Update libpng (1.6.35 --> 1.6.36)

28 files changed, 659 insertions, 460 deletions

diff --git a/drivers/png/SCsub b/drivers/png/SCsub
index 22fb1817d1..97ba1de3db 100644
--- a/drivers/png/SCsub
+++ b/drivers/png/SCsub
@@ -50,6 +50,7 @@ if env['builtin_libpng']:
         neon_sources.append(env_neon.Object(thirdparty_dir + "/arm/arm_init.c"))
         neon_sources.append(env_neon.Object(thirdparty_dir + "/arm/filter_neon_intrinsics.c"))
         neon_sources.append(env_neon.Object(thirdparty_dir + "/arm/filter_neon.S"))
+        neon_sources.append(env_neon.Object(thirdparty_dir + "/arm/palette_neon_intrinsics.c"))
         env.drivers_sources += neon_sources
 
 # Godot source files
diff --git a/thirdparty/libpng/LICENSE b/thirdparty/libpng/LICENSE
index 6ee9c8f554..62ab8e48dc 100644
--- a/thirdparty/libpng/LICENSE
+++ b/thirdparty/libpng/LICENSE
@@ -1,14 +1,43 @@
+COPYRIGHT NOTICE, DISCLAIMER, and LICENSE
+=========================================
 
-This copy of the libpng notices is provided for your convenience.  In case of
-any discrepancy between this copy and the notices in the file png.h that is
-included in the libpng distribution, the latter shall prevail.
+PNG Reference Library License version 2
+---------------------------------------
 
-COPYRIGHT NOTICE, DISCLAIMER, and LICENSE:
+ * Copyright (c) 1995-2018 The PNG Reference Library Authors.
+ * Copyright (c) 2018 Cosmin Truta.
+ * Copyright (c) 2000-2002, 2004, 2006-2018 Glenn Randers-Pehrson.
+ * Copyright (c) 1996-1997 Andreas Dilger.
+ * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
 
-If you modify libpng you may insert additional notices immediately following
-this sentence.
+The software is supplied "as is", without warranty of any kind,
+express or implied, including, without limitation, the warranties
+of merchantability, fitness for a particular purpose, title, and
+non-infringement.  In no even shall the Copyright owners, or
+anyone distributing the software, be liable for any damages or
+other liability, whether in contract, tort or otherwise, arising
+from, out of, or in connection with the software, or the use or
+other dealings in the software, even if advised of the possibility
+of such damage.
 
-This code is released under the libpng license.
+Permission is hereby granted to use, copy, modify, and distribute
+this software, or portions hereof, for any purpose, without fee,
+subject to the following restrictions:
+
+ 1. The origin of this software must not be misrepresented; you
+    must not claim that you wrote the original software.  If you
+    use this software in a product, an acknowledgment in the product
+    documentation would be appreciated, but is not required.
+
+ 2. Altered source versions must be plainly marked as such, and must
+    not be misrepresented as being the original software.
+
+ 3. This Copyright notice may not be removed or altered from any
+    source or altered source distribution.
+
+
+PNG Reference Library License version 1 (for libpng 0.5 through 1.6.35)
+-----------------------------------------------------------------------
 
 libpng versions 1.0.7, July 1, 2000 through 1.6.35, July 15, 2018 are
 Copyright (c) 2000-2002, 2004, 2006-2018 Glenn Randers-Pehrson, are
@@ -16,38 +45,38 @@ 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:
 
-   Simon-Pierre Cadieux
-   Eric S. Raymond
-   Mans Rullgard
-   Cosmin Truta
-   Gilles Vollant
-   James Yu
-   Mandar Sahastrabuddhe
-   Google Inc.
-   Vadim Barkov
+    Simon-Pierre Cadieux
+    Eric S. Raymond
+    Mans Rullgard
+    Cosmin Truta
+    Gilles Vollant
+    James Yu
+    Mandar Sahastrabuddhe
+    Google Inc.
+    Vadim Barkov
 
 and with the following additions to the disclaimer:
 
-   There is no warranty against interference with your enjoyment of the
-   library or against infringement.  There is no warranty that our
-   efforts or the library will fulfill any of your particular purposes
-   or needs.  This library is provided with all faults, and the entire
-   risk of satisfactory quality, performance, accuracy, and effort is with
-   the user.
+    There is no warranty against interference with your enjoyment of
+    the library or against infringement.  There is no warranty that our
+    efforts or the library will fulfill any of your particular purposes
+    or needs.  This library is provided with all faults, and the entire
+    risk of satisfactory quality, performance, accuracy, and effort is
+    with the user.
 
 Some files in the "contrib" directory and some configure-generated
-files that are distributed with libpng have other copyright owners and
+files that are distributed with libpng have other copyright owners, and
 are released under other open source licenses.
 
 libpng versions 0.97, January 1998, through 1.0.6, March 20, 2000, are
 Copyright (c) 1998-2000 Glenn Randers-Pehrson, are derived from
 libpng-0.96, and are distributed according to the same disclaimer and
-license as libpng-0.96, with the following individuals added to the list
-of Contributing Authors:
+license as libpng-0.96, with the following individuals added to the
+list of Contributing Authors:
 
-   Tom Lane
-   Glenn Randers-Pehrson
-   Willem van Schaik
+    Tom Lane
+    Glenn Randers-Pehrson
+    Willem van Schaik
 
 libpng versions 0.89, June 1996, through 0.96, May 1997, are
 Copyright (c) 1996-1997 Andreas Dilger, are derived from libpng-0.88,
@@ -55,14 +84,14 @@ and are distributed according to the same disclaimer and license as
 libpng-0.88, with the following individuals added to the list of
 Contributing Authors:
 
-   John Bowler
-   Kevin Bracey
-   Sam Bushell
-   Magnus Holmgren
-   Greg Roelofs
-   Tom Tanner
+    John Bowler
+    Kevin Bracey
+    Sam Bushell
+    Magnus Holmgren
+    Greg Roelofs
+    Tom Tanner
 
-Some files in the "scripts" directory have other copyright owners
+Some files in the "scripts" directory have other copyright owners,
 but are released under this license.
 
 libpng versions 0.5, May 1995, through 0.88, January 1996, are
@@ -71,63 +100,35 @@ Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
 For the purposes of this copyright and license, "Contributing Authors"
 is defined as the following set of individuals:
 
-   Andreas Dilger
-   Dave Martindale
-   Guy Eric Schalnat
-   Paul Schmidt
-   Tim Wegner
-
-The PNG Reference Library is supplied "AS IS".  The Contributing Authors
-and Group 42, Inc. disclaim all warranties, expressed or implied,
-including, without limitation, the warranties of merchantability and of
-fitness for any purpose.  The Contributing Authors and Group 42, Inc.
-assume no liability for direct, indirect, incidental, special, exemplary,
-or consequential damages, which may result from the use of the PNG
-Reference Library, even if advised of the possibility of such damage.
+    Andreas Dilger
+    Dave Martindale
+    Guy Eric Schalnat
+    Paul Schmidt
+    Tim Wegner
+
+The PNG Reference Library is supplied "AS IS".  The Contributing
+Authors and Group 42, Inc. disclaim all warranties, expressed or
+implied, including, without limitation, the warranties of
+merchantability and of fitness for any purpose.  The Contributing
+Authors and Group 42, Inc. assume no liability for direct, indirect,
+incidental, special, exemplary, or consequential damages, which may
+result from the use of the PNG Reference Library, even if advised of
+the possibility of such damage.
 
 Permission is hereby granted to use, copy, modify, and distribute this
 source code, or portions hereof, for any purpose, without fee, subject
 to the following restrictions:
 
-  1. The origin of this source code must not be misrepresented.
-
-  2. Altered versions must be plainly marked as such and must not
-     be misrepresented as being the original source.
-
-  3. This Copyright notice may not be removed or altered from any
-     source or altered source distribution.
-
-The Contributing Authors and Group 42, Inc. specifically permit, without
-fee, and encourage the use of this source code as a component to
-supporting the PNG file format in commercial products.  If you use this
-source code in a product, acknowledgment is not required but would be
-appreciated.
-
-END OF COPYRIGHT NOTICE, DISCLAIMER, and LICENSE.
-
-TRADEMARK:
-
-The name "libpng" has not been registered by the Copyright owner
-as a trademark in any jurisdiction.  However, because libpng has
-been distributed and maintained world-wide, continually since 1995,
-the Copyright owner claims "common-law trademark protection" in any
-jurisdiction where common-law trademark is recognized.
-
-OSI CERTIFICATION:
-
-Libpng is OSI Certified Open Source Software.  OSI Certified Open Source is
-a certification mark of the Open Source Initiative. OSI has not addressed
-the additional disclaimers inserted at version 1.0.7.
+ 1. The origin of this source code must not be misrepresented.
 
-EXPORT CONTROL:
+ 2. Altered versions must be plainly marked as such and must not
+    be misrepresented as being the original source.
 
-The Copyright owner believes that the Export Control Classification
-Number (ECCN) for libpng is EAR99, which means not subject to export
-controls or International Traffic in Arms Regulations (ITAR) because
-it is open source, publicly available software, that does not contain
-any encryption software.  See the EAR, paragraphs 734.3(b)(3) and
-734.7(b).
+ 3. This Copyright notice may not be removed or altered from any
+    source or altered source distribution.
 
-Glenn Randers-Pehrson
-glennrp at users.sourceforge.net
-July 15, 2018
+The Contributing Authors and Group 42, Inc. specifically permit,
+without fee, and encourage the use of this source code as a component
+to supporting the PNG file format in commercial products.  If you use
+this source code in a product, acknowledgment is not required but would
+be appreciated.
diff --git a/thirdparty/libpng/arm/arm_init.c b/thirdparty/libpng/arm/arm_init.c
index 02df812e77..a34ecdbef7 100644
--- a/thirdparty/libpng/arm/arm_init.c
+++ b/thirdparty/libpng/arm/arm_init.c
@@ -1,14 +1,15 @@
 
 /* arm_init.c - NEON optimised filter functions
  *
+ * Copyright (c) 2018 Cosmin Truta
  * Copyright (c) 2014,2016 Glenn Randers-Pehrson
  * Written by Mans Rullgard, 2011.
- * Last changed in libpng 1.6.22 [May 26, 2016]
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
  * and license in png.h
  */
+
 /* Below, after checking __linux__, various non-C90 POSIX 1003.1 functions are
  * called.
  */
diff --git a/thirdparty/libpng/arm/filter_neon.S b/thirdparty/libpng/arm/filter_neon.S
index 000764cd21..2308aad13e 100644
--- a/thirdparty/libpng/arm/filter_neon.S
+++ b/thirdparty/libpng/arm/filter_neon.S
@@ -1,9 +1,9 @@
 
 /* filter_neon.S - NEON optimised filter functions
  *
+ * Copyright (c) 2018 Cosmin Truta
  * Copyright (c) 2014,2017 Glenn Randers-Pehrson
  * Written by Mans Rullgard, 2011.
- * Last changed in libpng 1.6.31 [July 27, 2017]
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
diff --git a/thirdparty/libpng/arm/filter_neon_intrinsics.c b/thirdparty/libpng/arm/filter_neon_intrinsics.c
index ea7e356bcc..553c0be21c 100644
--- a/thirdparty/libpng/arm/filter_neon_intrinsics.c
+++ b/thirdparty/libpng/arm/filter_neon_intrinsics.c
@@ -1,12 +1,11 @@
 
 /* filter_neon_intrinsics.c - NEON optimised filter functions
  *
+ * Copyright (c) 2018 Cosmin Truta
  * Copyright (c) 2014,2016 Glenn Randers-Pehrson
  * Written by James Yu <james.yu at linaro.org>, October 2013.
  * Based on filter_neon.S, written by Mans Rullgard, 2011.
  *
- * Last changed in libpng 1.6.22 [May 26, 2016]
- *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
  * and license in png.h
@@ -19,7 +18,11 @@
 /* This code requires -mfpu=neon on the command line: */
 #if PNG_ARM_NEON_IMPLEMENTATION == 1 /* intrinsics code from pngpriv.h */
 
-#include <arm_neon.h>
+#if defined(_MSC_VER) && defined(_M_ARM64)
+#  include <arm64_neon.h>
+#else
+#  include <arm_neon.h>
+#endif
 
 /* libpng row pointers are not necessarily aligned to any particular boundary,
  * however this code will only work with appropriate alignment.  arm/arm_init.c
@@ -33,6 +36,11 @@
  * 'type'.  This is written this way just to hide the GCC strict aliasing
  * warning; note that the code is safe because there never is an alias between
  * the input and output pointers.
+ *
+ * When compiling with MSVC ARM64, the png_ldr macro can't be passed directly
+ * to vst4_lane_u32, because of an internal compiler error inside MSVC.
+ * To avoid this compiler bug, we use a temporary variable (vdest_val) to store
+ * the result of png_ldr.
  */
 #define png_ldr(type,pointer)\
    (temp_pointer = png_ptr(type,pointer), *temp_pointer)
@@ -125,12 +133,15 @@ png_read_filter_row_sub4_neon(png_row_infop row_info, png_bytep row,
       uint8x8x4_t *vrpt = png_ptr(uint8x8x4_t,&vtmp);
       uint8x8x4_t vrp = *vrpt;
       uint32x2x4_t *temp_pointer;
+      uint32x2x4_t vdest_val;
 
       vdest.val[0] = vadd_u8(vdest.val[3], vrp.val[0]);
       vdest.val[1] = vadd_u8(vdest.val[0], vrp.val[1]);
       vdest.val[2] = vadd_u8(vdest.val[1], vrp.val[2]);
       vdest.val[3] = vadd_u8(vdest.val[2], vrp.val[3]);
-      vst4_lane_u32(png_ptr(uint32_t,rp), png_ldr(uint32x2x4_t,&vdest), 0);
+
+      vdest_val = png_ldr(uint32x2x4_t, &vdest);
+      vst4_lane_u32(png_ptr(uint32_t,rp), vdest_val, 0);
    }
 
    PNG_UNUSED(prev_row)
@@ -223,6 +234,7 @@ png_read_filter_row_avg4_neon(png_row_infop row_info, png_bytep row,
       uint8x8x4_t *vrpt, *vppt;
       uint8x8x4_t vrp, vpp;
       uint32x2x4_t *temp_pointer;
+      uint32x2x4_t vdest_val;
 
       vtmp = vld4_u32(png_ptr(uint32_t,rp));
       vrpt = png_ptr(uint8x8x4_t,&vtmp);
@@ -240,7 +252,8 @@ png_read_filter_row_avg4_neon(png_row_infop row_info, png_bytep row,
       vdest.val[3] = vhadd_u8(vdest.val[2], vpp.val[3]);
       vdest.val[3] = vadd_u8(vdest.val[3], vrp.val[3]);
 
-      vst4_lane_u32(png_ptr(uint32_t,rp), png_ldr(uint32x2x4_t,&vdest), 0);
+      vdest_val = png_ldr(uint32x2x4_t, &vdest);
+      vst4_lane_u32(png_ptr(uint32_t,rp), vdest_val, 0);
    }
 }
 
@@ -359,6 +372,7 @@ png_read_filter_row_paeth4_neon(png_row_infop row_info, png_bytep row,
       uint8x8x4_t *vrpt, *vppt;
       uint8x8x4_t vrp, vpp;
       uint32x2x4_t *temp_pointer;
+      uint32x2x4_t vdest_val;
 
       vtmp = vld4_u32(png_ptr(uint32_t,rp));
       vrpt = png_ptr(uint8x8x4_t,&vtmp);
@@ -378,7 +392,8 @@ png_read_filter_row_paeth4_neon(png_row_infop row_info, png_bytep row,
 
       vlast = vpp.val[3];
 
-      vst4_lane_u32(png_ptr(uint32_t,rp), png_ldr(uint32x2x4_t,&vdest), 0);
+      vdest_val = png_ldr(uint32x2x4_t, &vdest);
+      vst4_lane_u32(png_ptr(uint32_t,rp), vdest_val, 0);
    }
 }
 
diff --git a/thirdparty/libpng/arm/palette_neon_intrinsics.c b/thirdparty/libpng/arm/palette_neon_intrinsics.c
new file mode 100644
index 0000000000..fa02d6a8b3
--- /dev/null
+++ b/thirdparty/libpng/arm/palette_neon_intrinsics.c
@@ -0,0 +1,149 @@
+
+/* palette_neon_intrinsics.c - NEON optimised palette expansion functions
+ *
+ * Copyright (c) 2018 Cosmin Truta
+ * Copyright (c) 2017-2018 Arm Holdings. All rights reserved.
+ * Written by Richard Townsend <Richard.Townsend@arm.com>, February 2017.
+ *
+ * This code is released under the libpng license.
+ * For conditions of distribution and use, see the disclaimer
+ * and license in png.h
+ */
+
+#include "../pngpriv.h"
+
+#if PNG_ARM_NEON_IMPLEMENTATION == 1
+
+#if defined(_MSC_VER) && defined(_M_ARM64)
+#  include <arm64_neon.h>
+#else
+#  include <arm_neon.h>
+#endif
+
+/* Build an RGBA palette from the RGB and separate alpha palettes. */
+void
+png_riffle_palette_rgba(png_structrp png_ptr, png_row_infop row_info)
+{
+   png_const_colorp palette = png_ptr->palette;
+   png_bytep riffled_palette = png_ptr->riffled_palette;
+   png_const_bytep trans_alpha = png_ptr->trans_alpha;
+   int num_trans = png_ptr->num_trans;
+   int i;
+
+   /* Initially black, opaque. */
+   uint8x16x4_t w = {{
+      vdupq_n_u8(0x00),
+      vdupq_n_u8(0x00),
+      vdupq_n_u8(0x00),
+      vdupq_n_u8(0xff),
+   }};
+
+   if (row_info->bit_depth != 8)
+   {
+      png_error(png_ptr, "bit_depth must be 8 for png_riffle_palette_rgba");
+      return;
+   }
+
+   /* First, riffle the RGB colours into a RGBA palette, the A value is
+    * set to opaque for now.
+    */
+   for (i = 0; i < (1 << row_info->bit_depth); i += 16)
+   {
+      uint8x16x3_t v = vld3q_u8((png_const_bytep)(palette + i));
+      w.val[0] = v.val[0];
+      w.val[1] = v.val[1];
+      w.val[2] = v.val[2];
+      vst4q_u8(riffled_palette + (i << 2), w);
+   }
+
+   /* Fix up the missing transparency values. */
+   for (i = 0; i < num_trans; i++)
+      riffled_palette[(i << 2) + 3] = trans_alpha[i];
+}
+
+/* Expands a palettized row into RGBA. */
+int
+png_do_expand_palette_neon_rgba(png_structrp png_ptr, png_row_infop row_info,
+    png_const_bytep row, png_bytepp ssp, png_bytepp ddp)
+{
+   png_uint_32 row_width = row_info->width;
+   const png_uint_32 *riffled_palette =
+      (const png_uint_32 *)png_ptr->riffled_palette;
+   const png_int_32 pixels_per_chunk = 4;
+   int i;
+
+   if (row_width < pixels_per_chunk)
+      return 0;
+
+   /* This function originally gets the last byte of the output row.
+    * The NEON part writes forward from a given position, so we have
+    * to seek this back by 4 pixels x 4 bytes.
+    */
+   *ddp = *ddp - ((pixels_per_chunk * sizeof(png_uint_32)) - 1);
+
+   for (i = 0; i < row_width; i += pixels_per_chunk)
+   {
+      uint32x4_t cur;
+      png_bytep sp = *ssp - i, dp = *ddp - (i << 2);
+      cur = vld1q_dup_u32 (riffled_palette + *(sp - 3));
+      cur = vld1q_lane_u32(riffled_palette + *(sp - 2), cur, 1);
+      cur = vld1q_lane_u32(riffled_palette + *(sp - 1), cur, 2);
+      cur = vld1q_lane_u32(riffled_palette + *(sp - 0), cur, 3);
+      vst1q_u32((void *)dp, cur);
+   }
+   if (i != row_width)
+   {
+      /* Remove the amount that wasn't processed. */
+      i -= pixels_per_chunk;
+   }
+
+   /* Decrement output pointers. */
+   *ssp = *ssp - i;
+   *ddp = *ddp - (i << 2);
+   return i;
+}
+
+/* Expands a palettized row into RGB format. */
+int
+png_do_expand_palette_neon_rgb(png_structrp png_ptr, png_row_infop row_info,
+    png_const_bytep row, png_bytepp ssp, png_bytepp ddp)
+{
+   png_uint_32 row_width = row_info->width;
+   png_const_bytep palette = (png_const_bytep)png_ptr->palette;
+   const png_uint_32 pixels_per_chunk = 8;
+   int i;
+
+   if (row_width <= pixels_per_chunk)
+      return 0;
+
+   /* Seeking this back by 8 pixels x 3 bytes. */
+   *ddp = *ddp - ((pixels_per_chunk * sizeof(png_color)) - 1);
+
+   for (i = 0; i < row_width; i += pixels_per_chunk)
+   {
+      uint8x8x3_t cur;
+      png_bytep sp = *ssp - i, dp = *ddp - ((i << 1) + i);
+      cur = vld3_dup_u8(palette + sizeof(png_color) * (*(sp - 7)));
+      cur = vld3_lane_u8(palette + sizeof(png_color) * (*(sp - 6)), cur, 1);
+      cur = vld3_lane_u8(palette + sizeof(png_color) * (*(sp - 5)), cur, 2);
+      cur = vld3_lane_u8(palette + sizeof(png_color) * (*(sp - 4)), cur, 3);
+      cur = vld3_lane_u8(palette + sizeof(png_color) * (*(sp - 3)), cur, 4);
+      cur = vld3_lane_u8(palette + sizeof(png_color) * (*(sp - 2)), cur, 5);
+      cur = vld3_lane_u8(palette + sizeof(png_color) * (*(sp - 1)), cur, 6);
+      cur = vld3_lane_u8(palette + sizeof(png_color) * (*(sp - 0)), cur, 7);
+      vst3_u8((void *)dp, cur);
+   }
+
+   if (i != row_width)
+   {
+      /* Remove the amount that wasn't processed. */
+      i -= pixels_per_chunk;
+   }
+
+   /* Decrement output pointers. */
+   *ssp = *ssp - i;
+   *ddp = *ddp - ((i << 1) + i);
+   return i;
+}
+
+#endif /* PNG_ARM_NEON_IMPLEMENTATION */
diff --git a/thirdparty/libpng/png.c b/thirdparty/libpng/png.c
index a25afebcc8..3dce191d17 100644
--- a/thirdparty/libpng/png.c
+++ b/thirdparty/libpng/png.c
@@ -1,10 +1,10 @@
 
 /* png.c - location for general purpose libpng functions
  *
- * Last changed in libpng 1.6.35 [July 15, 2018]
+ * Copyright (c) 2018 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2018 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.)
+ * Copyright (c) 1996-1997 Andreas Dilger
+ * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
@@ -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_35 Your_png_h_is_not_version_1_6_35;
+typedef png_libpng_version_1_6_36 Your_png_h_is_not_version_1_6_36;
 
 #ifdef __GNUC__
 /* The version tests may need to be added to, but the problem warning has
@@ -736,7 +736,7 @@ png_save_int_32(png_bytep buf, png_int_32 i)
 int PNGAPI
 png_convert_to_rfc1123_buffer(char out[29], png_const_timep ptime)
 {
-   static PNG_CONST char short_months[12][4] =
+   static const char short_months[12][4] =
         {"Jan", "Feb", "Mar", "Apr", "May", "Jun",
          "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
 
@@ -814,20 +814,14 @@ png_get_copyright(png_const_structrp png_ptr)
 #ifdef PNG_STRING_COPYRIGHT
    return PNG_STRING_COPYRIGHT
 #else
-#  ifdef __STDC__
    return PNG_STRING_NEWLINE \
-      "libpng version 1.6.35 - July 15, 2018" PNG_STRING_NEWLINE \
+      "libpng version 1.6.36" PNG_STRING_NEWLINE \
+      "Copyright (c) 2018 Cosmin Truta" PNG_STRING_NEWLINE \
       "Copyright (c) 1998-2002,2004,2006-2018 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 1.6.35 - July 15, 2018\
-      Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson\
-      Copyright (c) 1996-1997 Andreas Dilger\
-      Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.";
-#  endif
 #endif
 }
 
@@ -1121,7 +1115,7 @@ png_colorspace_set_gamma(png_const_structrp png_ptr,
     png_colorspacerp colorspace, png_fixed_point gAMA)
 {
    /* Changed in libpng-1.5.4 to limit the values to ensure overflow can't
-    * occur.  Since the fixed point representation is asymetrical it is
+    * occur.  Since the fixed point representation is asymmetrical it is
     * possible for 1/gamma to overflow the limit of 21474 and this means the
     * gamma value must be at least 5/100000 and hence at most 20000.0.  For
     * safety the limits here are a little narrower.  The values are 0.00016 to
@@ -3134,11 +3128,11 @@ png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, size_t size,
             /* The total output count (max) is now 4+precision */
 
             /* Check for an exponent, if we don't need one we are
-             * done and just need to terminate the string.  At
-             * this point exp_b10==(-1) is effectively a flag - it got
-             * to '-1' because of the decrement after outputting
-             * the decimal point above (the exponent required is
-             * *not* -1!)
+             * done and just need to terminate the string.  At this
+             * point, exp_b10==(-1) is effectively a flag: it got
+             * to '-1' because of the decrement, after outputting
+             * the decimal point above. (The exponent required is
+             * *not* -1.)
              */
             if (exp_b10 >= (-1) && exp_b10 <= 2)
             {
@@ -3976,18 +3970,18 @@ png_gamma_correct(png_structrp png_ptr, unsigned int value,
  */
 static void
 png_build_16bit_table(png_structrp png_ptr, png_uint_16pp *ptable,
-    PNG_CONST unsigned int shift, PNG_CONST png_fixed_point gamma_val)
+    unsigned int shift, png_fixed_point gamma_val)
 {
    /* Various values derived from 'shift': */
-   PNG_CONST unsigned int num = 1U << (8U - shift);
+   unsigned int num = 1U << (8U - shift);
 #ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
    /* CSE the division and work round wacky GCC warnings (see the comments
     * in png_gamma_8bit_correct for where these come from.)
     */
-   PNG_CONST double fmax = 1./(((png_int_32)1 << (16U - shift))-1);
+   double fmax = 1.0 / (((png_int_32)1 << (16U - shift)) - 1);
 #endif
-   PNG_CONST unsigned int max = (1U << (16U - shift))-1U;
-   PNG_CONST unsigned int max_by_2 = 1U << (15U-shift);
+   unsigned int max = (1U << (16U - shift)) - 1U;
+   unsigned int max_by_2 = 1U << (15U - shift);
    unsigned int i;
 
    png_uint_16pp table = *ptable =
@@ -4053,10 +4047,10 @@ png_build_16bit_table(png_structrp png_ptr, png_uint_16pp *ptable,
  */
 static void
 png_build_16to8_table(png_structrp png_ptr, png_uint_16pp *ptable,
-    PNG_CONST unsigned int shift, PNG_CONST png_fixed_point gamma_val)
+    unsigned int shift, png_fixed_point gamma_val)
 {
-   PNG_CONST unsigned int num = 1U << (8U - shift);
-   PNG_CONST unsigned int max = (1U << (16U - shift))-1U;
+   unsigned int num = 1U << (8U - shift);
+   unsigned int max = (1U << (16U - shift))-1U;
    unsigned int i;
    png_uint_32 last;
 
@@ -4121,7 +4115,7 @@ png_build_16to8_table(png_structrp png_ptr, png_uint_16pp *ptable,
  */
 static void
 png_build_8bit_table(png_structrp png_ptr, png_bytepp ptable,
-    PNG_CONST png_fixed_point gamma_val)
+    png_fixed_point gamma_val)
 {
    unsigned int i;
    png_bytep table = *ptable = (png_bytep)png_malloc(png_ptr, 256);
diff --git a/thirdparty/libpng/png.h b/thirdparty/libpng/png.h
index 19e464cc17..8e272a0553 100644
--- a/thirdparty/libpng/png.h
+++ b/thirdparty/libpng/png.h
@@ -1,29 +1,65 @@
 
 /* png.h - header file for PNG reference library
  *
- * libpng version 1.6.35, July 15, 2018
+ * libpng version 1.6.36 - December 1, 2018
  *
+ * Copyright (c) 2018 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2018 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.)
+ * Copyright (c) 1996-1997 Andreas Dilger
+ * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
  *
- * This code is released under the libpng license (See LICENSE, below)
+ * This code is released under the libpng license. (See LICENSE, below.)
  *
  * 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 1.6.35, July 15, 2018:
+ *   libpng versions 0.97, January 1998, through 1.6.35, July 2018:
  *     Glenn Randers-Pehrson.
+ *   libpng version 1.6.36, December 1, 2018: Cosmin Truta
  *   See also "Contributing Authors", below.
  */
 
 /*
- * COPYRIGHT NOTICE, DISCLAIMER, and LICENSE:
+ * COPYRIGHT NOTICE, DISCLAIMER, and LICENSE
+ * =========================================
+ *
+ * PNG Reference Library License version 2
+ * ---------------------------------------
+ *
+ *  * Copyright (c) 1995-2018 The PNG Reference Library Authors.
+ *  * Copyright (c) 2018 Cosmin Truta.
+ *  * Copyright (c) 2000-2002, 2004, 2006-2018 Glenn Randers-Pehrson.
+ *  * Copyright (c) 1996-1997 Andreas Dilger.
+ *  * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
+ *
+ * The software is supplied "as is", without warranty of any kind,
+ * express or implied, including, without limitation, the warranties
+ * of merchantability, fitness for a particular purpose, title, and
+ * non-infringement.  In no even shall the Copyright owners, or
+ * anyone distributing the software, be liable for any damages or
+ * other liability, whether in contract, tort or otherwise, arising
+ * from, out of, or in connection with the software, or the use or
+ * other dealings in the software, even if advised of the possibility
+ * of such damage.
+ *
+ * Permission is hereby granted to use, copy, modify, and distribute
+ * this software, or portions hereof, for any purpose, without fee,
+ * subject to the following restrictions:
  *
- * If you modify libpng you may insert additional notices immediately following
- * this sentence.
+ *  1. The origin of this software must not be misrepresented; you
+ *     must not claim that you wrote the original software.  If you
+ *     use this software in a product, an acknowledgment in the product
+ *     documentation would be appreciated, but is not required.
  *
- * This code is released under the libpng license.
+ *  2. Altered source versions must be plainly marked as such, and must
+ *     not be misrepresented as being the original software.
+ *
+ *  3. This Copyright notice may not be removed or altered from any
+ *     source or altered source distribution.
+ *
+ *
+ * PNG Reference Library License version 1 (for libpng 0.5 through 1.6.35)
+ * -----------------------------------------------------------------------
  *
  * libpng versions 1.0.7, July 1, 2000 through 1.6.35, July 15, 2018 are
  * Copyright (c) 2000-2002, 2004, 2006-2018 Glenn Randers-Pehrson, are
@@ -31,38 +67,38 @@
  * disclaimer and license as libpng-1.0.6 with the following individuals
  * added to the list of Contributing Authors:
  *
- *    Simon-Pierre Cadieux
- *    Eric S. Raymond
- *    Mans Rullgard
- *    Cosmin Truta
- *    Gilles Vollant
- *    James Yu
- *    Mandar Sahastrabuddhe
- *    Google Inc.
- *    Vadim Barkov
+ *     Simon-Pierre Cadieux
+ *     Eric S. Raymond
+ *     Mans Rullgard
+ *     Cosmin Truta
+ *     Gilles Vollant
+ *     James Yu
+ *     Mandar Sahastrabuddhe
+ *     Google Inc.
+ *     Vadim Barkov
  *
  * and with the following additions to the disclaimer:
  *
- *    There is no warranty against interference with your enjoyment of the
- *    library or against infringement.  There is no warranty that our
- *    efforts or the library will fulfill any of your particular purposes
- *    or needs.  This library is provided with all faults, and the entire
- *    risk of satisfactory quality, performance, accuracy, and effort is with
- *    the user.
+ *     There is no warranty against interference with your enjoyment of
+ *     the library or against infringement.  There is no warranty that our
+ *     efforts or the library will fulfill any of your particular purposes
+ *     or needs.  This library is provided with all faults, and the entire
+ *     risk of satisfactory quality, performance, accuracy, and effort is
+ *     with the user.
  *
  * Some files in the "contrib" directory and some configure-generated
- * files that are distributed with libpng have other copyright owners and
+ * files that are distributed with libpng have other copyright owners, and
  * are released under other open source licenses.
  *
  * libpng versions 0.97, January 1998, through 1.0.6, March 20, 2000, are
  * Copyright (c) 1998-2000 Glenn Randers-Pehrson, are derived from
  * libpng-0.96, and are distributed according to the same disclaimer and
- * license as libpng-0.96, with the following individuals added to the list
- * of Contributing Authors:
+ * license as libpng-0.96, with the following individuals added to the
+ * list of Contributing Authors:
  *
- *    Tom Lane
- *    Glenn Randers-Pehrson
- *    Willem van Schaik
+ *     Tom Lane
+ *     Glenn Randers-Pehrson
+ *     Willem van Schaik
  *
  * libpng versions 0.89, June 1996, through 0.96, May 1997, are
  * Copyright (c) 1996-1997 Andreas Dilger, are derived from libpng-0.88,
@@ -70,14 +106,14 @@
  * libpng-0.88, with the following individuals added to the list of
  * Contributing Authors:
  *
- *    John Bowler
- *    Kevin Bracey
- *    Sam Bushell
- *    Magnus Holmgren
- *    Greg Roelofs
- *    Tom Tanner
+ *     John Bowler
+ *     Kevin Bracey
+ *     Sam Bushell
+ *     Magnus Holmgren
+ *     Greg Roelofs
+ *     Tom Tanner
  *
- * Some files in the "scripts" directory have other copyright owners
+ * Some files in the "scripts" directory have other copyright owners,
  * but are released under this license.
  *
  * libpng versions 0.5, May 1995, through 0.88, January 1996, are
@@ -86,62 +122,49 @@
  * For the purposes of this copyright and license, "Contributing Authors"
  * is defined as the following set of individuals:
  *
- *    Andreas Dilger
- *    Dave Martindale
- *    Guy Eric Schalnat
- *    Paul Schmidt
- *    Tim Wegner
- *
- * The PNG Reference Library is supplied "AS IS".  The Contributing Authors
- * and Group 42, Inc. disclaim all warranties, expressed or implied,
- * including, without limitation, the warranties of merchantability and of
- * fitness for any purpose.  The Contributing Authors and Group 42, Inc.
- * assume no liability for direct, indirect, incidental, special, exemplary,
- * or consequential damages, which may result from the use of the PNG
- * Reference Library, even if advised of the possibility of such damage.
+ *     Andreas Dilger
+ *     Dave Martindale
+ *     Guy Eric Schalnat
+ *     Paul Schmidt
+ *     Tim Wegner
+ *
+ * The PNG Reference Library is supplied "AS IS".  The Contributing
+ * Authors and Group 42, Inc. disclaim all warranties, expressed or
+ * implied, including, without limitation, the warranties of
+ * merchantability and of fitness for any purpose.  The Contributing
+ * Authors and Group 42, Inc. assume no liability for direct, indirect,
+ * incidental, special, exemplary, or consequential damages, which may
+ * result from the use of the PNG Reference Library, even if advised of
+ * the possibility of such damage.
  *
  * Permission is hereby granted to use, copy, modify, and distribute this
  * source code, or portions hereof, for any purpose, without fee, subject
  * to the following restrictions:
  *
- *   1. The origin of this source code must not be misrepresented.
+ *  1. The origin of this source code must not be misrepresented.
  *
- *   2. Altered versions must be plainly marked as such and must not
- *      be misrepresented as being the original source.
+ *  2. Altered versions must be plainly marked as such and must not
+ *     be misrepresented as being the original source.
  *
- *   3. This Copyright notice may not be removed or altered from any
- *      source or altered source distribution.
+ *  3. This Copyright notice may not be removed or altered from any
+ *     source or altered source distribution.
  *
- * The Contributing Authors and Group 42, Inc. specifically permit, without
- * fee, and encourage the use of this source code as a component to
- * supporting the PNG file format in commercial products.  If you use this
- * source code in a product, acknowledgment is not required but would be
- * appreciated.
+ * The Contributing Authors and Group 42, Inc. specifically permit,
+ * without fee, and encourage the use of this source code as a component
+ * to supporting the PNG file format in commercial products.  If you use
+ * this source code in a product, acknowledgment is not required but would
+ * be appreciated.
  *
  * END OF COPYRIGHT NOTICE, DISCLAIMER, and LICENSE.
  *
- * TRADEMARK:
+ * TRADEMARK
+ * =========
  *
- * The name "libpng" has not been registered by the Copyright owner
+ * The name "libpng" has not been registered by the Copyright owners
  * as a trademark in any jurisdiction.  However, because libpng has
  * been distributed and maintained world-wide, continually since 1995,
- * the Copyright owner claims "common-law trademark protection" in any
+ * the Copyright owners claim "common-law trademark protection" in any
  * jurisdiction where common-law trademark is recognized.
- *
- * OSI CERTIFICATION:
- *
- * Libpng is OSI Certified Open Source Software.  OSI Certified Open Source is
- * a certification mark of the Open Source Initiative. OSI has not addressed
- * the additional disclaimers inserted at version 1.0.7.
- *
- * EXPORT CONTROL:
- *
- * The Copyright owner believes that the Export Control Classification
- * Number (ECCN) for libpng is EAR99, which means not subject to export
- * controls or International Traffic in Arms Regulations (ITAR) because
- * it is open source, publicly available software, that does not contain
- * any encryption software.  See the EAR, paragraphs 734.3(b)(3) and
- * 734.7(b).
  */
 
 /*
@@ -207,23 +230,25 @@
  *    1.0.7rc1-2               1    10007  2.1.0.7rc1-2 (binary compatible)
  *    1.0.7                    1    10007  (still compatible)
  *    ...
- *    1.0.19                  10    10019  10.so.0.19[.0]
+ *    1.0.69                  10    10069  10.so.0.69[.0]
  *    ...
- *    1.2.59                  13    10257  12.so.0.59[.0]
+ *    1.2.59                  13    10259  12.so.0.59[.0]
  *    ...
- *    1.5.30                  15    10527  15.so.15.30[.0]
+ *    1.4.20                  14    10420  14.so.0.20[.0]
  *    ...
- *    1.6.35                  16    10635  16.so.16.35[.0]
- *
- *    Henceforth the source version will match the shared-library major
- *    and minor numbers; the shared-library major version number will be
- *    used for changes in backward compatibility, as it is intended.  The
- *    PNG_LIBPNG_VER macro, which is not used within libpng but is available
- *    for applications, is an unsigned integer of the form xyyzz corresponding
- *    to the source version x.y.z (leading zeros in y and z).  Beta versions
- *    were given the previous public release number plus a letter, until
- *    version 1.0.6j; from then on they were given the upcoming public
- *    release number plus "betaNN" or "rcNN".
+ *    1.5.30                  15    10530  15.so.15.30[.0]
+ *    ...
+ *    1.6.36                  16    10636  16.so.16.36[.0]
+ *
+ *    Henceforth the source version will match the shared-library major and
+ *    minor numbers; the shared-library major version number will be used for
+ *    changes in backward compatibility, as it is intended.
+ *    The PNG_LIBPNG_VER macro, which is not used within libpng but is
+ *    available for applications, is an unsigned integer of the form XYYZZ
+ *    corresponding to the source version X.Y.Z (leading zeros in Y and Z).
+ *    Beta versions were given the previous public release number plus a
+ *    letter, until version 1.0.6j; from then on they were given the upcoming
+ *    public release number plus "betaNN" or "rcNN".
  *
  *    Binary incompatibility exists only when applications make direct access
  *    to the info_ptr or png_ptr members through png.h, and the compiled
@@ -233,65 +258,8 @@
  *    in binary compatibility (e.g., when a new feature is added).
  *
  * See libpng.txt or libpng.3 for more information.  The PNG specification
- * is available as a W3C Recommendation and as an ISO Specification,
- * <https://www.w3.org/TR/2003/REC-PNG-20031110/
- */
-
-/*
- * Y2K compliance in libpng:
- * =========================
- *
- *    July 15, 2018
- *
- *    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 1.6.35 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
- *    that will hold years up to 65535.  The other, which is deprecated,
- *    holds the date in text format, and will hold years up to 9999.
- *
- *    The integer is
- *        "png_uint_16 year" in png_time_struct.
- *
- *    The string is
- *        "char time_buffer[29]" in png_struct.  This is no longer used
- *    in libpng-1.6.x and will be removed from libpng-1.7.0.
- *
- *    There are seven time-related functions:
- *        png.c: png_convert_to_rfc_1123_buffer() in png.c
- *          (formerly png_convert_to_rfc_1123() prior to libpng-1.5.x and
- *          png_convert_to_rfc_1152() in error prior to libpng-0.98)
- *        png_convert_from_struct_tm() in pngwrite.c, called in pngwrite.c
- *        png_convert_from_time_t() in pngwrite.c
- *        png_get_tIME() in pngget.c
- *        png_handle_tIME() in pngrutil.c, called in pngread.c
- *        png_set_tIME() in pngset.c
- *        png_write_tIME() in pngwutil.c, called in pngwrite.c
- *
- *    All handle dates properly in a Y2K environment.  The
- *    png_convert_from_time_t() function calls gmtime() to convert from system
- *    clock time, which returns (year - 1900), which we properly convert to
- *    the full 4-digit year.  There is a possibility that libpng applications
- *    are not passing 4-digit years into the png_convert_to_rfc_1123_buffer()
- *    function, or that they are incorrectly passing only a 2-digit year
- *    instead of "year - 1900" into the png_convert_from_struct_tm() function,
- *    but this is not under our control.  The libpng documentation has always
- *    stated that it works with 4-digit years, and the APIs have been
- *    documented as such.
- *
- *    The tIME chunk itself is also Y2K compliant.  It uses a 2-byte unsigned
- *    integer to hold the year, and can hold years as large as 65535.
- *
- *    zlib, upon which libpng depends, is also Y2K compliant.  It contains
- *    no date-related code.
- *
- *       Glenn Randers-Pehrson
- *       libpng maintainer
- *       PNG Development Group
+ * is available as a W3C Recommendation and as an ISO/IEC Standard; see
+ * <https://www.w3.org/TR/2003/REC-PNG-20031110/>
  */
 
 #ifndef PNG_H
@@ -309,8 +277,8 @@
  */
 
 /* Version information for png.h - this should match the version in png.c */
-#define PNG_LIBPNG_VER_STRING "1.6.35"
-#define PNG_HEADER_VERSION_STRING " libpng version 1.6.35 - July 15, 2018\n"
+#define PNG_LIBPNG_VER_STRING "1.6.36"
+#define PNG_HEADER_VERSION_STRING " libpng version 1.6.36 - December 1, 2018\n"
 
 #define PNG_LIBPNG_VER_SONUM   16
 #define PNG_LIBPNG_VER_DLLNUM  16
@@ -318,13 +286,13 @@
 /* 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 35
+#define PNG_LIBPNG_VER_RELEASE 36
 
 /* This should match the numeric part of the final component of
  * PNG_LIBPNG_VER_STRING, omitting any leading zero:
  */
 
-#define PNG_LIBPNG_VER_BUILD  02
+#define PNG_LIBPNG_VER_BUILD  0
 
 /* Release Status */
 #define PNG_LIBPNG_BUILD_ALPHA    1
@@ -341,15 +309,16 @@
 #define PNG_LIBPNG_BUILD_SPECIAL 32 /* Cannot be OR'ed with
                                        PNG_LIBPNG_BUILD_PRIVATE */
 
-#define PNG_LIBPNG_BUILD_BASE_TYPE PNG_LIBPNG_BUILD_BETA
+#define PNG_LIBPNG_BUILD_BASE_TYPE PNG_LIBPNG_BUILD_STABLE
 
-/* Careful here.  At one time, Guy wanted to use 082, but that would be octal.
- * We must not include leading zeros.
- * Versions 0.7 through 1.0.0 were in the range 0 to 100 here (only
- * 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
+/* Careful here.  At one time, Guy wanted to use 082, but that
+ * would be octal.  We must not include leading zeros.
+ * Versions 0.7 through 1.0.0 were in the range 0 to 100 here
+ * (only version 1.0.0 was mis-numbered 100 instead of 10000).
+ * From version 1.0.1 it is:
+ * XXYYZZ, where XX=major, YY=minor, ZZ=release
  */
-#define PNG_LIBPNG_VER 10635 /* 1.6.35 */
+#define PNG_LIBPNG_VER 10636 /* 1.6.36 */
 
 /* Library configuration: these options cannot be changed after
  * the library has been built.
@@ -459,7 +428,7 @@ 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_35;
+typedef char* png_libpng_version_1_6_36;
 
 /* Basic control structions.  Read libpng-manual.txt or libpng.3 for more info.
  *
@@ -2013,12 +1982,12 @@ PNG_FIXED_EXPORT(233, void, png_set_cHRM_XYZ_fixed, (png_const_structrp png_ptr,
 PNG_EXPORT(246, png_uint_32, png_get_eXIf, (png_const_structrp png_ptr,
     png_inforp info_ptr, png_bytep *exif));
 PNG_EXPORT(247, void, png_set_eXIf, (png_const_structrp png_ptr,
-    png_inforp info_ptr, const png_bytep exif));
+    png_inforp info_ptr, png_bytep exif));
 
 PNG_EXPORT(248, png_uint_32, png_get_eXIf_1, (png_const_structrp png_ptr,
     png_const_inforp info_ptr, png_uint_32 *num_exif, png_bytep *exif));
 PNG_EXPORT(249, void, png_set_eXIf_1, (png_const_structrp png_ptr,
-    png_inforp info_ptr, const png_uint_32 num_exif, const png_bytep exif));
+    png_inforp info_ptr, png_uint_32 num_exif, png_bytep exif));
 #endif
 
 #ifdef PNG_gAMA_SUPPORTED
@@ -2764,7 +2733,7 @@ typedef struct
  *
  * When the simplified API needs to convert between sRGB and linear colorspaces,
  * the actual sRGB transfer curve defined in the sRGB specification (see the
- * article at https://en.wikipedia.org/wiki/SRGB) is used, not the gamma=1/2.2
+ * article at <https://en.wikipedia.org/wiki/SRGB>) is used, not the gamma=1/2.2
  * approximation used elsewhere in libpng.
  *
  * When an alpha channel is present it is expected to denote pixel coverage
@@ -2967,7 +2936,7 @@ typedef struct
  * 'flags' field of png_image.
  */
 #define PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB 0x01
-   /* This indicates the the RGB values of the in-memory bitmap do not
+   /* This indicates that the RGB values of the in-memory bitmap do not
     * correspond to the red, green and blue end-points defined by sRGB.
     */
 
diff --git a/thirdparty/libpng/pngconf.h b/thirdparty/libpng/pngconf.h
index a4646bab85..5e641b2509 100644
--- a/thirdparty/libpng/pngconf.h
+++ b/thirdparty/libpng/pngconf.h
@@ -1,11 +1,12 @@
 
 /* pngconf.h - machine configurable file for libpng
  *
- * libpng version 1.6.35, July 15, 2018
+ * libpng version 1.6.36
  *
+ * Copyright (c) 2018 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2016,2018 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.)
+ * Copyright (c) 1996-1997 Andreas Dilger
+ * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
@@ -57,14 +58,13 @@
 
 #endif /* PNG_BUILDING_SYMBOL_TABLE */
 
-/* Prior to 1.6.0 it was possible to turn off 'const' in declarations using
- * PNG_NO_CONST; this is no longer supported except for data declarations which
- * apparently still cause problems in 2011 on some compilers.
+/* Prior to 1.6.0, it was possible to turn off 'const' in declarations,
+ * using PNG_NO_CONST.  This is no longer supported.
  */
 #define PNG_CONST const /* backward compatibility only */
 
-/* This controls optimization of the reading of 16-bit and 32-bit values
- * from PNG files.  It can be set on a per-app-file basis - it
+/* This controls optimization of the reading of 16-bit and 32-bit
+ * values from PNG files.  It can be set on a per-app-file basis: it
  * just changes whether a macro is used when the function is called.
  * The library builder sets the default; if read functions are not
  * built into the library the macro implementation is forced on.
diff --git a/thirdparty/libpng/pngdebug.h b/thirdparty/libpng/pngdebug.h
index 15a7ed0c95..00d5a4569e 100644
--- a/thirdparty/libpng/pngdebug.h
+++ b/thirdparty/libpng/pngdebug.h
@@ -1,10 +1,10 @@
 
 /* pngdebug.h - Debugging macros for libpng, also used in pngtest.c
  *
- * Last changed in libpng 1.6.8 [December 19, 2013]
+ * Copyright (c) 2018 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2013 Glenn Randers-Pehrson
- * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
- * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
+ * Copyright (c) 1996-1997 Andreas Dilger
+ * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
diff --git a/thirdparty/libpng/pngerror.c b/thirdparty/libpng/pngerror.c
index ad48bfb986..ec3a709b9d 100644
--- a/thirdparty/libpng/pngerror.c
+++ b/thirdparty/libpng/pngerror.c
@@ -1,10 +1,10 @@
 
 /* pngerror.c - stub functions for i/o and memory allocation
  *
- * Last changed in libpng 1.6.31 [July 27, 2017]
+ * Copyright (c) 2018 Cosmin Truta
  * 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.)
+ * Copyright (c) 1996-1997 Andreas Dilger
+ * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
@@ -425,7 +425,7 @@ png_app_error(png_const_structrp png_ptr, png_const_charp error_message)
  * if the character is invalid.
  */
 #define isnonalpha(c) ((c) < 65 || (c) > 122 || ((c) > 90 && (c) < 97))
-static PNG_CONST char png_digit[16] = {
+static const char png_digit[16] = {
    '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
    'A', 'B', 'C', 'D', 'E', 'F'
 };
@@ -885,7 +885,7 @@ PNG_FUNCTION(void /* PRIVATE */, (PNGCBAPI
 png_safe_error),(png_structp png_nonconst_ptr, png_const_charp error_message),
     PNG_NORETURN)
 {
-   const png_const_structrp png_ptr = png_nonconst_ptr;
+   png_const_structrp png_ptr = png_nonconst_ptr;
    png_imagep image = png_voidcast(png_imagep, png_ptr->error_ptr);
 
    /* An error is always logged here, overwriting anything (typically a warning)
@@ -920,7 +920,7 @@ png_safe_error),(png_structp png_nonconst_ptr, png_const_charp error_message),
 void /* PRIVATE */ PNGCBAPI
 png_safe_warning(png_structp png_nonconst_ptr, png_const_charp warning_message)
 {
-   const png_const_structrp png_ptr = png_nonconst_ptr;
+   png_const_structrp png_ptr = png_nonconst_ptr;
    png_imagep image = png_voidcast(png_imagep, png_ptr->error_ptr);
 
    /* A warning is only logged if there is no prior warning or error. */
diff --git a/thirdparty/libpng/pngget.c b/thirdparty/libpng/pngget.c
index 2325508f1d..5abf1efd9f 100644
--- a/thirdparty/libpng/pngget.c
+++ b/thirdparty/libpng/pngget.c
@@ -1,10 +1,10 @@
 
 /* pngget.c - retrieval of values from info struct
  *
- * Last changed in libpng 1.6.35 [July 15, 2018]
+ * Copyright (c) 2018 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2018 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.)
+ * Copyright (c) 1996-1997 Andreas Dilger
+ * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
diff --git a/thirdparty/libpng/pnginfo.h b/thirdparty/libpng/pnginfo.h
index 2fcf868dac..1f98dedc42 100644
--- a/thirdparty/libpng/pnginfo.h
+++ b/thirdparty/libpng/pnginfo.h
@@ -1,10 +1,10 @@
 
 /* pnginfo.h - header file for PNG reference library
  *
- * Last changed in libpng 1.6.35 [July 15, 2018]
+ * Copyright (c) 2018 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2013,2018 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.)
+ * Copyright (c) 1996-1997 Andreas Dilger
+ * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
diff --git a/thirdparty/libpng/pnglibconf.h b/thirdparty/libpng/pnglibconf.h
index 00acecc69b..00340c678b 100644
--- a/thirdparty/libpng/pnglibconf.h
+++ b/thirdparty/libpng/pnglibconf.h
@@ -1,10 +1,9 @@
-/* libpng 1.6.35 STANDARD API DEFINITION */
-
 /* pnglibconf.h - library build configuration */
 
-/* Libpng version 1.6.35 - July 15, 2018 */
+/* libpng version 1.6.36 */
 
-/* Copyright (c) 1998-2018 Glenn Randers-Pehrson */
+/* Copyright (c) 2018 Cosmin Truta */
+/* Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson */
 
 /* This code is released under the libpng license. */
 /* For conditions of distribution and use, see the disclaimer */
@@ -20,8 +19,6 @@
 #define PNG_ALIGNED_MEMORY_SUPPORTED
 /*#undef PNG_ARM_NEON_API_SUPPORTED*/
 /*#undef PNG_ARM_NEON_CHECK_SUPPORTED*/
-/*#undef PNG_POWERPC_VSX_API_SUPPORTED*/
-/*#undef PNG_POWERPC_VSX_CHECK_SUPPORTED*/
 #define PNG_BENIGN_ERRORS_SUPPORTED
 #define PNG_BENIGN_READ_ERRORS_SUPPORTED
 /*#undef PNG_BENIGN_WRITE_ERRORS_SUPPORTED*/
@@ -46,6 +43,8 @@
 #define PNG_IO_STATE_SUPPORTED
 #define PNG_MNG_FEATURES_SUPPORTED
 #define PNG_POINTER_INDEXING_SUPPORTED
+/*#undef PNG_POWERPC_VSX_API_SUPPORTED*/
+/*#undef PNG_POWERPC_VSX_CHECK_SUPPORTED*/
 #define PNG_PROGRESSIVE_READ_SUPPORTED
 #define PNG_READ_16BIT_SUPPORTED
 #define PNG_READ_ALPHA_MODE_SUPPORTED
diff --git a/thirdparty/libpng/pngmem.c b/thirdparty/libpng/pngmem.c
index ff3ef7e88c..09ed9c1c99 100644
--- a/thirdparty/libpng/pngmem.c
+++ b/thirdparty/libpng/pngmem.c
@@ -1,10 +1,10 @@
 
 /* pngmem.c - stub functions for memory allocation
  *
- * Last changed in libpng 1.6.26 [October 20, 2016]
+ * Copyright (c) 2018 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2014,2016 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.)
+ * Copyright (c) 1996-1997 Andreas Dilger
+ * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
diff --git a/thirdparty/libpng/pngpread.c b/thirdparty/libpng/pngpread.c
index c4ba51c4d4..e283627b77 100644
--- a/thirdparty/libpng/pngpread.c
+++ b/thirdparty/libpng/pngpread.c
@@ -1,10 +1,10 @@
 
 /* pngpread.c - read a png file in push mode
  *
- * Last changed in libpng 1.6.35 [July 15, 2018]
+ * Copyright (c) 2018 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2018 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.)
+ * Copyright (c) 1996-1997 Andreas Dilger
+ * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
@@ -972,20 +972,20 @@ png_read_push_finish_row(png_structrp png_ptr)
    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
 
    /* Start of interlace block */
-   static PNG_CONST png_byte png_pass_start[] = {0, 4, 0, 2, 0, 1, 0};
+   static const png_byte png_pass_start[] = {0, 4, 0, 2, 0, 1, 0};
 
    /* Offset to next interlace block */
-   static PNG_CONST png_byte png_pass_inc[] = {8, 8, 4, 4, 2, 2, 1};
+   static const png_byte png_pass_inc[] = {8, 8, 4, 4, 2, 2, 1};
 
    /* Start of interlace block in the y direction */
-   static PNG_CONST png_byte png_pass_ystart[] = {0, 0, 4, 0, 2, 0, 1};
+   static const png_byte png_pass_ystart[] = {0, 0, 4, 0, 2, 0, 1};
 
    /* Offset to next interlace block in the y direction */
-   static PNG_CONST png_byte png_pass_yinc[] = {8, 8, 8, 4, 4, 2, 2};
+   static const png_byte 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
-   static PNG_CONST png_byte png_pass_height[] = {8, 8, 4, 4, 2, 2, 1};
+   static const png_byte png_pass_height[] = {8, 8, 4, 4, 2, 2, 1};
    */
 #endif
 
diff --git a/thirdparty/libpng/pngpriv.h b/thirdparty/libpng/pngpriv.h
index 3581f67919..973c3eac1f 100644
--- a/thirdparty/libpng/pngpriv.h
+++ b/thirdparty/libpng/pngpriv.h
@@ -1,10 +1,10 @@
 
 /* pngpriv.h - private declarations for use inside libpng
  *
- * Last changed in libpng 1.6.35 [July 15, 2018]
+ * Copyright (c) 2018 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2018 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.)
+ * Copyright (c) 1996-1997 Andreas Dilger
+ * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
@@ -174,7 +174,10 @@
 #     else /* !defined __ARM_NEON__ */
          /* The 'intrinsics' code simply won't compile without this -mfpu=neon:
           */
-#        define PNG_ARM_NEON_IMPLEMENTATION 2
+#        if !defined(__aarch64__)
+            /* The assembler code currently does not work on ARM64 */
+#          define PNG_ARM_NEON_IMPLEMENTATION 2
+#        endif /* __aarch64__ */
 #     endif /* __ARM_NEON__ */
 #  endif /* !PNG_ARM_NEON_IMPLEMENTATION */
 
@@ -1534,10 +1537,10 @@ PNG_INTERNAL_FUNCTION(void,png_handle_zTXt,(png_structrp png_ptr,
 #endif
 
 PNG_INTERNAL_FUNCTION(void,png_check_chunk_name,(png_const_structrp png_ptr,
-    const png_uint_32 chunk_name),PNG_EMPTY);
+    png_uint_32 chunk_name),PNG_EMPTY);
 
 PNG_INTERNAL_FUNCTION(void,png_check_chunk_length,(png_const_structrp png_ptr,
-    const png_uint_32 chunk_length),PNG_EMPTY);
+    png_uint_32 chunk_length),PNG_EMPTY);
 
 PNG_INTERNAL_FUNCTION(void,png_handle_unknown,(png_structrp png_ptr,
     png_inforp info_ptr, png_uint_32 length, int keep),PNG_EMPTY);
@@ -2114,6 +2117,29 @@ PNG_INTERNAL_FUNCTION(void, png_init_filter_functions_sse2,
 PNG_INTERNAL_FUNCTION(png_uint_32, png_check_keyword, (png_structrp png_ptr,
    png_const_charp key, png_bytep new_key), PNG_EMPTY);
 
+#if PNG_ARM_NEON_IMPLEMENTATION == 1
+PNG_INTERNAL_FUNCTION(void,
+                      png_riffle_palette_rgba,
+                      (png_structrp, png_row_infop),
+                      PNG_EMPTY);
+PNG_INTERNAL_FUNCTION(int,
+                      png_do_expand_palette_neon_rgba,
+                      (png_structrp,
+                       png_row_infop,
+                       png_const_bytep,
+                       const png_bytepp,
+                       const png_bytepp),
+                      PNG_EMPTY);
+PNG_INTERNAL_FUNCTION(int,
+                      png_do_expand_palette_neon_rgb,
+                      (png_structrp,
+                       png_row_infop,
+                       png_const_bytep,
+                       const png_bytepp,
+                       const png_bytepp),
+                      PNG_EMPTY);
+#endif
+
 /* Maintainer: Put new private prototypes here ^ */
 
 #include "pngdebug.h"
diff --git a/thirdparty/libpng/pngread.c b/thirdparty/libpng/pngread.c
index bff7503ee3..f8e762196e 100644
--- a/thirdparty/libpng/pngread.c
+++ b/thirdparty/libpng/pngread.c
@@ -1,10 +1,10 @@
 
 /* pngread.c - read a PNG file
  *
- * Last changed in libpng 1.6.35 [July 15, 2018]
+ * Copyright (c) 2018 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2018 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.)
+ * Copyright (c) 1996-1997 Andreas Dilger
+ * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
@@ -1621,7 +1621,7 @@ png_image_skip_unused_chunks(png_structrp png_ptr)
     * errors (which are unfortunately quite common.)
     */
    {
-         static PNG_CONST png_byte chunks_to_process[] = {
+         static const png_byte chunks_to_process[] = {
             98,  75,  71,  68, '\0',  /* bKGD */
             99,  72,  82,  77, '\0',  /* cHRM */
            103,  65,  77,  65, '\0',  /* gAMA */
@@ -1758,9 +1758,9 @@ png_create_colormap_entry(png_image_read_control *display,
     png_uint_32 alpha, int encoding)
 {
    png_imagep image = display->image;
-   const int output_encoding = (image->format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
+   int output_encoding = (image->format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
        P_LINEAR : P_sRGB;
-   const int convert_to_Y = (image->format & PNG_FORMAT_FLAG_COLOR) == 0 &&
+   int convert_to_Y = (image->format & PNG_FORMAT_FLAG_COLOR) == 0 &&
        (red != green || green != blue);
 
    if (ip > 255)
@@ -1869,13 +1869,13 @@ png_create_colormap_entry(png_image_read_control *display,
    /* Store the value. */
    {
 #     ifdef PNG_FORMAT_AFIRST_SUPPORTED
-         const int afirst = (image->format & PNG_FORMAT_FLAG_AFIRST) != 0 &&
+         int afirst = (image->format & PNG_FORMAT_FLAG_AFIRST) != 0 &&
             (image->format & PNG_FORMAT_FLAG_ALPHA) != 0;
 #     else
 #        define afirst 0
 #     endif
 #     ifdef PNG_FORMAT_BGR_SUPPORTED
-         const int bgr = (image->format & PNG_FORMAT_FLAG_BGR) != 0 ? 2 : 0;
+         int bgr = (image->format & PNG_FORMAT_FLAG_BGR) != 0 ? 2 : 0;
 #     else
 #        define bgr 0
 #     endif
@@ -2085,11 +2085,11 @@ png_image_read_colormap(png_voidp argument)
 {
    png_image_read_control *display =
       png_voidcast(png_image_read_control*, argument);
-   const png_imagep image = display->image;
+   png_imagep image = display->image;
 
-   const png_structrp png_ptr = image->opaque->png_ptr;
-   const png_uint_32 output_format = image->format;
-   const int output_encoding = (output_format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
+   png_structrp png_ptr = image->opaque->png_ptr;
+   png_uint_32 output_format = image->format;
+   int output_encoding = (output_format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
       P_LINEAR : P_sRGB;
 
    unsigned int cmap_entries;
@@ -2802,7 +2802,7 @@ png_image_read_colormap(png_voidp argument)
             unsigned int num_trans = png_ptr->num_trans;
             png_const_bytep trans = num_trans > 0 ? png_ptr->trans_alpha : NULL;
             png_const_colorp colormap = png_ptr->palette;
-            const int do_background = trans != NULL &&
+            int do_background = trans != NULL &&
                (output_format & PNG_FORMAT_FLAG_ALPHA) == 0;
             unsigned int i;
 
@@ -3946,7 +3946,7 @@ png_image_read_direct(png_voidp argument)
        */
       if (linear != 0)
       {
-         PNG_CONST png_uint_16 le = 0x0001;
+         png_uint_16 le = 0x0001;
 
          if ((*(png_const_bytep) & le) != 0)
             png_set_swap(png_ptr);
@@ -4108,7 +4108,7 @@ png_image_finish_read(png_imagep image, png_const_colorp background,
        * original PNG format because it may not occur in the output PNG format
        * and libpng deals with the issues of reading the original.
        */
-      const unsigned int channels = PNG_IMAGE_PIXEL_CHANNELS(image->format);
+      unsigned int channels = PNG_IMAGE_PIXEL_CHANNELS(image->format);
 
       /* The following checks just the 'row_stride' calculation to ensure it
        * fits in a signed 32-bit value.  Because channels/components can be
@@ -4119,7 +4119,7 @@ png_image_finish_read(png_imagep image, png_const_colorp background,
       if (image->width <= 0x7fffffffU/channels) /* no overflow */
       {
          png_uint_32 check;
-         const png_uint_32 png_row_stride = image->width * channels;
+         png_uint_32 png_row_stride = image->width * channels;
 
          if (row_stride == 0)
             row_stride = (png_int_32)/*SAFE*/png_row_stride;
diff --git a/thirdparty/libpng/pngrio.c b/thirdparty/libpng/pngrio.c
index 372221483f..7946358101 100644
--- a/thirdparty/libpng/pngrio.c
+++ b/thirdparty/libpng/pngrio.c
@@ -1,10 +1,10 @@
 
 /* pngrio.c - functions for data input
  *
- * Last changed in libpng 1.6.35 [July 15, 2018]
+ * Copyright (c) 2018 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2016,2018 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.)
+ * Copyright (c) 1996-1997 Andreas Dilger
+ * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
diff --git a/thirdparty/libpng/pngrtran.c b/thirdparty/libpng/pngrtran.c
index 67d1f249a6..ccc58ce6f1 100644
--- a/thirdparty/libpng/pngrtran.c
+++ b/thirdparty/libpng/pngrtran.c
@@ -1,10 +1,10 @@
 
 /* pngrtran.c - transforms the data in a row for PNG readers
  *
- * Last changed in libpng 1.6.35 [July 15, 2018]
+ * Copyright (c) 2018 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2018 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.)
+ * Copyright (c) 1996-1997 Andreas Dilger
+ * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
@@ -18,6 +18,17 @@
 
 #include "pngpriv.h"
 
+#ifdef PNG_ARM_NEON_IMPLEMENTATION
+#  if PNG_ARM_NEON_IMPLEMENTATION == 1
+#    define PNG_ARM_NEON_INTRINSICS_AVAILABLE
+#    if defined(_MSC_VER) && defined(_M_ARM64)
+#      include <arm64_neon.h>
+#    else
+#      include <arm_neon.h>
+#    endif
+#  endif
+#endif
+
 #ifdef PNG_READ_SUPPORTED
 
 /* Set the action on getting a CRC error for an ancillary or critical chunk. */
@@ -2986,7 +2997,6 @@ png_do_gray_to_rgb(png_row_infop row_info, png_bytep row)
  */
 static int
 png_do_rgb_to_gray(png_structrp png_ptr, png_row_infop row_info, png_bytep row)
-
 {
    int rgb_error = 0;
 
@@ -2995,12 +3005,11 @@ png_do_rgb_to_gray(png_structrp png_ptr, png_row_infop row_info, png_bytep row)
    if ((row_info->color_type & PNG_COLOR_MASK_PALETTE) == 0 &&
        (row_info->color_type & PNG_COLOR_MASK_COLOR) != 0)
    {
-      PNG_CONST png_uint_32 rc = png_ptr->rgb_to_gray_red_coeff;
-      PNG_CONST png_uint_32 gc = png_ptr->rgb_to_gray_green_coeff;
-      PNG_CONST png_uint_32 bc = 32768 - rc - gc;
-      PNG_CONST png_uint_32 row_width = row_info->width;
-      PNG_CONST int have_alpha =
-         (row_info->color_type & PNG_COLOR_MASK_ALPHA) != 0;
+      png_uint_32 rc = png_ptr->rgb_to_gray_red_coeff;
+      png_uint_32 gc = png_ptr->rgb_to_gray_green_coeff;
+      png_uint_32 bc = 32768 - rc - gc;
+      png_uint_32 row_width = row_info->width;
+      int have_alpha = (row_info->color_type & PNG_COLOR_MASK_ALPHA) != 0;
 
       if (row_info->bit_depth == 8)
       {
@@ -4143,12 +4152,11 @@ png_do_encode_alpha(png_row_infop row_info, png_bytep row, png_structrp png_ptr)
    {
       if (row_info->bit_depth == 8)
       {
-         PNG_CONST png_bytep table = png_ptr->gamma_from_1;
+         png_bytep table = png_ptr->gamma_from_1;
 
          if (table != NULL)
          {
-            PNG_CONST int step =
-               (row_info->color_type & PNG_COLOR_MASK_COLOR) ? 4 : 2;
+            int step = (row_info->color_type & PNG_COLOR_MASK_COLOR) ? 4 : 2;
 
             /* The alpha channel is the last component: */
             row += step - 1;
@@ -4162,13 +4170,12 @@ png_do_encode_alpha(png_row_infop row_info, png_bytep row, png_structrp png_ptr)
 
       else if (row_info->bit_depth == 16)
       {
-         PNG_CONST png_uint_16pp table = png_ptr->gamma_16_from_1;
-         PNG_CONST int gamma_shift = png_ptr->gamma_shift;
+         png_uint_16pp table = png_ptr->gamma_16_from_1;
+         int gamma_shift = png_ptr->gamma_shift;
 
          if (table != NULL)
          {
-            PNG_CONST int step =
-               (row_info->color_type & PNG_COLOR_MASK_COLOR) ? 8 : 4;
+            int step = (row_info->color_type & PNG_COLOR_MASK_COLOR) ? 8 : 4;
 
             /* The alpha channel is the last component: */
             row += step - 2;
@@ -4199,8 +4206,9 @@ png_do_encode_alpha(png_row_infop row_info, png_bytep row, png_structrp png_ptr)
  * upon whether you supply trans and num_trans.
  */
 static void
-png_do_expand_palette(png_row_infop row_info, png_bytep row,
-    png_const_colorp palette, png_const_bytep trans_alpha, int num_trans)
+png_do_expand_palette(png_structrp png_ptr, png_row_infop row_info,
+    png_bytep row, png_const_colorp palette, png_const_bytep trans_alpha,
+    int num_trans)
 {
    int shift, value;
    png_bytep sp, dp;
@@ -4304,14 +4312,25 @@ png_do_expand_palette(png_row_infop row_info, png_bytep row,
                sp = row + (size_t)row_width - 1;
                dp = row + ((size_t)row_width << 2) - 1;
 
-               for (i = 0; i < row_width; i++)
+               i = 0;
+#ifdef PNG_ARM_NEON_INTRINSICS_AVAILABLE
+               if (png_ptr->riffled_palette != NULL)
+               {
+                  /* The RGBA optimization works with png_ptr->bit_depth == 8
+                   * but sometimes row_info->bit_depth has been changed to 8.
+                   * In these cases, the palette hasn't been riffled.
+                   */
+                  i = png_do_expand_palette_neon_rgba(png_ptr, row_info, row,
+                      &sp, &dp);
+               }
+#endif
+
+               for (; i < row_width; i++)
                {
                   if ((int)(*sp) >= num_trans)
                      *dp-- = 0xff;
-
                   else
                      *dp-- = trans_alpha[*sp];
-
                   *dp-- = palette[*sp].blue;
                   *dp-- = palette[*sp].green;
                   *dp-- = palette[*sp].red;
@@ -4328,8 +4347,13 @@ png_do_expand_palette(png_row_infop row_info, png_bytep row,
             {
                sp = row + (size_t)row_width - 1;
                dp = row + (size_t)(row_width * 3) - 1;
+               i = 0;
+#ifdef PNG_ARM_NEON_INTRINSICS_AVAILABLE
+               i = png_do_expand_palette_neon_rgb(png_ptr, row_info, row,
+                   &sp, &dp);
+#endif
 
-               for (i = 0; i < row_width; i++)
+               for (; i < row_width; i++)
                {
                   *dp-- = palette[*sp].blue;
                   *dp-- = palette[*sp].green;
@@ -4743,8 +4767,22 @@ png_do_read_transformations(png_structrp png_ptr, png_row_infop row_info)
    {
       if (row_info->color_type == PNG_COLOR_TYPE_PALETTE)
       {
-         png_do_expand_palette(row_info, png_ptr->row_buf + 1,
-             png_ptr->palette, png_ptr->trans_alpha, png_ptr->num_trans);
+#ifdef PNG_ARM_NEON_INTRINSICS_AVAILABLE
+         if ((png_ptr->num_trans > 0) && (png_ptr->bit_depth == 8))
+         {
+            /* Allocate space for the decompressed full palette. */
+            if (png_ptr->riffled_palette == NULL)
+            {
+               png_ptr->riffled_palette = png_malloc(png_ptr, 256*4);
+               if (png_ptr->riffled_palette == NULL)
+                  png_error(png_ptr, "NULL row buffer");
+               /* Build the RGBA palette. */
+               png_riffle_palette_rgba(png_ptr, row_info);
+            }
+         }
+#endif
+         png_do_expand_palette(png_ptr, row_info, png_ptr->row_buf + 1,
+            png_ptr->palette, png_ptr->trans_alpha, png_ptr->num_trans);
       }
 
       else
diff --git a/thirdparty/libpng/pngrutil.c b/thirdparty/libpng/pngrutil.c
index 7001f1976e..d5fa08c397 100644
--- a/thirdparty/libpng/pngrutil.c
+++ b/thirdparty/libpng/pngrutil.c
@@ -1,10 +1,10 @@
 
 /* pngrutil.c - utilities to read a PNG file
  *
- * Last changed in libpng 1.6.35 [July 15, 2018]
+ * Copyright (c) 2018 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2018 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.)
+ * Copyright (c) 1996-1997 Andreas Dilger
+ * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
@@ -1461,8 +1461,7 @@ png_handle_iCCP(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
                {
                   /* We have the ICC profile header; do the basic header checks.
                    */
-                  const png_uint_32 profile_length =
-                     png_get_uint_32(profile_header);
+                  png_uint_32 profile_length = png_get_uint_32(profile_header);
 
                   if (png_icc_check_length(png_ptr, &png_ptr->colorspace,
                       keyword, profile_length) != 0)
@@ -1479,8 +1478,8 @@ png_handle_iCCP(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
                          * profile.  The header check has already validated
                          * that none of this stuff will overflow.
                          */
-                        const png_uint_32 tag_count = png_get_uint_32(
-                            profile_header+128);
+                        png_uint_32 tag_count =
+                           png_get_uint_32(profile_header + 128);
                         png_bytep profile = png_read_buffer(png_ptr,
                             profile_length, 2/*silent*/);
 
@@ -3132,7 +3131,7 @@ png_handle_unknown(png_structrp png_ptr, png_inforp info_ptr,
  */
 
 void /* PRIVATE */
-png_check_chunk_name(png_const_structrp png_ptr, const png_uint_32 chunk_name)
+png_check_chunk_name(png_const_structrp png_ptr, png_uint_32 chunk_name)
 {
    int i;
    png_uint_32 cn=chunk_name;
@@ -3151,7 +3150,7 @@ png_check_chunk_name(png_const_structrp png_ptr, const png_uint_32 chunk_name)
 }
 
 void /* PRIVATE */
-png_check_chunk_length(png_const_structrp png_ptr, const png_uint_32 length)
+png_check_chunk_length(png_const_structrp png_ptr, png_uint_32 length)
 {
    png_alloc_size_t limit = PNG_UINT_31_MAX;
 
@@ -3363,7 +3362,7 @@ png_combine_row(png_const_structrp png_ptr, png_bytep dp, int display)
          /* Hence the pre-compiled masks indexed by PACKSWAP (or not), depth and
           * then pass:
           */
-         static PNG_CONST png_uint_32 row_mask[2/*PACKSWAP*/][3/*depth*/][6] =
+         static const png_uint_32 row_mask[2/*PACKSWAP*/][3/*depth*/][6] =
          {
             /* Little-endian byte masks for PACKSWAP */
             { S_MASKS(1,0), S_MASKS(2,0), S_MASKS(4,0) },
@@ -3374,7 +3373,7 @@ png_combine_row(png_const_structrp png_ptr, png_bytep dp, int display)
          /* display_mask has only three entries for the odd passes, so index by
           * pass>>1.
           */
-         static PNG_CONST png_uint_32 display_mask[2][3][3] =
+         static const png_uint_32 display_mask[2][3][3] =
          {
             /* Little-endian byte masks for PACKSWAP */
             { B_MASKS(1,0), B_MASKS(2,0), B_MASKS(4,0) },
@@ -3687,7 +3686,7 @@ png_do_read_interlace(png_row_infop row_info, png_bytep row, int pass,
 {
    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
    /* Offset to next interlace block */
-   static PNG_CONST unsigned int png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
+   static const unsigned 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)
@@ -4329,16 +4328,16 @@ png_read_finish_row(png_structrp png_ptr)
    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
 
    /* Start of interlace block */
-   static PNG_CONST png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
+   static const png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
 
    /* Offset to next interlace block */
-   static PNG_CONST png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
+   static const png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
 
    /* Start of interlace block in the y direction */
-   static PNG_CONST png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
+   static const png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
 
    /* Offset to next interlace block in the y direction */
-   static PNG_CONST png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
+   static const png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
 
    png_debug(1, "in png_read_finish_row");
    png_ptr->row_number++;
@@ -4394,16 +4393,16 @@ png_read_start_row(png_structrp png_ptr)
    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
 
    /* Start of interlace block */
-   static PNG_CONST png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
+   static const png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
 
    /* Offset to next interlace block */
-   static PNG_CONST png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
+   static const png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
 
    /* Start of interlace block in the y direction */
-   static PNG_CONST png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
+   static const png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
 
    /* Offset to next interlace block in the y direction */
-   static PNG_CONST png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
+   static const png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
 
    unsigned int max_pixel_depth;
    size_t row_bytes;
diff --git a/thirdparty/libpng/pngset.c b/thirdparty/libpng/pngset.c
index 7cf54d9248..ec75dbe369 100644
--- a/thirdparty/libpng/pngset.c
+++ b/thirdparty/libpng/pngset.c
@@ -1,10 +1,10 @@
 
 /* pngset.c - storage of image information into info struct
  *
- * Last changed in libpng 1.6.35 [July 15, 2018]
+ * Copyright (c) 2018 Cosmin Truta
  * Copyright (c) 1998-2018 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.)
+ * Copyright (c) 1996-1997 Andreas Dilger
+ * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
@@ -137,7 +137,7 @@ png_set_cHRM_XYZ(png_const_structrp png_ptr, png_inforp info_ptr, double red_X,
 #ifdef PNG_eXIf_SUPPORTED
 void PNGAPI
 png_set_eXIf(png_const_structrp png_ptr, png_inforp info_ptr,
-    const png_bytep eXIf_buf)
+    png_bytep eXIf_buf)
 {
   png_warning(png_ptr, "png_set_eXIf does not work; use png_set_eXIf_1");
   PNG_UNUSED(info_ptr)
@@ -146,7 +146,7 @@ png_set_eXIf(png_const_structrp png_ptr, png_inforp info_ptr,
 
 void PNGAPI
 png_set_eXIf_1(png_const_structrp png_ptr, png_inforp info_ptr,
-    const png_uint_32 num_exif, const png_bytep eXIf_buf)
+    png_uint_32 num_exif, png_bytep eXIf_buf)
 {
    int i;
 
@@ -1399,7 +1399,7 @@ png_set_keep_unknown_chunks(png_structrp png_ptr, int keep,
       /* Ignore all unknown chunks and all chunks recognized by
        * libpng except for IHDR, PLTE, tRNS, IDAT, and IEND
        */
-      static PNG_CONST png_byte chunks_to_ignore[] = {
+      static const png_byte chunks_to_ignore[] = {
          98,  75,  71,  68, '\0',  /* bKGD */
          99,  72,  82,  77, '\0',  /* cHRM */
         101,  88,  73, 102, '\0',  /* eXIf */
diff --git a/thirdparty/libpng/pngstruct.h b/thirdparty/libpng/pngstruct.h
index 699e8ac68a..94a6d041ff 100644
--- a/thirdparty/libpng/pngstruct.h
+++ b/thirdparty/libpng/pngstruct.h
@@ -1,10 +1,10 @@
 
 /* pngstruct.h - header file for PNG reference library
  *
- * Last changed in libpng 1.6.35 [July 15, 2018]
+ * Copyright (c) 2018 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2018 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.)
+ * Copyright (c) 1996-1997 Andreas Dilger
+ * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
@@ -228,6 +228,10 @@ struct png_struct_def
                                * big_row_buf; while writing it is separately
                                * allocated.
                                */
+#ifdef PNG_READ_EXPAND_SUPPORTED
+   /* Buffer to accelerate palette transformations. */
+   png_bytep riffled_palette;
+#endif
 #ifdef PNG_WRITE_FILTER_SUPPORTED
    png_bytep try_row;    /* buffer to save trial row when filtering */
    png_bytep tst_row;    /* buffer to save best trial row when filtering */
diff --git a/thirdparty/libpng/pngtrans.c b/thirdparty/libpng/pngtrans.c
index de84aa6d6b..1100f46ebe 100644
--- a/thirdparty/libpng/pngtrans.c
+++ b/thirdparty/libpng/pngtrans.c
@@ -1,10 +1,10 @@
 
 /* pngtrans.c - transforms the data in a row (used by both readers and writers)
  *
- * Last changed in libpng 1.6.35 [July 15, 2018]
+ * Copyright (c) 2018 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2018 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.)
+ * Copyright (c) 1996-1997 Andreas Dilger
+ * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
@@ -345,7 +345,7 @@ png_do_swap(png_row_infop row_info, png_bytep row)
 #endif
 
 #if defined(PNG_READ_PACKSWAP_SUPPORTED)||defined(PNG_WRITE_PACKSWAP_SUPPORTED)
-static PNG_CONST png_byte onebppswaptable[256] = {
+static const png_byte onebppswaptable[256] = {
    0x00, 0x80, 0x40, 0xC0, 0x20, 0xA0, 0x60, 0xE0,
    0x10, 0x90, 0x50, 0xD0, 0x30, 0xB0, 0x70, 0xF0,
    0x08, 0x88, 0x48, 0xC8, 0x28, 0xA8, 0x68, 0xE8,
@@ -380,7 +380,7 @@ static PNG_CONST png_byte onebppswaptable[256] = {
    0x1F, 0x9F, 0x5F, 0xDF, 0x3F, 0xBF, 0x7F, 0xFF
 };
 
-static PNG_CONST png_byte twobppswaptable[256] = {
+static const png_byte twobppswaptable[256] = {
    0x00, 0x40, 0x80, 0xC0, 0x10, 0x50, 0x90, 0xD0,
    0x20, 0x60, 0xA0, 0xE0, 0x30, 0x70, 0xB0, 0xF0,
    0x04, 0x44, 0x84, 0xC4, 0x14, 0x54, 0x94, 0xD4,
@@ -415,7 +415,7 @@ static PNG_CONST png_byte twobppswaptable[256] = {
    0x2F, 0x6F, 0xAF, 0xEF, 0x3F, 0x7F, 0xBF, 0xFF
 };
 
-static PNG_CONST png_byte fourbppswaptable[256] = {
+static const png_byte fourbppswaptable[256] = {
    0x00, 0x10, 0x20, 0x30, 0x40, 0x50, 0x60, 0x70,
    0x80, 0x90, 0xA0, 0xB0, 0xC0, 0xD0, 0xE0, 0xF0,
    0x01, 0x11, 0x21, 0x31, 0x41, 0x51, 0x61, 0x71,
diff --git a/thirdparty/libpng/pngwio.c b/thirdparty/libpng/pngwio.c
index e5391687a2..10e919dd03 100644
--- a/thirdparty/libpng/pngwio.c
+++ b/thirdparty/libpng/pngwio.c
@@ -1,10 +1,10 @@
 
 /* pngwio.c - functions for data output
  *
- * Last changed in libpng 1.6.35 [July 15, 2018]
+ * Copyright (c) 2018 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2014,2016,2018 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.)
+ * Copyright (c) 1996-1997 Andreas Dilger
+ * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
diff --git a/thirdparty/libpng/pngwrite.c b/thirdparty/libpng/pngwrite.c
index 5bd87f373e..160c877d38 100644
--- a/thirdparty/libpng/pngwrite.c
+++ b/thirdparty/libpng/pngwrite.c
@@ -1,10 +1,10 @@
 
 /* pngwrite.c - general routines to write a PNG file
  *
- * Last changed in libpng 1.6.35 [July 15, 2018]
+ * Copyright (c) 2018 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2018 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.)
+ * Copyright (c) 1996-1997 Andreas Dilger
+ * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
@@ -469,7 +469,7 @@ png_write_end(png_structrp png_ptr, png_inforp info_ptr)
 
 #ifdef PNG_CONVERT_tIME_SUPPORTED
 void PNGAPI
-png_convert_from_struct_tm(png_timep ptime, PNG_CONST struct tm * ttime)
+png_convert_from_struct_tm(png_timep ptime, const struct tm * ttime)
 {
    png_debug(1, "in png_convert_from_struct_tm");
 
@@ -948,6 +948,10 @@ png_write_destroy(png_structrp png_ptr)
    png_free_buffer_list(png_ptr, &png_ptr->zbuffer_list);
    png_free(png_ptr, png_ptr->row_buf);
    png_ptr->row_buf = NULL;
+#ifdef PNG_READ_EXPANDED_SUPPORTED
+   png_free(png_ptr, png_ptr->riffled_palette);
+   png_ptr->riffled_palette = NULL;
+#endif
 #ifdef PNG_WRITE_FILTER_SUPPORTED
    png_free(png_ptr, png_ptr->prev_row);
    png_free(png_ptr, png_ptr->try_row);
@@ -1536,7 +1540,7 @@ png_write_image_16bit(png_voidp argument)
        display->first_row);
    png_uint_16p output_row = png_voidcast(png_uint_16p, display->local_row);
    png_uint_16p row_end;
-   const unsigned int channels = (image->format & PNG_FORMAT_FLAG_COLOR) != 0 ?
+   unsigned int channels = (image->format & PNG_FORMAT_FLAG_COLOR) != 0 ?
        3 : 1;
    int aindex = 0;
    png_uint_32 y = image->height;
@@ -1573,7 +1577,7 @@ png_write_image_16bit(png_voidp argument)
 
       while (out_ptr < row_end)
       {
-         const png_uint_16 alpha = in_ptr[aindex];
+         png_uint_16 alpha = in_ptr[aindex];
          png_uint_32 reciprocal = 0;
          int c;
 
@@ -1695,7 +1699,7 @@ png_write_image_8bit(png_voidp argument)
        display->first_row);
    png_bytep output_row = png_voidcast(png_bytep, display->local_row);
    png_uint_32 y = image->height;
-   const unsigned int channels = (image->format & PNG_FORMAT_FLAG_COLOR) != 0 ?
+   unsigned int channels = (image->format & PNG_FORMAT_FLAG_COLOR) != 0 ?
        3 : 1;
 
    if ((image->format & PNG_FORMAT_FLAG_ALPHA) != 0)
@@ -1783,25 +1787,25 @@ png_write_image_8bit(png_voidp argument)
 static void
 png_image_set_PLTE(png_image_write_control *display)
 {
-   const png_imagep image = display->image;
+   png_imagep image = display->image;
    const void *cmap = display->colormap;
-   const int entries = image->colormap_entries > 256 ? 256 :
+   int entries = image->colormap_entries > 256 ? 256 :
        (int)image->colormap_entries;
 
    /* NOTE: the caller must check for cmap != NULL and entries != 0 */
-   const png_uint_32 format = image->format;
-   const unsigned int channels = PNG_IMAGE_SAMPLE_CHANNELS(format);
+   png_uint_32 format = image->format;
+   unsigned int channels = PNG_IMAGE_SAMPLE_CHANNELS(format);
 
 #   if defined(PNG_FORMAT_BGR_SUPPORTED) &&\
       defined(PNG_SIMPLIFIED_WRITE_AFIRST_SUPPORTED)
-      const int afirst = (format & PNG_FORMAT_FLAG_AFIRST) != 0 &&
+      int afirst = (format & PNG_FORMAT_FLAG_AFIRST) != 0 &&
           (format & PNG_FORMAT_FLAG_ALPHA) != 0;
 #   else
 #     define afirst 0
 #   endif
 
 #   ifdef PNG_FORMAT_BGR_SUPPORTED
-      const int bgr = (format & PNG_FORMAT_FLAG_BGR) != 0 ? 2 : 0;
+      int bgr = (format & PNG_FORMAT_FLAG_BGR) != 0 ? 2 : 0;
 #   else
 #     define bgr 0
 #   endif
@@ -1951,12 +1955,12 @@ png_image_write_main(png_voidp argument)
     * and total image size to ensure that they are within the system limits.
     */
    {
-      const unsigned int channels = PNG_IMAGE_PIXEL_CHANNELS(image->format);
+      unsigned int channels = PNG_IMAGE_PIXEL_CHANNELS(image->format);
 
       if (image->width <= 0x7fffffffU/channels) /* no overflow */
       {
          png_uint_32 check;
-         const png_uint_32 png_row_stride = image->width * channels;
+         png_uint_32 png_row_stride = image->width * channels;
 
          if (display->row_stride == 0)
             display->row_stride = (png_int_32)/*SAFE*/png_row_stride;
@@ -2052,7 +2056,7 @@ png_image_write_main(png_voidp argument)
     */
    if (write_16bit != 0)
    {
-      PNG_CONST png_uint_16 le = 0x0001;
+      png_uint_16 le = 0x0001;
 
       if ((*(png_const_bytep) & le) != 0)
          png_set_swap(png_ptr);
@@ -2166,7 +2170,7 @@ image_memory_write)(png_structp png_ptr, png_bytep/*const*/ data, size_t size)
 {
    png_image_write_control *display = png_voidcast(png_image_write_control*,
        png_ptr->io_ptr/*backdoor: png_get_io_ptr(png_ptr)*/);
-   const png_alloc_size_t ob = display->output_bytes;
+   png_alloc_size_t ob = display->output_bytes;
 
    /* Check for overflow; this should never happen: */
    if (size <= ((png_alloc_size_t)-1) - ob)
diff --git a/thirdparty/libpng/pngwtran.c b/thirdparty/libpng/pngwtran.c
index 3a1e0a21d2..49a13c1e98 100644
--- a/thirdparty/libpng/pngwtran.c
+++ b/thirdparty/libpng/pngwtran.c
@@ -1,10 +1,10 @@
 
 /* pngwtran.c - transforms the data in a row for PNG writers
  *
- * Last changed in libpng 1.6.35 [July 15, 2018]
+ * Copyright (c) 2018 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2016,2018 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.)
+ * Copyright (c) 1996-1997 Andreas Dilger
+ * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
@@ -254,8 +254,7 @@ png_do_shift(png_row_infop row_info, png_bytep row,
 
          for (i = 0; i < istop; i++, bp++)
          {
-
-            const unsigned int c = i%channels;
+            unsigned int c = i%channels;
             int j;
             unsigned int v, out;
 
@@ -283,7 +282,7 @@ png_do_shift(png_row_infop row_info, png_bytep row,
 
          for (bp = row, i = 0; i < istop; i++)
          {
-            const unsigned int c = i%channels;
+            unsigned int c = i%channels;
             int j;
             unsigned int value, v;
 
diff --git a/thirdparty/libpng/pngwutil.c b/thirdparty/libpng/pngwutil.c
index ab431e712c..16345e4c0b 100644
--- a/thirdparty/libpng/pngwutil.c
+++ b/thirdparty/libpng/pngwutil.c
@@ -1,10 +1,10 @@
 
 /* pngwutil.c - utilities to write a PNG file
  *
- * Last changed in libpng 1.6.35 [July 15, 2018]
+ * Copyright (c) 2018 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2018 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.)
+ * Copyright (c) 1996-1997 Andreas Dilger
+ * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
@@ -1893,16 +1893,16 @@ png_write_start_row(png_structrp png_ptr)
    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
 
    /* Start of interlace block */
-   static PNG_CONST png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
+   static const png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
 
    /* Offset to next interlace block */
-   static PNG_CONST png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
+   static const png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
 
    /* Start of interlace block in the y direction */
-   static PNG_CONST png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
+   static const png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
 
    /* Offset to next interlace block in the y direction */
-   static PNG_CONST png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
+   static const png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
 #endif
 
    png_alloc_size_t buf_size;
@@ -2008,16 +2008,16 @@ png_write_finish_row(png_structrp png_ptr)
    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
 
    /* Start of interlace block */
-   static PNG_CONST png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
+   static const png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
 
    /* Offset to next interlace block */
-   static PNG_CONST png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
+   static const png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
 
    /* Start of interlace block in the y direction */
-   static PNG_CONST png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
+   static const png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
 
    /* Offset to next interlace block in the y direction */
-   static PNG_CONST png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
+   static const png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
 #endif
 
    png_debug(1, "in png_write_finish_row");
@@ -2098,10 +2098,10 @@ png_do_write_interlace(png_row_infop row_info, png_bytep row, int pass)
    /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
 
    /* Start of interlace block */
-   static PNG_CONST png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
+   static const png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
 
    /* Offset to next interlace block */
-   static PNG_CONST png_byte  png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
+   static const png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
 
    png_debug(1, "in png_do_write_interlace");
 
@@ -2276,7 +2276,7 @@ png_write_filtered_row(png_structrp png_ptr, png_bytep filtered_row,
 
 #ifdef PNG_WRITE_FILTER_SUPPORTED
 static size_t /* PRIVATE */
-png_setup_sub_row(png_structrp png_ptr, const png_uint_32 bpp,
+png_setup_sub_row(png_structrp png_ptr, png_uint_32 bpp,
     size_t row_bytes, size_t lmins)
 {
    png_bytep rp, dp, lp;
@@ -2315,7 +2315,7 @@ png_setup_sub_row(png_structrp png_ptr, const png_uint_32 bpp,
 }
 
 static void /* PRIVATE */
-png_setup_sub_row_only(png_structrp png_ptr, const png_uint_32 bpp,
+png_setup_sub_row_only(png_structrp png_ptr, png_uint_32 bpp,
     size_t row_bytes)
 {
    png_bytep rp, dp, lp;
@@ -2380,7 +2380,7 @@ png_setup_up_row_only(png_structrp png_ptr, size_t row_bytes)
 }
 
 static size_t /* PRIVATE */
-png_setup_avg_row(png_structrp png_ptr, const png_uint_32 bpp,
+png_setup_avg_row(png_structrp png_ptr, png_uint_32 bpp,
     size_t row_bytes, size_t lmins)
 {
    png_bytep rp, dp, pp, lp;
@@ -2420,7 +2420,7 @@ png_setup_avg_row(png_structrp png_ptr, const png_uint_32 bpp,
    return (sum);
 }
 static void /* PRIVATE */
-png_setup_avg_row_only(png_structrp png_ptr, const png_uint_32 bpp,
+png_setup_avg_row_only(png_structrp png_ptr, png_uint_32 bpp,
     size_t row_bytes)
 {
    png_bytep rp, dp, pp, lp;
@@ -2442,7 +2442,7 @@ png_setup_avg_row_only(png_structrp png_ptr, const png_uint_32 bpp,
 }
 
 static size_t /* PRIVATE */
-png_setup_paeth_row(png_structrp png_ptr, const png_uint_32 bpp,
+png_setup_paeth_row(png_structrp png_ptr, png_uint_32 bpp,
     size_t row_bytes, size_t lmins)
 {
    png_bytep rp, dp, pp, cp, lp;
@@ -2503,7 +2503,7 @@ png_setup_paeth_row(png_structrp png_ptr, const png_uint_32 bpp,
    return (sum);
 }
 static void /* PRIVATE */
-png_setup_paeth_row_only(png_structrp png_ptr, const png_uint_32 bpp,
+png_setup_paeth_row_only(png_structrp png_ptr, png_uint_32 bpp,
     size_t row_bytes)
 {
    png_bytep rp, dp, pp, cp, lp;