Merge pull request #12049 from ISylvox/libpng-1.6.33

Update LibPNG to v1.6.33

11 files changed, 87 insertions, 77 deletions

diff --git a/thirdparty/README.md b/thirdparty/README.md
index 6e1dcb8df4..335fcdd80b 100644
--- a/thirdparty/README.md
+++ b/thirdparty/README.md
@@ -121,7 +121,7 @@ Files extracted from upstream source:
 ## libpng
 
 - Upstream: http://libpng.org/pub/png/libpng.html
-- Version: 1.6.32
+- Version: 1.6.33
 - License: libpng/zlib
 
 Files extracted from upstream source:
diff --git a/thirdparty/libpng/LICENSE b/thirdparty/libpng/LICENSE
index b7ad4b9eaf..57c366feea 100644
--- a/thirdparty/libpng/LICENSE
+++ b/thirdparty/libpng/LICENSE
@@ -10,8 +10,8 @@ this sentence.
 
 This code is released under the libpng license.
 
-libpng versions 1.0.7, July 1, 2000 through 1.6.23, June 9, 2016 are
-Copyright (c) 2000-2002, 2004, 2006-2016 Glenn Randers-Pehrson, are
+libpng versions 1.0.7, July 1, 2000 through 1.6.33, September 28, 2017 are
+Copyright (c) 2000-2002, 2004, 2006-2017 Glenn Randers-Pehrson, are
 derived from libpng-1.0.6, and are distributed according to the same
 disclaimer and license as libpng-1.0.6 with the following individuals
 added to the list of Contributing Authors:
@@ -22,6 +22,9 @@ added to the list of Contributing Authors:
    Cosmin Truta
    Gilles Vollant
    James Yu
+   Mandar Sahastrabuddhe
+   Google Inc.
+   Vadim Barkov
 
 and with the following additions to the disclaimer:
 
@@ -127,4 +130,4 @@ any encryption software.  See the EAR, paragraphs 734.3(b)(3) and
 
 Glenn Randers-Pehrson
 glennrp at users.sourceforge.net
-June 9, 2016
+September 28, 2017
diff --git a/thirdparty/libpng/png.c b/thirdparty/libpng/png.c
index 2352df13cb..55134729c7 100644
--- a/thirdparty/libpng/png.c
+++ b/thirdparty/libpng/png.c
@@ -1,7 +1,7 @@
 
 /* png.c - location for general purpose libpng functions
  *
- * Last changed in libpng 1.6.32 [August 24, 2017]
+ * Last changed in libpng 1.6.33 [September 28, 2017]
  * Copyright (c) 1998-2002,2004,2006-2017 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_6_32 Your_png_h_is_not_version_1_6_32;
+typedef png_libpng_version_1_6_33 Your_png_h_is_not_version_1_6_33;
 
 #ifdef __GNUC__
 /* The version tests may need to be added to, but the problem warning has
@@ -816,14 +816,14 @@ png_get_copyright(png_const_structrp png_ptr)
 #else
 #  ifdef __STDC__
    return PNG_STRING_NEWLINE \
-      "libpng version 1.6.32 - August 24, 2017" PNG_STRING_NEWLINE \
+      "libpng version 1.6.33 - September 28, 2017" PNG_STRING_NEWLINE \
       "Copyright (c) 1998-2002,2004,2006-2017 Glenn Randers-Pehrson" \
       PNG_STRING_NEWLINE \
       "Copyright (c) 1996-1997 Andreas Dilger" PNG_STRING_NEWLINE \
       "Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc." \
       PNG_STRING_NEWLINE;
 #  else
-   return "libpng version 1.6.32 - August 24, 2017\
+   return "libpng version 1.6.33 - September 28, 2017\
       Copyright (c) 1998-2002,2004,2006-2017 Glenn Randers-Pehrson\
       Copyright (c) 1996-1997 Andreas Dilger\
       Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.";
@@ -1913,12 +1913,12 @@ png_colorspace_set_sRGB(png_const_structrp png_ptr, png_colorspacerp colorspace,
     */
    if (intent < 0 || intent >= PNG_sRGB_INTENT_LAST)
       return png_icc_profile_error(png_ptr, colorspace, "sRGB",
-          (unsigned)intent, "invalid sRGB rendering intent");
+          (png_alloc_size_t)intent, "invalid sRGB rendering intent");
 
    if ((colorspace->flags & PNG_COLORSPACE_HAVE_INTENT) != 0 &&
        colorspace->rendering_intent != intent)
       return png_icc_profile_error(png_ptr, colorspace, "sRGB",
-         (unsigned)intent, "inconsistent rendering intents");
+         (png_alloc_size_t)intent, "inconsistent rendering intents");
 
    if ((colorspace->flags & PNG_COLORSPACE_FROM_sRGB) != 0)
    {
@@ -1979,7 +1979,6 @@ icc_check_length(png_const_structrp png_ptr, png_colorspacerp colorspace,
    if (profile_length < 132)
       return png_icc_profile_error(png_ptr, colorspace, name, profile_length,
           "too short");
-
    return 1;
 }
 
@@ -2224,22 +2223,23 @@ png_icc_check_tag_table(png_const_structrp png_ptr, png_colorspacerp colorspace,
        * being in range.  All defined tag types have an 8 byte header - a 4 byte
        * type signature then 0.
        */
+
+      /* This is a hard error; potentially it can cause read outside the
+       * profile.
+       */
+      if (tag_start > profile_length || tag_length > profile_length - tag_start)
+         return png_icc_profile_error(png_ptr, colorspace, name, tag_id,
+             "ICC profile tag outside profile");
+
       if ((tag_start & 3) != 0)
       {
-         /* CNHP730S.icc shipped with Microsoft Windows 64 violates this, it is
+         /* CNHP730S.icc shipped with Microsoft Windows 64 violates this; it is
           * only a warning here because libpng does not care about the
           * alignment.
           */
          (void)png_icc_profile_error(png_ptr, NULL, name, tag_id,
              "ICC profile tag start not a multiple of 4");
       }
-
-      /* This is a hard error; potentially it can cause read outside the
-       * profile.
-       */
-      if (tag_start > profile_length || tag_length > profile_length - tag_start)
-         return png_icc_profile_error(png_ptr, colorspace, name, tag_id,
-             "ICC profile tag outside profile");
    }
 
    return 1; /* success, maybe with warnings */
@@ -3761,7 +3761,7 @@ png_log16bit(png_uint_32 x)
  * of getting this accuracy in practice.
  *
  * To deal with this the following exp() function works out the exponent of the
- * frational part of the logarithm by using an accurate 32-bit value from the
+ * fractional part of the logarithm by using an accurate 32-bit value from the
  * top four fractional bits then multiplying in the remaining bits.
  */
 static const png_uint_32
diff --git a/thirdparty/libpng/png.h b/thirdparty/libpng/png.h
index 51ac8abe74..a5f142b89c 100644
--- a/thirdparty/libpng/png.h
+++ b/thirdparty/libpng/png.h
@@ -1,7 +1,7 @@
 
 /* png.h - header file for PNG reference library
  *
- * libpng version 1.6.32, August 24, 2017
+ * libpng version 1.6.33, September 28, 2017
  *
  * Copyright (c) 1998-2002,2004,2006-2017 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
@@ -12,7 +12,7 @@
  * Authors and maintainers:
  *   libpng versions 0.71, May 1995, through 0.88, January 1996: Guy Schalnat
  *   libpng versions 0.89, June 1996, through 0.96, May 1997: Andreas Dilger
- *   libpng versions 0.97, January 1998, through 1.6.32, August 24, 2017:
+ *   libpng versions 0.97, January 1998, through 1.6.33, September 28, 2017:
  *     Glenn Randers-Pehrson.
  *   See also "Contributing Authors", below.
  */
@@ -25,7 +25,7 @@
  *
  * This code is released under the libpng license.
  *
- * libpng versions 1.0.7, July 1, 2000 through 1.6.32, August 24, 2017 are
+ * libpng versions 1.0.7, July 1, 2000 through 1.6.33, September 28, 2017 are
  * Copyright (c) 2000-2002, 2004, 2006-2017 Glenn Randers-Pehrson, are
  * derived from libpng-1.0.6, and are distributed according to the same
  * disclaimer and license as libpng-1.0.6 with the following individuals
@@ -213,7 +213,7 @@
  *    ...
  *    1.5.28                  15    10527  15.so.15.28[.0]
  *    ...
- *    1.6.32                  16    10632  16.so.16.32[.0]
+ *    1.6.33                  16    10633  16.so.16.33[.0]
  *
  *    Henceforth the source version will match the shared-library major
  *    and minor numbers; the shared-library major version number will be
@@ -241,13 +241,13 @@
  * Y2K compliance in libpng:
  * =========================
  *
- *    August 24, 2017
+ *    September 28, 2017
  *
  *    Since the PNG Development group is an ad-hoc body, we can't make
  *    an official declaration.
  *
  *    This is your unofficial assurance that libpng from version 0.71 and
- *    upward through 1.6.32 are Y2K compliant.  It is my belief that
+ *    upward through 1.6.33 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
@@ -309,8 +309,8 @@
  */
 
 /* Version information for png.h - this should match the version in png.c */
-#define PNG_LIBPNG_VER_STRING "1.6.32"
-#define PNG_HEADER_VERSION_STRING " libpng version 1.6.32 - August 24, 2017\n"
+#define PNG_LIBPNG_VER_STRING "1.6.33"
+#define PNG_HEADER_VERSION_STRING " libpng version 1.6.33 - September 28, 2017\n"
 
 #define PNG_LIBPNG_VER_SONUM   16
 #define PNG_LIBPNG_VER_DLLNUM  16
@@ -318,7 +318,7 @@
 /* These should match the first 3 components of PNG_LIBPNG_VER_STRING: */
 #define PNG_LIBPNG_VER_MAJOR   1
 #define PNG_LIBPNG_VER_MINOR   6
-#define PNG_LIBPNG_VER_RELEASE 32
+#define PNG_LIBPNG_VER_RELEASE 33
 
 /* This should match the numeric part of the final component of
  * PNG_LIBPNG_VER_STRING, omitting any leading zero:
@@ -349,7 +349,7 @@
  * version 1.0.0 was mis-numbered 100 instead of 10000).  From
  * version 1.0.1 it's    xxyyzz, where x=major, y=minor, z=release
  */
-#define PNG_LIBPNG_VER 10632 /* 1.6.32 */
+#define PNG_LIBPNG_VER 10633 /* 1.6.33 */
 
 /* Library configuration: these options cannot be changed after
  * the library has been built.
@@ -459,7 +459,7 @@ extern "C" {
 /* 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_6_32;
+typedef char* png_libpng_version_1_6_33;
 
 /* Basic control structions.  Read libpng-manual.txt or libpng.3 for more info.
  *
@@ -2819,6 +2819,8 @@ typedef struct
 #  define PNG_FORMAT_FLAG_AFIRST 0x20U /* alpha channel comes first */
 #endif
 
+#define PNG_FORMAT_FLAG_ASSOCIATED_ALPHA 0x40U /* alpha channel is associated */
+
 /* Commonly used formats have predefined macros.
  *
  * First the single byte (sRGB) formats:
diff --git a/thirdparty/libpng/pngconf.h b/thirdparty/libpng/pngconf.h
index c0f15547be..e99e827dda 100644
--- a/thirdparty/libpng/pngconf.h
+++ b/thirdparty/libpng/pngconf.h
@@ -1,7 +1,7 @@
 
 /* pngconf.h - machine configurable file for libpng
  *
- * libpng version 1.6.32, August 24, 2017
+ * libpng version 1.6.33, September 28, 2017
  *
  * Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
diff --git a/thirdparty/libpng/pnglibconf.h b/thirdparty/libpng/pnglibconf.h
index 9e45f73129..cbf715dd93 100644
--- a/thirdparty/libpng/pnglibconf.h
+++ b/thirdparty/libpng/pnglibconf.h
@@ -1,8 +1,8 @@
-/* libpng 1.6.32 STANDARD API DEFINITION */
+/* libpng 1.6.33 STANDARD API DEFINITION */
 
 /* pnglibconf.h - library build configuration */
 
-/* Libpng version 1.6.32 - August 24, 2017 */
+/* Libpng version 1.6.33 - September 28, 2017 */
 
 /* Copyright (c) 1998-2017 Glenn Randers-Pehrson */
 
diff --git a/thirdparty/libpng/pngread.c b/thirdparty/libpng/pngread.c
index e34ddd99a0..da32e9ad9c 100644
--- a/thirdparty/libpng/pngread.c
+++ b/thirdparty/libpng/pngread.c
@@ -1,7 +1,7 @@
 
 /* pngread.c - read a PNG file
  *
- * Last changed in libpng 1.6.32 [August 24, 2017]
+ * Last changed in libpng 1.6.33 [September 28, 2017]
  * Copyright (c) 1998-2002,2004,2006-2017 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.)
@@ -3759,7 +3759,13 @@ png_image_read_direct(png_voidp argument)
          mode = PNG_ALPHA_PNG;
          output_gamma = PNG_DEFAULT_sRGB;
       }
-
+      
+      if ((change & PNG_FORMAT_FLAG_ASSOCIATED_ALPHA) != 0)
+      {
+         mode = PNG_ALPHA_OPTIMIZED;
+         change &= ~PNG_FORMAT_FLAG_ASSOCIATED_ALPHA;
+      }
+      
       /* If 'do_local_background' is set check for the presence of gamma
        * correction; this is part of the work-round for the libpng bug
        * described above.
@@ -3985,6 +3991,10 @@ png_image_read_direct(png_voidp argument)
       else if (do_local_compose != 0) /* internal error */
          png_error(png_ptr, "png_image_read: alpha channel lost");
 
+      if ((format & PNG_FORMAT_FLAG_ASSOCIATED_ALPHA) != 0) {
+         info_format |= PNG_FORMAT_FLAG_ASSOCIATED_ALPHA;
+      }
+
       if (info_ptr->bit_depth == 16)
          info_format |= PNG_FORMAT_FLAG_LINEAR;
 
diff --git a/thirdparty/libpng/pngrtran.c b/thirdparty/libpng/pngrtran.c
index 9a30ddf22b..c189650313 100644
--- a/thirdparty/libpng/pngrtran.c
+++ b/thirdparty/libpng/pngrtran.c
@@ -1,7 +1,7 @@
 
 /* pngrtran.c - transforms the data in a row for PNG readers
  *
- * Last changed in libpng 1.6.31 [July 27, 2017]
+ * Last changed in libpng 1.6.33 [September 28, 2017]
  * Copyright (c) 1998-2002,2004,2006-2017 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.)
@@ -430,7 +430,7 @@ png_set_quantize(png_structrp png_ptr, png_colorp palette,
       int i;
 
       png_ptr->quantize_index = (png_bytep)png_malloc(png_ptr,
-          (png_uint_32)((png_uint_32)num_palette * (sizeof (png_byte))));
+          (png_alloc_size_t)((png_uint_32)num_palette * (sizeof (png_byte))));
       for (i = 0; i < num_palette; i++)
          png_ptr->quantize_index[i] = (png_byte)i;
    }
@@ -447,7 +447,7 @@ png_set_quantize(png_structrp png_ptr, png_colorp palette,
 
          /* Initialize an array to sort colors */
          png_ptr->quantize_sort = (png_bytep)png_malloc(png_ptr,
-             (png_uint_32)((png_uint_32)num_palette * (sizeof (png_byte))));
+             (png_alloc_size_t)((png_uint_32)num_palette * (sizeof (png_byte))));
 
          /* Initialize the quantize_sort array */
          for (i = 0; i < num_palette; i++)
@@ -581,9 +581,11 @@ png_set_quantize(png_structrp png_ptr, png_colorp palette,
 
          /* Initialize palette index arrays */
          png_ptr->index_to_palette = (png_bytep)png_malloc(png_ptr,
-             (png_uint_32)((png_uint_32)num_palette * (sizeof (png_byte))));
+             (png_alloc_size_t)((png_uint_32)num_palette *
+             (sizeof (png_byte))));
          png_ptr->palette_to_index = (png_bytep)png_malloc(png_ptr,
-             (png_uint_32)((png_uint_32)num_palette * (sizeof (png_byte))));
+             (png_alloc_size_t)((png_uint_32)num_palette *
+             (sizeof (png_byte))));
 
          /* Initialize the sort array */
          for (i = 0; i < num_palette; i++)
@@ -592,7 +594,7 @@ png_set_quantize(png_structrp png_ptr, png_colorp palette,
             png_ptr->palette_to_index[i] = (png_byte)i;
          }
 
-         hash = (png_dsortpp)png_calloc(png_ptr, (png_uint_32)(769 *
+         hash = (png_dsortpp)png_calloc(png_ptr, (png_alloc_size_t)(769 *
              (sizeof (png_dsortp))));
 
          num_new_palette = num_palette;
@@ -623,7 +625,7 @@ png_set_quantize(png_structrp png_ptr, png_colorp palette,
                   {
 
                      t = (png_dsortp)png_malloc_warn(png_ptr,
-                         (png_uint_32)(sizeof (png_dsort)));
+                         (png_alloc_size_t)(sizeof (png_dsort)));
 
                      if (t == NULL)
                          break;
@@ -748,9 +750,9 @@ png_set_quantize(png_structrp png_ptr, png_colorp palette,
       png_size_t num_entries = ((png_size_t)1 << total_bits);
 
       png_ptr->palette_lookup = (png_bytep)png_calloc(png_ptr,
-          (png_uint_32)(num_entries * (sizeof (png_byte))));
+          (png_alloc_size_t)(num_entries * (sizeof (png_byte))));
 
-      distance = (png_bytep)png_malloc(png_ptr, (png_uint_32)(num_entries *
+      distance = (png_bytep)png_malloc(png_ptr, (png_alloc_size_t)(num_entries *
           (sizeof (png_byte))));
 
       memset(distance, 0xff, num_entries * (sizeof (png_byte)));
@@ -3322,7 +3324,7 @@ png_do_compose(png_row_infop row_info, png_bytep row, png_structrp png_ptr)
                             == png_ptr->trans_color.gray)
                         {
                            unsigned int tmp = *sp & (0x0f0f >> (4 - shift));
-                           tmp |= 
+                           tmp |=
                               (unsigned int)(png_ptr->background.gray << shift);
                            *sp = (png_byte)(tmp & 0xff);
                         }
diff --git a/thirdparty/libpng/pngrutil.c b/thirdparty/libpng/pngrutil.c
index a4fa71457b..8692933bd8 100644
--- a/thirdparty/libpng/pngrutil.c
+++ b/thirdparty/libpng/pngrutil.c
@@ -1,7 +1,7 @@
 
 /* pngrutil.c - utilities to read a PNG file
  *
- * Last changed in libpng 1.6.32 [August 24, 2017]
+ * Last changed in libpng 1.6.33 [September 28, 2017]
  * Copyright (c) 1998-2002,2004,2006-2017 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.)
@@ -314,6 +314,7 @@ png_read_buffer(png_structrp png_ptr, png_alloc_size_t new_size, int warn)
 
       if (buffer != NULL)
       {
+         memset(buffer, 0, new_size); /* just in case */
          png_ptr->read_buffer = buffer;
          png_ptr->read_buffer_size = new_size;
       }
@@ -673,6 +674,8 @@ png_decompress_chunk(png_structrp png_ptr,
 
                if (text != NULL)
                {
+                  memset(text, 0, buffer_size);
+
                   ret = png_inflate(png_ptr, png_ptr->chunk_name, 1/*finish*/,
                       png_ptr->read_buffer + prefix_size, &lzsize,
                       text + prefix_size, newlength);
@@ -736,9 +739,7 @@ png_decompress_chunk(png_structrp png_ptr,
             {
                /* inflateReset failed, store the error message */
                png_zstream_error(png_ptr, ret);
-
-               if (ret == Z_STREAM_END)
-                  ret = PNG_UNEXPECTED_ZLIB_RETURN;
+               ret = PNG_UNEXPECTED_ZLIB_RETURN;
             }
          }
 
@@ -1476,7 +1477,7 @@ png_handle_iCCP(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
                         /* Now read the tag table; a variable size buffer is
                          * needed at this point, allocate one for the whole
                          * profile.  The header check has already validated
-                         * that none of these stuff will overflow.
+                         * that none of this stuff will overflow.
                          */
                         const png_uint_32 tag_count = png_get_uint_32(
                             profile_header+128);
@@ -1583,19 +1584,11 @@ png_handle_iCCP(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
                                        return;
                                     }
                                  }
-
-                                 else if (size > 0)
-                                    errmsg = "truncated";
-
-#ifndef __COVERITY__
-                                 else
+                                 if (errmsg == NULL)
                                     errmsg = png_ptr->zstream.msg;
-#endif
                               }
-
                               /* else png_icc_check_tag_table output an error */
                            }
-
                            else /* profile truncated */
                               errmsg = png_ptr->zstream.msg;
                         }
@@ -3144,28 +3137,28 @@ png_check_chunk_length(png_const_structrp png_ptr, const png_uint_32 length)
 {
    png_alloc_size_t limit = PNG_UINT_31_MAX;
 
-   if (png_ptr->chunk_name != png_IDAT)
-   {
 # ifdef PNG_SET_USER_LIMITS_SUPPORTED
-      if (png_ptr->user_chunk_malloc_max > 0 &&
-          png_ptr->user_chunk_malloc_max < limit)
-         limit = png_ptr->user_chunk_malloc_max;
+   if (png_ptr->user_chunk_malloc_max > 0 &&
+       png_ptr->user_chunk_malloc_max < limit)
+      limit = png_ptr->user_chunk_malloc_max;
 # elif PNG_USER_CHUNK_MALLOC_MAX > 0
-      if (PNG_USER_CHUNK_MALLOC_MAX < limit)
-         limit = PNG_USER_CHUNK_MALLOC_MAX;
+   if (PNG_USER_CHUNK_MALLOC_MAX < limit)
+      limit = PNG_USER_CHUNK_MALLOC_MAX;
 # endif
-   }
-   else
+   if (png_ptr->chunk_name == png_IDAT)
    {
+      png_alloc_size_t idat_limit = PNG_UINT_31_MAX;
       size_t row_factor =
          (png_ptr->width * png_ptr->channels * (png_ptr->bit_depth > 8? 2: 1)
           + 1 + (png_ptr->interlaced? 6: 0));
       if (png_ptr->height > PNG_UINT_32_MAX/row_factor)
-         limit=PNG_UINT_31_MAX;
+         idat_limit=PNG_UINT_31_MAX;
       else
-         limit = png_ptr->height * row_factor;
-      limit += 6 + 5*(limit/32566+1); /* zlib+deflate overhead */
-      limit=limit < PNG_UINT_31_MAX? limit : PNG_UINT_31_MAX;
+         idat_limit = png_ptr->height * row_factor;
+      row_factor = row_factor > 32566? 32566 : row_factor;
+      idat_limit += 6 + 5*(idat_limit/row_factor+1); /* zlib+deflate overhead */
+      idat_limit=idat_limit < PNG_UINT_31_MAX? idat_limit : PNG_UINT_31_MAX;
+      limit = limit < idat_limit? idat_limit : limit;
    }
 
    if (length > limit)
diff --git a/thirdparty/libpng/pngtrans.c b/thirdparty/libpng/pngtrans.c
index 326ac33f0e..6882f0fd7b 100644
--- a/thirdparty/libpng/pngtrans.c
+++ b/thirdparty/libpng/pngtrans.c
@@ -1,7 +1,7 @@
 
 /* pngtrans.c - transforms the data in a row (used by both readers and writers)
  *
- * Last changed in libpng 1.6.30 [June 28, 2017]
+ * Last changed in libpng 1.6.33 [September 28, 2017]
  * Copyright (c) 1998-2002,2004,2006-2017 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.)
@@ -609,7 +609,7 @@ png_do_strip_channel(png_row_infop row_info, png_bytep row, int at_start)
       return; /* The filler channel has gone already */
 
    /* Fix the rowbytes value. */
-   row_info->rowbytes = (unsigned int)(dp-row);
+   row_info->rowbytes = (png_size_t)(dp-row);
 }
 #endif
 
@@ -708,7 +708,7 @@ png_do_check_palette_indexes(png_structrp png_ptr, png_row_infop row_info)
        * forms produced on either GCC or MSVC.
        */
       int padding = PNG_PADBITS(row_info->pixel_depth, row_info->width);
-      png_bytep rp = png_ptr->row_buf + row_info->rowbytes;
+      png_bytep rp = png_ptr->row_buf + row_info->rowbytes - 1;
 
       switch (row_info->bit_depth)
       {
diff --git a/thirdparty/libpng/pngwrite.c b/thirdparty/libpng/pngwrite.c
index a7662acb71..a16d77ce00 100644
--- a/thirdparty/libpng/pngwrite.c
+++ b/thirdparty/libpng/pngwrite.c
@@ -1940,7 +1940,7 @@ png_image_write_main(png_voidp argument)
    int colormap = (format & PNG_FORMAT_FLAG_COLORMAP);
    int linear = !colormap && (format & PNG_FORMAT_FLAG_LINEAR); /* input */
    int alpha = !colormap && (format & PNG_FORMAT_FLAG_ALPHA);
-   int write_16bit = linear && !colormap && (display->convert_to_8bit == 0);
+   int write_16bit = linear && (display->convert_to_8bit == 0);
 
 #   ifdef PNG_BENIGN_ERRORS_SUPPORTED
       /* Make sure we error out on any bad situation */