                   }
+
                   else
                      dshift += s_inc;
                }
+
                if (sshift == s_end)
                {
                   sshift = s_start;
                   sp--;
                }
+
                else
                   sshift += s_inc;
             }
             break;
          }
+
          case 2:
          {
             png_bytep sp = row + (png_uint_32)((row_info->width - 1) >> 2);
@@ -2785,6 +3358,7 @@ png_do_read_interlace(png_structp png_ptr)
                s_end = 0;
                s_inc = -2;
             }
+
             else
 #endif
             {
@@ -2805,24 +3379,29 @@ png_do_read_interlace(png_structp png_ptr)
                {
                   *dp &= (png_byte)((0x3f3f >> (6 - dshift)) & 0xff);
                   *dp |= (png_byte)(v << dshift);
+
                   if (dshift == s_end)
                   {
                      dshift = s_start;
                      dp--;
                   }
+
                   else
                      dshift += s_inc;
                }
+
                if (sshift == s_end)
                {
                   sshift = s_start;
                   sp--;
                }
+
                else
                   sshift += s_inc;
             }
             break;
          }
+
          case 4:
          {
             png_bytep sp = row + (png_size_t)((row_info->width - 1) >> 1);
@@ -2841,6 +3420,7 @@ png_do_read_interlace(png_structp png_ptr)
                s_end = 0;
                s_inc = -4;
             }
+
             else
 #endif
             {
@@ -2853,36 +3433,43 @@ png_do_read_interlace(png_structp png_ptr)
 
             for (i = 0; i < row_info->width; i++)
             {
-               png_byte v = (png_byte)((*sp >> sshift) & 0xf);
+               png_byte v = (png_byte)((*sp >> sshift) & 0x0f);
                int j;
 
                for (j = 0; j < jstop; j++)
                {
                   *dp &= (png_byte)((0xf0f >> (4 - dshift)) & 0xff);
                   *dp |= (png_byte)(v << dshift);
+
                   if (dshift == s_end)
                   {
                      dshift = s_start;
                      dp--;
                   }
+
                   else
                      dshift += s_inc;
                }
+
                if (sshift == s_end)
                {
                   sshift = s_start;
                   sp--;
                }
+
                else
                   sshift += s_inc;
             }
             break;
          }
+
          default:
          {
             png_size_t pixel_bytes = (row_info->pixel_depth >> 3);
+
             png_bytep sp = row + (png_size_t)(row_info->width - 1)
                 * pixel_bytes;
+
             png_bytep dp = row + (png_size_t)(final_width - 1) * pixel_bytes;
 
             int jstop = png_pass_inc[pass];
@@ -2894,146 +3481,274 @@ png_do_read_interlace(png_structp png_ptr)
                int j;
 
                png_memcpy(v, sp, pixel_bytes);
+
                for (j = 0; j < jstop; j++)
                {
                   png_memcpy(dp, v, pixel_bytes);
                   dp -= pixel_bytes;
                }
+
                sp -= pixel_bytes;
             }
             break;
          }
       }
+
       row_info->width = final_width;
       row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, final_width);
    }
 #ifndef PNG_READ_PACKSWAP_SUPPORTED
-   transformations = transformations; /* Silence compiler warning */
+   PNG_UNUSED(transformations)  /* Silence compiler warning */
 #endif
 }
 #endif /* PNG_READ_INTERLACING_SUPPORTED */
 
-void /* PRIVATE */
-png_read_filter_row(png_structp png_ptr, png_row_infop row_info, png_bytep row,
-   png_bytep prev_row, int filter)
+static void
+png_read_filter_row_sub(png_row_infop row_info, png_bytep row,
+   png_const_bytep prev_row)
 {
-   png_debug(1, "in png_read_filter_row");
-   png_debug2(2, "row = %lu, filter = %d", png_ptr->row_number, filter);
-   switch (filter)
+   png_size_t i;
+   png_size_t istop = row_info->rowbytes;
+   unsigned int bpp = (row_info->pixel_depth + 7) >> 3;
+   png_bytep rp = row + bpp;
+
+   PNG_UNUSED(prev_row)
+
+   for (i = bpp; i < istop; i++)
    {
-      case PNG_FILTER_VALUE_NONE:
-         break;
-      case PNG_FILTER_VALUE_SUB:
-      {
-         png_uint_32 i;
-         png_uint_32 istop = row_info->rowbytes;
-         png_uint_32 bpp = (row_info->pixel_depth + 7) >> 3;
-         png_bytep rp = row + bpp;
-         png_bytep lp = row;
+      *rp = (png_byte)(((int)(*rp) + (int)(*(rp-bpp))) & 0xff);
+      rp++;
+   }
+}
 
-         for (i = bpp; i < istop; i++)
-         {
-            *rp = (png_byte)(((int)(*rp) + (int)(*lp++)) & 0xff);
-            rp++;
-         }
-         break;
-      }
-      case PNG_FILTER_VALUE_UP:
-      {
-         png_uint_32 i;
-         png_uint_32 istop = row_info->rowbytes;
-         png_bytep rp = row;
-         png_bytep pp = prev_row;
+static void
+png_read_filter_row_up(png_row_infop row_info, png_bytep row,
+   png_const_bytep prev_row)
+{
+   png_size_t i;
+   png_size_t istop = row_info->rowbytes;
+   png_bytep rp = row;
+   png_const_bytep pp = prev_row;
 
-         for (i = 0; i < istop; i++)
-         {
-            *rp = (png_byte)(((int)(*rp) + (int)(*pp++)) & 0xff);
-            rp++;
-         }
-         break;
-      }
-      case PNG_FILTER_VALUE_AVG:
-      {
-         png_uint_32 i;
-         png_bytep rp = row;
-         png_bytep pp = prev_row;
-         png_bytep lp = row;
-         png_uint_32 bpp = (row_info->pixel_depth + 7) >> 3;
-         png_uint_32 istop = row_info->rowbytes - bpp;
-
-         for (i = 0; i < bpp; i++)
-         {
-            *rp = (png_byte)(((int)(*rp) +
-               ((int)(*pp++) / 2 )) & 0xff);
-            rp++;
-         }
+   for (i = 0; i < istop; i++)
+   {
+      *rp = (png_byte)(((int)(*rp) + (int)(*pp++)) & 0xff);
+      rp++;
+   }
+}
 
-         for (i = 0; i < istop; i++)
-         {
-            *rp = (png_byte)(((int)(*rp) +
-               (int)(*pp++ + *lp++) / 2 ) & 0xff);
-            rp++;
-         }
-         break;
-      }
-      case PNG_FILTER_VALUE_PAETH:
-      {
-         png_uint_32 i;
-         png_bytep rp = row;
-         png_bytep pp = prev_row;
-         png_bytep lp = row;
-         png_bytep cp = prev_row;
-         png_uint_32 bpp = (row_info->pixel_depth + 7) >> 3;
-         png_uint_32 istop=row_info->rowbytes - bpp;
-
-         for (i = 0; i < bpp; i++)
-         {
-            *rp = (png_byte)(((int)(*rp) + (int)(*pp++)) & 0xff);
-            rp++;
-         }
+static void
+png_read_filter_row_avg(png_row_infop row_info, png_bytep row,
+   png_const_bytep prev_row)
+{
+   png_size_t i;
+   png_bytep rp = row;
+   png_const_bytep pp = prev_row;
+   unsigned int bpp = (row_info->pixel_depth + 7) >> 3;
+   png_size_t istop = row_info->rowbytes - bpp;
 
-         for (i = 0; i < istop; i++)   /* Use leftover rp,pp */
-         {
-            int a, b, c, pa, pb, pc, p;
+   for (i = 0; i < bpp; i++)
+   {
+      *rp = (png_byte)(((int)(*rp) +
+         ((int)(*pp++) / 2 )) & 0xff);
 
-            a = *lp++;
-            b = *pp++;
-            c = *cp++;
+      rp++;
+   }
 
-            p = b - c;
-            pc = a - c;
+   for (i = 0; i < istop; i++)
+   {
+      *rp = (png_byte)(((int)(*rp) +
+         (int)(*pp++ + *(rp-bpp)) / 2 ) & 0xff);
 
-#ifdef PNG_USE_ABS
-            pa = abs(p);
-            pb = abs(pc);
-            pc = abs(p + pc);
-#else
-            pa = p < 0 ? -p : p;
-            pb = pc < 0 ? -pc : pc;
-            pc = (p + pc) < 0 ? -(p + pc) : p + pc;
-#endif
+      rp++;
+   }
+}
 
-            /*
-               if (pa <= pb && pa <= pc)
-                  p = a;
-               else if (pb <= pc)
-                  p = b;
-               else
-                  p = c;
-             */
+static void
+png_read_filter_row_paeth_1byte_pixel(png_row_infop row_info, png_bytep row,
+   png_const_bytep prev_row)
+{
+   png_bytep rp_end = row + row_info->rowbytes;
+   int a, c;
 
-            p = (pa <= pb && pa <= pc) ? a : (pb <= pc) ? b : c;
+   /* First pixel/byte */
+   c = *prev_row++;
+   a = *row + c;
+   *row++ = (png_byte)a;
 
-            *rp = (png_byte)(((int)(*rp) + p) & 0xff);
-            rp++;
-         }
+   /* Remainder */
+   while (row < rp_end)
+   {
+      int b, pa, pb, pc, p;
+
+      a &= 0xff; /* From previous iteration or start */
+      b = *prev_row++;
+
+      p = b - c;
+      pc = a - c;
+
+#     ifdef PNG_USE_ABS
+         pa = abs(p);
+         pb = abs(pc);
+         pc = abs(p + pc);
+#     else
+         pa = p < 0 ? -p : p;
+         pb = pc < 0 ? -pc : pc;
+         pc = (p + pc) < 0 ? -(p + pc) : p + pc;
+#     endif
+
+      /* Find the best predictor, the least of pa, pb, pc favoring the earlier
+       * ones in the case of a tie.
+       */
+      if (pb < pa) pa = pb, a = b;
+      if (pc < pa) a = c;
+
+      /* Calculate the current pixel in a, and move the previous row pixel to c
+       * for the next time round the loop
+       */
+      c = b;
+      a += *row;
+      *row++ = (png_byte)a;
+   }
+}
+
+static void
+png_read_filter_row_paeth_multibyte_pixel(png_row_infop row_info, png_bytep row,
+   png_const_bytep prev_row)
+{
+   int bpp = (row_info->pixel_depth + 7) >> 3;
+   png_bytep rp_end = row + bpp;
+
+   /* Process the first pixel in the row completely (this is the same as 'up'
+    * because there is only one candidate predictor for the first row).
+    */
+   while (row < rp_end)
+   {
+      int a = *row + *prev_row++;
+      *row++ = (png_byte)a;
+   }
+
+   /* Remainder */
+   rp_end += row_info->rowbytes - bpp;
+
+   while (row < rp_end)
+   {
+      int a, b, c, pa, pb, pc, p;
+
+      c = *(prev_row - bpp);
+      a = *(row - bpp);
+      b = *prev_row++;
+
+      p = b - c;
+      pc = a - c;
+
+#     ifdef PNG_USE_ABS
+         pa = abs(p);
+         pb = abs(pc);
+         pc = abs(p + pc);
+#     else
+         pa = p < 0 ? -p : p;
+         pb = pc < 0 ? -pc : pc;
+         pc = (p + pc) < 0 ? -(p + pc) : p + pc;
+#     endif
+
+      if (pb < pa) pa = pb, a = b;
+      if (pc < pa) a = c;
+
+      c = b;
+      a += *row;
+      *row++ = (png_byte)a;
+   }
+}
+
+#ifdef PNG_ARM_NEON
+
+#ifdef __linux__
+#include <stdio.h>
+#include <elf.h>
+#include <asm/hwcap.h>
+
+static int png_have_hwcap(unsigned cap)
+{
+   FILE *f = fopen("/proc/self/auxv", "r");
+   Elf32_auxv_t aux;
+   int have_cap = 0;
+
+   if (!f)
+      return 0;
+
+   while (fread(&aux, sizeof(aux), 1, f) > 0)
+   {
+      if (aux.a_type == AT_HWCAP &&
+          aux.a_un.a_val & cap)
+      {
+         have_cap = 1;
          break;
       }
-      default:
-         png_warning(png_ptr, "Ignoring bad adaptive filter type");
-         *row = 0;
-         break;
    }
+
+   fclose(f);
+
+   return have_cap;
+}
+#endif /* __linux__ */
+
+static void
+png_init_filter_functions_neon(png_structp pp, unsigned int bpp)
+{
+#ifdef __linux__
+   if (!png_have_hwcap(HWCAP_NEON))
+      return;
+#endif
+
+   pp->read_filter[PNG_FILTER_VALUE_UP-1] = png_read_filter_row_up_neon;
+
+   if (bpp == 3)
+   {
+      pp->read_filter[PNG_FILTER_VALUE_SUB-1] = png_read_filter_row_sub3_neon;
+      pp->read_filter[PNG_FILTER_VALUE_AVG-1] = png_read_filter_row_avg3_neon;
+      pp->read_filter[PNG_FILTER_VALUE_PAETH-1] = 
+         png_read_filter_row_paeth3_neon;
+   }
+
+   else if (bpp == 4)
+   {
+      pp->read_filter[PNG_FILTER_VALUE_SUB-1] = png_read_filter_row_sub4_neon;
+      pp->read_filter[PNG_FILTER_VALUE_AVG-1] = png_read_filter_row_avg4_neon;
+      pp->read_filter[PNG_FILTER_VALUE_PAETH-1] =
+          png_read_filter_row_paeth4_neon;
+   }
+}
+#endif /* PNG_ARM_NEON */
+
+static void
+png_init_filter_functions(png_structp pp)
+{
+   unsigned int bpp = (pp->pixel_depth + 7) >> 3;
+
+   pp->read_filter[PNG_FILTER_VALUE_SUB-1] = png_read_filter_row_sub;
+   pp->read_filter[PNG_FILTER_VALUE_UP-1] = png_read_filter_row_up;
+   pp->read_filter[PNG_FILTER_VALUE_AVG-1] = png_read_filter_row_avg;
+   if (bpp == 1)
+      pp->read_filter[PNG_FILTER_VALUE_PAETH-1] =
+         png_read_filter_row_paeth_1byte_pixel;
+   else
+      pp->read_filter[PNG_FILTER_VALUE_PAETH-1] =
+         png_read_filter_row_paeth_multibyte_pixel;
+
+#ifdef PNG_ARM_NEON
+   png_init_filter_functions_neon(pp, bpp);
+#endif
+}
+
+void /* PRIVATE */
+png_read_filter_row(png_structp pp, png_row_infop row_info, png_bytep row,
+   png_const_bytep prev_row, int filter)
+{
+   if (pp->read_filter[0] == NULL)
+      png_init_filter_functions(pp);
+   if (filter > PNG_FILTER_VALUE_NONE && filter < PNG_FILTER_VALUE_LAST)
+      pp->read_filter[filter-1](row_info, row, prev_row);
 }
 
 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
@@ -3044,16 +3759,16 @@ png_read_finish_row(png_structp png_ptr)
    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
 
    /* Start of interlace block */
-   PNG_CONST int png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
+   static PNG_CONST png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
 
    /* Offset to next interlace block */
-   PNG_CONST int png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
+   static PNG_CONST png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
 
    /* Start of interlace block in the y direction */
-   PNG_CONST int png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
+   static PNG_CONST png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
 
    /* Offset to next interlace block in the y direction */
-   PNG_CONST int png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
+   static PNG_CONST png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
 #endif /* PNG_READ_INTERLACING_SUPPORTED */
 
    png_debug(1, "in png_read_finish_row");
@@ -3065,13 +3780,19 @@ png_read_finish_row(png_structp png_ptr)
    if (png_ptr->interlaced)
    {
       png_ptr->row_number = 0;
-      png_memset(png_ptr->prev_row, 0,
-         png_ptr->rowbytes + 1);
+
+      /* TO DO: don't do this if prev_row isn't needed (requires
+       * read-ahead of the next row's filter byte.
+       */
+      png_memset(png_ptr->prev_row, 0, png_ptr->rowbytes + 1);
+
       do
       {
          png_ptr->pass++;
+
          if (png_ptr->pass >= 7)
             break;
+
          png_ptr->iwidth = (png_ptr->width +
             png_pass_inc[png_ptr->pass] - 1 -
             png_pass_start[png_ptr->pass]) /
@@ -3080,15 +3801,15 @@ png_read_finish_row(png_structp png_ptr)
          if (!(png_ptr->transformations & PNG_INTERLACE))
          {
             png_ptr->num_rows = (png_ptr->height +
-               png_pass_yinc[png_ptr->pass] - 1 -
-               png_pass_ystart[png_ptr->pass]) /
-               png_pass_yinc[png_ptr->pass];
-            if (!(png_ptr->num_rows))
-               continue;
+                png_pass_yinc[png_ptr->pass] - 1 -
+                png_pass_ystart[png_ptr->pass]) /
+                png_pass_yinc[png_ptr->pass];
          }
+
          else  /* if (png_ptr->transformations & PNG_INTERLACE) */
-            break;
-      } while (png_ptr->iwidth == 0);
+            break; /* libpng deinterlacing sees every row */
+
+      } while (png_ptr->num_rows == 0 || png_ptr->iwidth == 0);
 
       if (png_ptr->pass < 7)
          return;
@@ -3097,50 +3818,50 @@ png_read_finish_row(png_structp png_ptr)
 
    if (!(png_ptr->flags & PNG_FLAG_ZLIB_FINISHED))
    {
-      PNG_IDAT;
       char extra;
       int ret;
 
       png_ptr->zstream.next_out = (Byte *)&extra;
       png_ptr->zstream.avail_out = (uInt)1;
+
       for (;;)
       {
          if (!(png_ptr->zstream.avail_in))
          {
             while (!png_ptr->idat_size)
             {
-               png_byte chunk_length[4];
-
                png_crc_finish(png_ptr, 0);
-
-               png_read_data(png_ptr, chunk_length, 4);
-               png_ptr->idat_size = png_get_uint_31(png_ptr, chunk_length);
-               png_reset_crc(png_ptr);
-               png_crc_read(png_ptr, png_ptr->chunk_name, 4);
-               if (png_memcmp(png_ptr->chunk_name, png_IDAT, 4))
+               png_ptr->idat_size = png_read_chunk_header(png_ptr);
+               if (png_ptr->chunk_name != png_IDAT)
                   png_error(png_ptr, "Not enough image data");
-
             }
+
             png_ptr->zstream.avail_in = (uInt)png_ptr->zbuf_size;
             png_ptr->zstream.next_in = png_ptr->zbuf;
+
             if (png_ptr->zbuf_size > png_ptr->idat_size)
                png_ptr->zstream.avail_in = (uInt)png_ptr->idat_size;
+
             png_crc_read(png_ptr, png_ptr->zbuf, png_ptr->zstream.avail_in);
             png_ptr->idat_size -= png_ptr->zstream.avail_in;
          }
+
          ret = inflate(&png_ptr->zstream, Z_PARTIAL_FLUSH);
+
          if (ret == Z_STREAM_END)
          {
             if (!(png_ptr->zstream.avail_out) || png_ptr->zstream.avail_in ||
-               png_ptr->idat_size)
+                png_ptr->idat_size)
                png_warning(png_ptr, "Extra compressed data");
+
             png_ptr->mode |= PNG_AFTER_IDAT;
             png_ptr->flags |= PNG_FLAG_ZLIB_FINISHED;
             break;
          }
+
          if (ret != Z_OK)
             png_error(png_ptr, png_ptr->zstream.msg ? png_ptr->zstream.msg :
-                      "Decompression Error");
+                "Decompression Error");
 
          if (!(png_ptr->zstream.avail_out))
          {
@@ -3170,16 +3891,16 @@ png_read_start_row(png_structp png_ptr)
    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
 
    /* Start of interlace block */
-   PNG_CONST int png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
+   static PNG_CONST png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
 
    /* Offset to next interlace block */
-   PNG_CONST int png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
+   static PNG_CONST png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
 
    /* Start of interlace block in the y direction */
-   PNG_CONST int png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
+   static PNG_CONST png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
 
    /* Offset to next interlace block in the y direction */
-   PNG_CONST int png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
+   static PNG_CONST png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
 #endif
 
    int max_pixel_depth;
@@ -3187,29 +3908,44 @@ png_read_start_row(png_structp png_ptr)
 
    png_debug(1, "in png_read_start_row");
    png_ptr->zstream.avail_in = 0;
+#ifdef PNG_READ_TRANSFORMS_SUPPORTED
    png_init_read_transformations(png_ptr);
+#endif
 #ifdef PNG_READ_INTERLACING_SUPPORTED
    if (png_ptr->interlaced)
    {
       if (!(png_ptr->transformations & PNG_INTERLACE))
          png_ptr->num_rows = (png_ptr->height + png_pass_yinc[0] - 1 -
-            png_pass_ystart[0]) / png_pass_yinc[0];
+             png_pass_ystart[0]) / png_pass_yinc[0];
+
       else
          png_ptr->num_rows = png_ptr->height;
 
       png_ptr->iwidth = (png_ptr->width +
-         png_pass_inc[png_ptr->pass] - 1 -
-         png_pass_start[png_ptr->pass]) /
-         png_pass_inc[png_ptr->pass];
+          png_pass_inc[png_ptr->pass] - 1 -
+          png_pass_start[png_ptr->pass]) /
+          png_pass_inc[png_ptr->pass];
    }
+
    else
 #endif /* PNG_READ_INTERLACING_SUPPORTED */
    {
       png_ptr->num_rows = png_ptr->height;
       png_ptr->iwidth = png_ptr->width;
    }
+
    max_pixel_depth = png_ptr->pixel_depth;
 
+   /* WARNING: * png_read_transform_info (pngrtran.c) performs a simpliar set of
+    * calculations to calculate the final pixel depth, then
+    * png_do_read_transforms actually does the transforms.  This means that the
+    * code which effectively calculates this value is actually repeated in three
+    * separate places.  They must all match.  Innocent changes to the order of
+    * transformations can and will break libpng in a way that causes memory
+    * overwrites.
+    *
+    * TODO: fix this.
+    */
 #ifdef PNG_READ_PACK_SUPPORTED
    if ((png_ptr->transformations & PNG_PACK) && png_ptr->bit_depth < 8)
       max_pixel_depth = 8;
@@ -3222,16 +3958,20 @@ png_read_start_row(png_structp png_ptr)
       {
          if (png_ptr->num_trans)
             max_pixel_depth = 32;
+
          else
             max_pixel_depth = 24;
       }
+
       else if (png_ptr->color_type == PNG_COLOR_TYPE_GRAY)
       {
          if (max_pixel_depth < 8)
             max_pixel_depth = 8;
+
          if (png_ptr->num_trans)
             max_pixel_depth *= 2;
       }
+
       else if (png_ptr->color_type == PNG_COLOR_TYPE_RGB)
       {
          if (png_ptr->num_trans)
@@ -3243,22 +3983,42 @@ png_read_start_row(png_structp png_ptr)
    }
 #endif
 
+#ifdef PNG_READ_EXPAND_16_SUPPORTED
+   if (png_ptr->transformations & PNG_EXPAND_16)
+   {
+#     ifdef PNG_READ_EXPAND_SUPPORTED
+         /* In fact it is an error if it isn't supported, but checking is
+          * the safe way.
+          */
+         if (png_ptr->transformations & PNG_EXPAND)
+         {
+            if (png_ptr->bit_depth < 16)
+               max_pixel_depth *= 2;
+         }
+         else
+#     endif
+         png_ptr->transformations &= ~PNG_EXPAND_16;
+   }
+#endif
+
 #ifdef PNG_READ_FILLER_SUPPORTED
    if (png_ptr->transformations & (PNG_FILLER))
    {
-      if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
-         max_pixel_depth = 32;
-      else if (png_ptr->color_type == PNG_COLOR_TYPE_GRAY)
+      if (png_ptr->color_type == PNG_COLOR_TYPE_GRAY)
       {
          if (max_pixel_depth <= 8)
             max_pixel_depth = 16;
+
          else
             max_pixel_depth = 32;
       }
-      else if (png_ptr->color_type == PNG_COLOR_TYPE_RGB)
+
+      else if (png_ptr->color_type == PNG_COLOR_TYPE_RGB ||
+         png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
       {
          if (max_pixel_depth <= 32)
             max_pixel_depth = 32;
+
          else
             max_pixel_depth = 64;
       }
@@ -3270,29 +4030,34 @@ png_read_start_row(png_structp png_ptr)
    {
       if (
 #ifdef PNG_READ_EXPAND_SUPPORTED
-        (png_ptr->num_trans && (png_ptr->transformations & PNG_EXPAND)) ||
+          (png_ptr->num_trans && (png_ptr->transformations & PNG_EXPAND)) ||
 #endif
 #ifdef PNG_READ_FILLER_SUPPORTED
-        (png_ptr->transformations & (PNG_FILLER)) ||
+          (png_ptr->transformations & (PNG_FILLER)) ||
 #endif
-        png_ptr->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
+          png_ptr->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
       {
          if (max_pixel_depth <= 16)
             max_pixel_depth = 32;
+
          else
             max_pixel_depth = 64;
       }
+
       else
       {
          if (max_pixel_depth <= 8)
-           {
-             if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
+         {
+            if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
                max_pixel_depth = 32;
-             else
+
+            else
                max_pixel_depth = 24;
-           }
+         }
+
          else if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
             max_pixel_depth = 64;
+
          else
             max_pixel_depth = 48;
       }
@@ -3302,14 +4067,21 @@ png_read_start_row(png_structp png_ptr)
 #if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) && \
 defined(PNG_USER_TRANSFORM_PTR_SUPPORTED)
    if (png_ptr->transformations & PNG_USER_TRANSFORM)
-     {
-       int user_pixel_depth = png_ptr->user_transform_depth*
+   {
+      int user_pixel_depth = png_ptr->user_transform_depth *
          png_ptr->user_transform_channels;
-       if (user_pixel_depth > max_pixel_depth)
-         max_pixel_depth=user_pixel_depth;
-     }
+
+      if (user_pixel_depth > max_pixel_depth)
+         max_pixel_depth = user_pixel_depth;
+   }
 #endif
 
+   /* This value is stored in png_struct and double checked in the row read
+    * code.
+    */
+   png_ptr->maximum_pixel_depth = (png_byte)max_pixel_depth;
+   png_ptr->transformed_pixel_depth = 0; /* calculated on demand */
+
    /* Align the width on the next larger 8 pixels.  Mainly used
     * for interlacing
     */
@@ -3318,7 +4090,8 @@ defined(PNG_USER_TRANSFORM_PTR_SUPPORTED)
     * for safety's sake
     */
    row_bytes = PNG_ROWBYTES(max_pixel_depth, row_bytes) +
-      1 + ((max_pixel_depth + 7) >> 3);
+       1 + ((max_pixel_depth + 7) >> 3);
+
 #ifdef PNG_MAX_MALLOC_64K
    if (row_bytes > (png_uint_32)65536L)
       png_error(png_ptr, "This image requires a row greater than 64KB");
@@ -3327,52 +4100,60 @@ defined(PNG_USER_TRANSFORM_PTR_SUPPORTED)
    if (row_bytes + 48 > png_ptr->old_big_row_buf_size)
    {
      png_free(png_ptr, png_ptr->big_row_buf);
+     png_free(png_ptr, png_ptr->big_prev_row);
+
      if (png_ptr->interlaced)
         png_ptr->big_row_buf = (png_bytep)png_calloc(png_ptr,
             row_bytes + 48);
+
      else
-        png_ptr->big_row_buf = (png_bytep)png_malloc(png_ptr,
-            row_bytes + 48);
-     png_ptr->old_big_row_buf_size = row_bytes + 48;
+        png_ptr->big_row_buf = (png_bytep)png_malloc(png_ptr, row_bytes + 48);
+
+     png_ptr->big_prev_row = (png_bytep)png_malloc(png_ptr, row_bytes + 48);
 
 #ifdef PNG_ALIGNED_MEMORY_SUPPORTED
      /* Use 16-byte aligned memory for row_buf with at least 16 bytes
-      * of padding before and after row_buf.
+      * of padding before and after row_buf; treat prev_row similarly.
+      * NOTE: the alignment is to the start of the pixels, one beyond the start
+      * of the buffer, because of the filter byte.  Prior to libpng 1.5.6 this
+      * was incorrect; the filter byte was aligned, which had the exact
+      * opposite effect of that intended.
       */
-     png_ptr->row_buf = png_ptr->big_row_buf + 32
-         - (((png_alloc_size_t)&(png_ptr->big_row_buf[0]) + 15) % 16);
-     png_ptr->old_big_row_buf_size = row_bytes + 48;
+     {
+        png_bytep temp = png_ptr->big_row_buf + 32;
+        int extra = (int)((temp - (png_bytep)0) & 0x0f);
+        png_ptr->row_buf = temp - extra - 1/*filter byte*/;
+
+        temp = png_ptr->big_prev_row + 32;
+        extra = (int)((temp - (png_bytep)0) & 0x0f);
+        png_ptr->prev_row = temp - extra - 1/*filter byte*/;
+     }
+
 #else
-     /* Use 32 bytes of padding before and 16 bytes after row_buf. */
-     png_ptr->row_buf = png_ptr->big_row_buf + 32;
+     /* Use 31 bytes of padding before and 17 bytes after row_buf. */
+     png_ptr->row_buf = png_ptr->big_row_buf + 31;
+     png_ptr->prev_row = png_ptr->big_prev_row + 31;
 #endif
      png_ptr->old_big_row_buf_size = row_bytes + 48;
    }
 
 #ifdef PNG_MAX_MALLOC_64K
-   if ((png_uint_32)png_ptr->rowbytes + 1 > (png_uint_32)65536L)
+   if (png_ptr->rowbytes > 65535)
       png_error(png_ptr, "This image requires a row greater than 64KB");
+
 #endif
-   if ((png_uint_32)png_ptr->rowbytes > (png_uint_32)(PNG_SIZE_MAX - 1))
+   if (png_ptr->rowbytes > (PNG_SIZE_MAX - 1))
       png_error(png_ptr, "Row has too many bytes to allocate in memory");
 
-   if (png_ptr->rowbytes + 1 > png_ptr->old_prev_row_size)
-   {
-      png_free(png_ptr, png_ptr->prev_row);
-      png_ptr->prev_row = (png_bytep)png_malloc(png_ptr, (png_uint_32)(
-        png_ptr->rowbytes + 1));
-      png_ptr->old_prev_row_size = png_ptr->rowbytes + 1;
-   }
-
    png_memset(png_ptr->prev_row, 0, png_ptr->rowbytes + 1);
 
-   png_debug1(3, "width = %lu,", png_ptr->width);
-   png_debug1(3, "height = %lu,", png_ptr->height);
-   png_debug1(3, "iwidth = %lu,", png_ptr->iwidth);
-   png_debug1(3, "num_rows = %lu,", png_ptr->num_rows);
-   png_debug1(3, "rowbytes = %lu,", png_ptr->rowbytes);
+   png_debug1(3, "width = %u,", png_ptr->width);
+   png_debug1(3, "height = %u,", png_ptr->height);
+   png_debug1(3, "iwidth = %u,", png_ptr->iwidth);
+   png_debug1(3, "num_rows = %u,", png_ptr->num_rows);
+   png_debug1(3, "rowbytes = %lu,", (unsigned long)png_ptr->rowbytes);
    png_debug1(3, "irowbytes = %lu",
-       PNG_ROWBYTES(png_ptr->pixel_depth, png_ptr->iwidth) + 1);
+       (unsigned long)PNG_ROWBYTES(png_ptr->pixel_depth, png_ptr->iwidth) + 1);
 
    png_ptr->flags |= PNG_FLAG_ROW_INIT;
 }