[libpng15] Bump version to libpng-1.5.6beta02
diff --git a/ANNOUNCE b/ANNOUNCE
index 179b601..7c684d2 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -1,5 +1,5 @@
 
-Libpng 1.5.6beta01 - September 22, 2011
+Libpng 1.5.6beta02 - September 22, 2011
 
 This is not intended to be a public release.  It will be replaced
 within a few weeks by a public version or by another test version.
@@ -9,99 +9,36 @@
 Source files with LF line endings (for Unix/Linux) and with a
 "configure" script
 
-   1.5.6beta01.tar.xz (LZMA-compressed, recommended)
-   1.5.6beta01.tar.gz
-   1.5.6beta01.tar.bz2
+   1.5.6beta02.tar.xz (LZMA-compressed, recommended)
+   1.5.6beta02.tar.gz
+   1.5.6beta02.tar.bz2
 
 Source files with CRLF line endings (for Windows), without the
 "configure" script
 
-   lp156b01.7z  (LZMA-compressed, recommended)
-   lp156b01.zip
+   lp156b02.7z  (LZMA-compressed, recommended)
+   lp156b02.zip
 
 Other information:
 
-   1.5.6beta01-README.txt
-   1.5.6beta01-LICENSE.txt
+   1.5.6beta02-README.txt
+   1.5.6beta02-LICENSE.txt
 
-Changes since the last public release (1.5.4):
+Changes since the last public release (1.5.5):
 
-Version 1.5.5beta01 [July 13, 2011]
-  Fixed some typos and made other minor changes in the manual.
-  Updated contrib/pngminus/makefile.std (Samuli Souminen)
-
-Version 1.5.5beta02 [July 14, 2011]
-  Revised Makefile.am and Makefile.in to look in the right directory for
-    pnglibconf.h.prebuilt
-
-Version 1.5.5beta03 [July 27, 2011]
-  Enabled compilation with g++ compiler.  This compiler does not recognize
-    the file extension, so it always compiles with C++ rules.  Made minor
-    changes to pngrutil.c to cast results where C++ expects it but C does not.
-  Minor editing of libpng.3 and libpng-manual.txt.
-
-Version 1.5.5beta04 [July 29, 2011]
-  Revised CMakeLists.txt (Clifford Yapp)
-  Updated commentary about the png_rgb_to_gray() default coefficients
-    in the manual and in pngrtran.c
-
-Version 1.5.5beta05 [August 17, 2011]
-  Prevent unexpected API exports from non-libpng DLLs on Windows.  The "_DLL"
-    is removed from the test of whether a DLL is being built (this erroneously
-    caused the libpng APIs to be marked as DLL exports in static builds under
-    Microsoft Visual Studio).  Almost all of the libpng building configuration
-    is moved from pngconf.h to pngpriv.h, but PNG_DLL_EXPORT remains in
-    pngconf.h, though, so that it is colocated with the import definition (it
-    is no longer used anywhere in the installed headers).  The VStudio project
-    definitions have been cleaned up: "_USRDLL" has been removed from the
-    static library builds (this was incorrect), and PNG_USE_DLL has been added
-    to pngvalid to test the functionality (pngtest does not supply it,
-    deliberately).  The spurious "_EXPORTS" has been removed from the
-    libpng build (all these errors were a result of copy/paste between project
-    configurations.)
-  Added new types and internal functions for CIE RGB end point handling to
-    pngpriv.h (functions yet to be implemented).
-
-Version 1.5.5beta06 [August 26, 2011]
-  Ensure the CMAKE_LIBRARY_OUTPUT_DIRECTORY is set in CMakeLists.txt
-    (Clifford Yap)
-  Fixes to rgb_to_gray and cHRM XYZ APIs (John Bowler):
-    The rgb_to_gray code had errors when combined with gamma correction.
-    Some pixels were treated as true grey when they weren't and such pixels
-    and true grey ones were not gamma corrected (the original value of the
-    red component was used instead).  APIs to get and set cHRM using color
-    space end points have been added and the rgb_to_gray code that defaults
-    based on cHRM, and the divide-by-zero bug in png_handle_cHRM (CERT
-    VU#477046, CVE-2011-3328, introduced in 1.5.4) have been corrected.
-  A considerable number of tests has been added to pngvalid for the
-    rgb_to_gray transform.
-  Arithmetic errors in rgb_to_gray whereby the calculated gray value was
-    truncated to the bit depth rather than rounded have been fixed except in
-    the 8-bit non-gamma-corrected case (where consistency seems more important
-    than correctness.)  The code still has considerable inaccuracies in the
-    8-bit case because 8-bit linear arithmetic is used.
-
-Version 1.5.5beta07 [September 7, 2011]
-  Added "$(ARCH)" option to makefile.darwin
-  Added SunOS support to configure.ac and Makefile.am
-  Changed png_chunk_benign_error() to png_warning() in png.c, in
-    png_XYZ_from_xy_checked().
-
-Version 1.5.5beta08 [September 10, 2011]
-  Fixed 64-bit compilation errors (gcc). The errors fixed relate
-    to conditions where types that are 32 bits in the GCC 32-bit
-    world (uLong and png_size_t) become 64 bits in the 64-bit
-    world.  This produces potential truncation errors that the
-    compiler correctly flags.
-  Relocated new HAVE_SOLARIS_LD definition in configure.ac
-  Constant changes for 64-bit compatibility (removal of L suffixes). The
-    16-bit cases still use "L" as we don't have a 16-bit test system.
-
-Version 1.5.5rc01 [September 17, 2011]
-  Removed "L" suffixes from constants in pngpriv.h
-
-Version 1.5.5 [September 22, 2011]
-  No changes.
+Version 1.5.6beta01 [September 22, 2011]
+  Fixed some 64-bit type conversion warnings in pngrtran.c
+  Moved row_info from png_struct to a local variable.
+  The various interlace mask arrays have been made into arrays of
+    bytes and made PNG_CONST and static (previously some arrays were
+    marked PNG_CONST and some weren't).
+  Additional checks have been added to the transform code to validate the
+    pixel depths after the transforms on both read and write.
+  Removed some redundant code from pngwrite.c, in png_desgtroy_write_struct().
+  Changed chunk reading/writing code to use png_uint_32 instead of png_byte[4].
+    This removes the need to allocate temporary strings for chunk names on
+    the stack in the read/write code.  Unknown chunk handling still uses the
+    string form because this is exposed in the API.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net:
 (subscription required; visit
diff --git a/CHANGES b/CHANGES
index dd31a96..6556584 100644
--- a/CHANGES
+++ b/CHANGES
@@ -3575,18 +3575,34 @@
   Fixed 64-bit compilation errors (gcc). The errors fixed relate
     to conditions where types that are 32 bits in the GCC 32-bit
     world (uLong and png_size_t) become 64 bits in the 64-bit
-    world.  This produces potential truncation errors that the
+    world.  This produces potential truncation errors which the
     compiler correctly flags.
   Relocated new HAVE_SOLARIS_LD definition in configure.ac
   Constant changes for 64-bit compatibility (removal of L suffixes). The
     16-bit cases still use "L" as we don't have a 16-bit test system.
 
-Version 1.5.5rc01 [September 17, 2011]
-  Removed "L" suffixes from constants in pngpriv.h
+Version 1.5.5rc01 [September 15, 2011]
+  Removed "L" suffixes in pngpriv.h
 
 Version 1.5.5 [September 22, 2011]
   No changes.
 
+Version 1.5.6beta01 [September 22, 2011]
+  Fixed some 64-bit type conversion warnings in pngrtran.c
+  Moved row_info from png_struct to a local variable.
+  The various interlace mask arrays have been made into arrays of
+    bytes and made PNG_CONST and static (previously some arrays were
+    marked PNG_CONST and some weren't).
+  Additional checks have been added to the transform code to validate the
+    pixel depths after the transforms on both read and write.
+  Removed some redundant code from pngwrite.c, in png_destroy_write_struct().
+  Changed chunk reading/writing code to use png_uint_32 instead of png_byte[4].
+    This removes the need to allocate temporary strings for chunk names on
+    the stack in the read/write code.  Unknown chunk handling still uses the
+    string form because this is exposed in the API.
+
+Version 1.5.6beta02 [September 22, 2011]
+
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
 https://lists.sourceforge.net/lists/listinfo/png-mng-implement
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4bcd794..9b828dd 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -262,7 +262,7 @@
 # SET UP LINKS
 if(PNG_SHARED)
   set_target_properties(${PNG_LIB_NAME} PROPERTIES
-#   VERSION 15.${PNGLIB_RELEASE}.1.5.6beta01
+#   VERSION 15.${PNGLIB_RELEASE}.1.5.6beta02
     VERSION 15.${PNGLIB_RELEASE}.0
     SOVERSION 15
     CLEAN_DIRECT_OUTPUT 1)
diff --git a/LICENSE b/LICENSE
index 586268a..f5664ea 100644
--- a/LICENSE
+++ b/LICENSE
@@ -10,7 +10,7 @@
 
 This code is released under the libpng license.
 
-libpng versions 1.2.6, August 15, 2004, through 1.5.6beta01, September 22, 2011, are
+libpng versions 1.2.6, August 15, 2004, through 1.5.6beta02, September 22, 2011, are
 Copyright (c) 2004, 2006-2011 Glenn Randers-Pehrson, and are
 distributed according to the same disclaimer and license as libpng-1.2.5
 with the following individual added to the list of Contributing Authors
diff --git a/README b/README
index 31398bd..25d8844 100644
--- a/README
+++ b/README
@@ -1,4 +1,4 @@
-README for libpng version 1.5.6beta01 - September 22, 2011 (shared library 15.0)
+README for libpng version 1.5.6beta02 - September 22, 2011 (shared library 15.0)
 See the note about version numbers near the top of png.h
 
 See INSTALL for instructions on how to install libpng.
diff --git a/configure b/configure
index e22b3fc..a1ac4f8 100755
--- a/configure
+++ b/configure
@@ -1,6 +1,6 @@
 #! /bin/sh
 # Guess values for system-dependent variables and create Makefiles.
-# Generated by GNU Autoconf 2.68 for libpng 1.5.6beta01.
+# Generated by GNU Autoconf 2.68 for libpng 1.5.6beta02.
 #
 # Report bugs to <png-mng-implement@lists.sourceforge.net>.
 #
@@ -570,8 +570,8 @@
 # Identity of this package.
 PACKAGE_NAME='libpng'
 PACKAGE_TARNAME='libpng'
-PACKAGE_VERSION='1.5.6beta01'
-PACKAGE_STRING='libpng 1.5.6beta01'
+PACKAGE_VERSION='1.5.6beta02'
+PACKAGE_STRING='libpng 1.5.6beta02'
 PACKAGE_BUGREPORT='png-mng-implement@lists.sourceforge.net'
 PACKAGE_URL=''
 
@@ -1308,7 +1308,7 @@
   # Omit some internal or obsolete options to make the list less imposing.
   # This message is too long to be a string in the A/UX 3.1 sh.
   cat <<_ACEOF
-\`configure' configures libpng 1.5.6beta01 to adapt to many kinds of systems.
+\`configure' configures libpng 1.5.6beta02 to adapt to many kinds of systems.
 
 Usage: $0 [OPTION]... [VAR=VALUE]...
 
@@ -1378,7 +1378,7 @@
 
 if test -n "$ac_init_help"; then
   case $ac_init_help in
-     short | recursive ) echo "Configuration of libpng 1.5.6beta01:";;
+     short | recursive ) echo "Configuration of libpng 1.5.6beta02:";;
    esac
   cat <<\_ACEOF
 
@@ -1486,7 +1486,7 @@
 test -n "$ac_init_help" && exit $ac_status
 if $ac_init_version; then
   cat <<\_ACEOF
-libpng configure 1.5.6beta01
+libpng configure 1.5.6beta02
 generated by GNU Autoconf 2.68
 
 Copyright (C) 2010 Free Software Foundation, Inc.
@@ -1909,7 +1909,7 @@
 This file contains any messages produced by compilers while
 running configure, to aid debugging if configure makes a mistake.
 
-It was created by libpng $as_me 1.5.6beta01, which was
+It was created by libpng $as_me 1.5.6beta02, which was
 generated by GNU Autoconf 2.68.  Invocation command line was
 
   $ $0 $@
@@ -2724,7 +2724,7 @@
 
 # Define the identity of the package.
  PACKAGE='libpng'
- VERSION='1.5.6beta01'
+ VERSION='1.5.6beta02'
 
 
 cat >>confdefs.h <<_ACEOF
@@ -2788,7 +2788,7 @@
 
 
 
-PNGLIB_VERSION=1.5.6beta01
+PNGLIB_VERSION=1.5.6beta02
 PNGLIB_MAJOR=1
 PNGLIB_MINOR=5
 PNGLIB_RELEASE=6
@@ -13073,7 +13073,7 @@
 # report actual input values of CONFIG_FILES etc. instead of their
 # values after options handling.
 ac_log="
-This file was extended by libpng $as_me 1.5.6beta01, which was
+This file was extended by libpng $as_me 1.5.6beta02, which was
 generated by GNU Autoconf 2.68.  Invocation command line was
 
   CONFIG_FILES    = $CONFIG_FILES
@@ -13139,7 +13139,7 @@
 cat >>$CONFIG_STATUS <<_ACEOF || ac_write_fail=1
 ac_cs_config="`$as_echo "$ac_configure_args" | sed 's/^ //; s/[\\""\`\$]/\\\\&/g'`"
 ac_cs_version="\\
-libpng config.status 1.5.6beta01
+libpng config.status 1.5.6beta02
 configured by $0, generated by GNU Autoconf 2.68,
   with options \\"\$ac_cs_config\\"
 
diff --git a/configure.ac b/configure.ac
index 3a93763..144181d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -18,12 +18,12 @@
 
 dnl Version number stuff here:
 
-AC_INIT([libpng], [1.5.6beta01], [png-mng-implement@lists.sourceforge.net])
+AC_INIT([libpng], [1.5.6beta02], [png-mng-implement@lists.sourceforge.net])
 AM_INIT_AUTOMAKE
 dnl stop configure from automagically running automake
 AM_MAINTAINER_MODE
 
-PNGLIB_VERSION=1.5.6beta01
+PNGLIB_VERSION=1.5.6beta02
 PNGLIB_MAJOR=1
 PNGLIB_MINOR=5
 PNGLIB_RELEASE=6
diff --git a/libpng-manual.txt b/libpng-manual.txt
index b17753f..a80d7eb 100644
--- a/libpng-manual.txt
+++ b/libpng-manual.txt
@@ -1,6 +1,6 @@
 libpng-manual.txt - A description on how to use and modify libpng
 
- libpng version 1.5.6beta01 - September 22, 2011
+ libpng version 1.5.6beta02 - September 22, 2011
  Updated and distributed by Glenn Randers-Pehrson
  <glennrp at users.sourceforge.net>
  Copyright (c) 1998-2011 Glenn Randers-Pehrson
@@ -11,7 +11,7 @@
 
  Based on:
 
- libpng versions 0.97, January 1998, through 1.5.6beta01 - September 22, 2011
+ libpng versions 0.97, January 1998, through 1.5.6beta02 - September 22, 2011
  Updated and distributed by Glenn Randers-Pehrson
  Copyright (c) 1998-2011 Glenn Randers-Pehrson
 
@@ -4566,7 +4566,7 @@
 an official declaration.
 
 This is your unofficial assurance that libpng from version 0.71 and
-upward through 1.5.6beta01 are Y2K compliant.  It is my belief that earlier
+upward through 1.5.6beta02 are Y2K compliant.  It is my belief that earlier
 versions were also Y2K compliant.
 
 Libpng only has three year fields.  One is a 2-byte unsigned integer that
diff --git a/libpng.3 b/libpng.3
index c9ad0dd..f02668d 100644
--- a/libpng.3
+++ b/libpng.3
@@ -1,6 +1,6 @@
 .TH LIBPNG 3 "September 22, 2011"
 .SH NAME
-libpng \- Portable Network Graphics (PNG) Reference Library 1.5.6beta01
+libpng \- Portable Network Graphics (PNG) Reference Library 1.5.6beta02
 .SH SYNOPSIS
 \fI\fB
 
@@ -977,7 +977,7 @@
 .SH LIBPNG.TXT
 libpng-manual.txt - A description on how to use and modify libpng
 
- libpng version 1.5.6beta01 - September 22, 2011
+ libpng version 1.5.6beta02 - September 22, 2011
  Updated and distributed by Glenn Randers-Pehrson
  <glennrp at users.sourceforge.net>
  Copyright (c) 1998-2011 Glenn Randers-Pehrson
@@ -988,7 +988,7 @@
 
  Based on:
 
- libpng versions 0.97, January 1998, through 1.5.6beta01 - September 22, 2011
+ libpng versions 0.97, January 1998, through 1.5.6beta02 - September 22, 2011
  Updated and distributed by Glenn Randers-Pehrson
  Copyright (c) 1998-2011 Glenn Randers-Pehrson
 
@@ -5544,7 +5544,7 @@
 an official declaration.
 
 This is your unofficial assurance that libpng from version 0.71 and
-upward through 1.5.6beta01 are Y2K compliant.  It is my belief that earlier
+upward through 1.5.6beta02 are Y2K compliant.  It is my belief that earlier
 versions were also Y2K compliant.
 
 Libpng only has three year fields.  One is a 2-byte unsigned integer that
@@ -5743,6 +5743,7 @@
  1.5.5beta01-08      15    10505  15.so.15.5[.0]
  1.5.5rc01           15    10505  15.so.15.5[.0]
  1.5.5               15    10505  15.so.15.5[.0]
+ 1.5.6beta01-02      15    10506  15.so.15.6[.0]
 
 Henceforth the source version will match the shared-library minor
 and patch numbers; the shared-library major version number will be
@@ -5799,7 +5800,7 @@
 
 Thanks to Frank J. T. Wojcik for helping with the documentation.
 
-Libpng version 1.5.6beta01 - September 22, 2011:
+Libpng version 1.5.6beta02 - September 22, 2011:
 Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc.
 Currently maintained by Glenn Randers-Pehrson (glennrp at users.sourceforge.net).
 
@@ -5822,7 +5823,7 @@
 
 This code is released under the libpng license.
 
-libpng versions 1.2.6, August 15, 2004, through 1.5.6beta01, September 22, 2011, are
+libpng versions 1.2.6, August 15, 2004, through 1.5.6beta02, September 22, 2011, are
 Copyright (c) 2004,2006-2007 Glenn Randers-Pehrson, and are
 distributed according to the same disclaimer and license as libpng-1.2.5
 with the following individual added to the list of Contributing Authors
diff --git a/libpngpf.3 b/libpngpf.3
index 68f3b4f..6c9ccd5 100644
--- a/libpngpf.3
+++ b/libpngpf.3
@@ -1,6 +1,6 @@
 .TH LIBPNGPF 3 "September 22, 2011"
 .SH NAME
-libpng \- Portable Network Graphics (PNG) Reference Library 1.5.6beta01
+libpng \- Portable Network Graphics (PNG) Reference Library 1.5.6beta02
 (private functions)
 .SH SYNOPSIS
 \fB#include \fI"pngpriv.h"
diff --git a/png.c b/png.c
index 6d073c6..4f80710 100644
--- a/png.c
+++ b/png.c
@@ -1,7 +1,7 @@
 
 /* png.c - location for general purpose libpng functions
  *
- * Last changed in libpng 1.5.5 [(PENDING RELEASE)]
+ * Last changed in libpng 1.5.6 [(PENDING RELEASE)]
  * 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.)
@@ -14,7 +14,7 @@
 #include "pngpriv.h"
 
 /* Generate a compiler error if there is an old png.h in the search path. */
-typedef png_libpng_version_1_5_6beta01 Your_png_h_is_not_version_1_5_6beta01;
+typedef png_libpng_version_1_5_6beta02 Your_png_h_is_not_version_1_5_6beta02;
 
 /* Tells libpng that we have already handled the first "num_bytes" bytes
  * of the PNG file signature.  If the PNG data is embedded into another
@@ -121,14 +121,14 @@
 {
    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;
@@ -645,13 +645,13 @@
 #else
 #  ifdef __STDC__
    return PNG_STRING_NEWLINE \
-     "libpng version 1.5.6beta01 - September 22, 2011" PNG_STRING_NEWLINE \
+     "libpng version 1.5.6beta02 - September 22, 2011" PNG_STRING_NEWLINE \
      "Copyright (c) 1998-2011 Glenn Randers-Pehrson" PNG_STRING_NEWLINE \
      "Copyright (c) 1996-1997 Andreas Dilger" PNG_STRING_NEWLINE \
      "Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc." \
      PNG_STRING_NEWLINE;
 #  else
-      return "libpng version 1.5.6beta01 - September 22, 2011\
+      return "libpng version 1.5.6beta02 - September 22, 2011\
       Copyright (c) 1998-2011 Glenn Randers-Pehrson\
       Copyright (c) 1996-1997 Andreas Dilger\
       Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.";
@@ -698,25 +698,43 @@
 #endif
 }
 
-#if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
-#  ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
+#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
 int PNGAPI
 png_handle_as_unknown(png_structp png_ptr, png_const_bytep chunk_name)
 {
    /* Check chunk_name and return "keep" value if it's on the list, else 0 */
-   int i;
-   png_bytep p;
-   if (png_ptr == NULL || chunk_name == NULL || png_ptr->num_chunk_list<=0)
-      return 0;
+   png_const_bytep p, p_end;
 
-   p = png_ptr->chunk_list + png_ptr->num_chunk_list*5 - 5;
-   for (i = png_ptr->num_chunk_list; i; i--, p -= 5)
+   if (png_ptr == NULL || chunk_name == NULL || png_ptr->num_chunk_list <= 0)
+      return PNG_HANDLE_CHUNK_AS_DEFAULT;
+
+   p_end = png_ptr->chunk_list;
+   p = p_end + png_ptr->num_chunk_list*5; /* beyond end */
+
+   /* The code is the fifth byte after each four byte string.  Historically this
+    * code was always searched from the end of the list, so it should continue
+    * to do so in case there are duplicated entries.
+    */
+   do /* num_chunk_list > 0, so at least one */
+   {
+      p -= 5;
       if (!png_memcmp(chunk_name, p, 4))
-        return ((int)*(p + 4));
-   return 0;
+         return p[4];
+   }
+   while (p > p_end);
+
+   return PNG_HANDLE_CHUNK_AS_DEFAULT;
 }
-#  endif
-#endif /* defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) */
+
+int /* PRIVATE */
+png_chunk_unknown_handling(png_structp png_ptr, png_uint_32 chunk_name)
+{
+   png_byte chunk_string[5];
+
+   PNG_CSTRING_FROM_CHUNK(chunk_string, chunk_name);
+   return png_handle_as_unknown(png_ptr, chunk_string);
+}
+#endif
 
 #ifdef PNG_READ_SUPPORTED
 /* This function, added to libpng-1.0.6g, is untested. */
diff --git a/png.h b/png.h
index bb551d6..b2ab3c9 100644
--- a/png.h
+++ b/png.h
@@ -1,7 +1,7 @@
 
 /* png.h - header file for PNG reference library
  *
- * libpng version 1.5.6beta01 - September 22, 2011
+ * libpng version 1.5.6beta02 - September 22, 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.)
@@ -11,7 +11,7 @@
  * Authors and maintainers:
  *   libpng versions 0.71, May 1995, through 0.88, January 1996: Guy Schalnat
  *   libpng versions 0.89c, June 1996, through 0.96, May 1997: Andreas Dilger
- *   libpng versions 0.97, January 1998, through 1.5.6beta01 - September 22, 2011: Glenn
+ *   libpng versions 0.97, January 1998, through 1.5.6beta02 - September 22, 2011: Glenn
  *   See also "Contributing Authors", below.
  *
  * Note about libpng version numbers:
@@ -160,6 +160,7 @@
  *    1.5.5beta01-08          15    10505  15.so.15.5[.0]
  *    1.5.5rc01               15    10505  15.so.15.5[.0]
  *    1.5.5                   15    10505  15.so.15.5[.0]
+ *    1.5.6beta01-02          15    10506  15.so.15.6[.0]
  *
  *   Henceforth the source version will match the shared-library major
  *   and minor numbers; the shared-library major version number will be
@@ -191,7 +192,7 @@
  *
  * This code is released under the libpng license.
  *
- * libpng versions 1.2.6, August 15, 2004, through 1.5.6beta01, September 22, 2011, are
+ * libpng versions 1.2.6, August 15, 2004, through 1.5.6beta02, September 22, 2011, are
  * Copyright (c) 2004, 2006-2011 Glenn Randers-Pehrson, and are
  * distributed according to the same disclaimer and license as libpng-1.2.5
  * with the following individual added to the list of Contributing Authors:
@@ -309,7 +310,7 @@
  *    an official declaration.
  *
  *    This is your unofficial assurance that libpng from version 0.71 and
- *    upward through 1.5.6beta01 are Y2K compliant.  It is my belief that
+ *    upward through 1.5.6beta02 are Y2K compliant.  It is my belief that
  *    earlier versions were also Y2K compliant.
  *
  *    Libpng only has two year fields.  One is a 2-byte unsigned integer
@@ -364,9 +365,9 @@
  */
 
 /* Version information for png.h - this should match the version in png.c */
-#define PNG_LIBPNG_VER_STRING "1.5.6beta01"
+#define PNG_LIBPNG_VER_STRING "1.5.6beta02"
 #define PNG_HEADER_VERSION_STRING \
-     " libpng version 1.5.6beta01 - September 22, 2011\n"
+     " libpng version 1.5.6beta02 - September 22, 2011\n"
 
 #define PNG_LIBPNG_VER_SONUM   15
 #define PNG_LIBPNG_VER_DLLNUM  15
@@ -379,7 +380,7 @@
  * PNG_LIBPNG_VER_STRING, omitting any leading zero:
  */
 
-#define PNG_LIBPNG_VER_BUILD  01
+#define PNG_LIBPNG_VER_BUILD  02
 
 /* Release Status */
 #define PNG_LIBPNG_BUILD_ALPHA    1
@@ -526,7 +527,7 @@
 /* This triggers a compiler error in png.c, if png.c and png.h
  * do not agree upon the version number.
  */
-typedef char* png_libpng_version_1_5_6beta01;
+typedef char* png_libpng_version_1_5_6beta02;
 
 /* Three color definitions.  The order of the red, green, and blue, (and the
  * exact size) is not important, although the size of the fields need to
@@ -2305,15 +2306,21 @@
 /* Provide a list of chunks and how they are to be handled, if the built-in
    handling or default unknown chunk handling is not desired.  Any chunks not
    listed will be handled in the default manner.  The IHDR and IEND chunks
-   must not be listed.
-      keep = 0: follow default behavior
-           = 1: do not keep
-           = 2: keep only if safe-to-copy
-           = 3: keep even if unsafe-to-copy
+   must not be listed.  Because this turns off the default handling for chunks
+   that would otherwise be recognized the behavior of libpng transformations may
+   well become incorrect!
+      keep = 0: PNG_HANDLE_CHUNK_AS_DEFAULT: follow default behavior
+           = 1: PNG_HANDLE_CHUNK_NEVER:      do not keep
+           = 2: PNG_HANDLE_CHUNK_IF_SAFE:    keep only if safe-to-copy
+           = 3: PNG_HANDLE_CHUNK_ALWAYS:     keep even if unsafe-to-copy
 */
 PNG_EXPORT(172, void, png_set_keep_unknown_chunks,
     (png_structp png_ptr, int keep,
     png_const_bytep chunk_list, int num_chunks));
+
+/* The handling code is returned; the result is therefore true (non-zero) if
+ * special handling is required, false for the default handling.
+ */
 PNG_EXPORT(173, int, png_handle_as_unknown, (png_structp png_ptr,
     png_const_bytep chunk_name));
 #endif
diff --git a/pngconf.h b/pngconf.h
index 851a6e5..e24a2f9 100644
--- a/pngconf.h
+++ b/pngconf.h
@@ -1,7 +1,7 @@
 
 /* pngconf.h - machine configurable file for libpng
  *
- * libpng version 1.5.6beta01 - September 22, 2011
+ * libpng version 1.5.6beta02 - September 22, 2011
  *
  * Copyright (c) 1998-2011 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
diff --git a/pngerror.c b/pngerror.c
index 4d4ceba..e77c1e6 100644
--- a/pngerror.c
+++ b/pngerror.c
@@ -1,7 +1,7 @@
 
 /* pngerror.c - stub functions for i/o and memory allocation
  *
- * Last changed in libpng 1.5.4 [July 7, 2011]
+ * Last changed in libpng 1.5.6 [(PENDING RELEASE)]
  * 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.)
@@ -374,11 +374,14 @@
 png_format_buffer(png_structp png_ptr, png_charp buffer, png_const_charp
     error_message)
 {
-   int iout = 0, iin = 0;
+   png_uint_32 chunk_name = png_ptr->chunk_name;
+   int iout = 0, ishift = 24;
 
-   while (iin < 4)
+   while (ishift >= 0)
    {
-      int c = png_ptr->chunk_name[iin++];
+      int c = (int)(chunk_name >> ishift) & 0xff;
+
+      ishift -= 8;
       if (isnonalpha(c))
       {
          buffer[iout++] = PNG_LITERAL_LEFT_SQUARE_BRACKET;
@@ -389,7 +392,7 @@
 
       else
       {
-         buffer[iout++] = (png_byte)c;
+         buffer[iout++] = (char)c;
       }
    }
 
@@ -398,10 +401,11 @@
 
    else
    {
+      int iin = 0;
+
       buffer[iout++] = ':';
       buffer[iout++] = ' ';
 
-      iin = 0;
       while (iin < PNG_MAX_ERROR_TEXT-1 && error_message[iin] != '\0')
          buffer[iout++] = error_message[iin++];
 
diff --git a/pngget.c b/pngget.c
index 770c123..4330921 100644
--- a/pngget.c
+++ b/pngget.c
@@ -1,7 +1,7 @@
 
 /* pngget.c - retrieval of values from info struct
  *
- * Last changed in libpng 1.5.5 [(PENDING RELEASE)]
+ * Last changed in libpng 1.5.6 [(PENDING RELEASE)]
  * 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.)
@@ -950,9 +950,8 @@
 {
    if (png_ptr != NULL && info_ptr != NULL && info_ptr->num_text > 0)
    {
-      png_debug1(1, "in %s retrieval function",
-          (png_ptr->chunk_name[0] == '\0' ? "text" :
-          (png_const_charp)png_ptr->chunk_name));
+      png_debug1(1, "in 0x%lx retrieval function",
+         (unsigned long)png_ptr->chunk_name);
 
       if (text_ptr != NULL)
          *text_ptr = info_ptr->text;
@@ -1111,16 +1110,14 @@
 png_uint_32 PNGAPI
 png_get_io_chunk_type (png_const_structp png_ptr)
 {
-   return ((png_ptr->chunk_name[0] << 24) +
-           (png_ptr->chunk_name[1] << 16) +
-           (png_ptr->chunk_name[2] <<  8) +
-           (png_ptr->chunk_name[3]));
+   return png_ptr->chunk_name;
 }
 
 png_const_bytep PNGAPI
 png_get_io_chunk_name (png_structp png_ptr)
 {
-   return png_ptr->chunk_name;
+   PNG_CSTRING_FROM_CHUNK(png_ptr->io_chunk_string, png_ptr->chunk_name);
+   return png_ptr->io_chunk_string;
 }
 #endif /* ?PNG_IO_STATE_SUPPORTED */
 
diff --git a/pngpread.c b/pngpread.c
index a50292a..3c666dc 100644
--- a/pngpread.c
+++ b/pngpread.c
@@ -1,7 +1,7 @@
 
 /* pngpread.c - read a png file in push mode
  *
- * Last changed in libpng 1.5.2 [March 31, 2011]
+ * Last changed in libpng 1.5.6 [(PENDING RELEASE)]
  * 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.)
@@ -208,61 +208,7 @@
 void /* PRIVATE */
 png_push_read_chunk(png_structp png_ptr, png_infop info_ptr)
 {
-      PNG_IHDR;
-      PNG_IDAT;
-      PNG_IEND;
-      PNG_PLTE;
-#ifdef PNG_READ_bKGD_SUPPORTED
-      PNG_bKGD;
-#endif
-#ifdef PNG_READ_cHRM_SUPPORTED
-      PNG_cHRM;
-#endif
-#ifdef PNG_READ_gAMA_SUPPORTED
-      PNG_gAMA;
-#endif
-#ifdef PNG_READ_hIST_SUPPORTED
-      PNG_hIST;
-#endif
-#ifdef PNG_READ_iCCP_SUPPORTED
-      PNG_iCCP;
-#endif
-#ifdef PNG_READ_iTXt_SUPPORTED
-      PNG_iTXt;
-#endif
-#ifdef PNG_READ_oFFs_SUPPORTED
-      PNG_oFFs;
-#endif
-#ifdef PNG_READ_pCAL_SUPPORTED
-      PNG_pCAL;
-#endif
-#ifdef PNG_READ_pHYs_SUPPORTED
-      PNG_pHYs;
-#endif
-#ifdef PNG_READ_sBIT_SUPPORTED
-      PNG_sBIT;
-#endif
-#ifdef PNG_READ_sCAL_SUPPORTED
-      PNG_sCAL;
-#endif
-#ifdef PNG_READ_sRGB_SUPPORTED
-      PNG_sRGB;
-#endif
-#ifdef PNG_READ_sPLT_SUPPORTED
-      PNG_sPLT;
-#endif
-#ifdef PNG_READ_tEXt_SUPPORTED
-      PNG_tEXt;
-#endif
-#ifdef PNG_READ_tIME_SUPPORTED
-      PNG_tIME;
-#endif
-#ifdef PNG_READ_tRNS_SUPPORTED
-      PNG_tRNS;
-#endif
-#ifdef PNG_READ_zTXt_SUPPORTED
-      PNG_zTXt;
-#endif
+   png_uint_32 chunk_name;
 
    /* First we make sure we have enough data for the 4 byte chunk name
     * and the 4 byte chunk length before proceeding with decoding the
@@ -273,6 +219,7 @@
    if (!(png_ptr->mode & PNG_HAVE_CHUNK_HEADER))
    {
       png_byte chunk_length[4];
+      png_byte chunk_tag[4];
 
       if (png_ptr->buffer_size < 8)
       {
@@ -283,16 +230,19 @@
       png_push_fill_buffer(png_ptr, chunk_length, 4);
       png_ptr->push_length = png_get_uint_31(png_ptr, chunk_length);
       png_reset_crc(png_ptr);
-      png_crc_read(png_ptr, png_ptr->chunk_name, 4);
+      png_crc_read(png_ptr, chunk_tag, 4);
+      png_ptr->chunk_name = PNG_CHUNK_FROM_STRING(chunk_tag);
       png_check_chunk_name(png_ptr, png_ptr->chunk_name);
       png_ptr->mode |= PNG_HAVE_CHUNK_HEADER;
    }
 
-   if (!png_memcmp(png_ptr->chunk_name, png_IDAT, 4))
+   chunk_name = png_ptr->chunk_name;
+
+   if (chunk_name == png_IDAT)
       if (png_ptr->mode & PNG_AFTER_IDAT)
          png_ptr->mode |= PNG_HAVE_CHUNK_AFTER_IDAT;
 
-   if (!png_memcmp(png_ptr->chunk_name, png_IHDR, 4))
+   if (chunk_name == png_IHDR)
    {
       if (png_ptr->push_length != 13)
          png_error(png_ptr, "Invalid IHDR length");
@@ -306,7 +256,7 @@
       png_handle_IHDR(png_ptr, info_ptr, png_ptr->push_length);
    }
 
-   else if (!png_memcmp(png_ptr->chunk_name, png_IEND, 4))
+   else if (chunk_name == png_IEND)
    {
       if (png_ptr->push_length + 4 > png_ptr->buffer_size)
       {
@@ -321,7 +271,7 @@
    }
 
 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
-   else if (png_handle_as_unknown(png_ptr, png_ptr->chunk_name))
+   else if (png_chunk_unknown_handling(png_ptr, chunk_name))
    {
       if (png_ptr->push_length + 4 > png_ptr->buffer_size)
       {
@@ -329,15 +279,15 @@
          return;
       }
 
-      if (!png_memcmp(png_ptr->chunk_name, png_IDAT, 4))
+      if (chunk_name == png_IDAT)
          png_ptr->mode |= PNG_HAVE_IDAT;
 
       png_handle_unknown(png_ptr, info_ptr, png_ptr->push_length);
 
-      if (!png_memcmp(png_ptr->chunk_name, png_PLTE, 4))
+      if (chunk_name == png_PLTE)
          png_ptr->mode |= PNG_HAVE_PLTE;
 
-      else if (!png_memcmp(png_ptr->chunk_name, png_IDAT, 4))
+      else if (chunk_name == png_IDAT)
       {
          if (!(png_ptr->mode & PNG_HAVE_IHDR))
             png_error(png_ptr, "Missing IHDR before IDAT");
@@ -349,7 +299,7 @@
    }
 
 #endif
-   else if (!png_memcmp(png_ptr->chunk_name, png_PLTE, 4))
+   else if (chunk_name == png_PLTE)
    {
       if (png_ptr->push_length + 4 > png_ptr->buffer_size)
       {
@@ -359,7 +309,7 @@
       png_handle_PLTE(png_ptr, info_ptr, png_ptr->push_length);
    }
 
-   else if (!png_memcmp(png_ptr->chunk_name, png_IDAT, 4))
+   else if (chunk_name == png_IDAT)
    {
       /* If we reach an IDAT chunk, this means we have read all of the
        * header chunks, and we can start reading the image (or if this
@@ -395,7 +345,7 @@
    }
 
 #ifdef PNG_READ_gAMA_SUPPORTED
-   else if (!png_memcmp(png_ptr->chunk_name, png_gAMA, 4))
+   else if (png_ptr->chunk_name == png_gAMA)
    {
       if (png_ptr->push_length + 4 > png_ptr->buffer_size)
       {
@@ -408,7 +358,7 @@
 
 #endif
 #ifdef PNG_READ_sBIT_SUPPORTED
-   else if (!png_memcmp(png_ptr->chunk_name, png_sBIT, 4))
+   else if (png_ptr->chunk_name == png_sBIT)
    {
       if (png_ptr->push_length + 4 > png_ptr->buffer_size)
       {
@@ -421,7 +371,7 @@
 
 #endif
 #ifdef PNG_READ_cHRM_SUPPORTED
-   else if (!png_memcmp(png_ptr->chunk_name, png_cHRM, 4))
+   else if (png_ptr->chunk_name == png_cHRM)
    {
       if (png_ptr->push_length + 4 > png_ptr->buffer_size)
       {
@@ -434,7 +384,7 @@
 
 #endif
 #ifdef PNG_READ_sRGB_SUPPORTED
-   else if (!png_memcmp(png_ptr->chunk_name, png_sRGB, 4))
+   else if (chunk_name == png_sRGB)
    {
       if (png_ptr->push_length + 4 > png_ptr->buffer_size)
       {
@@ -447,7 +397,7 @@
 
 #endif
 #ifdef PNG_READ_iCCP_SUPPORTED
-   else if (!png_memcmp(png_ptr->chunk_name, png_iCCP, 4))
+   else if (png_ptr->chunk_name == png_iCCP)
    {
       if (png_ptr->push_length + 4 > png_ptr->buffer_size)
       {
@@ -460,7 +410,7 @@
 
 #endif
 #ifdef PNG_READ_sPLT_SUPPORTED
-   else if (!png_memcmp(png_ptr->chunk_name, png_sPLT, 4))
+   else if (chunk_name == png_sPLT)
    {
       if (png_ptr->push_length + 4 > png_ptr->buffer_size)
       {
@@ -473,7 +423,7 @@
 
 #endif
 #ifdef PNG_READ_tRNS_SUPPORTED
-   else if (!png_memcmp(png_ptr->chunk_name, png_tRNS, 4))
+   else if (chunk_name == png_tRNS)
    {
       if (png_ptr->push_length + 4 > png_ptr->buffer_size)
       {
@@ -486,7 +436,7 @@
 
 #endif
 #ifdef PNG_READ_bKGD_SUPPORTED
-   else if (!png_memcmp(png_ptr->chunk_name, png_bKGD, 4))
+   else if (chunk_name == png_bKGD)
    {
       if (png_ptr->push_length + 4 > png_ptr->buffer_size)
       {
@@ -499,7 +449,7 @@
 
 #endif
 #ifdef PNG_READ_hIST_SUPPORTED
-   else if (!png_memcmp(png_ptr->chunk_name, png_hIST, 4))
+   else if (chunk_name == png_hIST)
    {
       if (png_ptr->push_length + 4 > png_ptr->buffer_size)
       {
@@ -512,7 +462,7 @@
 
 #endif
 #ifdef PNG_READ_pHYs_SUPPORTED
-   else if (!png_memcmp(png_ptr->chunk_name, png_pHYs, 4))
+   else if (chunk_name == png_pHYs)
    {
       if (png_ptr->push_length + 4 > png_ptr->buffer_size)
       {
@@ -525,7 +475,7 @@
 
 #endif
 #ifdef PNG_READ_oFFs_SUPPORTED
-   else if (!png_memcmp(png_ptr->chunk_name, png_oFFs, 4))
+   else if (chunk_name == png_oFFs)
    {
       if (png_ptr->push_length + 4 > png_ptr->buffer_size)
       {
@@ -538,7 +488,7 @@
 #endif
 
 #ifdef PNG_READ_pCAL_SUPPORTED
-   else if (!png_memcmp(png_ptr->chunk_name, png_pCAL, 4))
+   else if (chunk_name == png_pCAL)
    {
       if (png_ptr->push_length + 4 > png_ptr->buffer_size)
       {
@@ -551,7 +501,7 @@
 
 #endif
 #ifdef PNG_READ_sCAL_SUPPORTED
-   else if (!png_memcmp(png_ptr->chunk_name, png_sCAL, 4))
+   else if (chunk_name == png_sCAL)
    {
       if (png_ptr->push_length + 4 > png_ptr->buffer_size)
       {
@@ -564,7 +514,7 @@
 
 #endif
 #ifdef PNG_READ_tIME_SUPPORTED
-   else if (!png_memcmp(png_ptr->chunk_name, png_tIME, 4))
+   else if (chunk_name == png_tIME)
    {
       if (png_ptr->push_length + 4 > png_ptr->buffer_size)
       {
@@ -577,7 +527,7 @@
 
 #endif
 #ifdef PNG_READ_tEXt_SUPPORTED
-   else if (!png_memcmp(png_ptr->chunk_name, png_tEXt, 4))
+   else if (chunk_name == png_tEXt)
    {
       if (png_ptr->push_length + 4 > png_ptr->buffer_size)
       {
@@ -590,7 +540,7 @@
 
 #endif
 #ifdef PNG_READ_zTXt_SUPPORTED
-   else if (!png_memcmp(png_ptr->chunk_name, png_zTXt, 4))
+   else if (chunk_name == png_zTXt)
    {
       if (png_ptr->push_length + 4 > png_ptr->buffer_size)
       {
@@ -603,7 +553,7 @@
 
 #endif
 #ifdef PNG_READ_iTXt_SUPPORTED
-   else if (!png_memcmp(png_ptr->chunk_name, png_iTXt, 4))
+   else if (chunk_name == png_iTXt)
    {
       if (png_ptr->push_length + 4 > png_ptr->buffer_size)
       {
@@ -809,11 +759,12 @@
 void /* PRIVATE */
 png_push_read_IDAT(png_structp png_ptr)
 {
-   PNG_IDAT;
    if (!(png_ptr->mode & PNG_HAVE_CHUNK_HEADER))
    {
       png_byte chunk_length[4];
+      png_byte chunk_tag[4];
 
+      /* TODO: this code can be commoned up with the same code in push_read */
       if (png_ptr->buffer_size < 8)
       {
          png_push_save_buffer(png_ptr);
@@ -823,10 +774,11 @@
       png_push_fill_buffer(png_ptr, chunk_length, 4);
       png_ptr->push_length = png_get_uint_31(png_ptr, chunk_length);
       png_reset_crc(png_ptr);
-      png_crc_read(png_ptr, png_ptr->chunk_name, 4);
+      png_crc_read(png_ptr, chunk_tag, 4);
+      png_ptr->chunk_name = PNG_CHUNK_FROM_STRING(chunk_tag);
       png_ptr->mode |= PNG_HAVE_CHUNK_HEADER;
 
-      if (png_memcmp(png_ptr->chunk_name, png_IDAT, 4))
+      if (png_ptr->chunk_name != png_IDAT)
       {
          png_ptr->process_mode = PNG_READ_CHUNK_MODE;
 
@@ -838,6 +790,7 @@
 
       png_ptr->idat_size = png_ptr->push_length;
    }
+
    if (png_ptr->idat_size && png_ptr->save_buffer_size)
    {
       png_size_t save_size = png_ptr->save_buffer_size;
@@ -1011,36 +964,56 @@
 void /* PRIVATE */
 png_push_process_row(png_structp png_ptr)
 {
-   png_ptr->row_info.color_type = png_ptr->color_type;
-   png_ptr->row_info.width = png_ptr->iwidth;
-   png_ptr->row_info.channels = png_ptr->channels;
-   png_ptr->row_info.bit_depth = png_ptr->bit_depth;
-   png_ptr->row_info.pixel_depth = png_ptr->pixel_depth;
+   /* 1.5.6: row_info moved out of png_struct to a local here. */
+   png_row_info row_info;
 
-   png_ptr->row_info.rowbytes = PNG_ROWBYTES(png_ptr->row_info.pixel_depth,
-       png_ptr->row_info.width);
+   row_info.width = png_ptr->iwidth; /* NOTE: width of current interlaced row */
+   row_info.color_type = png_ptr->color_type;
+   row_info.bit_depth = png_ptr->bit_depth;
+   row_info.channels = png_ptr->channels;
+   row_info.pixel_depth = png_ptr->pixel_depth;
+   row_info.rowbytes = PNG_ROWBYTES(row_info.pixel_depth, row_info.width);
 
-   png_read_filter_row(png_ptr, &(png_ptr->row_info),
-       png_ptr->row_buf + 1, png_ptr->prev_row + 1,
-       (int)(png_ptr->row_buf[0]));
+   if (png_ptr->row_buf[0] > PNG_FILTER_VALUE_NONE)
+   {
+      if (png_ptr->row_buf[0] < PNG_FILTER_VALUE_LAST)
+         png_read_filter_row(&row_info, png_ptr->row_buf + 1,
+            png_ptr->prev_row + 1, png_ptr->row_buf[0]);
+      else
+         png_error(png_ptr, "bad adaptive filter value");
+   }
 
-   png_memcpy(png_ptr->prev_row, png_ptr->row_buf, png_ptr->rowbytes + 1);
+   /* libpng 1.5.6: the following line was copying png_ptr->rowbytes before
+    * 1.5.6, while the buffer really is this big in current versions of libpng
+    * it may not be in the future, so this was changed just to copy the
+    * interlaced row count:
+    */
+   png_memcpy(png_ptr->prev_row, png_ptr->row_buf, row_info.rowbytes + 1);
 
 #ifdef PNG_READ_TRANSFORMS_SUPPORTED
    if (png_ptr->transformations)
-      png_do_read_transformations(png_ptr);
+      png_do_read_transformations(png_ptr, &row_info);
 #endif
 
+   /* The transformed pixel depth should match the depth now in row_info. */
+   if (png_ptr->transformed_pixel_depth == 0)
+   {
+      png_ptr->transformed_pixel_depth = row_info.pixel_depth;
+      if (row_info.pixel_depth > png_ptr->maximum_pixel_depth)
+         png_error(png_ptr, "progressive row overflow");
+   }
+
+   else if (png_ptr->transformed_pixel_depth != row_info.pixel_depth)
+      png_error(png_ptr, "internal progressive row size calculation error");
+
+
 #ifdef PNG_READ_INTERLACING_SUPPORTED
    /* Blow up interlaced rows to full size */
    if (png_ptr->interlaced && (png_ptr->transformations & PNG_INTERLACE))
    {
       if (png_ptr->pass < 6)
-/*       old interface (pre-1.0.9):
-         png_do_read_interlace(&(png_ptr->row_info),
-             png_ptr->row_buf + 1, png_ptr->pass, png_ptr->transformations);
- */
-         png_do_read_interlace(png_ptr);
+         png_do_read_interlace(&row_info, png_ptr->row_buf + 1, png_ptr->pass,
+            png_ptr->transformations);
 
     switch (png_ptr->pass)
     {
@@ -1223,20 +1196,20 @@
    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
 
    /* Start of interlace block */
-   PNG_CONST int FARDATA png_pass_start[] = {0, 4, 0, 2, 0, 1, 0};
+   static PNG_CONST png_byte FARDATA png_pass_start[] = {0, 4, 0, 2, 0, 1, 0};
 
    /* Offset to next interlace block */
-   PNG_CONST int FARDATA png_pass_inc[] = {8, 8, 4, 4, 2, 2, 1};
+   static PNG_CONST png_byte FARDATA png_pass_inc[] = {8, 8, 4, 4, 2, 2, 1};
 
    /* Start of interlace block in the y direction */
-   PNG_CONST int FARDATA png_pass_ystart[] = {0, 0, 4, 0, 2, 0, 1};
+   static PNG_CONST png_byte FARDATA png_pass_ystart[] = {0, 0, 4, 0, 2, 0, 1};
 
    /* Offset to next interlace block in the y direction */
-   PNG_CONST int FARDATA png_pass_yinc[] = {8, 8, 8, 4, 4, 2, 2};
+   static PNG_CONST png_byte FARDATA png_pass_yinc[] = {8, 8, 8, 4, 4, 2, 2};
 
    /* Height of interlace block.  This is not currently used - if you need
     * it, uncomment it here and in png.h
-   PNG_CONST int FARDATA png_pass_height[] = {8, 8, 4, 4, 2, 2, 1};
+   static PNG_CONST png_byte FARDATA png_pass_height[] = {8, 8, 4, 4, 2, 2, 1};
    */
 
    png_ptr->row_number++;
@@ -1714,11 +1687,12 @@
     length)
 {
    png_uint_32 skip = 0;
+   png_uint_32 chunk_name = png_ptr->chunk_name;
 
-   if (!(png_ptr->chunk_name[0] & 0x20))
+   if (PNG_CHUNK_CRITICAL(chunk_name))
    {
 #ifdef PNG_READ_UNKNOWN_CHUNKS_SUPPORTED
-      if (png_handle_as_unknown(png_ptr, png_ptr->chunk_name) !=
+      if (png_chunk_unknown_handling(png_ptr, chunk_name) !=
           PNG_HANDLE_CHUNK_ALWAYS
 #ifdef PNG_READ_USER_CHUNKS_SUPPORTED
           && png_ptr->read_user_chunk_fn == NULL
@@ -1731,22 +1705,26 @@
    }
 
 #ifdef PNG_READ_UNKNOWN_CHUNKS_SUPPORTED
+   /* TODO: the code below is apparently just using the
+    * png_struct::unknown_chunk member as a temporarily variable, it should be
+    * possible to eliminate both it and the temporary buffer.
+    */
    if (png_ptr->flags & PNG_FLAG_KEEP_UNKNOWN_CHUNKS)
    {
 #ifdef PNG_MAX_MALLOC_64K
-      if (length > (png_uint_32)65535L)
+      if (length > 65535)
       {
          png_warning(png_ptr, "unknown chunk too large to fit in memory");
-         skip = length - (png_uint_32)65535L;
-         length = (png_uint_32)65535L;
+         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';
+      /* This is just a record for the user; libpng doesn't use the character
+       * form of the name.
+       */
+      PNG_CSTRING_FROM_CHUNK(png_ptr->unknown_chunk.name, png_ptr->chunk_name);
 
+      /* The following cast should be safe because of the check above. */
       png_ptr->unknown_chunk.size = (png_size_t)length;
 
       if (length == 0)
@@ -1755,8 +1733,9 @@
       else
       {
          png_ptr->unknown_chunk.data = (png_bytep)png_malloc(png_ptr,
-             (png_size_t)length);
-         png_crc_read(png_ptr, (png_bytep)png_ptr->unknown_chunk.data, length);
+            png_ptr->unknown_chunk.size);
+         png_crc_read(png_ptr, (png_bytep)png_ptr->unknown_chunk.data,
+            png_ptr->unknown_chunk.size);
       }
 
 #ifdef PNG_READ_USER_CHUNKS_SUPPORTED
@@ -1772,8 +1751,8 @@
 
          if (ret == 0)
          {
-            if (!(png_ptr->chunk_name[0] & 0x20))
-               if (png_handle_as_unknown(png_ptr, png_ptr->chunk_name) !=
+            if (PNG_CHUNK_CRITICAL(png_ptr->chunk_name))
+               if (png_chunk_unknown_handling(png_ptr, chunk_name) !=
                    PNG_HANDLE_CHUNK_ALWAYS)
                   png_chunk_error(png_ptr, "unknown critical chunk");
             png_set_unknown_chunks(png_ptr, info_ptr,
@@ -1820,7 +1799,7 @@
 png_progressive_combine_row (png_structp png_ptr, png_bytep old_row,
     png_const_bytep new_row)
 {
-   PNG_CONST int FARDATA png_pass_dsp_mask[7] =
+   static PNG_CONST png_byte FARDATA png_pass_dsp_mask[7] =
       {0xff, 0x0f, 0xff, 0x33, 0xff, 0x55, 0xff};
 
    if (png_ptr == NULL)
diff --git a/pngpriv.h b/pngpriv.h
index 8ca5d1a..4a73b66 100644
--- a/pngpriv.h
+++ b/pngpriv.h
@@ -502,32 +502,70 @@
 #endif
 #endif
 
-/* Constant strings for known chunk types.  If you need to add a chunk,
- * define the name here, and add an invocation of the macro wherever it's
- * needed.
+/* Constants for known chunk types.  If you need to add a chunk, define the name
+ * here.  For historical reasons these constants have the form png_<name>; i.e.
+ * the prefix is lower case.  Please use decimal values as the parameters to
+ * match the ISO PNG specification and to avoid relying on the C locale
+ * interpretation of character values.
+ *
+ * Prior to 1.5.6 these constants were strings, as of 1.5.6 png_uint_32 values
+ * are computed and a new macro (PNG_STRING_FROM_CHUNK) added to allow a string
+ * to be generated if required.
+ *
+ * PNG_32b correctly produces a value shifted by up to 24 bits, even on
+ * architectures where (int) is only 16 bits.
  */
-#define PNG_IHDR PNG_CONST png_byte png_IHDR[5] = { 73,  72,  68,  82, '\0'}
-#define PNG_IDAT PNG_CONST png_byte png_IDAT[5] = { 73,  68,  65,  84, '\0'}
-#define PNG_IEND PNG_CONST png_byte png_IEND[5] = { 73,  69,  78,  68, '\0'}
-#define PNG_PLTE PNG_CONST png_byte png_PLTE[5] = { 80,  76,  84,  69, '\0'}
-#define PNG_bKGD PNG_CONST png_byte png_bKGD[5] = { 98,  75,  71,  68, '\0'}
-#define PNG_cHRM PNG_CONST png_byte png_cHRM[5] = { 99,  72,  82,  77, '\0'}
-#define PNG_gAMA PNG_CONST png_byte png_gAMA[5] = {103,  65,  77,  65, '\0'}
-#define PNG_hIST PNG_CONST png_byte png_hIST[5] = {104,  73,  83,  84, '\0'}
-#define PNG_iCCP PNG_CONST png_byte png_iCCP[5] = {105,  67,  67,  80, '\0'}
-#define PNG_iTXt PNG_CONST png_byte png_iTXt[5] = {105,  84,  88, 116, '\0'}
-#define PNG_oFFs PNG_CONST png_byte png_oFFs[5] = {111,  70,  70, 115, '\0'}
-#define PNG_pCAL PNG_CONST png_byte png_pCAL[5] = {112,  67,  65,  76, '\0'}
-#define PNG_sCAL PNG_CONST png_byte png_sCAL[5] = {115,  67,  65,  76, '\0'}
-#define PNG_pHYs PNG_CONST png_byte png_pHYs[5] = {112,  72,  89, 115, '\0'}
-#define PNG_sBIT PNG_CONST png_byte png_sBIT[5] = {115,  66,  73,  84, '\0'}
-#define PNG_sPLT PNG_CONST png_byte png_sPLT[5] = {115,  80,  76,  84, '\0'}
-#define PNG_sRGB PNG_CONST png_byte png_sRGB[5] = {115,  82,  71,  66, '\0'}
-#define PNG_sTER PNG_CONST png_byte png_sTER[5] = {115,  84,  69,  82, '\0'}
-#define PNG_tEXt PNG_CONST png_byte png_tEXt[5] = {116,  69,  88, 116, '\0'}
-#define PNG_tIME PNG_CONST png_byte png_tIME[5] = {116,  73,  77,  69, '\0'}
-#define PNG_tRNS PNG_CONST png_byte png_tRNS[5] = {116,  82,  78,  83, '\0'}
-#define PNG_zTXt PNG_CONST png_byte png_zTXt[5] = {122,  84,  88, 116, '\0'}
+#define PNG_32b(b,s) ((png_uint_32)(b) << (s))
+#define PNG_CHUNK(b1,b2,b3,b4) \
+   (PNG_32b(b1,24) | PNG_32b(b2,16) | PNG_32b(b3,8) | PNG_32b(b4,0))
+
+#define png_IHDR PNG_CHUNK( 73,  72,  68,  82)
+#define png_IDAT PNG_CHUNK( 73,  68,  65,  84)
+#define png_IEND PNG_CHUNK( 73,  69,  78,  68)
+#define png_PLTE PNG_CHUNK( 80,  76,  84,  69)
+#define png_bKGD PNG_CHUNK( 98,  75,  71,  68)
+#define png_cHRM PNG_CHUNK( 99,  72,  82,  77)
+#define png_gAMA PNG_CHUNK(103,  65,  77,  65)
+#define png_hIST PNG_CHUNK(104,  73,  83,  84)
+#define png_iCCP PNG_CHUNK(105,  67,  67,  80)
+#define png_iTXt PNG_CHUNK(105,  84,  88, 116)
+#define png_oFFs PNG_CHUNK(111,  70,  70, 115)
+#define png_pCAL PNG_CHUNK(112,  67,  65,  76)
+#define png_sCAL PNG_CHUNK(115,  67,  65,  76)
+#define png_pHYs PNG_CHUNK(112,  72,  89, 115)
+#define png_sBIT PNG_CHUNK(115,  66,  73,  84)
+#define png_sPLT PNG_CHUNK(115,  80,  76,  84)
+#define png_sRGB PNG_CHUNK(115,  82,  71,  66)
+#define png_sTER PNG_CHUNK(115,  84,  69,  82)
+#define png_tEXt PNG_CHUNK(116,  69,  88, 116)
+#define png_tIME PNG_CHUNK(116,  73,  77,  69)
+#define png_tRNS PNG_CHUNK(116,  82,  78,  83)
+#define png_zTXt PNG_CHUNK(122,  84,  88, 116)
+
+/* The following will work on (signed char*) strings, whereas the get_uint_32
+ * macro will fail on top-bit-set values because of the sign extension.
+ */
+#define PNG_CHUNK_FROM_STRING(s)\
+   PNG_CHUNK(0xff&(s)[0], 0xff&(s)[1], 0xff&(s)[2], 0xff&(s)[3])
+
+/* This uses (char), not (png_byte) to avoid warnings on systems where (char) is
+ * signed and the argument is a (char[])  This macro will fail miserably on
+ * systems where (char) is more than 8 bits.
+ */
+#define PNG_STRING_FROM_CHUNK(s,c)\
+   (void)(((char*)(s))[0]=(char)((c)>>24), ((char*)(s))[1]=(char)((c)>>16),\
+   ((char*)(s))[3]=(char)((c)>>8), ((char*)(s))[3]=(char)((c)))
+
+/* Do the same but terminate with a null character. */
+#define PNG_CSTRING_FROM_CHUNK(s,c)\
+   (void)(PNG_STRING_FROM_CHUNK(s,c), ((char*)(s))[4] = 0)
+
+/* Test on flag values as defined in the spec (section 5.4): */
+#define PNG_CHUNK_ANCILLIARY(c)   (1 & ((c) >> 29))
+#define PNG_CHUNK_CRITICAL(c)     (!PNG_CHUNK_ANCILLIARY(c))
+#define PNG_CHUNK_PRIVATE(c)      (1 & ((c) >> 21))
+#define PNG_CHUNK_RESERVED(c)     (1 & ((c) >> 13))
+#define PNG_CHUNK_SAFE_TO_COPY(c) (1 & ((c) >>  5))
 
 /* Gamma values (new at libpng-1.5.4): */
 #define PNG_GAMMA_MAC_OLD 151724  /* Assume '1.8' is really 2.2/1.45! */
@@ -784,17 +822,20 @@
 /* Internal use only.   Called before first row of data */
 PNG_EXTERN void png_write_start_row PNGARG((png_structp png_ptr));
 
-/* Combine a row of data, dealing with alpha, etc. if requested */
+/* Combine a row of data, dealing with alpha, etc. if requested.  'row' is an
+ * array of png_ptr->width pixels, 'mask' is a mask of the pixels to copy from
+ * png_ptr->row_buf+1.  'mask' describes each block of 8 pixels - only the low 8
+ * bits are used.  This function is only ever used to write to row buffers
+ * provided by the caller of the relevant libpng API and the row must have
+ * already been transformed by the read transformations.
+ */
 PNG_EXTERN void png_combine_row PNGARG((png_structp png_ptr, png_bytep row,
     int mask));
 
 #ifdef PNG_READ_INTERLACING_SUPPORTED
 /* Expand an interlaced row */
-/* OLD pre-1.0.9 interface:
 PNG_EXTERN void png_do_read_interlace PNGARG((png_row_infop row_info,
     png_bytep row, int pass, png_uint_32 transformations));
- */
-PNG_EXTERN void png_do_read_interlace PNGARG((png_structp png_ptr));
 #endif
 
 /* GRR TO DO (2.0 or whenever):  simplify other internal calling interfaces */
@@ -805,10 +846,11 @@
     png_bytep row, int pass));
 #endif
 
-/* Unfilter a row */
-PNG_EXTERN void png_read_filter_row PNGARG((png_structp png_ptr,
-    png_row_infop row_info, png_bytep row, png_const_bytep prev_row,
-    int filter));
+/* Unfilter a row: check the filter value before calling this, there is no point
+ * calling it for PNG_FILTER_VALUE_NONE.
+ */
+PNG_EXTERN void png_read_filter_row PNGARG((png_row_infop row_info,
+    png_bytep row, png_const_bytep prev_row, int filter));
 
 /* Choose the best filter to use and filter the row data */
 PNG_EXTERN void png_write_find_filter PNGARG((png_structp png_ptr,
@@ -1058,18 +1100,30 @@
     png_uint_32 length));
 #endif
 
+#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
 PNG_EXTERN void png_handle_unknown PNGARG((png_structp png_ptr,
     png_infop info_ptr, png_uint_32 length));
+#endif
 
 PNG_EXTERN void png_check_chunk_name PNGARG((png_structp png_ptr,
-    png_const_bytep chunk_name));
+    png_uint_32 chunk_name));
+
+#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
+/* Exactly as png_handle_as_unknown() except that the argument is a 32-bit chunk
+ * name, not a string.
+ */
+PNG_EXTERN int png_chunk_unknown_handling PNGARG((png_structp png_ptr,
+    png_uint_32 chunk_name));
+#endif
 
 /* Handle the transformations for reading and writing */
 #ifdef PNG_READ_TRANSFORMS_SUPPORTED
-PNG_EXTERN void png_do_read_transformations PNGARG((png_structp png_ptr));
+PNG_EXTERN void png_do_read_transformations PNGARG((png_structp png_ptr,
+   png_row_infop row_info));
 #endif
 #ifdef PNG_WRITE_TRANSFORMS_SUPPORTED
-PNG_EXTERN void png_do_write_transformations PNGARG((png_structp png_ptr));
+PNG_EXTERN void png_do_write_transformations PNGARG((png_structp png_ptr,
+   png_row_infop row_info));
 #endif
 
 #ifdef PNG_READ_TRANSFORMS_SUPPORTED
diff --git a/pngread.c b/pngread.c
index be3df47..3747ebe 100644
--- a/pngread.c
+++ b/pngread.c
@@ -1,7 +1,7 @@
 
 /* pngread.c - read a PNG file
  *
- * Last changed in libpng 1.5.4 [July 7, 2011]
+ * Last changed in libpng 1.5.6 [(PENDING RELEASE)]
  * 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.)
@@ -190,89 +190,35 @@
 
    for (;;)
    {
-      PNG_IHDR;
-      PNG_IDAT;
-      PNG_IEND;
-      PNG_PLTE;
-#ifdef PNG_READ_bKGD_SUPPORTED
-      PNG_bKGD;
-#endif
-#ifdef PNG_READ_cHRM_SUPPORTED
-      PNG_cHRM;
-#endif
-#ifdef PNG_READ_gAMA_SUPPORTED
-      PNG_gAMA;
-#endif
-#ifdef PNG_READ_hIST_SUPPORTED
-      PNG_hIST;
-#endif
-#ifdef PNG_READ_iCCP_SUPPORTED
-      PNG_iCCP;
-#endif
-#ifdef PNG_READ_iTXt_SUPPORTED
-      PNG_iTXt;
-#endif
-#ifdef PNG_READ_oFFs_SUPPORTED
-      PNG_oFFs;
-#endif
-#ifdef PNG_READ_pCAL_SUPPORTED
-      PNG_pCAL;
-#endif
-#ifdef PNG_READ_pHYs_SUPPORTED
-      PNG_pHYs;
-#endif
-#ifdef PNG_READ_sBIT_SUPPORTED
-      PNG_sBIT;
-#endif
-#ifdef PNG_READ_sCAL_SUPPORTED
-      PNG_sCAL;
-#endif
-#ifdef PNG_READ_sPLT_SUPPORTED
-      PNG_sPLT;
-#endif
-#ifdef PNG_READ_sRGB_SUPPORTED
-      PNG_sRGB;
-#endif
-#ifdef PNG_READ_tEXt_SUPPORTED
-      PNG_tEXt;
-#endif
-#ifdef PNG_READ_tIME_SUPPORTED
-      PNG_tIME;
-#endif
-#ifdef PNG_READ_tRNS_SUPPORTED
-      PNG_tRNS;
-#endif
-#ifdef PNG_READ_zTXt_SUPPORTED
-      PNG_zTXt;
-#endif
       png_uint_32 length = png_read_chunk_header(png_ptr);
-      PNG_CONST png_bytep chunk_name = png_ptr->chunk_name;
+      png_uint_32 chunk_name = png_ptr->chunk_name;
 
       /* This should be a binary subdivision search or a hash for
        * matching the chunk name rather than a linear search.
        */
-      if (!png_memcmp(chunk_name, png_IDAT, 4))
+      if (chunk_name == png_IDAT)
          if (png_ptr->mode & PNG_AFTER_IDAT)
             png_ptr->mode |= PNG_HAVE_CHUNK_AFTER_IDAT;
 
-      if (!png_memcmp(chunk_name, png_IHDR, 4))
+      if (chunk_name == png_IHDR)
          png_handle_IHDR(png_ptr, info_ptr, length);
 
-      else if (!png_memcmp(chunk_name, png_IEND, 4))
+      else if (chunk_name == png_IEND)
          png_handle_IEND(png_ptr, info_ptr, length);
 
 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
-      else if (png_handle_as_unknown(png_ptr, chunk_name))
+      else if (png_chunk_unknown_handling(png_ptr, chunk_name) !=
+         PNG_HANDLE_CHUNK_AS_DEFAULT)
       {
-         if (!png_memcmp(chunk_name, png_IDAT, 4))
+         if (chunk_name == png_IDAT)
             png_ptr->mode |= PNG_HAVE_IDAT;
 
          png_handle_unknown(png_ptr, info_ptr, length);
 
-         if (!png_memcmp(chunk_name, png_PLTE, 4))
+         if (chunk_name == png_PLTE)
             png_ptr->mode |= PNG_HAVE_PLTE;
 
-         else if (!png_memcmp(chunk_name, png_IDAT, 4))
+         else if (chunk_name == png_IDAT)
          {
             if (!(png_ptr->mode & PNG_HAVE_IHDR))
                png_error(png_ptr, "Missing IHDR before IDAT");
@@ -285,10 +231,10 @@
          }
       }
 #endif
-      else if (!png_memcmp(chunk_name, png_PLTE, 4))
+      else if (chunk_name == png_PLTE)
          png_handle_PLTE(png_ptr, info_ptr, length);
 
-      else if (!png_memcmp(chunk_name, png_IDAT, 4))
+      else if (chunk_name == png_IDAT)
       {
          if (!(png_ptr->mode & PNG_HAVE_IHDR))
             png_error(png_ptr, "Missing IHDR before IDAT");
@@ -303,87 +249,87 @@
       }
 
 #ifdef PNG_READ_bKGD_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_bKGD, 4))
+      else if (chunk_name == png_bKGD)
          png_handle_bKGD(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_cHRM_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_cHRM, 4))
+      else if (chunk_name == png_cHRM)
          png_handle_cHRM(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_gAMA_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_gAMA, 4))
+      else if (chunk_name == png_gAMA)
          png_handle_gAMA(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_hIST_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_hIST, 4))
+      else if (chunk_name == png_hIST)
          png_handle_hIST(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_oFFs_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_oFFs, 4))
+      else if (chunk_name == png_oFFs)
          png_handle_oFFs(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_pCAL_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_pCAL, 4))
+      else if (chunk_name == png_pCAL)
          png_handle_pCAL(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_sCAL_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_sCAL, 4))
+      else if (chunk_name == png_sCAL)
          png_handle_sCAL(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_pHYs_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_pHYs, 4))
+      else if (chunk_name == png_pHYs)
          png_handle_pHYs(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_sBIT_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_sBIT, 4))
+      else if (chunk_name == png_sBIT)
          png_handle_sBIT(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_sRGB_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_sRGB, 4))
+      else if (chunk_name == png_sRGB)
          png_handle_sRGB(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_iCCP_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_iCCP, 4))
+      else if (chunk_name == png_iCCP)
          png_handle_iCCP(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_sPLT_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_sPLT, 4))
+      else if (chunk_name == png_sPLT)
          png_handle_sPLT(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_tEXt_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_tEXt, 4))
+      else if (chunk_name == png_tEXt)
          png_handle_tEXt(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_tIME_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_tIME, 4))
+      else if (chunk_name == png_tIME)
          png_handle_tIME(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_tRNS_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_tRNS, 4))
+      else if (chunk_name == png_tRNS)
          png_handle_tRNS(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_zTXt_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_zTXt, 4))
+      else if (chunk_name == png_zTXt)
          png_handle_zTXt(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_iTXt_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_iTXt, 4))
+      else if (chunk_name == png_iTXt)
          png_handle_iTXt(png_ptr, info_ptr, length);
 #endif
 
@@ -444,7 +390,6 @@
 void PNGAPI
 png_read_row(png_structp png_ptr, png_bytep row, png_bytep dsp_row)
 {
-   PNG_IDAT;
 #ifdef PNG_READ_INTERLACING_SUPPORTED
    PNG_CONST int png_pass_dsp_mask[7] = {0xff, 0x0f, 0xff, 0x33, 0xff, 0x55,
        0xff};
@@ -452,15 +397,28 @@
 #endif
    int ret;
 
+   png_row_info row_info;
+
    if (png_ptr == NULL)
       return;
 
    png_debug2(1, "in png_read_row (row %lu, pass %d)",
        (unsigned long)png_ptr->row_number, png_ptr->pass);
 
+   /* png_read_start_row sets the information (in particular iwidth) for this
+    * interlace pass.
+    */
    if (!(png_ptr->flags & PNG_FLAG_ROW_INIT))
       png_read_start_row(png_ptr);
 
+   /* 1.5.6: row_info moved out of png_struct to a local here. */
+   row_info.width = png_ptr->iwidth; /* NOTE: width of current interlaced row */
+   row_info.color_type = png_ptr->color_type;
+   row_info.bit_depth = png_ptr->bit_depth;
+   row_info.channels = png_ptr->channels;
+   row_info.pixel_depth = png_ptr->pixel_depth;
+   row_info.rowbytes = PNG_ROWBYTES(row_info.pixel_depth, row_info.width);
+
    if (png_ptr->row_number == 0 && png_ptr->pass == 0)
    {
    /* Check for transforms that have been set but were defined out */
@@ -502,7 +460,12 @@
    }
 
 #ifdef PNG_READ_INTERLACING_SUPPORTED
-   /* If interlaced and we do not need a new row, combine row and return */
+   /* If interlaced and we do not need a new row, combine row and return.
+    * Notice that the pixels we have from previous rows have been transformed
+    * already; we can only combine like with like (transformed or
+    * untransformed) and, because of the libpng API for interlaced images, this
+    * means we must transform before de-interlacing.
+    */
    if (png_ptr->interlaced && (png_ptr->transformations & PNG_INTERLACE))
    {
       switch (png_ptr->pass)
@@ -606,7 +569,7 @@
             png_crc_finish(png_ptr, 0);
 
             png_ptr->idat_size = png_read_chunk_header(png_ptr);
-            if (png_memcmp(png_ptr->chunk_name, png_IDAT, 4))
+            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;
@@ -636,47 +599,56 @@
 
    } while (png_ptr->zstream.avail_out);
 
-   png_ptr->row_info.color_type = png_ptr->color_type;
-   png_ptr->row_info.width = png_ptr->iwidth;
-   png_ptr->row_info.channels = png_ptr->channels;
-   png_ptr->row_info.bit_depth = png_ptr->bit_depth;
-   png_ptr->row_info.pixel_depth = png_ptr->pixel_depth;
-   png_ptr->row_info.rowbytes = PNG_ROWBYTES(png_ptr->row_info.pixel_depth,
-       png_ptr->row_info.width);
+   if (png_ptr->row_buf[0] > PNG_FILTER_VALUE_NONE)
+   {
+      if (png_ptr->row_buf[0] < PNG_FILTER_VALUE_LAST)
+         png_read_filter_row(&row_info, png_ptr->row_buf + 1,
+            png_ptr->prev_row + 1, png_ptr->row_buf[0]);
+      else
+         png_error(png_ptr, "bad adaptive filter value");
+   }
 
-   if (png_ptr->row_buf[0])
-   png_read_filter_row(png_ptr, &(png_ptr->row_info),
-       png_ptr->row_buf + 1, png_ptr->prev_row + 1,
-       (int)(png_ptr->row_buf[0]));
-
-   png_memcpy(png_ptr->prev_row, png_ptr->row_buf, png_ptr->rowbytes + 1);
+   /* libpng 1.5.6: the following line was copying png_ptr->rowbytes before
+    * 1.5.6, while the buffer really is this big in current versions of libpng
+    * it may not be in the future, so this was changed just to copy the
+    * interlaced count:
+    */
+   png_memcpy(png_ptr->prev_row, png_ptr->row_buf, row_info.rowbytes + 1);
 
 #ifdef PNG_MNG_FEATURES_SUPPORTED
    if ((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) &&
        (png_ptr->filter_type == PNG_INTRAPIXEL_DIFFERENCING))
    {
       /* Intrapixel differencing */
-      png_do_read_intrapixel(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_read_intrapixel(&row_info, png_ptr->row_buf + 1);
    }
 #endif
 
 
 #ifdef PNG_READ_TRANSFORMS_SUPPORTED
    if (png_ptr->transformations)
-      png_do_read_transformations(png_ptr);
+      png_do_read_transformations(png_ptr, &row_info);
 #endif
 
+   /* The transformed pixel depth should match the depth now in row_info. */
+   if (png_ptr->transformed_pixel_depth == 0)
+   {
+      png_ptr->transformed_pixel_depth = row_info.pixel_depth;
+      if (row_info.pixel_depth > png_ptr->maximum_pixel_depth)
+         png_error(png_ptr, "sequential row overflow");
+   }
+
+   else if (png_ptr->transformed_pixel_depth != row_info.pixel_depth)
+      png_error(png_ptr, "internal sequential row size calculation error");
+
 #ifdef PNG_READ_INTERLACING_SUPPORTED
    /* Blow up interlaced rows to full size */
    if (png_ptr->interlaced &&
       (png_ptr->transformations & PNG_INTERLACE))
    {
       if (png_ptr->pass < 6)
-         /* Old interface (pre-1.0.9):
-          * png_do_read_interlace(&(png_ptr->row_info),
-          *    png_ptr->row_buf + 1, png_ptr->pass, png_ptr->transformations);
-          */
-         png_do_read_interlace(png_ptr);
+         png_do_read_interlace(&row_info, png_ptr->row_buf + 1, png_ptr->pass,
+            png_ptr->transformations);
 
       if (dsp_row != NULL)
          png_combine_row(png_ptr, dsp_row, png_pass_dsp_mask[png_ptr->pass]);
@@ -858,85 +830,31 @@
 
    do
    {
-      PNG_IHDR;
-      PNG_IDAT;
-      PNG_IEND;
-      PNG_PLTE;
-#ifdef PNG_READ_bKGD_SUPPORTED
-      PNG_bKGD;
-#endif
-#ifdef PNG_READ_cHRM_SUPPORTED
-      PNG_cHRM;
-#endif
-#ifdef PNG_READ_gAMA_SUPPORTED
-      PNG_gAMA;
-#endif
-#ifdef PNG_READ_hIST_SUPPORTED
-      PNG_hIST;
-#endif
-#ifdef PNG_READ_iCCP_SUPPORTED
-      PNG_iCCP;
-#endif
-#ifdef PNG_READ_iTXt_SUPPORTED
-      PNG_iTXt;
-#endif
-#ifdef PNG_READ_oFFs_SUPPORTED
-      PNG_oFFs;
-#endif
-#ifdef PNG_READ_pCAL_SUPPORTED
-      PNG_pCAL;
-#endif
-#ifdef PNG_READ_pHYs_SUPPORTED
-      PNG_pHYs;
-#endif
-#ifdef PNG_READ_sBIT_SUPPORTED
-      PNG_sBIT;
-#endif
-#ifdef PNG_READ_sCAL_SUPPORTED
-      PNG_sCAL;
-#endif
-#ifdef PNG_READ_sPLT_SUPPORTED
-      PNG_sPLT;
-#endif
-#ifdef PNG_READ_sRGB_SUPPORTED
-      PNG_sRGB;
-#endif
-#ifdef PNG_READ_tEXt_SUPPORTED
-      PNG_tEXt;
-#endif
-#ifdef PNG_READ_tIME_SUPPORTED
-      PNG_tIME;
-#endif
-#ifdef PNG_READ_tRNS_SUPPORTED
-      PNG_tRNS;
-#endif
-#ifdef PNG_READ_zTXt_SUPPORTED
-      PNG_zTXt;
-#endif
       png_uint_32 length = png_read_chunk_header(png_ptr);
-      PNG_CONST png_bytep chunk_name = png_ptr->chunk_name;
+      png_uint_32 chunk_name = png_ptr->chunk_name;
 
-      if (!png_memcmp(chunk_name, png_IHDR, 4))
+      if (chunk_name == png_IHDR)
          png_handle_IHDR(png_ptr, info_ptr, length);
 
-      else if (!png_memcmp(chunk_name, png_IEND, 4))
+      else if (chunk_name == png_IEND)
          png_handle_IEND(png_ptr, info_ptr, length);
 
 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
-      else if (png_handle_as_unknown(png_ptr, chunk_name))
+      else if (png_chunk_unknown_handling(png_ptr, chunk_name) !=
+         PNG_HANDLE_CHUNK_AS_DEFAULT)
       {
-         if (!png_memcmp(chunk_name, png_IDAT, 4))
+         if (chunk_name == png_IDAT)
          {
             if ((length > 0) || (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT))
                png_benign_error(png_ptr, "Too many IDATs found");
          }
          png_handle_unknown(png_ptr, info_ptr, length);
-         if (!png_memcmp(chunk_name, png_PLTE, 4))
+         if (chunk_name == png_PLTE)
             png_ptr->mode |= PNG_HAVE_PLTE;
       }
 #endif
 
-      else if (!png_memcmp(chunk_name, png_IDAT, 4))
+      else if (chunk_name == png_IDAT)
       {
          /* Zero length IDATs are legal after the last IDAT has been
           * read, but not after other chunks have been read.
@@ -946,91 +864,91 @@
 
          png_crc_finish(png_ptr, length);
       }
-      else if (!png_memcmp(chunk_name, png_PLTE, 4))
+      else if (chunk_name == png_PLTE)
          png_handle_PLTE(png_ptr, info_ptr, length);
 
 #ifdef PNG_READ_bKGD_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_bKGD, 4))
+      else if (chunk_name == png_bKGD)
          png_handle_bKGD(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_cHRM_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_cHRM, 4))
+      else if (chunk_name == png_cHRM)
          png_handle_cHRM(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_gAMA_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_gAMA, 4))
+      else if (chunk_name == png_gAMA)
          png_handle_gAMA(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_hIST_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_hIST, 4))
+      else if (chunk_name == png_hIST)
          png_handle_hIST(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_oFFs_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_oFFs, 4))
+      else if (chunk_name == png_oFFs)
          png_handle_oFFs(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_pCAL_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_pCAL, 4))
+      else if (chunk_name == png_pCAL)
          png_handle_pCAL(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_sCAL_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_sCAL, 4))
+      else if (chunk_name == png_sCAL)
          png_handle_sCAL(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_pHYs_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_pHYs, 4))
+      else if (chunk_name == png_pHYs)
          png_handle_pHYs(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_sBIT_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_sBIT, 4))
+      else if (chunk_name == png_sBIT)
          png_handle_sBIT(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_sRGB_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_sRGB, 4))
+      else if (chunk_name == png_sRGB)
          png_handle_sRGB(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_iCCP_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_iCCP, 4))
+      else if (chunk_name == png_iCCP)
          png_handle_iCCP(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_sPLT_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_sPLT, 4))
+      else if (chunk_name == png_sPLT)
          png_handle_sPLT(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_tEXt_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_tEXt, 4))
+      else if (chunk_name == png_tEXt)
          png_handle_tEXt(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_tIME_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_tIME, 4))
+      else if (chunk_name == png_tIME)
          png_handle_tIME(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_tRNS_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_tRNS, 4))
+      else if (chunk_name == png_tRNS)
          png_handle_tRNS(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_zTXt_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_zTXt, 4))
+      else if (chunk_name == png_zTXt)
          png_handle_zTXt(png_ptr, info_ptr, length);
 #endif
 
 #ifdef PNG_READ_iTXt_SUPPORTED
-      else if (!png_memcmp(chunk_name, png_iTXt, 4))
+      else if (chunk_name == png_iTXt)
          png_handle_iTXt(png_ptr, info_ptr, length);
 #endif
 
diff --git a/pngrtran.c b/pngrtran.c
index c6dd288..7379700 100644
--- a/pngrtran.c
+++ b/pngrtran.c
@@ -1,7 +1,7 @@
 
 /* pngrtran.c - transforms the data in a row for PNG readers
  *
- * Last changed in libpng 1.5.5 [(PENDING RELEASE)]
+ * Last changed in libpng 1.5.6 [(PENDING RELEASE)]
  * 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.)
@@ -1198,53 +1198,44 @@
    {
       {
          /* Expand background and tRNS chunks */
+         int gray = png_ptr->background.gray;
+         int trans_gray = png_ptr->trans_color.gray;
+
          switch (png_ptr->bit_depth)
          {
             case 1:
-               png_ptr->background.gray *= (png_uint_16)0xff;
-               png_ptr->background.red = png_ptr->background.green
-                   =  png_ptr->background.blue = png_ptr->background.gray;
-               if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
-               {
-                 png_ptr->trans_color.gray *= (png_uint_16)0xff;
-                 png_ptr->trans_color.red = png_ptr->trans_color.green
-                     = png_ptr->trans_color.blue = png_ptr->trans_color.gray;
-               }
+               gray *= 0xff;
+               trans_gray *= 0xff;
                break;
 
             case 2:
-               png_ptr->background.gray *= (png_uint_16)0x55;
-               png_ptr->background.red = png_ptr->background.green
-                   = png_ptr->background.blue = png_ptr->background.gray;
-               if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
-               {
-                  png_ptr->trans_color.gray *= (png_uint_16)0x55;
-                  png_ptr->trans_color.red = png_ptr->trans_color.green
-                      = png_ptr->trans_color.blue = png_ptr->trans_color.gray;
-               }
+               gray *= 0x55;
+               trans_gray *= 0x55;
                break;
 
             case 4:
-               png_ptr->background.gray *= (png_uint_16)0x11;
-               png_ptr->background.red = png_ptr->background.green
-                   = png_ptr->background.blue = png_ptr->background.gray;
-               if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
-               {
-                  png_ptr->trans_color.gray *= (png_uint_16)0x11;
-                  png_ptr->trans_color.red = png_ptr->trans_color.green
-                      = png_ptr->trans_color.blue = png_ptr->trans_color.gray;
-               }
+               gray *= 0x11;
+               trans_gray *= 0x11;
                break;
 
             default:
 
             case 8:
+               /* Already 8 bits, fall through */
 
             case 16:
-               png_ptr->background.red = png_ptr->background.green
-                   = png_ptr->background.blue = png_ptr->background.gray;
+               /* Already a full 16 bits */
                break;
          }
+
+         png_ptr->background.red = png_ptr->background.green =
+            png_ptr->background.blue = (png_uint_16)gray;
+
+         if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
+         {
+            png_ptr->trans_color.red = png_ptr->trans_color.green =
+               png_ptr->trans_color.blue = (png_uint_16)trans_gray;
+         }
       }
    } /* background expand and (therefore) no alpha association. */
 #endif /* PNG_READ_EXPAND_SUPPORTED && PNG_READ_BACKGROUND_SUPPORTED */
@@ -1788,26 +1779,38 @@
    if ((png_ptr->transformations & PNG_SHIFT) &&
        (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE))
    {
-      png_uint_16 i;
-      png_uint_16 istop = png_ptr->num_palette;
-      int sr = 8 - png_ptr->sig_bit.red;
-      int sg = 8 - png_ptr->sig_bit.green;
-      int sb = 8 - png_ptr->sig_bit.blue;
+      int i;
+      int istop = png_ptr->num_palette;
+      int shift = 8 - png_ptr->sig_bit.red;
 
-      if (sr < 0 || sr > 8)
-         sr = 0;
-
-      if (sg < 0 || sg > 8)
-         sg = 0;
-
-      if (sb < 0 || sb > 8)
-         sb = 0;
-
-      for (i = 0; i < istop; i++)
+      /* significant bits can be in the range 1 to 7 for a meaninful result, if
+       * the number of significant bits is 0 then no shift is done (this is an
+       * error condition which is silently ignored.)
+       */
+      if (shift > 0 && shift < 8) for (i=0; i<istop; ++i)
       {
-         png_ptr->palette[i].red >>= sr;
-         png_ptr->palette[i].green >>= sg;
-         png_ptr->palette[i].blue >>= sb;
+         int component = png_ptr->palette[i].red;
+
+         component >>= shift;
+         png_ptr->palette[i].red = (png_byte)component;
+      }
+
+      shift = 8 - png_ptr->sig_bit.green;
+      if (shift > 0 && shift < 8) for (i=0; i<istop; ++i)
+      {
+         int component = png_ptr->palette[i].green;
+
+         component >>= shift;
+         png_ptr->palette[i].green = (png_byte)component;
+      }
+
+      shift = 8 - png_ptr->sig_bit.blue;
+      if (shift > 0 && shift < 8) for (i=0; i<istop; ++i)
+      {
+         int component = png_ptr->palette[i].blue;
+
+         component >>= shift;
+         png_ptr->palette[i].blue = (png_byte)component;
       }
    }
 #endif  /* PNG_READ_SHIFT_SUPPORTED */
@@ -1913,12 +1916,14 @@
 
 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
    if (png_ptr->transformations & PNG_GRAY_TO_RGB)
-      info_ptr->color_type |= PNG_COLOR_MASK_COLOR;
+      info_ptr->color_type = (png_byte)(info_ptr->color_type |
+         PNG_COLOR_MASK_COLOR);
 #endif
 
 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
    if (png_ptr->transformations & PNG_RGB_TO_GRAY)
-      info_ptr->color_type &= ~PNG_COLOR_MASK_COLOR;
+      info_ptr->color_type = (png_byte)(info_ptr->color_type &
+         ~PNG_COLOR_MASK_COLOR);
 #endif
 
 #ifdef PNG_READ_QUANTIZE_SUPPORTED
@@ -1958,7 +1963,8 @@
 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
    if (png_ptr->transformations & PNG_STRIP_ALPHA)
    {
-      info_ptr->color_type &= ~PNG_COLOR_MASK_ALPHA;
+      info_ptr->color_type = (png_byte)(info_ptr->color_type &
+         ~PNG_COLOR_MASK_ALPHA);
       info_ptr->num_trans = 0;
    }
 #endif
@@ -2015,7 +2021,7 @@
  * decide how it fits in with the other transformations here.
  */
 void /* PRIVATE */
-png_do_read_transformations(png_structp png_ptr)
+png_do_read_transformations(png_structp png_ptr, png_row_infop row_info)
 {
    png_debug(1, "in png_do_read_transformations");
 
@@ -2046,9 +2052,9 @@
 #ifdef PNG_READ_EXPAND_SUPPORTED
    if (png_ptr->transformations & PNG_EXPAND)
    {
-      if (png_ptr->row_info.color_type == PNG_COLOR_TYPE_PALETTE)
+      if (row_info->color_type == PNG_COLOR_TYPE_PALETTE)
       {
-         png_do_expand_palette(&(png_ptr->row_info), png_ptr->row_buf + 1,
+         png_do_expand_palette(row_info, png_ptr->row_buf + 1,
              png_ptr->palette, png_ptr->trans_alpha, png_ptr->num_trans);
       }
 
@@ -2056,11 +2062,11 @@
       {
          if (png_ptr->num_trans &&
              (png_ptr->transformations & PNG_EXPAND_tRNS))
-            png_do_expand(&(png_ptr->row_info), png_ptr->row_buf + 1,
+            png_do_expand(row_info, png_ptr->row_buf + 1,
                 &(png_ptr->trans_color));
 
          else
-            png_do_expand(&(png_ptr->row_info), png_ptr->row_buf + 1,
+            png_do_expand(row_info, png_ptr->row_buf + 1,
                 NULL);
       }
    }
@@ -2069,9 +2075,9 @@
 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
    if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&
       !(png_ptr->transformations & PNG_COMPOSE) &&
-      (png_ptr->row_info.color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
-      png_ptr->row_info.color_type == PNG_COLOR_TYPE_GRAY_ALPHA))
-      png_do_strip_channel(&(png_ptr->row_info), png_ptr->row_buf + 1,
+      (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
+      row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA))
+      png_do_strip_channel(row_info, png_ptr->row_buf + 1,
          0 /* at_start == false, because SWAP_ALPHA happens later */);
 #endif
 
@@ -2079,7 +2085,7 @@
    if (png_ptr->transformations & PNG_RGB_TO_GRAY)
    {
       int rgb_error =
-          png_do_rgb_to_gray(png_ptr, &(png_ptr->row_info),
+          png_do_rgb_to_gray(png_ptr, row_info,
               png_ptr->row_buf + 1);
 
       if (rgb_error)
@@ -2133,13 +2139,13 @@
     */
    if ((png_ptr->transformations & PNG_GRAY_TO_RGB) &&
        !(png_ptr->mode & PNG_BACKGROUND_IS_GRAY))
-      png_do_gray_to_rgb(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_gray_to_rgb(row_info, png_ptr->row_buf + 1);
 #endif
 
 #if (defined PNG_READ_BACKGROUND_SUPPORTED) ||\
    (defined PNG_READ_ALPHA_MODE_SUPPORTED)
    if (png_ptr->transformations & PNG_COMPOSE)
-      png_do_compose(&(png_ptr->row_info), png_ptr->row_buf + 1, png_ptr);
+      png_do_compose(row_info, png_ptr->row_buf + 1, png_ptr);
 #endif
 
 #ifdef PNG_READ_GAMMA_SUPPORTED
@@ -2151,27 +2157,27 @@
        (png_ptr->color_type & PNG_COLOR_MASK_ALPHA))) &&
 #endif
        (png_ptr->color_type != PNG_COLOR_TYPE_PALETTE))
-      png_do_gamma(&(png_ptr->row_info), png_ptr->row_buf + 1, png_ptr);
+      png_do_gamma(row_info, png_ptr->row_buf + 1, png_ptr);
 #endif
 
 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
    if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&
       (png_ptr->transformations & PNG_COMPOSE) &&
-      (png_ptr->row_info.color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
-      png_ptr->row_info.color_type == PNG_COLOR_TYPE_GRAY_ALPHA))
-      png_do_strip_channel(&(png_ptr->row_info), png_ptr->row_buf + 1,
+      (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
+      row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA))
+      png_do_strip_channel(row_info, png_ptr->row_buf + 1,
          0 /* at_start == false, because SWAP_ALPHA happens later */);
 #endif
 
 #ifdef PNG_READ_ALPHA_MODE_SUPPORTED
    if ((png_ptr->transformations & PNG_ENCODE_ALPHA) &&
-      (png_ptr->row_info.color_type & PNG_COLOR_MASK_ALPHA))
-      png_do_encode_alpha(&(png_ptr->row_info), png_ptr->row_buf + 1, png_ptr);
+      (row_info->color_type & PNG_COLOR_MASK_ALPHA))
+      png_do_encode_alpha(row_info, png_ptr->row_buf + 1, png_ptr);
 #endif
 
 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
    if (png_ptr->transformations & PNG_SCALE_16_TO_8)
-      png_do_scale_16_to_8(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_scale_16_to_8(row_info, png_ptr->row_buf + 1);
 #endif
 
 #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
@@ -2180,16 +2186,16 @@
     * calling the API or in a TRANSFORM flag) this is what happens.
     */
    if (png_ptr->transformations & PNG_16_TO_8)
-      png_do_chop(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_chop(row_info, png_ptr->row_buf + 1);
 #endif
 
 #ifdef PNG_READ_QUANTIZE_SUPPORTED
    if (png_ptr->transformations & PNG_QUANTIZE)
    {
-      png_do_quantize(&(png_ptr->row_info), png_ptr->row_buf + 1,
+      png_do_quantize(row_info, png_ptr->row_buf + 1,
           png_ptr->palette_lookup, png_ptr->quantize_index);
 
-      if (png_ptr->row_info.rowbytes == 0)
+      if (row_info->rowbytes == 0)
          png_error(png_ptr, "png_do_quantize returned rowbytes=0");
    }
 #endif /* PNG_READ_QUANTIZE_SUPPORTED */
@@ -2201,62 +2207,62 @@
     * better accuracy results faster!)
     */
    if (png_ptr->transformations & PNG_EXPAND_16)
-      png_do_expand_16(&png_ptr->row_info, png_ptr->row_buf + 1);
+      png_do_expand_16(row_info, png_ptr->row_buf + 1);
 #endif
 
 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
    /*NOTE: moved here in 1.5.4 (from much later in this list.) */
    if ((png_ptr->transformations & PNG_GRAY_TO_RGB) &&
        (png_ptr->mode & PNG_BACKGROUND_IS_GRAY))
-      png_do_gray_to_rgb(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_gray_to_rgb(row_info, png_ptr->row_buf + 1);
 #endif
 
 #ifdef PNG_READ_INVERT_SUPPORTED
    if (png_ptr->transformations & PNG_INVERT_MONO)
-      png_do_invert(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_invert(row_info, png_ptr->row_buf + 1);
 #endif
 
 #ifdef PNG_READ_SHIFT_SUPPORTED
    if (png_ptr->transformations & PNG_SHIFT)
-      png_do_unshift(&(png_ptr->row_info), png_ptr->row_buf + 1,
+      png_do_unshift(row_info, png_ptr->row_buf + 1,
           &(png_ptr->shift));
 #endif
 
 #ifdef PNG_READ_PACK_SUPPORTED
    if (png_ptr->transformations & PNG_PACK)
-      png_do_unpack(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_unpack(row_info, png_ptr->row_buf + 1);
 #endif
 
 #ifdef PNG_READ_BGR_SUPPORTED
    if (png_ptr->transformations & PNG_BGR)
-      png_do_bgr(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_bgr(row_info, png_ptr->row_buf + 1);
 #endif
 
 #ifdef PNG_READ_PACKSWAP_SUPPORTED
    if (png_ptr->transformations & PNG_PACKSWAP)
-      png_do_packswap(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_packswap(row_info, png_ptr->row_buf + 1);
 #endif
 
 #ifdef PNG_READ_FILLER_SUPPORTED
    if (png_ptr->transformations & PNG_FILLER)
-      png_do_read_filler(&(png_ptr->row_info), png_ptr->row_buf + 1,
+      png_do_read_filler(row_info, png_ptr->row_buf + 1,
           (png_uint_32)png_ptr->filler, png_ptr->flags);
 #endif
 
 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
    if (png_ptr->transformations & PNG_INVERT_ALPHA)
-      png_do_read_invert_alpha(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_read_invert_alpha(row_info, png_ptr->row_buf + 1);
 #endif
 
 #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
    if (png_ptr->transformations & PNG_SWAP_ALPHA)
-      png_do_read_swap_alpha(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_read_swap_alpha(row_info, png_ptr->row_buf + 1);
 #endif
 
 #ifdef PNG_READ_16BIT_SUPPORTED
 #ifdef PNG_READ_SWAP_SUPPORTED
    if (png_ptr->transformations & PNG_SWAP_BYTES)
-      png_do_swap(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_swap(row_info, png_ptr->row_buf + 1);
 #endif
 #endif
 
@@ -2265,8 +2271,8 @@
     {
       if (png_ptr->read_user_transform_fn != NULL)
          (*(png_ptr->read_user_transform_fn)) /* User read transform function */
-             (png_ptr,                    /* png_ptr */
-             &(png_ptr->row_info),     /* row_info: */
+             (png_ptr,     /* png_ptr */
+             row_info,     /* row_info: */
                 /*  png_uint_32 width;       width of row */
                 /*  png_size_t rowbytes;     number of bytes in row */
                 /*  png_byte color_type;     color type of pixels */
@@ -2276,16 +2282,15 @@
              png_ptr->row_buf + 1);    /* start of pixel data for row */
 #ifdef PNG_USER_TRANSFORM_PTR_SUPPORTED
       if (png_ptr->user_transform_depth)
-         png_ptr->row_info.bit_depth = png_ptr->user_transform_depth;
+         row_info->bit_depth = png_ptr->user_transform_depth;
 
       if (png_ptr->user_transform_channels)
-         png_ptr->row_info.channels = png_ptr->user_transform_channels;
+         row_info->channels = png_ptr->user_transform_channels;
 #endif
-      png_ptr->row_info.pixel_depth = (png_byte)(png_ptr->row_info.bit_depth *
-          png_ptr->row_info.channels);
+      row_info->pixel_depth = (png_byte)(row_info->bit_depth *
+          row_info->channels);
 
-      png_ptr->row_info.rowbytes = PNG_ROWBYTES(png_ptr->row_info.pixel_depth,
-          png_ptr->row_info.width);
+      row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_info->width);
    }
 #endif
 }
@@ -2399,105 +2404,128 @@
 png_do_unshift(png_row_infop row_info, png_bytep row,
     png_const_color_8p sig_bits)
 {
+   int color_type;
+
    png_debug(1, "in png_do_unshift");
 
-   if (
-       row_info->color_type != PNG_COLOR_TYPE_PALETTE)
+   /* The palette case has already been handled in the _init routine. */
+   color_type = row_info->color_type;
+
+   if (color_type != PNG_COLOR_TYPE_PALETTE)
    {
       int shift[4];
       int channels = 0;
-      int c;
-      png_uint_16 value = 0;
-      png_uint_32 row_width = row_info->width;
+      int bit_depth = row_info->bit_depth;
 
-      if (row_info->color_type & PNG_COLOR_MASK_COLOR)
+      if (color_type & PNG_COLOR_MASK_COLOR)
       {
-         shift[channels++] = row_info->bit_depth - sig_bits->red;
-         shift[channels++] = row_info->bit_depth - sig_bits->green;
-         shift[channels++] = row_info->bit_depth - sig_bits->blue;
+         shift[channels++] = bit_depth - sig_bits->red;
+         shift[channels++] = bit_depth - sig_bits->green;
+         shift[channels++] = bit_depth - sig_bits->blue;
       }
 
       else
       {
-         shift[channels++] = row_info->bit_depth - sig_bits->gray;
+         shift[channels++] = bit_depth - sig_bits->gray;
       }
 
-      if (row_info->color_type & PNG_COLOR_MASK_ALPHA)
+      if (color_type & PNG_COLOR_MASK_ALPHA)
       {
-         shift[channels++] = row_info->bit_depth - sig_bits->alpha;
+         shift[channels++] = bit_depth - sig_bits->alpha;
       }
 
-      for (c = 0; c < channels; c++)
       {
-         if (shift[c] <= 0)
-            shift[c] = 0;
+         int c, have_shift;
 
-         else
-            value = 1;
+         for (c = have_shift = 0; c < channels; ++c)
+         {
+            /* A shift of more than the bit depth is an error condition but it
+             * gets ignored here.
+             */
+            if (shift[c] <= 0 || shift[c] >= bit_depth)
+               shift[c] = 0;
+
+            else
+               have_shift = 1;
+         }
+
+         if (!have_shift)
+            return;
       }
 
-      if (!value)
-         return;
-
-      switch (row_info->bit_depth)
+      switch (bit_depth)
       {
          default:
+         /* Must be 1bpp gray: should not be here! */
+            /* NOTREACHED */
             break;
 
          case 2:
+         /* Must be 2bpp gray */
+         /* assert(channels == 1 && shift[0] == 1) */
          {
-            png_bytep bp;
-            png_size_t i;
-            png_size_t istop = row_info->rowbytes;
+            png_bytep bp = row;
+            png_bytep bp_end = bp + row_info->rowbytes;
 
-            for (bp = row, i = 0; i < istop; i++)
+            while (bp < bp_end)
             {
-               *bp >>= 1;
-               *bp++ &= 0x55;
+               int byte = (*bp >> 1) & 0x55;
+               *bp++ = (png_byte)byte;
             }
             break;
          }
 
          case 4:
+         /* Must be 4bpp gray */
+         /* assert(channels == 1) */
          {
             png_bytep bp = row;
-            png_size_t i;
-            png_size_t istop = row_info->rowbytes;
-            png_byte mask = (png_byte)((((int)0xf0 >> shift[0]) & (int)0xf0) |
-                (png_byte)((int)0xf >> shift[0]));
+            png_bytep bp_end = bp + row_info->rowbytes;
+            int gray_shift = shift[0];
+            int mask =  0xf >> gray_shift;
 
-            for (i = 0; i < istop; i++)
+            mask |= mask << 4;
+
+            while (bp < bp_end)
             {
-               *bp >>= shift[0];
-               *bp++ &= mask;
+               int byte = (*bp >> gray_shift) & mask;
+               *bp++ = (png_byte)byte;
             }
             break;
          }
 
          case 8:
+         /* Single byte components, G, GA, RGB, RGBA */
          {
             png_bytep bp = row;
-            png_uint_32 i;
-            png_uint_32 istop = row_width * channels;
+            png_bytep bp_end = bp + row_info->rowbytes;
+            int channel = 0;
 
-            for (i = 0; i < istop; i++)
+            while (bp < bp_end)
             {
-               *bp++ >>= shift[i%channels];
+               int byte = *bp >> shift[channel];
+               if (++channel >= channels)
+                  channel = 0;
+               *bp++ = (png_byte)byte;
             }
             break;
          }
 
 #ifdef PNG_READ_16BIT_SUPPORTED
          case 16:
+         /* Double byte components, G, GA, RGB, RGBA */
          {
             png_bytep bp = row;
-            png_uint_32 i;
-            png_uint_32 istop = channels * row_width;
+            png_bytep bp_end = bp + row_info->rowbytes;
+            int channel = 0;
 
-            for (i = 0; i < istop; i++)
+            while (bp < bp_end)
             {
-               value = (png_uint_16)((*bp << 8) + *(bp + 1));
-               value >>= shift[i%channels];
+               int value = (bp[0] << 8) + bp[1];
+
+               value >>= shift[channel];
+               if (++channel >= channels)
+                  channel = 0;
                *bp++ = (png_byte)(value >> 8);
                *bp++ = (png_byte)(value & 0xff);
             }
@@ -3060,7 +3088,7 @@
             }
          }
       }
-      row_info->channels += (png_byte)2;
+      row_info->channels = (png_byte)(row_info->channels + 2);
       row_info->color_type |= PNG_COLOR_MASK_COLOR;
       row_info->pixel_depth = (png_byte)(row_info->channels *
           row_info->bit_depth);
@@ -3306,7 +3334,7 @@
          }
       }
 
-      row_info->channels -= 2;
+      row_info->channels = (png_byte)(row_info->channels - 2);
       row_info->color_type = (png_byte)(row_info->color_type &
           ~PNG_COLOR_MASK_COLOR);
       row_info->pixel_depth = (png_byte)(row_info->channels *
diff --git a/pngrutil.c b/pngrutil.c
index a74353d..62b3afc 100644
--- a/pngrutil.c
+++ b/pngrutil.c
@@ -1,7 +1,7 @@
 
 /* pngrutil.c - utilities to read a PNG file
  *
- * Last changed in libpng 1.5.5 [(PENDING RELEASE)]
+ * Last changed in libpng 1.5.6 [(PENDING RELEASE)]
  * 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.)
@@ -165,14 +165,14 @@
    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);
+   png_ptr->chunk_name = PNG_CHUNK_FROM_STRING(buf+4);
 
-   png_debug2(0, "Reading %s chunk, length = %u",
-       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. */
    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. */
    png_check_chunk_name(png_ptr, png_ptr->chunk_name);
@@ -218,10 +218,9 @@
 
    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");
       }
@@ -248,14 +247,14 @@
    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;
@@ -2641,16 +2640,14 @@
 
    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) !=
+      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
@@ -2668,21 +2665,20 @@
        )
    {
 #ifdef PNG_MAX_MALLOC_64K
-      if (length > (png_uint_32)65535L)
+      if (length > 65535)
       {
          png_warning(png_ptr, "unknown chunk too large to fit in memory");
-         skip = length - (png_uint_32)65535L;
-         length = (png_uint_32)65535L;
+         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';
-
+      /* 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)
@@ -2691,7 +2687,7 @@
       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
@@ -2708,10 +2704,10 @@
 
          if (ret == 0)
          {
-            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) !=
+               if (png_chunk_unknown_handling(png_ptr, png_ptr->chunk_name) !=
                    PNG_HANDLE_CHUNK_ALWAYS)
 #endif
                   png_chunk_error(png_ptr, "unknown critical chunk");
@@ -2748,16 +2744,26 @@
  * 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_const_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;
    }
 }
 
@@ -2776,25 +2782,33 @@
 void /* PRIVATE */
 png_combine_row(png_structp png_ptr, png_bytep row, int mask)
 {
+   int pixel_depth = png_ptr->transformed_pixel_depth;
+
    png_debug(1, "in png_combine_row");
 
-   /* Added in 1.5.4: the row_info should match the information returned by any
-    * call to png_read_update_info at this point.  Do not continue if we got
+   /* 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(png_ptr->row_info.pixel_depth, png_ptr->width))
+          PNG_ROWBYTES(pixel_depth, png_ptr->width))
       png_error(png_ptr, "internal row size calculation error");
 
    if (mask == 0xff)
    {
       png_memcpy(row, png_ptr->row_buf + 1,
-          PNG_ROWBYTES(png_ptr->row_info.pixel_depth, png_ptr->width));
+          PNG_ROWBYTES(pixel_depth, png_ptr->width));
    }
 
    else
    {
-      switch (png_ptr->row_info.pixel_depth)
+      switch (pixel_depth)
       {
          case 1:
          {
@@ -2971,7 +2985,7 @@
          {
             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_size_t pixel_bytes = pixel_depth >> 3;
             png_uint_32 i;
             png_uint_32 row_width = png_ptr->width;
             png_byte m = 0x80;
@@ -3000,15 +3014,12 @@
 
 #ifdef PNG_READ_INTERLACING_SUPPORTED
 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)
@@ -3241,12 +3252,13 @@
 }
 #endif /* PNG_READ_INTERLACING_SUPPORTED */
 
+/* 1.5.6: Changed to just take a png_row_info (not png_ptr) and to ignore bad
+ * adaptive filter bytes.
+ */
 void /* PRIVATE */
-png_read_filter_row(png_structp png_ptr, png_row_infop row_info, png_bytep row,
-    png_const_bytep prev_row, int filter)
+png_read_filter_row(png_row_infop row_info, png_bytep row,
+   png_const_bytep prev_row, int filter)
 {
-   png_debug(1, "in png_read_filter_row");
-   png_debug2(2, "row = %u, filter = %d", png_ptr->row_number, filter);
    switch (filter)
    {
       case PNG_FILTER_VALUE_NONE:
@@ -3363,8 +3375,7 @@
          break;
       }
       default:
-         png_error(png_ptr, "Ignoring bad adaptive filter type");
-         /*NOT REACHED */
+         /* NOT REACHED */
          break;
    }
 }
@@ -3377,16 +3388,16 @@
    /* 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");
@@ -3433,7 +3444,6 @@
 
    if (!(png_ptr->flags & PNG_FLAG_ZLIB_FINISHED))
    {
-      PNG_IDAT;
       char extra;
       int ret;
 
@@ -3448,7 +3458,7 @@
             {
                png_crc_finish(png_ptr, 0);
                png_ptr->idat_size = png_read_chunk_header(png_ptr);
-               if (png_memcmp(png_ptr->chunk_name, png_IDAT, 4))
+               if (png_ptr->chunk_name != png_IDAT)
                   png_error(png_ptr, "Not enough image data");
             }
 
@@ -3507,16 +3517,16 @@
    /* 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;
@@ -3676,14 +3686,20 @@
 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;
+         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
     */
diff --git a/pngset.c b/pngset.c
index 373d21b..b643721 100644
--- a/pngset.c
+++ b/pngset.c
@@ -1,7 +1,7 @@
 
 /* pngset.c - storage of image information into info struct
  *
- * Last changed in libpng 1.5.5 [(PENDING RELEASE)]
+ * Last changed in libpng 1.5.6 [(PENDING RELEASE)]
  * 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.)
@@ -681,9 +681,8 @@
 {
    int i;
 
-   png_debug1(1, "in %s storage function", ((png_ptr == NULL ||
-       png_ptr->chunk_name[0] == '\0') ?
-       "text" : (png_const_charp)png_ptr->chunk_name));
+   png_debug1(1, "in %lx storage function", png_ptr == NULL ? "unexpected" :
+      (unsigned long)png_ptr->chunk_name);
 
    if (png_ptr == NULL || info_ptr == NULL || num_text == 0)
       return(0);
diff --git a/pngstruct.h b/pngstruct.h
index b4e5f3b..f4dbc61 100644
--- a/pngstruct.h
+++ b/pngstruct.h
@@ -104,13 +104,13 @@
    png_size_t rowbytes;       /* size of row in bytes */
    png_uint_32 iwidth;        /* width of current interlaced row in pixels */
    png_uint_32 row_number;    /* current row in interlace pass */
+   png_uint_32 chunk_name;    /* PNG_CHUNK() id of current chunk */
    png_bytep prev_row;        /* buffer to save previous (unfiltered) row */
    png_bytep row_buf;         /* buffer to save current (unfiltered) row */
    png_bytep sub_row;         /* buffer to save "sub" row when filtering */
    png_bytep up_row;          /* buffer to save "up" row when filtering */
    png_bytep avg_row;         /* buffer to save "avg" row when filtering */
    png_bytep paeth_row;       /* buffer to save "Paeth" row when filtering */
-   png_row_info row_info;     /* used for transformation routines */
    png_size_t info_rowbytes;  /* Added in 1.5.4: cache of updated row bytes */
 
    png_uint_32 idat_size;     /* current IDAT size for read */
@@ -118,7 +118,6 @@
    png_colorp palette;        /* palette from the input file */
    png_uint_16 num_palette;   /* number of color entries in palette */
    png_uint_16 num_trans;     /* number of transparency values */
-   png_byte chunk_name[5];    /* null-terminated name of current chunk */
    png_byte compression;      /* file compression type (always 0) */
    png_byte filter;           /* file filter type (always 0) */
    png_byte interlaced;       /* PNG_INTERLACE_NONE, PNG_INTERLACE_ADAM7 */
@@ -126,11 +125,17 @@
    png_byte do_filter;        /* row filter flags (see PNG_FILTER_ below ) */
    png_byte color_type;       /* color type of file */
    png_byte bit_depth;        /* bit depth of file */
-   png_byte usr_bit_depth;    /* bit depth of users row */
+   png_byte usr_bit_depth;    /* bit depth of users row: write only */
    png_byte pixel_depth;      /* number of bits per pixel */
    png_byte channels;         /* number of channels in file */
-   png_byte usr_channels;     /* channels at start of write */
+   png_byte usr_channels;     /* channels at start of write: write only */
    png_byte sig_bytes;        /* magic bytes read/written from start of file */
+   png_byte maximum_pixel_depth;
+                              /* pixel depth used for the row buffers */
+   png_byte transformed_pixel_depth;
+                              /* pixel depth after read/write transforms */
+   png_byte io_chunk_string[5];
+                              /* string name of chunk */
 
 #if defined(PNG_READ_FILLER_SUPPORTED) || defined(PNG_WRITE_FILLER_SUPPORTED)
    png_uint_16 filler;           /* filler bytes for pixel expansion */
diff --git a/pngtest.c b/pngtest.c
index 9c4615d..18ed38c 100644
--- a/pngtest.c
+++ b/pngtest.c
@@ -1794,4 +1794,4 @@
 }
 
 /* Generate a compiler error if there is an old png.h in the search path. */
-typedef png_libpng_version_1_5_6beta01 Your_png_h_is_not_version_1_5_6beta01;
+typedef png_libpng_version_1_5_6beta02 Your_png_h_is_not_version_1_5_6beta02;
diff --git a/pngvalid.c b/pngvalid.c
index 9d1ce79..ef915c5 100644
--- a/pngvalid.c
+++ b/pngvalid.c
@@ -1,7 +1,7 @@
 
 /* pngvalid.c - validate libpng by constructing then reading png files.
  *
- * Last changed in libpng 1.5.5 [(PENDING RELEASE)]
+ * Last changed in libpng 1.5.6 [(PENDING RELEASE)]
  * Copyright (c) 2011 Glenn Randers-Pehrson
  * Written by John Cunningham Bowler
  *
diff --git a/pngwrite.c b/pngwrite.c
index d1af9e8..b120df9 100644
--- a/pngwrite.c
+++ b/pngwrite.c
@@ -1,7 +1,7 @@
 
 /* pngwrite.c - general routines to write a PNG file
  *
- * Last changed in libpng 1.5.4 [July 7, 2011]
+ * Last changed in libpng 1.5.6 [(PENDING RELEASE)]
  * 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.)
@@ -608,6 +608,9 @@
 void PNGAPI
 png_write_row(png_structp png_ptr, png_const_bytep row)
 {
+   /* 1.5.6: moved from png_struct to be a local structure: */
+   png_row_info row_info;
+
    if (png_ptr == NULL)
       return;
 
@@ -731,36 +734,31 @@
 #endif
 
    /* Set up row info for transformations */
-   png_ptr->row_info.color_type = png_ptr->color_type;
-   png_ptr->row_info.width = png_ptr->usr_width;
-   png_ptr->row_info.channels = png_ptr->usr_channels;
-   png_ptr->row_info.bit_depth = png_ptr->usr_bit_depth;
-   png_ptr->row_info.pixel_depth = (png_byte)(png_ptr->row_info.bit_depth *
-      png_ptr->row_info.channels);
+   row_info.color_type = png_ptr->color_type;
+   row_info.width = png_ptr->usr_width;
+   row_info.channels = png_ptr->usr_channels;
+   row_info.bit_depth = png_ptr->usr_bit_depth;
+   row_info.pixel_depth = (png_byte)(row_info.bit_depth * row_info.channels);
+   row_info.rowbytes = PNG_ROWBYTES(row_info.pixel_depth, row_info.width);
 
-   png_ptr->row_info.rowbytes = PNG_ROWBYTES(png_ptr->row_info.pixel_depth,
-      png_ptr->row_info.width);
-
-   png_debug1(3, "row_info->color_type = %d", png_ptr->row_info.color_type);
-   png_debug1(3, "row_info->width = %u", png_ptr->row_info.width);
-   png_debug1(3, "row_info->channels = %d", png_ptr->row_info.channels);
-   png_debug1(3, "row_info->bit_depth = %d", png_ptr->row_info.bit_depth);
-   png_debug1(3, "row_info->pixel_depth = %d", png_ptr->row_info.pixel_depth);
-   png_debug1(3, "row_info->rowbytes = %lu",
-       (unsigned long)png_ptr->row_info.rowbytes);
+   png_debug1(3, "row_info->color_type = %d", row_info.color_type);
+   png_debug1(3, "row_info->width = %u", row_info.width);
+   png_debug1(3, "row_info->channels = %d", row_info.channels);
+   png_debug1(3, "row_info->bit_depth = %d", row_info.bit_depth);
+   png_debug1(3, "row_info->pixel_depth = %d", row_info.pixel_depth);
+   png_debug1(3, "row_info->rowbytes = %lu", (unsigned long)row_info.rowbytes);
 
    /* Copy user's row into buffer, leaving room for filter byte. */
-   png_memcpy(png_ptr->row_buf + 1, row, png_ptr->row_info.rowbytes);
+   png_memcpy(png_ptr->row_buf + 1, row, row_info.rowbytes);
 
 #ifdef PNG_WRITE_INTERLACING_SUPPORTED
    /* Handle interlacing */
    if (png_ptr->interlaced && png_ptr->pass < 6 &&
        (png_ptr->transformations & PNG_INTERLACE))
    {
-      png_do_write_interlace(&(png_ptr->row_info),
-          png_ptr->row_buf + 1, png_ptr->pass);
+      png_do_write_interlace(&row_info, png_ptr->row_buf + 1, png_ptr->pass);
       /* This should always get caught above, but still ... */
-      if (!(png_ptr->row_info.width))
+      if (!(row_info.width))
       {
          png_write_finish_row(png_ptr);
          return;
@@ -771,9 +769,16 @@
 #ifdef PNG_WRITE_TRANSFORMS_SUPPORTED
    /* Handle other transformations */
    if (png_ptr->transformations)
-      png_do_write_transformations(png_ptr);
+      png_do_write_transformations(png_ptr, &row_info);
 #endif
 
+   /* At this point the row_info pixel depth must match the 'transformed' depth,
+    * which is also the output depth.
+    */
+   if (row_info.pixel_depth != png_ptr->pixel_depth ||
+      row_info.pixel_depth != png_ptr->transformed_pixel_depth)
+      png_error(png_ptr, "internal write transform logic error");
+
 #ifdef PNG_MNG_FEATURES_SUPPORTED
    /* Write filter_method 64 (intrapixel differencing) only if
     * 1. Libpng was compiled with PNG_MNG_FEATURES_SUPPORTED and
@@ -788,12 +793,12 @@
        (png_ptr->filter_type == PNG_INTRAPIXEL_DIFFERENCING))
    {
       /* Intrapixel differencing */
-      png_do_write_intrapixel(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_write_intrapixel(&row_info, png_ptr->row_buf + 1);
    }
 #endif
 
    /* Find a filter if necessary, filter the row and write it out. */
-   png_write_find_filter(png_ptr, &(png_ptr->row_info));
+   png_write_find_filter(png_ptr, &row_info);
 
    if (png_ptr->write_row_fn != NULL)
       (*(png_ptr->write_row_fn))(png_ptr, png_ptr->row_number, png_ptr->pass);
@@ -879,13 +884,7 @@
    png_debug(1, "in png_destroy_write_struct");
 
    if (png_ptr_ptr != NULL)
-   {
       png_ptr = *png_ptr_ptr;
-#ifdef PNG_USER_MEM_SUPPORTED
-      free_fn = png_ptr->free_fn;
-      mem_ptr = png_ptr->mem_ptr;
-#endif
-   }
 
 #ifdef PNG_USER_MEM_SUPPORTED
    if (png_ptr != NULL)
diff --git a/pngwtran.c b/pngwtran.c
index 124d708..fc9fa16 100644
--- a/pngwtran.c
+++ b/pngwtran.c
@@ -1,7 +1,7 @@
 
 /* pngwtran.c - transforms the data in a row for PNG writers
  *
- * Last changed in libpng 1.5.4 [July 7, 2011]
+ * Last changed in libpng 1.5.6 [(PENDING RELEASE)]
  * 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.)
@@ -20,7 +20,7 @@
  * transformations is significant.
  */
 void /* PRIVATE */
-png_do_write_transformations(png_structp png_ptr)
+png_do_write_transformations(png_structp png_ptr, png_row_infop row_info)
 {
    png_debug(1, "in png_do_write_transformations");
 
@@ -32,8 +32,8 @@
       if (png_ptr->write_user_transform_fn != NULL)
          (*(png_ptr->write_user_transform_fn)) /* User write transform
                                                  function */
-             (png_ptr,                    /* png_ptr */
-             &(png_ptr->row_info),           /* row_info: */
+             (png_ptr,  /* png_ptr */
+             row_info,  /* row_info: */
                 /*  png_uint_32 width;       width of row */
                 /*  png_size_t rowbytes;     number of bytes in row */
                 /*  png_byte color_type;     color type of pixels */
@@ -45,50 +45,50 @@
 
 #ifdef PNG_WRITE_FILLER_SUPPORTED
    if (png_ptr->transformations & PNG_FILLER)
-      png_do_strip_channel(&(png_ptr->row_info), png_ptr->row_buf + 1,
+      png_do_strip_channel(row_info, png_ptr->row_buf + 1,
          !(png_ptr->flags & PNG_FLAG_FILLER_AFTER));
 #endif
 
 #ifdef PNG_WRITE_PACKSWAP_SUPPORTED
    if (png_ptr->transformations & PNG_PACKSWAP)
-      png_do_packswap(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_packswap(row_info, png_ptr->row_buf + 1);
 #endif
 
 #ifdef PNG_WRITE_PACK_SUPPORTED
    if (png_ptr->transformations & PNG_PACK)
-      png_do_pack(&(png_ptr->row_info), png_ptr->row_buf + 1,
+      png_do_pack(row_info, png_ptr->row_buf + 1,
           (png_uint_32)png_ptr->bit_depth);
 #endif
 
 #ifdef PNG_WRITE_SWAP_SUPPORTED
    if (png_ptr->transformations & PNG_SWAP_BYTES)
-      png_do_swap(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_swap(row_info, png_ptr->row_buf + 1);
 #endif
 
 #ifdef PNG_WRITE_SHIFT_SUPPORTED
    if (png_ptr->transformations & PNG_SHIFT)
-      png_do_shift(&(png_ptr->row_info), png_ptr->row_buf + 1,
+      png_do_shift(row_info, png_ptr->row_buf + 1,
           &(png_ptr->shift));
 #endif
 
 #ifdef PNG_WRITE_SWAP_ALPHA_SUPPORTED
    if (png_ptr->transformations & PNG_SWAP_ALPHA)
-      png_do_write_swap_alpha(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_write_swap_alpha(row_info, png_ptr->row_buf + 1);
 #endif
 
 #ifdef PNG_WRITE_INVERT_ALPHA_SUPPORTED
    if (png_ptr->transformations & PNG_INVERT_ALPHA)
-      png_do_write_invert_alpha(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_write_invert_alpha(row_info, png_ptr->row_buf + 1);
 #endif
 
 #ifdef PNG_WRITE_BGR_SUPPORTED
    if (png_ptr->transformations & PNG_BGR)
-      png_do_bgr(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_bgr(row_info, png_ptr->row_buf + 1);
 #endif
 
 #ifdef PNG_WRITE_INVERT_SUPPORTED
    if (png_ptr->transformations & PNG_INVERT_MONO)
-      png_do_invert(&(png_ptr->row_info), png_ptr->row_buf + 1);
+      png_do_invert(row_info, png_ptr->row_buf + 1);
 #endif
 }
 
diff --git a/pngwutil.c b/pngwutil.c
index bafa406..a9ebbce 100644
--- a/pngwutil.c
+++ b/pngwutil.c
@@ -1,7 +1,7 @@
 
 /* pngwutil.c - utilities to write a PNG file
  *
- * Last changed in libpng 1.5.5 [(PENDING RELEASE)]
+ * Last changed in libpng 1.5.6 [(PENDING RELEASE)]
  * 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.)
@@ -82,38 +82,17 @@
       png_ptr->mode |= PNG_HAVE_PNG_SIGNATURE;
 }
 
-/* Write a PNG chunk all at once.  The type is an array of ASCII characters
- * representing the chunk name.  The array must be at least 4 bytes in
- * length, and does not need to be null terminated.  To be safe, pass the
- * pre-defined chunk names here, and if you need a new one, define it
- * where the others are defined.  The length is the length of the data.
- * All the data must be present.  If that is not possible, use the
- * png_write_chunk_start(), png_write_chunk_data(), and png_write_chunk_end()
- * functions instead.
- */
-void PNGAPI
-png_write_chunk(png_structp png_ptr, png_const_bytep chunk_name,
-   png_const_bytep data, png_size_t length)
-{
-   if (png_ptr == NULL)
-      return;
-
-   png_write_chunk_start(png_ptr, chunk_name, (png_uint_32)length);
-   png_write_chunk_data(png_ptr, data, (png_size_t)length);
-   png_write_chunk_end(png_ptr);
-}
-
 /* Write the start of a PNG chunk.  The type is the chunk type.
  * The total_length is the sum of the lengths of all the data you will be
  * passing in png_write_chunk_data().
  */
-void PNGAPI
-png_write_chunk_start(png_structp png_ptr, png_const_bytep chunk_name,
+static void
+png_write_chunk_header(png_structp png_ptr, png_uint_32 chunk_name,
     png_uint_32 length)
 {
    png_byte buf[8];
 
-   png_debug2(0, "Writing %s chunk, length = %lu", chunk_name,
+   png_debug2(0, "Writing %s chunk, length = %lu", chunk_string,
       (unsigned long)length);
 
    if (png_ptr == NULL)
@@ -128,16 +107,16 @@
 
    /* Write the length and the chunk name */
    png_save_uint_32(buf, length);
-   png_memcpy(buf + 4, chunk_name, 4);
-   png_write_data(png_ptr, buf, (png_size_t)8);
+   png_save_uint_32(buf + 4, chunk_name);
+   png_write_data(png_ptr, buf, 8);
 
    /* Put the chunk name into png_ptr->chunk_name */
-   png_memcpy(png_ptr->chunk_name, chunk_name, 4);
+   png_ptr->chunk_name = chunk_name;
 
    /* Reset the crc and run it over the chunk name */
    png_reset_crc(png_ptr);
 
-   png_calculate_crc(png_ptr, chunk_name, 4);
+   png_calculate_crc(png_ptr, buf + 4, 4);
 
 #ifdef PNG_IO_STATE_SUPPORTED
    /* Inform the I/O callback that chunk data will (possibly) be written.
@@ -147,10 +126,17 @@
 #endif
 }
 
-/* Write the data of a PNG chunk started with png_write_chunk_start().
+void PNGAPI
+png_write_chunk_start(png_structp png_ptr, png_const_bytep chunk_string,
+    png_uint_32 length)
+{
+   png_write_chunk_header(png_ptr, PNG_CHUNK_FROM_STRING(chunk_string), length);
+}
+
+/* Write the data of a PNG chunk started with png_write_chunk_header().
  * Note that multiple calls to this function are allowed, and that the
  * sum of the lengths from these calls *must* add up to the total_length
- * given to png_write_chunk_start().
+ * given to png_write_chunk_header().
  */
 void PNGAPI
 png_write_chunk_data(png_structp png_ptr, png_const_bytep data,
@@ -171,7 +157,7 @@
    }
 }
 
-/* Finish a chunk started with png_write_chunk_start(). */
+/* Finish a chunk started with png_write_chunk_header(). */
 void PNGAPI
 png_write_chunk_end(png_structp png_ptr)
 {
@@ -192,6 +178,40 @@
    png_write_data(png_ptr, buf, (png_size_t)4);
 }
 
+/* Write a PNG chunk all at once.  The type is an array of ASCII characters
+ * representing the chunk name.  The array must be at least 4 bytes in
+ * length, and does not need to be null terminated.  To be safe, pass the
+ * pre-defined chunk names here, and if you need a new one, define it
+ * where the others are defined.  The length is the length of the data.
+ * All the data must be present.  If that is not possible, use the
+ * png_write_chunk_start(), png_write_chunk_data(), and png_write_chunk_end()
+ * functions instead.
+ */
+static void
+png_write_complete_chunk(png_structp png_ptr, png_uint_32 chunk_name,
+   png_const_bytep data, png_size_t length)
+{
+   if (png_ptr == NULL)
+      return;
+
+   /* On 64 bit architectures 'length' may not fit in a png_uint_32. */
+   if (length > PNG_UINT_32_MAX)
+      png_error(png_ptr, "length exceeds PNG maxima");
+
+   png_write_chunk_header(png_ptr, chunk_name, (png_uint_32)length);
+   png_write_chunk_data(png_ptr, data, length);
+   png_write_chunk_end(png_ptr);
+}
+
+/* This is the API that calls the internal function above. */
+void PNGAPI
+png_write_chunk(png_structp png_ptr, png_const_bytep chunk_string,
+   png_const_bytep data, png_size_t length)
+{
+   png_write_complete_chunk(png_ptr, PNG_CHUNK_FROM_STRING(chunk_string), data,
+      length);
+}
+
 /* Initialize the compressor for the appropriate type of compression. */
 static void
 png_zlib_claim(png_structp png_ptr, png_uint_32 state)
@@ -652,8 +672,6 @@
     int bit_depth, int color_type, int compression_type, int filter_type,
     int interlace_type)
 {
-   PNG_IHDR;
-
    png_byte buf[13]; /* Buffer to store the IHDR info */
 
    png_debug(1, "in png_write_IHDR");
@@ -795,7 +813,7 @@
    buf[12] = (png_byte)interlace_type;
 
    /* Write the chunk */
-   png_write_chunk(png_ptr, png_IHDR, buf, (png_size_t)13);
+   png_write_complete_chunk(png_ptr, png_IHDR, buf, (png_size_t)13);
 
    /* Initialize zlib with PNG info */
    png_ptr->zstream.zalloc = png_zalloc;
@@ -872,7 +890,6 @@
 png_write_PLTE(png_structp png_ptr, png_const_colorp palette,
     png_uint_32 num_pal)
 {
-   PNG_PLTE;
    png_uint_32 i;
    png_const_colorp pal_ptr;
    png_byte buf[3];
@@ -908,7 +925,7 @@
    png_ptr->num_palette = (png_uint_16)num_pal;
    png_debug1(3, "num_palette = %d", png_ptr->num_palette);
 
-   png_write_chunk_start(png_ptr, png_PLTE, (png_uint_32)(num_pal * 3));
+   png_write_chunk_header(png_ptr, png_PLTE, (png_uint_32)(num_pal * 3));
 #ifdef PNG_POINTER_INDEXING_SUPPORTED
 
    for (i = 0, pal_ptr = palette; i < num_pal; i++, pal_ptr++)
@@ -942,8 +959,6 @@
 void /* PRIVATE */
 png_write_IDAT(png_structp png_ptr, png_bytep data, png_size_t length)
 {
-   PNG_IDAT;
-
    png_debug(1, "in png_write_IDAT");
 
 #ifdef PNG_WRITE_OPTIMIZE_CMF_SUPPORTED
@@ -1014,7 +1029,7 @@
    }
 #endif /* PNG_WRITE_OPTIMIZE_CMF_SUPPORTED */
 
-   png_write_chunk(png_ptr, png_IDAT, data, length);
+   png_write_complete_chunk(png_ptr, png_IDAT, data, length);
    png_ptr->mode |= PNG_HAVE_IDAT;
 
    /* Prior to 1.5.4 this code was replicated in every caller (except at the
@@ -1029,11 +1044,9 @@
 void /* PRIVATE */
 png_write_IEND(png_structp png_ptr)
 {
-   PNG_IEND;
-
    png_debug(1, "in png_write_IEND");
 
-   png_write_chunk(png_ptr, png_IEND, NULL, (png_size_t)0);
+   png_write_complete_chunk(png_ptr, png_IEND, NULL, (png_size_t)0);
    png_ptr->mode |= PNG_HAVE_IEND;
 }
 
@@ -1042,14 +1055,13 @@
 void /* PRIVATE */
 png_write_gAMA_fixed(png_structp png_ptr, png_fixed_point file_gamma)
 {
-   PNG_gAMA;
    png_byte buf[4];
 
    png_debug(1, "in png_write_gAMA");
 
    /* file_gamma is saved in 1/100,000ths */
    png_save_uint_32(buf, (png_uint_32)file_gamma);
-   png_write_chunk(png_ptr, png_gAMA, buf, (png_size_t)4);
+   png_write_complete_chunk(png_ptr, png_gAMA, buf, (png_size_t)4);
 }
 #endif
 
@@ -1058,7 +1070,6 @@
 void /* PRIVATE */
 png_write_sRGB(png_structp png_ptr, int srgb_intent)
 {
-   PNG_sRGB;
    png_byte buf[1];
 
    png_debug(1, "in png_write_sRGB");
@@ -1068,7 +1079,7 @@
           "Invalid sRGB rendering intent specified");
 
    buf[0]=(png_byte)srgb_intent;
-   png_write_chunk(png_ptr, png_sRGB, buf, (png_size_t)1);
+   png_write_complete_chunk(png_ptr, png_sRGB, buf, (png_size_t)1);
 }
 #endif
 
@@ -1078,7 +1089,6 @@
 png_write_iCCP(png_structp png_ptr, png_const_charp name, int compression_type,
     png_const_charp profile, int profile_len)
 {
-   PNG_iCCP;
    png_size_t name_len;
    png_charp new_name;
    compression_state comp;
@@ -1139,7 +1149,7 @@
           (png_size_t)profile_len, PNG_COMPRESSION_TYPE_BASE, &comp);
 
    /* Make sure we include the NULL after the name and the compression type */
-   png_write_chunk_start(png_ptr, png_iCCP,
+   png_write_chunk_header(png_ptr, png_iCCP,
        (png_uint_32)(name_len + profile_len + 2));
 
    new_name[name_len + 1] = 0x00;
@@ -1163,7 +1173,6 @@
 void /* PRIVATE */
 png_write_sPLT(png_structp png_ptr, png_const_sPLT_tp spalette)
 {
-   PNG_sPLT;
    png_size_t name_len;
    png_charp new_name;
    png_byte entrybuf[10];
@@ -1180,7 +1189,7 @@
       return;
 
    /* Make sure we include the NULL after the name */
-   png_write_chunk_start(png_ptr, png_sPLT,
+   png_write_chunk_header(png_ptr, png_sPLT,
        (png_uint_32)(name_len + 2 + palette_size));
 
    png_write_chunk_data(png_ptr, (png_bytep)new_name,
@@ -1248,7 +1257,6 @@
 void /* PRIVATE */
 png_write_sBIT(png_structp png_ptr, png_const_color_8p sbit, int color_type)
 {
-   PNG_sBIT;
    png_byte buf[4];
    png_size_t size;
 
@@ -1299,7 +1307,7 @@
       buf[size++] = sbit->alpha;
    }
 
-   png_write_chunk(png_ptr, png_sBIT, buf, size);
+   png_write_complete_chunk(png_ptr, png_sBIT, buf, size);
 }
 #endif
 
@@ -1311,7 +1319,6 @@
     png_fixed_point green_x, png_fixed_point green_y, png_fixed_point blue_x,
     png_fixed_point blue_y)
 {
-   PNG_cHRM;
    png_byte buf[32];
 
    png_debug(1, "in png_write_cHRM");
@@ -1334,7 +1341,7 @@
       png_save_uint_32(buf + 24, (png_uint_32)blue_x);
       png_save_uint_32(buf + 28, (png_uint_32)blue_y);
 
-      png_write_chunk(png_ptr, png_cHRM, buf, (png_size_t)32);
+      png_write_complete_chunk(png_ptr, png_cHRM, buf, (png_size_t)32);
    }
 }
 #endif
@@ -1345,7 +1352,6 @@
 png_write_tRNS(png_structp png_ptr, png_const_bytep trans_alpha,
     png_const_color_16p tran, int num_trans, int color_type)
 {
-   PNG_tRNS;
    png_byte buf[6];
 
    png_debug(1, "in png_write_tRNS");
@@ -1359,7 +1365,7 @@
       }
 
       /* Write the chunk out as it is */
-      png_write_chunk(png_ptr, png_tRNS, trans_alpha, (png_size_t)num_trans);
+      png_write_complete_chunk(png_ptr, png_tRNS, trans_alpha, (png_size_t)num_trans);
    }
 
    else if (color_type == PNG_COLOR_TYPE_GRAY)
@@ -1374,7 +1380,7 @@
       }
 
       png_save_uint_16(buf, tran->gray);
-      png_write_chunk(png_ptr, png_tRNS, buf, (png_size_t)2);
+      png_write_complete_chunk(png_ptr, png_tRNS, buf, (png_size_t)2);
    }
 
    else if (color_type == PNG_COLOR_TYPE_RGB)
@@ -1394,7 +1400,7 @@
          return;
       }
 
-      png_write_chunk(png_ptr, png_tRNS, buf, (png_size_t)6);
+      png_write_complete_chunk(png_ptr, png_tRNS, buf, (png_size_t)6);
    }
 
    else
@@ -1409,7 +1415,6 @@
 void /* PRIVATE */
 png_write_bKGD(png_structp png_ptr, png_const_color_16p back, int color_type)
 {
-   PNG_bKGD;
    png_byte buf[6];
 
    png_debug(1, "in png_write_bKGD");
@@ -1428,7 +1433,7 @@
       }
 
       buf[0] = back->index;
-      png_write_chunk(png_ptr, png_bKGD, buf, (png_size_t)1);
+      png_write_complete_chunk(png_ptr, png_bKGD, buf, (png_size_t)1);
    }
 
    else if (color_type & PNG_COLOR_MASK_COLOR)
@@ -1448,7 +1453,7 @@
          return;
       }
 
-      png_write_chunk(png_ptr, png_bKGD, buf, (png_size_t)6);
+      png_write_complete_chunk(png_ptr, png_bKGD, buf, (png_size_t)6);
    }
 
    else
@@ -1462,7 +1467,7 @@
       }
 
       png_save_uint_16(buf, back->gray);
-      png_write_chunk(png_ptr, png_bKGD, buf, (png_size_t)2);
+      png_write_complete_chunk(png_ptr, png_bKGD, buf, (png_size_t)2);
    }
 }
 #endif
@@ -1472,7 +1477,6 @@
 void /* PRIVATE */
 png_write_hIST(png_structp png_ptr, png_const_uint_16p hist, int num_hist)
 {
-   PNG_hIST;
    int i;
    png_byte buf[3];
 
@@ -1487,7 +1491,7 @@
       return;
    }
 
-   png_write_chunk_start(png_ptr, png_hIST, (png_uint_32)(num_hist * 2));
+   png_write_chunk_header(png_ptr, png_hIST, (png_uint_32)(num_hist * 2));
 
    for (i = 0; i < num_hist; i++)
    {
@@ -1637,7 +1641,6 @@
 png_write_tEXt(png_structp png_ptr, png_const_charp key, png_const_charp text,
     png_size_t text_len)
 {
-   PNG_tEXt;
    png_size_t key_len;
    png_charp new_key;
 
@@ -1653,7 +1656,7 @@
       text_len = png_strlen(text);
 
    /* Make sure we include the 0 after the key */
-   png_write_chunk_start(png_ptr, png_tEXt,
+   png_write_chunk_header(png_ptr, png_tEXt,
        (png_uint_32)(key_len + text_len + 1));
    /*
     * We leave it to the application to meet PNG-1.0 requirements on the
@@ -1679,7 +1682,6 @@
 png_write_zTXt(png_structp png_ptr, png_const_charp key, png_const_charp text,
     png_size_t text_len, int compression)
 {
-   PNG_zTXt;
    png_size_t key_len;
    png_byte buf;
    png_charp new_key;
@@ -1713,7 +1715,7 @@
        &comp);
 
    /* Write start of chunk */
-   png_write_chunk_start(png_ptr, png_zTXt,
+   png_write_chunk_header(png_ptr, png_zTXt,
        (png_uint_32)(key_len+text_len + 2));
 
    /* Write key */
@@ -1742,7 +1744,6 @@
 png_write_iTXt(png_structp png_ptr, int compression, png_const_charp key,
     png_const_charp lang, png_const_charp lang_key, png_const_charp text)
 {
-   PNG_iTXt;
    png_size_t lang_len, key_len, lang_key_len, text_len;
    png_charp new_lang;
    png_charp new_key = NULL;
@@ -1787,7 +1788,7 @@
     * and the NULs after the key, lang, and lang_key parts
     */
 
-   png_write_chunk_start(png_ptr, png_iTXt, (png_uint_32)(
+   png_write_chunk_header(png_ptr, png_iTXt, (png_uint_32)(
         5 /* comp byte, comp flag, terminators for key, lang and lang_key */
         + key_len
         + lang_len
@@ -1836,7 +1837,6 @@
 png_write_oFFs(png_structp png_ptr, png_int_32 x_offset, png_int_32 y_offset,
     int unit_type)
 {
-   PNG_oFFs;
    png_byte buf[9];
 
    png_debug(1, "in png_write_oFFs");
@@ -1848,7 +1848,7 @@
    png_save_int_32(buf + 4, y_offset);
    buf[8] = (png_byte)unit_type;
 
-   png_write_chunk(png_ptr, png_oFFs, buf, (png_size_t)9);
+   png_write_complete_chunk(png_ptr, png_oFFs, buf, (png_size_t)9);
 }
 #endif
 #ifdef PNG_WRITE_pCAL_SUPPORTED
@@ -1858,7 +1858,6 @@
     png_int_32 X1, int type, int nparams, png_const_charp units,
     png_charpp params)
 {
-   PNG_pCAL;
    png_size_t purpose_len, units_len, total_len;
    png_size_tp params_len;
    png_byte buf[10];
@@ -1891,7 +1890,7 @@
    }
 
    png_debug1(3, "pCAL total length = %d", (int)total_len);
-   png_write_chunk_start(png_ptr, png_pCAL, (png_uint_32)total_len);
+   png_write_chunk_header(png_ptr, png_pCAL, (png_uint_32)total_len);
    png_write_chunk_data(png_ptr, (png_const_bytep)new_purpose, purpose_len);
    png_save_int_32(buf, X0);
    png_save_int_32(buf + 4, X1);
@@ -1918,7 +1917,6 @@
 png_write_sCAL_s(png_structp png_ptr, int unit, png_const_charp width,
     png_const_charp height)
 {
-   PNG_sCAL;
    png_byte buf[64];
    png_size_t wlen, hlen, total_len;
 
@@ -1939,7 +1937,7 @@
    png_memcpy(buf + wlen + 2, height, hlen);  /* Do NOT append the '\0' here */
 
    png_debug1(3, "sCAL total length = %u", (unsigned int)total_len);
-   png_write_chunk(png_ptr, png_sCAL, buf, total_len);
+   png_write_complete_chunk(png_ptr, png_sCAL, buf, total_len);
 }
 #endif
 
@@ -1950,7 +1948,6 @@
     png_uint_32 y_pixels_per_unit,
     int unit_type)
 {
-   PNG_pHYs;
    png_byte buf[9];
 
    png_debug(1, "in png_write_pHYs");
@@ -1962,7 +1959,7 @@
    png_save_uint_32(buf + 4, y_pixels_per_unit);
    buf[8] = (png_byte)unit_type;
 
-   png_write_chunk(png_ptr, png_pHYs, buf, (png_size_t)9);
+   png_write_complete_chunk(png_ptr, png_pHYs, buf, (png_size_t)9);
 }
 #endif
 
@@ -1973,7 +1970,6 @@
 void /* PRIVATE */
 png_write_tIME(png_structp png_ptr, png_const_timep mod_time)
 {
-   PNG_tIME;
    png_byte buf[7];
 
    png_debug(1, "in png_write_tIME");
@@ -1993,7 +1989,7 @@
    buf[5] = mod_time->minute;
    buf[6] = mod_time->second;
 
-   png_write_chunk(png_ptr, png_tIME, buf, (png_size_t)7);
+   png_write_complete_chunk(png_ptr, png_tIME, buf, (png_size_t)7);
 }
 #endif
 
@@ -2005,28 +2001,32 @@
    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
 
    /* Start of interlace block */
-   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 */
-   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 */
-   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 */
-   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_size_t buf_size;
+   png_alloc_size_t buf_size;
+   int usr_pixel_depth;
 
    png_debug(1, "in png_write_start_row");
 
-   buf_size = (png_size_t)(PNG_ROWBYTES(
-       png_ptr->usr_channels*png_ptr->usr_bit_depth, png_ptr->width) + 1);
+   usr_pixel_depth = png_ptr->usr_channels * png_ptr->usr_bit_depth;
+   buf_size = PNG_ROWBYTES(usr_pixel_depth, png_ptr->width) + 1;
+
+   /* 1.5.6: added to allow checking in the row write code. */
+   png_ptr->transformed_pixel_depth = png_ptr->pixel_depth;
+   png_ptr->maximum_pixel_depth = (png_byte)usr_pixel_depth;
 
    /* Set up row buffer */
-   png_ptr->row_buf = (png_bytep)png_malloc(png_ptr,
-       (png_alloc_size_t)buf_size);
+   png_ptr->row_buf = (png_bytep)png_malloc(png_ptr, buf_size);
 
    png_ptr->row_buf[0] = PNG_FILTER_VALUE_NONE;
 
@@ -2043,8 +2043,7 @@
    if (png_ptr->do_filter & (PNG_FILTER_AVG | PNG_FILTER_UP | PNG_FILTER_PAETH))
    {
       /* Set up previous row buffer */
-      png_ptr->prev_row = (png_bytep)png_calloc(png_ptr,
-          (png_alloc_size_t)buf_size);
+      png_ptr->prev_row = (png_bytep)png_calloc(png_ptr, buf_size);
 
       if (png_ptr->do_filter & PNG_FILTER_UP)
       {
@@ -2112,16 +2111,16 @@
    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
 
    /* Start of interlace block */
-   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 */
-   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 */
-   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 */
-   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 ret;
@@ -2239,10 +2238,10 @@
    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
 
    /* Start of interlace block */
-   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 */
-   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};
 
    png_debug(1, "in png_do_write_interlace");
 
@@ -2410,7 +2409,8 @@
  * been specified by the application, and then writes the row out with the
  * chosen filter.
  */
-static void png_write_filtered_row(png_structp png_ptr, png_bytep filtered_row);
+static void png_write_filtered_row(png_structp png_ptr, png_bytep filtered_row,
+   png_size_t row_bytes);
 
 #define PNG_MAXSUM (((png_uint_32)(-1)) >> 1)
 #define PNG_HISHIFT 10
@@ -2426,7 +2426,7 @@
    png_byte filter_to_do = png_ptr->do_filter;
    png_size_t row_bytes = row_info->rowbytes;
 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
-   int num_p_filters = (int)png_ptr->num_prev_filters;
+   int num_p_filters = png_ptr->num_prev_filters;
 #endif
 
    png_debug(1, "in png_write_find_filter");
@@ -3063,9 +3063,9 @@
       }
    }
 #endif /* PNG_WRITE_FILTER_SUPPORTED */
-   /* Do the actual writing of the filtered row data from the chosen filter. */
 
-   png_write_filtered_row(png_ptr, best_row);
+   /* Do the actual writing of the filtered row data from the chosen filter. */
+   png_write_filtered_row(png_ptr, best_row, row_info->rowbytes+1);
 
 #ifdef PNG_WRITE_FILTER_SUPPORTED
 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
@@ -3088,10 +3088,9 @@
 
 /* Do the actual writing of a previously filtered row. */
 static void
-png_write_filtered_row(png_structp png_ptr, png_bytep filtered_row)
+png_write_filtered_row(png_structp png_ptr, png_bytep filtered_row,
+   png_size_t avail/*includes filter byte*/)
 {
-   png_size_t avail;
-
    png_debug(1, "in png_write_filtered_row");
 
    png_debug1(2, "filter = %d", filtered_row[0]);
@@ -3099,7 +3098,6 @@
 
    png_ptr->zstream.next_in = filtered_row;
    png_ptr->zstream.avail_in = 0;
-   avail = png_ptr->row_info.rowbytes + 1;
    /* Repeat until we have compressed all the data */
    do
    {
diff --git a/projects/vstudio/readme.txt b/projects/vstudio/readme.txt
index 1e2a261..0d22d43 100644
--- a/projects/vstudio/readme.txt
+++ b/projects/vstudio/readme.txt
@@ -1,7 +1,7 @@
 
 VisualStudio instructions
 
-libpng version 1.5.6beta01 - September 22, 2011
+libpng version 1.5.6beta02 - September 22, 2011
 
 Copyright (c) 1998-2010 Glenn Randers-Pehrson
 
diff --git a/projects/vstudio/zlib.props b/projects/vstudio/zlib.props
index 10d9442..3810da7 100644
--- a/projects/vstudio/zlib.props
+++ b/projects/vstudio/zlib.props
@@ -2,7 +2,7 @@
 <!--
  * zlib.props - location of zlib source
  *
- * libpng version 1.5.6beta01 - September 22, 2011
+ * libpng version 1.5.6beta02 - September 22, 2011
  *
  * Copyright (c) 1998-2011 Glenn Randers-Pehrson
  *
diff --git a/scripts/README.txt b/scripts/README.txt
index a0a309b..56c38ed 100644
--- a/scripts/README.txt
+++ b/scripts/README.txt
@@ -1,9 +1,9 @@
 
-Makefiles for  libpng version 1.5.6beta01 - September 22, 2011
+Makefiles for  libpng version 1.5.6beta02 - September 22, 2011
 
 pnglibconf.h.prebuilt       =>  Stores configuration settings
  makefile.linux    =>  Linux/ELF makefile
-                       (gcc, creates libpng15.so.15.1.5.6beta01)
+                       (gcc, creates libpng15.so.15.1.5.6beta02)
  makefile.gcc      =>  Generic makefile (gcc, creates static libpng.a)
  makefile.knr      =>  Archaic UNIX Makefile that converts files with
                        ansi2knr (Requires ansi2knr.c from
@@ -20,7 +20,7 @@
  makefile.dec      =>  DEC Alpha UNIX makefile
  makefile.dj2      =>  DJGPP 2 makefile
  makefile.elf      =>  Linux/ELF makefile symbol versioning,
-                       (gcc, creates libpng15.so.15.1.5.6beta01)
+                       (gcc, creates libpng15.so.15.1.5.6beta02)
  makefile.freebsd  =>  FreeBSD makefile
  makefile.gcc      =>  Generic gcc makefile
  makefile.hpgcc    =>  HPUX makefile using gcc
@@ -35,12 +35,12 @@
  makefile.os2      =>  OS/2 Makefile (gcc and emx, requires libpng.def)
  makefile.sco      =>  For SCO OSr5  ELF and Unixware 7 with Native cc
  makefile.sggcc    =>  Silicon Graphics (gcc,
-                       creates libpng15.so.15.1.5.6beta01)
+                       creates libpng15.so.15.1.5.6beta02)
  makefile.sgi      =>  Silicon Graphics IRIX makefile (cc, creates static lib)
  makefile.solaris  =>  Solaris 2.X makefile (gcc,
-                       creates libpng15.so.15.1.5.6beta01)
+                       creates libpng15.so.15.1.5.6beta02)
  makefile.so9      =>  Solaris 9 makefile (gcc,
-                       creates libpng15.so.15.1.5.6beta01)
+                       creates libpng15.so.15.1.5.6beta02)
  makefile.std      =>  Generic UNIX makefile (cc, creates static libpng.a)
  makefile.sunos    =>  Sun makefile
  makefile.32sunu   =>  Sun Ultra 32-bit makefile
diff --git a/scripts/libpng-config-head.in b/scripts/libpng-config-head.in
index b38d6f4..970028f 100755
--- a/scripts/libpng-config-head.in
+++ b/scripts/libpng-config-head.in
@@ -11,7 +11,7 @@
 
 # Modeled after libxml-config.
 
-version=1.5.6beta01
+version=1.5.6beta02
 prefix=""
 libdir=""
 libs=""
diff --git a/scripts/libpng.pc.in b/scripts/libpng.pc.in
index b36ddce..2c885f3 100644
--- a/scripts/libpng.pc.in
+++ b/scripts/libpng.pc.in
@@ -5,6 +5,6 @@
 
 Name: libpng
 Description: Loads and saves PNG files
-Version: 1.5.6beta01
+Version: 1.5.6beta02
 Libs: -L${libdir} -lpng15
 Cflags: -I${includedir}
diff --git a/scripts/makefile.ne12bsd b/scripts/makefile.ne12bsd
index bc04bcc..9a3ac5b 100644
--- a/scripts/makefile.ne12bsd
+++ b/scripts/makefile.ne12bsd
@@ -17,7 +17,7 @@
 
 LIB=	png15
 SHLIB_MAJOR=	0
-SHLIB_MINOR=	1.5.6beta01
+SHLIB_MINOR=	1.5.6beta02
 SRCS=	png.c pngset.c pngget.c pngrutil.c pngtrans.c pngwutil.c \
 	pngread.c pngrio.c pngwio.c pngwrite.c pngrtran.c \
 	pngwtran.c pngmem.c pngerror.c pngpread.c
diff --git a/scripts/makefile.netbsd b/scripts/makefile.netbsd
index 7c84ecb..a8a1de2 100644
--- a/scripts/makefile.netbsd
+++ b/scripts/makefile.netbsd
@@ -17,7 +17,7 @@
 
 LIB=	png
 SHLIB_MAJOR=	15
-SHLIB_MINOR=	1.5.6beta01
+SHLIB_MINOR=	1.5.6beta02
 SRCS=	png.c pngset.c pngget.c pngrutil.c pngtrans.c pngwutil.c \
 	pngread.c pngrio.c pngwio.c pngwrite.c pngrtran.c \
 	pngwtran.c pngmem.c pngerror.c pngpread.c
diff --git a/scripts/makefile.openbsd b/scripts/makefile.openbsd
index 1c67228..8eee0fd 100644
--- a/scripts/makefile.openbsd
+++ b/scripts/makefile.openbsd
@@ -11,7 +11,7 @@
 MANDIR= ${PREFIX}/man/cat
 
 SHLIB_MAJOR=	15
-SHLIB_MINOR=	1.5.6beta01
+SHLIB_MINOR=	1.5.6beta02
 
 LIB=	png
 SRCS=	png.c pngerror.c pngget.c pngmem.c pngpread.c \
diff --git a/scripts/symbols.def b/scripts/symbols.def
index 8809de1..84827d9 100644
--- a/scripts/symbols.def
+++ b/scripts/symbols.def
@@ -5,7 +5,7 @@
 LIBRARY
 
 EXPORTS
-;Version 1.5.6beta01
+;Version 1.5.6beta02
  png_access_version_number @1
  png_set_sig_bytes @2
  png_sig_cmp @3