Merge pull request #28442 from akien-mga/libpng-1.6.37

libpng: Update to upstream 1.6.37

18 files changed, 1337 insertions, 92 deletions

diff --git a/thirdparty/README.md b/thirdparty/README.md
index c98f593920..e2c2334c0f 100644
--- a/thirdparty/README.md
+++ b/thirdparty/README.md
@@ -170,7 +170,7 @@ Files extracted from upstream source:
 ## libpng
 
 - Upstream: http://libpng.org/pub/png/libpng.html
-- Version: 1.6.35
+- Version: 1.6.37
 - License: libpng/zlib
 
 Files extracted from upstream source:
diff --git a/thirdparty/libpng/LICENSE b/thirdparty/libpng/LICENSE
index 62ab8e48dc..e0c5b531cf 100644
--- a/thirdparty/libpng/LICENSE
+++ b/thirdparty/libpng/LICENSE
@@ -4,8 +4,8 @@ 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) 1995-2019 The PNG Reference Library Authors.
+ * Copyright (c) 2018-2019 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.
@@ -13,7 +13,7 @@ PNG Reference Library License version 2
 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
+non-infringement.  In no event 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
@@ -39,7 +39,7 @@ subject to the following restrictions:
 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
+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
 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
diff --git a/thirdparty/libpng/arm/palette_neon_intrinsics.c b/thirdparty/libpng/arm/palette_neon_intrinsics.c
index fa02d6a8b3..b4d1fd2abf 100644
--- a/thirdparty/libpng/arm/palette_neon_intrinsics.c
+++ b/thirdparty/libpng/arm/palette_neon_intrinsics.c
@@ -1,7 +1,7 @@
 
 /* palette_neon_intrinsics.c - NEON optimised palette expansion functions
  *
- * Copyright (c) 2018 Cosmin Truta
+ * Copyright (c) 2018-2019 Cosmin Truta
  * Copyright (c) 2017-2018 Arm Holdings. All rights reserved.
  * Written by Richard Townsend <Richard.Townsend@arm.com>, February 2017.
  *
@@ -20,9 +20,9 @@
 #  include <arm_neon.h>
 #endif
 
-/* Build an RGBA palette from the RGB and separate alpha palettes. */
+/* Build an RGBA8 palette from the separate RGB and alpha palettes. */
 void
-png_riffle_palette_rgba(png_structrp png_ptr, png_row_infop row_info)
+png_riffle_palette_neon(png_structrp png_ptr)
 {
    png_const_colorp palette = png_ptr->palette;
    png_bytep riffled_palette = png_ptr->riffled_palette;
@@ -30,6 +30,8 @@ png_riffle_palette_rgba(png_structrp png_ptr, png_row_infop row_info)
    int num_trans = png_ptr->num_trans;
    int i;
 
+   png_debug(1, "in png_riffle_palette_neon");
+
    /* Initially black, opaque. */
    uint8x16x4_t w = {{
       vdupq_n_u8(0x00),
@@ -38,16 +40,10 @@ png_riffle_palette_rgba(png_structrp png_ptr, png_row_infop row_info)
       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.
+   /* First, riffle the RGB colours into an RGBA8 palette.
+    * The alpha component is set to opaque for now.
     */
-   for (i = 0; i < (1 << row_info->bit_depth); i += 16)
+   for (i = 0; i < 256; i += 16)
    {
       uint8x16x3_t v = vld3q_u8((png_const_bytep)(palette + i));
       w.val[0] = v.val[0];
@@ -61,9 +57,9 @@ png_riffle_palette_rgba(png_structrp png_ptr, png_row_infop row_info)
       riffled_palette[(i << 2) + 3] = trans_alpha[i];
 }
 
-/* Expands a palettized row into RGBA. */
+/* Expands a palettized row into RGBA8. */
 int
-png_do_expand_palette_neon_rgba(png_structrp png_ptr, png_row_infop row_info,
+png_do_expand_palette_rgba8_neon(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;
@@ -72,6 +68,8 @@ png_do_expand_palette_neon_rgba(png_structrp png_ptr, png_row_infop row_info,
    const png_int_32 pixels_per_chunk = 4;
    int i;
 
+   png_debug(1, "in png_do_expand_palette_rgba8_neon");
+
    if (row_width < pixels_per_chunk)
       return 0;
 
@@ -103,9 +101,9 @@ png_do_expand_palette_neon_rgba(png_structrp png_ptr, png_row_infop row_info,
    return i;
 }
 
-/* Expands a palettized row into RGB format. */
+/* Expands a palettized row into RGB8. */
 int
-png_do_expand_palette_neon_rgb(png_structrp png_ptr, png_row_infop row_info,
+png_do_expand_palette_rgb8_neon(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;
@@ -113,6 +111,8 @@ png_do_expand_palette_neon_rgb(png_structrp png_ptr, png_row_infop row_info,
    const png_uint_32 pixels_per_chunk = 8;
    int i;
 
+   png_debug(1, "in png_do_expand_palette_rgb8_neon");
+
    if (row_width <= pixels_per_chunk)
       return 0;
 
diff --git a/thirdparty/libpng/png.c b/thirdparty/libpng/png.c
index 3dce191d17..757c755f97 100644
--- a/thirdparty/libpng/png.c
+++ b/thirdparty/libpng/png.c
@@ -1,7 +1,7 @@
 
 /* png.c - location for general purpose libpng functions
  *
- * Copyright (c) 2018 Cosmin Truta
+ * Copyright (c) 2018-2019 Cosmin Truta
  * 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.
@@ -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_36 Your_png_h_is_not_version_1_6_36;
+typedef png_libpng_version_1_6_37 Your_png_h_is_not_version_1_6_37;
 
 #ifdef __GNUC__
 /* The version tests may need to be added to, but the problem warning has
@@ -815,8 +815,8 @@ png_get_copyright(png_const_structrp png_ptr)
    return PNG_STRING_COPYRIGHT
 #else
    return PNG_STRING_NEWLINE \
-      "libpng version 1.6.36" PNG_STRING_NEWLINE \
-      "Copyright (c) 2018 Cosmin Truta" PNG_STRING_NEWLINE \
+      "libpng version 1.6.37" PNG_STRING_NEWLINE \
+      "Copyright (c) 2018-2019 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 \
@@ -4588,8 +4588,7 @@ png_image_free(png_imagep image)
    if (image != NULL && image->opaque != NULL &&
       image->opaque->error_buf == NULL)
    {
-      /* Ignore errors here: */
-      (void)png_safe_execute(image, png_image_free_function, image);
+      png_image_free_function(image);
       image->opaque = NULL;
    }
 }
diff --git a/thirdparty/libpng/png.h b/thirdparty/libpng/png.h
index 8e272a0553..b12174ba35 100644
--- a/thirdparty/libpng/png.h
+++ b/thirdparty/libpng/png.h
@@ -1,9 +1,9 @@
 
 /* png.h - header file for PNG reference library
  *
- * libpng version 1.6.36 - December 1, 2018
+ * libpng version 1.6.37 - April 14, 2019
  *
- * Copyright (c) 2018 Cosmin Truta
+ * Copyright (c) 2018-2019 Cosmin Truta
  * 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.
@@ -14,8 +14,9 @@
  *   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 2018:
- *     Glenn Randers-Pehrson.
- *   libpng version 1.6.36, December 1, 2018: Cosmin Truta
+ *     Glenn Randers-Pehrson
+ *   libpng versions 1.6.36, December 2018, through 1.6.37, April 2019:
+ *     Cosmin Truta
  *   See also "Contributing Authors", below.
  */
 
@@ -26,8 +27,8 @@
  * PNG Reference Library License version 2
  * ---------------------------------------
  *
- *  * Copyright (c) 1995-2018 The PNG Reference Library Authors.
- *  * Copyright (c) 2018 Cosmin Truta.
+ *  * Copyright (c) 1995-2019 The PNG Reference Library Authors.
+ *  * Copyright (c) 2018-2019 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.
@@ -35,7 +36,7 @@
  * 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
+ * non-infringement.  In no event 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
@@ -61,7 +62,7 @@
  * 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
+ * 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
  * 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
@@ -238,7 +239,7 @@
  *    ...
  *    1.5.30                  15    10530  15.so.15.30[.0]
  *    ...
- *    1.6.36                  16    10636  16.so.16.36[.0]
+ *    1.6.37                  16    10637  16.so.16.37[.0]
  *
  *    Henceforth the source version will match the shared-library major and
  *    minor numbers; the shared-library major version number will be used for
@@ -277,8 +278,8 @@
  */
 
 /* Version information for png.h - this should match the version in png.c */
-#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_STRING "1.6.37"
+#define PNG_HEADER_VERSION_STRING " libpng version 1.6.37 - April 14, 2019\n"
 
 #define PNG_LIBPNG_VER_SONUM   16
 #define PNG_LIBPNG_VER_DLLNUM  16
@@ -286,12 +287,11 @@
 /* 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 36
+#define PNG_LIBPNG_VER_RELEASE 37
 
-/* This should match the numeric part of the final component of
- * PNG_LIBPNG_VER_STRING, omitting any leading zero:
+/* This should be zero for a public release, or non-zero for a
+ * development version.  [Deprecated]
  */
-
 #define PNG_LIBPNG_VER_BUILD  0
 
 /* Release Status */
@@ -318,7 +318,7 @@
  * From version 1.0.1 it is:
  * XXYYZZ, where XX=major, YY=minor, ZZ=release
  */
-#define PNG_LIBPNG_VER 10636 /* 1.6.36 */
+#define PNG_LIBPNG_VER 10637 /* 1.6.37 */
 
 /* Library configuration: these options cannot be changed after
  * the library has been built.
@@ -330,6 +330,10 @@
 #   include "pnglibconf.h"
 #endif
 
+#define PNG_APNG_SUPPORTED
+#define PNG_READ_APNG_SUPPORTED
+#define PNG_WRITE_APNG_SUPPORTED
+
 #ifndef PNG_VERSION_INFO_ONLY
 /* Machine specific configuration. */
 #  include "pngconf.h"
@@ -425,10 +429,21 @@ extern "C" {
  * See pngconf.h for base types that vary by machine/system
  */
 
+#ifdef PNG_APNG_SUPPORTED
+/* dispose_op flags from inside fcTL */
+#define PNG_DISPOSE_OP_NONE        0x00U
+#define PNG_DISPOSE_OP_BACKGROUND  0x01U
+#define PNG_DISPOSE_OP_PREVIOUS    0x02U
+
+/* blend_op flags from inside fcTL */
+#define PNG_BLEND_OP_SOURCE        0x00U
+#define PNG_BLEND_OP_OVER          0x01U
+#endif /* PNG_APNG_SUPPORTED */
+
 /* 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_36;
+typedef char* png_libpng_version_1_6_37;
 
 /* Basic control structions.  Read libpng-manual.txt or libpng.3 for more info.
  *
@@ -746,6 +761,10 @@ typedef png_unknown_chunk * * png_unknown_chunkpp;
 #define PNG_INFO_sCAL 0x4000U  /* ESR, 1.0.6 */
 #define PNG_INFO_IDAT 0x8000U  /* ESR, 1.0.6 */
 #define PNG_INFO_eXIf 0x10000U /* GR-P, 1.6.31 */
+#ifdef PNG_APNG_SUPPORTED
+#define PNG_INFO_acTL 0x20000U
+#define PNG_INFO_fcTL 0x40000U
+#endif
 
 /* This is used for the transformation routines, as some of them
  * change these values for the row.  It also should enable using
@@ -783,6 +802,10 @@ typedef PNG_CALLBACK(void, *png_write_status_ptr, (png_structp, png_uint_32,
 #ifdef PNG_PROGRESSIVE_READ_SUPPORTED
 typedef PNG_CALLBACK(void, *png_progressive_info_ptr, (png_structp, png_infop));
 typedef PNG_CALLBACK(void, *png_progressive_end_ptr, (png_structp, png_infop));
+#ifdef PNG_APNG_SUPPORTED
+typedef PNG_CALLBACK(void, *png_progressive_frame_ptr, (png_structp,
+    png_uint_32));
+#endif
 
 /* The following callback receives png_uint_32 row_number, int pass for the
  * png_bytep data of the row.  When transforming an interlaced image the
@@ -3226,6 +3249,74 @@ PNG_EXPORT(244, int, png_set_option, (png_structrp png_ptr, int option,
 /*******************************************************************************
  *  END OF HARDWARE AND SOFTWARE OPTIONS
  ******************************************************************************/
+#ifdef PNG_APNG_SUPPORTED
+PNG_EXPORT(250, png_uint_32, png_get_acTL, (png_structp png_ptr,
+   png_infop info_ptr, png_uint_32 *num_frames, png_uint_32 *num_plays));
+
+PNG_EXPORT(251, png_uint_32, png_set_acTL, (png_structp png_ptr,
+   png_infop info_ptr, png_uint_32 num_frames, png_uint_32 num_plays));
+
+PNG_EXPORT(252, png_uint_32, png_get_num_frames, (png_structp png_ptr,
+   png_infop info_ptr));
+
+PNG_EXPORT(253, png_uint_32, png_get_num_plays, (png_structp png_ptr,
+   png_infop info_ptr));
+
+PNG_EXPORT(254, png_uint_32, png_get_next_frame_fcTL,
+   (png_structp png_ptr, png_infop info_ptr, png_uint_32 *width,
+   png_uint_32 *height, png_uint_32 *x_offset, png_uint_32 *y_offset,
+   png_uint_16 *delay_num, png_uint_16 *delay_den, png_byte *dispose_op,
+   png_byte *blend_op));
+
+PNG_EXPORT(255, png_uint_32, png_set_next_frame_fcTL,
+   (png_structp png_ptr, png_infop info_ptr, png_uint_32 width,
+   png_uint_32 height, png_uint_32 x_offset, png_uint_32 y_offset,
+   png_uint_16 delay_num, png_uint_16 delay_den, png_byte dispose_op,
+   png_byte blend_op));
+
+PNG_EXPORT(256, png_uint_32, png_get_next_frame_width,
+   (png_structp png_ptr, png_infop info_ptr));
+PNG_EXPORT(257, png_uint_32, png_get_next_frame_height,
+   (png_structp png_ptr, png_infop info_ptr));
+PNG_EXPORT(258, png_uint_32, png_get_next_frame_x_offset,
+   (png_structp png_ptr, png_infop info_ptr));
+PNG_EXPORT(259, png_uint_32, png_get_next_frame_y_offset,
+   (png_structp png_ptr, png_infop info_ptr));
+PNG_EXPORT(260, png_uint_16, png_get_next_frame_delay_num,
+   (png_structp png_ptr, png_infop info_ptr));
+PNG_EXPORT(261, png_uint_16, png_get_next_frame_delay_den,
+   (png_structp png_ptr, png_infop info_ptr));
+PNG_EXPORT(262, png_byte, png_get_next_frame_dispose_op,
+   (png_structp png_ptr, png_infop info_ptr));
+PNG_EXPORT(263, png_byte, png_get_next_frame_blend_op,
+   (png_structp png_ptr, png_infop info_ptr));
+PNG_EXPORT(264, png_byte, png_get_first_frame_is_hidden,
+   (png_structp png_ptr, png_infop info_ptr));
+PNG_EXPORT(265, png_uint_32, png_set_first_frame_is_hidden,
+   (png_structp png_ptr, png_infop info_ptr, png_byte is_hidden));
+
+#ifdef PNG_READ_APNG_SUPPORTED
+PNG_EXPORT(266, void, png_read_frame_head, (png_structp png_ptr,
+   png_infop info_ptr));
+#ifdef PNG_PROGRESSIVE_READ_SUPPORTED
+PNG_EXPORT(267, void, png_set_progressive_frame_fn, (png_structp png_ptr,
+   png_progressive_frame_ptr frame_info_fn,
+   png_progressive_frame_ptr frame_end_fn));
+#endif /* PNG_PROGRESSIVE_READ_SUPPORTED */
+#endif /* PNG_READ_APNG_SUPPORTED */
+
+#ifdef PNG_WRITE_APNG_SUPPORTED
+PNG_EXPORT(268, void, png_write_frame_head, (png_structp png_ptr,
+   png_infop info_ptr, png_bytepp row_pointers,
+   png_uint_32 width, png_uint_32 height,
+   png_uint_32 x_offset, png_uint_32 y_offset,
+   png_uint_16 delay_num, png_uint_16 delay_den, png_byte dispose_op,
+   png_byte blend_op));
+
+PNG_EXPORT(269, void, png_write_frame_tail, (png_structp png_ptr,
+   png_infop info_ptr));
+#endif /* PNG_WRITE_APNG_SUPPORTED */
+#endif /* PNG_APNG_SUPPORTED */
 
 /* Maintainer: Put new public prototypes here ^, in libpng.3, in project
  * defs, and in scripts/symbols.def.
@@ -3235,7 +3326,11 @@ PNG_EXPORT(244, int, png_set_option, (png_structrp png_ptr, int option,
  * one to use is one more than this.)
  */
 #ifdef PNG_EXPORT_LAST_ORDINAL
+#ifdef PNG_APNG_SUPPORTED
+  PNG_EXPORT_LAST_ORDINAL(269);
+#else
   PNG_EXPORT_LAST_ORDINAL(249);
+#endif /* PNG_APNG_SUPPORTED */
 #endif
 
 #ifdef __cplusplus
diff --git a/thirdparty/libpng/pngconf.h b/thirdparty/libpng/pngconf.h
index 5e641b2509..927a769dbe 100644
--- a/thirdparty/libpng/pngconf.h
+++ b/thirdparty/libpng/pngconf.h
@@ -1,9 +1,9 @@
 
-/* pngconf.h - machine configurable file for libpng
+/* pngconf.h - machine-configurable file for libpng
  *
- * libpng version 1.6.36
+ * libpng version 1.6.37
  *
- * Copyright (c) 2018 Cosmin Truta
+ * Copyright (c) 2018-2019 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2016,2018 Glenn Randers-Pehrson
  * Copyright (c) 1996-1997 Andreas Dilger
  * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
diff --git a/thirdparty/libpng/pngget.c b/thirdparty/libpng/pngget.c
index 5abf1efd9f..9ed101aedc 100644
--- a/thirdparty/libpng/pngget.c
+++ b/thirdparty/libpng/pngget.c
@@ -1246,4 +1246,166 @@ png_get_palette_max(png_const_structp png_ptr, png_const_infop info_ptr)
 #  endif
 #endif
 
+#ifdef PNG_APNG_SUPPORTED
+png_uint_32 PNGAPI
+png_get_acTL(png_structp png_ptr, png_infop info_ptr,
+             png_uint_32 *num_frames, png_uint_32 *num_plays)
+{
+    png_debug1(1, "in %s retrieval function", "acTL");
+
+    if (png_ptr != NULL && info_ptr != NULL &&
+        (info_ptr->valid & PNG_INFO_acTL) &&
+        num_frames != NULL && num_plays != NULL)
+    {
+        *num_frames = info_ptr->num_frames;
+        *num_plays = info_ptr->num_plays;
+        return (1);
+    }
+
+    return (0);
+}
+
+png_uint_32 PNGAPI
+png_get_num_frames(png_structp png_ptr, png_infop info_ptr)
+{
+    png_debug(1, "in png_get_num_frames()");
+
+    if (png_ptr != NULL && info_ptr != NULL)
+        return (info_ptr->num_frames);
+    return (0);
+}
+
+png_uint_32 PNGAPI
+png_get_num_plays(png_structp png_ptr, png_infop info_ptr)
+{
+    png_debug(1, "in png_get_num_plays()");
+
+    if (png_ptr != NULL && info_ptr != NULL)
+        return (info_ptr->num_plays);
+    return (0);
+}
+
+png_uint_32 PNGAPI
+png_get_next_frame_fcTL(png_structp png_ptr, png_infop info_ptr,
+             png_uint_32 *width, png_uint_32 *height,
+             png_uint_32 *x_offset, png_uint_32 *y_offset,
+             png_uint_16 *delay_num, png_uint_16 *delay_den,
+             png_byte *dispose_op, png_byte *blend_op)
+{
+    png_debug1(1, "in %s retrieval function", "fcTL");
+
+    if (png_ptr != NULL && info_ptr != NULL &&
+        (info_ptr->valid & PNG_INFO_fcTL) &&
+        width != NULL && height != NULL &&
+        x_offset != NULL && y_offset != NULL &&
+        delay_num != NULL && delay_den != NULL &&
+        dispose_op != NULL && blend_op != NULL)
+    {
+        *width = info_ptr->next_frame_width;
+        *height = info_ptr->next_frame_height;
+        *x_offset = info_ptr->next_frame_x_offset;
+        *y_offset = info_ptr->next_frame_y_offset;
+        *delay_num = info_ptr->next_frame_delay_num;
+        *delay_den = info_ptr->next_frame_delay_den;
+        *dispose_op = info_ptr->next_frame_dispose_op;
+        *blend_op = info_ptr->next_frame_blend_op;
+        return (1);
+    }
+
+    return (0);
+}
+
+png_uint_32 PNGAPI
+png_get_next_frame_width(png_structp png_ptr, png_infop info_ptr)
+{
+    png_debug(1, "in png_get_next_frame_width()");
+
+    if (png_ptr != NULL && info_ptr != NULL)
+        return (info_ptr->next_frame_width);
+    return (0);
+}
+
+png_uint_32 PNGAPI
+png_get_next_frame_height(png_structp png_ptr, png_infop info_ptr)
+{
+    png_debug(1, "in png_get_next_frame_height()");
+
+    if (png_ptr != NULL && info_ptr != NULL)
+        return (info_ptr->next_frame_height);
+    return (0);
+}
+
+png_uint_32 PNGAPI
+png_get_next_frame_x_offset(png_structp png_ptr, png_infop info_ptr)
+{
+    png_debug(1, "in png_get_next_frame_x_offset()");
+
+    if (png_ptr != NULL && info_ptr != NULL)
+        return (info_ptr->next_frame_x_offset);
+    return (0);
+}
+
+png_uint_32 PNGAPI
+png_get_next_frame_y_offset(png_structp png_ptr, png_infop info_ptr)
+{
+    png_debug(1, "in png_get_next_frame_y_offset()");
+
+    if (png_ptr != NULL && info_ptr != NULL)
+        return (info_ptr->next_frame_y_offset);
+    return (0);
+}
+
+png_uint_16 PNGAPI
+png_get_next_frame_delay_num(png_structp png_ptr, png_infop info_ptr)
+{
+    png_debug(1, "in png_get_next_frame_delay_num()");
+
+    if (png_ptr != NULL && info_ptr != NULL)
+        return (info_ptr->next_frame_delay_num);
+    return (0);
+}
+
+png_uint_16 PNGAPI
+png_get_next_frame_delay_den(png_structp png_ptr, png_infop info_ptr)
+{
+    png_debug(1, "in png_get_next_frame_delay_den()");
+
+    if (png_ptr != NULL && info_ptr != NULL)
+        return (info_ptr->next_frame_delay_den);
+    return (0);
+}
+
+png_byte PNGAPI
+png_get_next_frame_dispose_op(png_structp png_ptr, png_infop info_ptr)
+{
+    png_debug(1, "in png_get_next_frame_dispose_op()");
+
+    if (png_ptr != NULL && info_ptr != NULL)
+        return (info_ptr->next_frame_dispose_op);
+    return (0);
+}
+
+png_byte PNGAPI
+png_get_next_frame_blend_op(png_structp png_ptr, png_infop info_ptr)
+{
+    png_debug(1, "in png_get_next_frame_blend_op()");
+
+    if (png_ptr != NULL && info_ptr != NULL)
+        return (info_ptr->next_frame_blend_op);
+    return (0);
+}
+
+png_byte PNGAPI
+png_get_first_frame_is_hidden(png_structp png_ptr, png_infop info_ptr)
+{
+    png_debug(1, "in png_first_frame_is_hidden()");
+
+    if (png_ptr != NULL)
+       return (png_byte)(png_ptr->apng_flags & PNG_FIRST_FRAME_HIDDEN);
+
+    PNG_UNUSED(info_ptr)
+
+    return 0;
+}
+#endif /* PNG_APNG_SUPPORTED */
 #endif /* READ || WRITE */
diff --git a/thirdparty/libpng/pnginfo.h b/thirdparty/libpng/pnginfo.h
index 1f98dedc42..ac7b269132 100644
--- a/thirdparty/libpng/pnginfo.h
+++ b/thirdparty/libpng/pnginfo.h
@@ -263,5 +263,18 @@ defined(PNG_READ_BACKGROUND_SUPPORTED)
    png_bytepp row_pointers;        /* the image bits */
 #endif
 
+#ifdef PNG_APNG_SUPPORTED
+   png_uint_32 num_frames; /* including default image */
+   png_uint_32 num_plays;
+   png_uint_32 next_frame_width;
+   png_uint_32 next_frame_height;
+   png_uint_32 next_frame_x_offset;
+   png_uint_32 next_frame_y_offset;
+   png_uint_16 next_frame_delay_num;
+   png_uint_16 next_frame_delay_den;
+   png_byte next_frame_dispose_op;
+   png_byte next_frame_blend_op;
+#endif
+
 };
 #endif /* PNGINFO_H */
diff --git a/thirdparty/libpng/pnglibconf.h b/thirdparty/libpng/pnglibconf.h
index 00340c678b..e1e27e957e 100644
--- a/thirdparty/libpng/pnglibconf.h
+++ b/thirdparty/libpng/pnglibconf.h
@@ -1,8 +1,8 @@
 /* pnglibconf.h - library build configuration */
 
-/* libpng version 1.6.36 */
+/* libpng version 1.6.37 */
 
-/* Copyright (c) 2018 Cosmin Truta */
+/* Copyright (c) 2018-2019 Cosmin Truta */
 /* Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson */
 
 /* This code is released under the libpng license. */
diff --git a/thirdparty/libpng/pngpread.c b/thirdparty/libpng/pngpread.c
index e283627b77..2eaeca08f7 100644
--- a/thirdparty/libpng/pngpread.c
+++ b/thirdparty/libpng/pngpread.c
@@ -195,6 +195,106 @@ png_push_read_chunk(png_structrp png_ptr, png_inforp info_ptr)
 
    chunk_name = png_ptr->chunk_name;
 
+#ifdef PNG_READ_APNG_SUPPORTED
+   if (png_ptr->num_frames_read > 0 &&
+       png_ptr->num_frames_read < info_ptr->num_frames)
+   {
+      if (chunk_name == png_IDAT)
+      {
+         /* Discard trailing IDATs for the first frame */
+         if (png_ptr->mode & PNG_HAVE_fcTL || png_ptr->num_frames_read > 1)
+            png_error(png_ptr, "out of place IDAT");
+
+         if (png_ptr->push_length + 4 > png_ptr->buffer_size)
+         {
+            png_push_save_buffer(png_ptr);
+            return;
+         }
+
+         png_ptr->mode &= ~PNG_HAVE_CHUNK_HEADER;
+         return;
+      }
+      else if (chunk_name == png_fdAT)
+      {
+         if (png_ptr->buffer_size < 4)
+         {
+            png_push_save_buffer(png_ptr);
+            return;
+         }
+
+         png_ensure_sequence_number(png_ptr, 4);
+
+         if (!(png_ptr->mode & PNG_HAVE_fcTL))
+         {
+            /* Discard trailing fdATs for frames other than the first */
+            if (png_ptr->num_frames_read < 2)
+               png_error(png_ptr, "out of place fdAT");
+
+            if (png_ptr->push_length + 4 > png_ptr->buffer_size)
+            {
+               png_push_save_buffer(png_ptr);
+               return;
+            }
+
+            png_ptr->mode &= ~PNG_HAVE_CHUNK_HEADER;
+            return;
+         }
+
+         else
+         {
+            /* frame data follows */
+            png_ptr->idat_size = png_ptr->push_length - 4;
+            png_ptr->mode |= PNG_HAVE_IDAT;
+            png_ptr->process_mode = PNG_READ_IDAT_MODE;
+
+            return;
+         }
+      }
+
+      else if (chunk_name == png_fcTL)
+      {
+         if (png_ptr->push_length + 4 > png_ptr->buffer_size)
+         {
+            png_push_save_buffer(png_ptr);
+            return;
+         }
+
+         png_read_reset(png_ptr);
+         png_ptr->mode &= ~PNG_HAVE_fcTL;
+
+         png_handle_fcTL(png_ptr, info_ptr, png_ptr->push_length);
+
+         if (!(png_ptr->mode & PNG_HAVE_fcTL))
+            png_error(png_ptr, "missing required fcTL chunk");
+
+         png_read_reinit(png_ptr, info_ptr);
+         png_progressive_read_reset(png_ptr);
+
+         if (png_ptr->frame_info_fn != NULL)
+            (*(png_ptr->frame_info_fn))(png_ptr, png_ptr->num_frames_read);
+
+         png_ptr->mode &= ~PNG_HAVE_CHUNK_HEADER;
+
+         return;
+      }
+
+      else
+      {
+         if (png_ptr->push_length + 4 > png_ptr->buffer_size)
+         {
+            png_push_save_buffer(png_ptr);
+            return;
+         }
+         png_warning(png_ptr, "Skipped (ignored) a chunk "
+                              "between APNG chunks");
+         png_ptr->mode &= ~PNG_HAVE_CHUNK_HEADER;
+         return;
+      }
+
+      return;
+   }
+#endif /* PNG_READ_APNG_SUPPORTED */
+
    if (chunk_name == png_IDAT)
    {
       if ((png_ptr->mode & PNG_AFTER_IDAT) != 0)
@@ -261,6 +361,9 @@ png_push_read_chunk(png_structrp png_ptr, png_inforp info_ptr)
 
    else if (chunk_name == png_IDAT)
    {
+#ifdef PNG_READ_APNG_SUPPORTED
+      png_have_info(png_ptr, info_ptr);
+#endif
       png_ptr->idat_size = png_ptr->push_length;
       png_ptr->process_mode = PNG_READ_IDAT_MODE;
       png_push_have_info(png_ptr, info_ptr);
@@ -406,6 +509,30 @@ png_push_read_chunk(png_structrp png_ptr, png_inforp info_ptr)
       png_handle_iTXt(png_ptr, info_ptr, png_ptr->push_length);
    }
 #endif
+#ifdef PNG_READ_APNG_SUPPORTED
+   else if (chunk_name == png_acTL)
+   {
+      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
+      {
+         png_push_save_buffer(png_ptr);
+         return;
+      }
+
+      png_handle_acTL(png_ptr, info_ptr, png_ptr->push_length);
+   }
+
+   else if (chunk_name == png_fcTL)
+   {
+      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
+      {
+         png_push_save_buffer(png_ptr);
+         return;
+      }
+
+      png_handle_fcTL(png_ptr, info_ptr, png_ptr->push_length);
+   }
+
+#endif /* PNG_READ_APNG_SUPPORTED */
 
    else
    {
@@ -539,7 +666,11 @@ png_push_read_IDAT(png_structrp png_ptr)
       png_byte chunk_tag[4];
 
       /* TODO: this code can be commoned up with the same code in push_read */
+#ifdef PNG_READ_APNG_SUPPORTED
+      PNG_PUSH_SAVE_BUFFER_IF_LT(12)
+#else
       PNG_PUSH_SAVE_BUFFER_IF_LT(8)
+#endif
       png_push_fill_buffer(png_ptr, chunk_length, 4);
       png_ptr->push_length = png_get_uint_31(png_ptr, chunk_length);
       png_reset_crc(png_ptr);
@@ -547,17 +678,64 @@ png_push_read_IDAT(png_structrp png_ptr)
       png_ptr->chunk_name = PNG_CHUNK_FROM_STRING(chunk_tag);
       png_ptr->mode |= PNG_HAVE_CHUNK_HEADER;
 
+#ifdef PNG_READ_APNG_SUPPORTED
+      if (png_ptr->chunk_name != png_fdAT && png_ptr->num_frames_read > 0)
+      {
+          if (png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED)
+          {
+              png_ptr->process_mode = PNG_READ_CHUNK_MODE;
+              if (png_ptr->frame_end_fn != NULL)
+                 (*(png_ptr->frame_end_fn))(png_ptr, png_ptr->num_frames_read);
+              png_ptr->num_frames_read++;
+              return;
+          }
+          else
+          {
+              if (png_ptr->chunk_name == png_IEND)
+                  png_error(png_ptr, "Not enough image data");
+              if (png_ptr->push_length + 4 > png_ptr->buffer_size)
+              {
+                 png_push_save_buffer(png_ptr);
+                 return;
+              }
+              png_warning(png_ptr, "Skipping (ignoring) a chunk between "
+                                   "APNG chunks");
+              png_crc_finish(png_ptr, png_ptr->push_length);
+              png_ptr->mode &= ~PNG_HAVE_CHUNK_HEADER;
+              return;
+          }
+      }
+      else
+#endif
+#ifdef PNG_READ_APNG_SUPPORTED
+      if (png_ptr->chunk_name != png_IDAT && png_ptr->num_frames_read == 0)
+#else
       if (png_ptr->chunk_name != png_IDAT)
+#endif
       {
          png_ptr->process_mode = PNG_READ_CHUNK_MODE;
 
          if ((png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED) == 0)
             png_error(png_ptr, "Not enough compressed data");
 
+#ifdef PNG_READ_APNG_SUPPORTED
+         if (png_ptr->frame_end_fn != NULL)
+            (*(png_ptr->frame_end_fn))(png_ptr, png_ptr->num_frames_read);
+         png_ptr->num_frames_read++;
+#endif
+
          return;
       }
 
       png_ptr->idat_size = png_ptr->push_length;
+
+#ifdef PNG_READ_APNG_SUPPORTED
+      if (png_ptr->num_frames_read > 0)
+      {
+         png_ensure_sequence_number(png_ptr, 4);
+         png_ptr->idat_size -= 4;
+      }
+#endif
    }
 
    if (png_ptr->idat_size != 0 && png_ptr->save_buffer_size != 0)
@@ -631,6 +809,15 @@ png_process_IDAT_data(png_structrp png_ptr, png_bytep buffer,
    if (!(buffer_length > 0) || buffer == NULL)
       png_error(png_ptr, "No IDAT data (internal error)");
 
+#ifdef PNG_READ_APNG_SUPPORTED
+   /* If the app is not APNG-aware, decode only the first frame */
+   if (!(png_ptr->apng_flags & PNG_APNG_APP) && png_ptr->num_frames_read > 0)
+   {
+     png_ptr->flags |= PNG_FLAG_ZSTREAM_ENDED;
+     return;
+   }
+#endif
+
    /* This routine must process all the data it has been given
     * before returning, calling the row callback as required to
     * handle the uncompressed results.
@@ -1085,6 +1272,18 @@ png_set_progressive_read_fn(png_structrp png_ptr, png_voidp progressive_ptr,
    png_set_read_fn(png_ptr, progressive_ptr, png_push_fill_buffer);
 }
 
+#ifdef PNG_READ_APNG_SUPPORTED
+void PNGAPI
+png_set_progressive_frame_fn(png_structp png_ptr,
+   png_progressive_frame_ptr frame_info_fn,
+   png_progressive_frame_ptr frame_end_fn)
+{
+   png_ptr->frame_info_fn = frame_info_fn;
+   png_ptr->frame_end_fn = frame_end_fn;
+   png_ptr->apng_flags |= PNG_APNG_APP;
+}
+#endif
+
 png_voidp PNGAPI
 png_get_progressive_ptr(png_const_structrp png_ptr)
 {
diff --git a/thirdparty/libpng/pngpriv.h b/thirdparty/libpng/pngpriv.h
index 973c3eac1f..57e1bf989b 100644
--- a/thirdparty/libpng/pngpriv.h
+++ b/thirdparty/libpng/pngpriv.h
@@ -1,7 +1,7 @@
 
 /* pngpriv.h - private declarations for use inside libpng
  *
- * Copyright (c) 2018 Cosmin Truta
+ * Copyright (c) 2018-2019 Cosmin Truta
  * 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.
@@ -637,6 +637,10 @@
 #define PNG_HAVE_CHUNK_AFTER_IDAT 0x2000U /* Have another chunk after IDAT */
                    /*             0x4000U (unused) */
 #define PNG_IS_READ_STRUCT        0x8000U /* Else is a write struct */
+#ifdef PNG_APNG_SUPPORTED
+#define PNG_HAVE_acTL            0x10000U
+#define PNG_HAVE_fcTL            0x20000U
+#endif
 
 /* Flags for the transformations the PNG library does on the image data */
 #define PNG_BGR                 0x0001U
@@ -873,6 +877,16 @@
 #define png_tRNS PNG_U32(116,  82,  78,  83)
 #define png_zTXt PNG_U32(122,  84,  88, 116)
 
+#ifdef PNG_APNG_SUPPORTED
+#define png_acTL PNG_U32( 97,  99,  84,  76)
+#define png_fcTL PNG_U32(102,  99,  84,  76)
+#define png_fdAT PNG_U32(102, 100,  65,  84)
+
+/* For png_struct.apng_flags: */
+#define PNG_FIRST_FRAME_HIDDEN       0x0001U
+#define PNG_APNG_APP                 0x0002U
+#endif
+
 /* The following will work on (signed char*) strings, whereas the get_uint_32
  * macro will fail on top-bit-set values because of the sign extension.
  */
@@ -1644,6 +1658,47 @@ PNG_INTERNAL_FUNCTION(void,png_colorspace_sync,(png_const_structrp png_ptr,
     */
 #endif
 
+#ifdef PNG_APNG_SUPPORTED
+PNG_INTERNAL_FUNCTION(void,png_ensure_fcTL_is_valid,(png_structp png_ptr,
+   png_uint_32 width, png_uint_32 height,
+   png_uint_32 x_offset, png_uint_32 y_offset,
+   png_uint_16 delay_num, png_uint_16 delay_den,
+   png_byte dispose_op, png_byte blend_op), PNG_EMPTY);
+
+#ifdef PNG_READ_APNG_SUPPORTED
+PNG_INTERNAL_FUNCTION(void,png_handle_acTL,(png_structp png_ptr, png_infop info_ptr,
+   png_uint_32 length),PNG_EMPTY);
+PNG_INTERNAL_FUNCTION(void,png_handle_fcTL,(png_structp png_ptr, png_infop info_ptr,
+   png_uint_32 length),PNG_EMPTY);
+PNG_INTERNAL_FUNCTION(void,png_handle_fdAT,(png_structp png_ptr, png_infop info_ptr,
+   png_uint_32 length),PNG_EMPTY);
+PNG_INTERNAL_FUNCTION(void,png_have_info,(png_structp png_ptr, png_infop info_ptr),PNG_EMPTY);
+PNG_INTERNAL_FUNCTION(void,png_ensure_sequence_number,(png_structp png_ptr,
+   png_uint_32 length),PNG_EMPTY);
+PNG_INTERNAL_FUNCTION(void,png_read_reset,(png_structp png_ptr),PNG_EMPTY);
+PNG_INTERNAL_FUNCTION(void,png_read_reinit,(png_structp png_ptr,
+   png_infop info_ptr),PNG_EMPTY);
+#ifdef PNG_PROGRESSIVE_READ_SUPPORTED
+PNG_INTERNAL_FUNCTION(void,png_progressive_read_reset,(png_structp png_ptr),PNG_EMPTY);
+#endif /* PNG_PROGRESSIVE_READ_SUPPORTED */
+#endif /* PNG_READ_APNG_SUPPORTED */
+
+#ifdef PNG_WRITE_APNG_SUPPORTED
+PNG_INTERNAL_FUNCTION(void,png_write_acTL,(png_structp png_ptr,
+   png_uint_32 num_frames, png_uint_32 num_plays),PNG_EMPTY);
+PNG_INTERNAL_FUNCTION(void,png_write_fcTL,(png_structp png_ptr,
+   png_uint_32 width, png_uint_32 height,
+   png_uint_32 x_offset, png_uint_32 y_offset,
+   png_uint_16 delay_num, png_uint_16 delay_den,
+   png_byte dispose_op, png_byte blend_op),PNG_EMPTY);
+PNG_INTERNAL_FUNCTION(void,png_write_fdAT,(png_structp png_ptr,
+   png_const_bytep data, png_size_t length),PNG_EMPTY);
+PNG_INTERNAL_FUNCTION(void,png_write_reset,(png_structp png_ptr),PNG_EMPTY);
+PNG_INTERNAL_FUNCTION(void,png_write_reinit,(png_structp png_ptr,
+   png_infop info_ptr, png_uint_32 width, png_uint_32 height),PNG_EMPTY);
+#endif /* PNG_WRITE_APNG_SUPPORTED */
+#endif /* PNG_APNG_SUPPORTED */
+
 /* Added at libpng version 1.4.0 */
 #ifdef PNG_COLORSPACE_SUPPORTED
 /* These internal functions are for maintaining the colorspace structure within
@@ -2119,11 +2174,11 @@ PNG_INTERNAL_FUNCTION(png_uint_32, png_check_keyword, (png_structrp png_ptr,
 
 #if PNG_ARM_NEON_IMPLEMENTATION == 1
 PNG_INTERNAL_FUNCTION(void,
-                      png_riffle_palette_rgba,
-                      (png_structrp, png_row_infop),
+                      png_riffle_palette_neon,
+                      (png_structrp),
                       PNG_EMPTY);
 PNG_INTERNAL_FUNCTION(int,
-                      png_do_expand_palette_neon_rgba,
+                      png_do_expand_palette_rgba8_neon,
                       (png_structrp,
                        png_row_infop,
                        png_const_bytep,
@@ -2131,7 +2186,7 @@ PNG_INTERNAL_FUNCTION(int,
                        const png_bytepp),
                       PNG_EMPTY);
 PNG_INTERNAL_FUNCTION(int,
-                      png_do_expand_palette_neon_rgb,
+                      png_do_expand_palette_rgb8_neon,
                       (png_structrp,
                        png_row_infop,
                        png_const_bytep,
diff --git a/thirdparty/libpng/pngread.c b/thirdparty/libpng/pngread.c
index f8e762196e..fa44d5a8e4 100644
--- a/thirdparty/libpng/pngread.c
+++ b/thirdparty/libpng/pngread.c
@@ -1,7 +1,7 @@
 
 /* pngread.c - read a PNG file
  *
- * Copyright (c) 2018 Cosmin Truta
+ * Copyright (c) 2018-2019 Cosmin Truta
  * 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.
@@ -161,6 +161,9 @@ png_read_info(png_structrp png_ptr, png_inforp info_ptr)
 
       else if (chunk_name == png_IDAT)
       {
+#ifdef PNG_READ_APNG_SUPPORTED
+         png_have_info(png_ptr, info_ptr);
+#endif
          png_ptr->idat_size = length;
          break;
       }
@@ -255,6 +258,17 @@ png_read_info(png_structrp png_ptr, png_inforp info_ptr)
          png_handle_iTXt(png_ptr, info_ptr, length);
 #endif
 
+#ifdef PNG_READ_APNG_SUPPORTED
+      else if (chunk_name == png_acTL)
+         png_handle_acTL(png_ptr, info_ptr, length);
+
+      else if (chunk_name == png_fcTL)
+         png_handle_fcTL(png_ptr, info_ptr, length);
+
+      else if (chunk_name == png_fdAT)
+         png_handle_fdAT(png_ptr, info_ptr, length);
+#endif
+
       else
          png_handle_unknown(png_ptr, info_ptr, length,
              PNG_HANDLE_CHUNK_AS_DEFAULT);
@@ -262,6 +276,72 @@ png_read_info(png_structrp png_ptr, png_inforp info_ptr)
 }
 #endif /* SEQUENTIAL_READ */
 
+#ifdef PNG_READ_APNG_SUPPORTED
+void PNGAPI
+png_read_frame_head(png_structp png_ptr, png_infop info_ptr)
+{
+    png_byte have_chunk_after_DAT; /* after IDAT or after fdAT */
+
+    png_debug(0, "Reading frame head");
+
+    if (!(png_ptr->mode & PNG_HAVE_acTL))
+        png_error(png_ptr, "attempt to png_read_frame_head() but "
+                           "no acTL present");
+
+    /* do nothing for the main IDAT */
+    if (png_ptr->num_frames_read == 0)
+        return;
+
+    png_read_reset(png_ptr);
+    png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
+    png_ptr->mode &= ~PNG_HAVE_fcTL;
+
+    have_chunk_after_DAT = 0;
+    for (;;)
+    {
+        png_uint_32 length = png_read_chunk_header(png_ptr);
+
+        if (png_ptr->chunk_name == png_IDAT)
+        {
+            /* discard trailing IDATs for the first frame */
+            if (have_chunk_after_DAT || png_ptr->num_frames_read > 1)
+                png_error(png_ptr, "png_read_frame_head(): out of place IDAT");
+            png_crc_finish(png_ptr, length);
+        }
+
+        else if (png_ptr->chunk_name == png_fcTL)
+        {
+            png_handle_fcTL(png_ptr, info_ptr, length);
+            have_chunk_after_DAT = 1;
+        }
+
+        else if (png_ptr->chunk_name == png_fdAT)
+        {
+            png_ensure_sequence_number(png_ptr, length);
+
+            /* discard trailing fdATs for frames other than the first */
+            if (!have_chunk_after_DAT && png_ptr->num_frames_read > 1)
+                png_crc_finish(png_ptr, length - 4);
+            else if(png_ptr->mode & PNG_HAVE_fcTL)
+            {
+                png_ptr->idat_size = length - 4;
+                png_ptr->mode |= PNG_HAVE_IDAT;
+
+                break;
+            }
+            else
+                png_error(png_ptr, "png_read_frame_head(): out of place fdAT");
+        }
+        else
+        {
+            png_warning(png_ptr, "Skipped (ignored) a chunk "
+                                 "between APNG chunks");
+            png_crc_finish(png_ptr, length);
+        }
+    }
+}
+#endif /* PNG_READ_APNG_SUPPORTED */
+
 /* Optional call to update the users info_ptr structure */
 void PNGAPI
 png_read_update_info(png_structrp png_ptr, png_inforp info_ptr)
@@ -994,6 +1074,12 @@ png_read_destroy(png_structrp png_ptr)
    png_ptr->chunk_list = NULL;
 #endif
 
+#if defined(PNG_READ_EXPAND_SUPPORTED) && \
+    defined(PNG_ARM_NEON_IMPLEMENTATION)
+   png_free(png_ptr, png_ptr->riffled_palette);
+   png_ptr->riffled_palette = NULL;
+#endif
+
    /* NOTE: the 'setjmp' buffer may still be allocated and the memory and error
     * callbacks are still set at this point.  They are required to complete the
     * destruction of the png_struct itself.
diff --git a/thirdparty/libpng/pngrtran.c b/thirdparty/libpng/pngrtran.c
index ccc58ce6f1..9a8fad9f4a 100644
--- a/thirdparty/libpng/pngrtran.c
+++ b/thirdparty/libpng/pngrtran.c
@@ -1,7 +1,7 @@
 
 /* pngrtran.c - transforms the data in a row for PNG readers
  *
- * Copyright (c) 2018 Cosmin Truta
+ * Copyright (c) 2018-2019 Cosmin Truta
  * 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.
@@ -1182,20 +1182,20 @@ png_init_palette_transformations(png_structrp png_ptr)
              png_ptr->palette[png_ptr->background.index].blue;
 
 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
-        if ((png_ptr->transformations & PNG_INVERT_ALPHA) != 0)
-        {
-           if ((png_ptr->transformations & PNG_EXPAND_tRNS) == 0)
-           {
-              /* Invert the alpha channel (in tRNS) unless the pixels are
-               * going to be expanded, in which case leave it for later
-               */
-              int i, istop = png_ptr->num_trans;
-
-              for (i=0; i<istop; i++)
-                 png_ptr->trans_alpha[i] = (png_byte)(255 -
-                    png_ptr->trans_alpha[i]);
-           }
-        }
+         if ((png_ptr->transformations & PNG_INVERT_ALPHA) != 0)
+         {
+            if ((png_ptr->transformations & PNG_EXPAND_tRNS) == 0)
+            {
+               /* Invert the alpha channel (in tRNS) unless the pixels are
+                * going to be expanded, in which case leave it for later
+                */
+               int i, istop = png_ptr->num_trans;
+
+               for (i = 0; i < istop; i++)
+                  png_ptr->trans_alpha[i] =
+                      (png_byte)(255 - png_ptr->trans_alpha[i]);
+            }
+         }
 #endif /* READ_INVERT_ALPHA */
       }
    } /* background expand and (therefore) no alpha association. */
@@ -4320,9 +4320,11 @@ png_do_expand_palette(png_structrp png_ptr, png_row_infop row_info,
                    * 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,
+                  i = png_do_expand_palette_rgba8_neon(png_ptr, row_info, row,
                       &sp, &dp);
                }
+#else
+               PNG_UNUSED(png_ptr)
 #endif
 
                for (; i < row_width; i++)
@@ -4349,8 +4351,10 @@ png_do_expand_palette(png_structrp png_ptr, png_row_infop row_info,
                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,
+               i = png_do_expand_palette_rgb8_neon(png_ptr, row_info, row,
                    &sp, &dp);
+#else
+               PNG_UNUSED(png_ptr)
 #endif
 
                for (; i < row_width; i++)
@@ -4770,19 +4774,17 @@ png_do_read_transformations(png_structrp png_ptr, png_row_infop row_info)
 #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);
+               /* Initialize the accelerated palette expansion. */
+               png_ptr->riffled_palette =
+                   (png_bytep)png_malloc(png_ptr, 256 * 4);
+               png_riffle_palette_neon(png_ptr);
             }
          }
 #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);
+             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 d5fa08c397..ae66a48a83 100644
--- a/thirdparty/libpng/pngrutil.c
+++ b/thirdparty/libpng/pngrutil.c
@@ -865,6 +865,11 @@ png_handle_IHDR(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
    filter_type = buf[11];
    interlace_type = buf[12];
 
+#ifdef PNG_READ_APNG_SUPPORTED
+   png_ptr->first_frame_width = width;
+   png_ptr->first_frame_height = height;
+#endif
+
    /* Set internal variables */
    png_ptr->width = width;
    png_ptr->height = height;
@@ -2857,6 +2862,179 @@ png_handle_iTXt(png_structrp png_ptr, png_inforp info_ptr, png_uint_32 length)
 }
 #endif
 
+#ifdef PNG_READ_APNG_SUPPORTED
+void /* PRIVATE */
+png_handle_acTL(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
+{
+    png_byte data[8];
+    png_uint_32 num_frames;
+    png_uint_32 num_plays;
+    png_uint_32 didSet;
+
+    png_debug(1, "in png_handle_acTL");
+
+    if (!(png_ptr->mode & PNG_HAVE_IHDR))
+    {
+        png_error(png_ptr, "Missing IHDR before acTL");
+    }
+    else if (png_ptr->mode & PNG_HAVE_IDAT)
+    {
+        png_warning(png_ptr, "Invalid acTL after IDAT skipped");
+        png_crc_finish(png_ptr, length);
+        return;
+    }
+    else if (png_ptr->mode & PNG_HAVE_acTL)
+    {
+        png_warning(png_ptr, "Duplicate acTL skipped");
+        png_crc_finish(png_ptr, length);
+        return;
+    }
+    else if (length != 8)
+    {
+        png_warning(png_ptr, "acTL with invalid length skipped");
+        png_crc_finish(png_ptr, length);
+        return;
+    }
+
+    png_crc_read(png_ptr, data, 8);
+    png_crc_finish(png_ptr, 0);
+
+    num_frames = png_get_uint_31(png_ptr, data);
+    num_plays = png_get_uint_31(png_ptr, data + 4);
+
+    /* the set function will do error checking on num_frames */
+    didSet = png_set_acTL(png_ptr, info_ptr, num_frames, num_plays);
+    if(didSet)
+        png_ptr->mode |= PNG_HAVE_acTL;
+}
+
+void /* PRIVATE */
+png_handle_fcTL(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
+{
+    png_byte data[22];
+    png_uint_32 width;
+    png_uint_32 height;
+    png_uint_32 x_offset;
+    png_uint_32 y_offset;
+    png_uint_16 delay_num;
+    png_uint_16 delay_den;
+    png_byte dispose_op;
+    png_byte blend_op;
+
+    png_debug(1, "in png_handle_fcTL");
+
+    png_ensure_sequence_number(png_ptr, length);
+
+    if (!(png_ptr->mode & PNG_HAVE_IHDR))
+    {
+        png_error(png_ptr, "Missing IHDR before fcTL");
+    }
+    else if (png_ptr->mode & PNG_HAVE_IDAT)
+    {
+        /* for any frames other then the first this message may be misleading,
+        * but correct. PNG_HAVE_IDAT is unset before the frame head is read
+        * i can't think of a better message */
+        png_warning(png_ptr, "Invalid fcTL after IDAT skipped");
+        png_crc_finish(png_ptr, length-4);
+        return;
+    }
+    else if (png_ptr->mode & PNG_HAVE_fcTL)
+    {
+        png_warning(png_ptr, "Duplicate fcTL within one frame skipped");
+        png_crc_finish(png_ptr, length-4);
+        return;
+    }
+    else if (length != 26)
+    {
+        png_warning(png_ptr, "fcTL with invalid length skipped");
+        png_crc_finish(png_ptr, length-4);
+        return;
+    }
+
+    png_crc_read(png_ptr, data, 22);
+    png_crc_finish(png_ptr, 0);
+
+    width = png_get_uint_31(png_ptr, data);
+    height = png_get_uint_31(png_ptr, data + 4);
+    x_offset = png_get_uint_31(png_ptr, data + 8);
+    y_offset = png_get_uint_31(png_ptr, data + 12);
+    delay_num = png_get_uint_16(data + 16);
+    delay_den = png_get_uint_16(data + 18);
+    dispose_op = data[20];
+    blend_op = data[21];
+
+    if (png_ptr->num_frames_read == 0 && (x_offset != 0 || y_offset != 0))
+    {
+        png_warning(png_ptr, "fcTL for the first frame must have zero offset");
+        return;
+    }
+
+    if (info_ptr != NULL)
+    {
+        if (png_ptr->num_frames_read == 0 &&
+            (width != info_ptr->width || height != info_ptr->height))
+        {
+            png_warning(png_ptr, "size in first frame's fcTL must match "
+                               "the size in IHDR");
+            return;
+        }
+
+        /* The set function will do more error checking */
+        png_set_next_frame_fcTL(png_ptr, info_ptr, width, height,
+                                x_offset, y_offset, delay_num, delay_den,
+                                dispose_op, blend_op);
+
+        png_read_reinit(png_ptr, info_ptr);
+
+        png_ptr->mode |= PNG_HAVE_fcTL;
+    }
+}
+
+void /* PRIVATE */
+png_have_info(png_structp png_ptr, png_infop info_ptr)
+{
+    if((info_ptr->valid & PNG_INFO_acTL) && !(info_ptr->valid & PNG_INFO_fcTL))
+    {
+        png_ptr->apng_flags |= PNG_FIRST_FRAME_HIDDEN;
+        info_ptr->num_frames++;
+    }
+}
+
+void /* PRIVATE */
+png_handle_fdAT(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
+{
+    png_ensure_sequence_number(png_ptr, length);
+
+    /* This function is only called from png_read_end(), png_read_info(),
+    * and png_push_read_chunk() which means that:
+    * - the user doesn't want to read this frame
+    * - or this is an out-of-place fdAT
+    * in either case it is safe to ignore the chunk with a warning */
+    png_warning(png_ptr, "ignoring fdAT chunk");
+    png_crc_finish(png_ptr, length - 4);
+    PNG_UNUSED(info_ptr)
+}
+
+void /* PRIVATE */
+png_ensure_sequence_number(png_structp png_ptr, png_uint_32 length)
+{
+    png_byte data[4];
+    png_uint_32 sequence_number;
+
+    if (length < 4)
+        png_error(png_ptr, "invalid fcTL or fdAT chunk found");
+
+    png_crc_read(png_ptr, data, 4);
+    sequence_number = png_get_uint_31(png_ptr, data);
+
+    if (sequence_number != png_ptr->next_seq_num)
+        png_error(png_ptr, "fcTL or fdAT chunk with out-of-order sequence "
+                           "number found");
+
+    png_ptr->next_seq_num++;
+}
+#endif /* PNG_READ_APNG_SUPPORTED */
+
 #ifdef PNG_READ_UNKNOWN_CHUNKS_SUPPORTED
 /* Utility function for png_handle_unknown; set up png_ptr::unknown_chunk */
 static int
@@ -4165,7 +4343,38 @@ png_read_IDAT_data(png_structrp png_ptr, png_bytep output,
       {
          uInt avail_in;
          png_bytep buffer;
+#ifdef PNG_READ_APNG_SUPPORTED
+         png_uint_32 bytes_to_skip = 0;
+
+         while (png_ptr->idat_size == 0 || bytes_to_skip != 0)
+         {
+            png_crc_finish(png_ptr, bytes_to_skip);
+            bytes_to_skip = 0;
+
+            png_ptr->idat_size = png_read_chunk_header(png_ptr);
+            if (png_ptr->num_frames_read == 0)
+            {
+               if (png_ptr->chunk_name != png_IDAT)
+                  png_error(png_ptr, "Not enough image data");
+            }
+            else
+            {
+               if (png_ptr->chunk_name == png_IEND)
+                  png_error(png_ptr, "Not enough image data");
+               if (png_ptr->chunk_name != png_fdAT)
+               {
+                  png_warning(png_ptr, "Skipped (ignored) a chunk "
+                                       "between APNG chunks");
+                  bytes_to_skip = png_ptr->idat_size;
+                  continue;
+               }
+
+               png_ensure_sequence_number(png_ptr, png_ptr->idat_size);
 
+               png_ptr->idat_size -= 4;
+            }
+         }
+#else
          while (png_ptr->idat_size == 0)
          {
             png_crc_finish(png_ptr, 0);
@@ -4177,7 +4386,7 @@ png_read_IDAT_data(png_structrp png_ptr, png_bytep output,
             if (png_ptr->chunk_name != png_IDAT)
                png_error(png_ptr, "Not enough image data");
          }
-
+#endif /* PNG_READ_APNG_SUPPORTED */
          avail_in = png_ptr->IDAT_read_size;
 
          if (avail_in > png_ptr->idat_size)
@@ -4240,6 +4449,9 @@ png_read_IDAT_data(png_structrp png_ptr, png_bytep output,
 
          png_ptr->mode |= PNG_AFTER_IDAT;
          png_ptr->flags |= PNG_FLAG_ZSTREAM_ENDED;
+#ifdef PNG_READ_APNG_SUPPORTED
+         png_ptr->num_frames_read++;
+#endif
 
          if (png_ptr->zstream.avail_in > 0 || png_ptr->idat_size > 0)
             png_chunk_benign_error(png_ptr, "Extra compressed data");
@@ -4678,4 +4890,80 @@ defined(PNG_USER_TRANSFORM_PTR_SUPPORTED)
 
    png_ptr->flags |= PNG_FLAG_ROW_INIT;
 }
+
+#ifdef PNG_READ_APNG_SUPPORTED
+/* This function is to be called after the main IDAT set has been read and
+ * before a new IDAT is read. It resets some parts of png_ptr
+ * to make them usable by the read functions again */
+void /* PRIVATE */
+png_read_reset(png_structp png_ptr)
+{
+    png_ptr->mode &= ~PNG_HAVE_IDAT;
+    png_ptr->mode &= ~PNG_AFTER_IDAT;
+    png_ptr->row_number = 0;
+    png_ptr->pass = 0;
+}
+
+void /* PRIVATE */
+png_read_reinit(png_structp png_ptr, png_infop info_ptr)
+{
+    png_ptr->width = info_ptr->next_frame_width;
+    png_ptr->height = info_ptr->next_frame_height;
+    png_ptr->rowbytes = PNG_ROWBYTES(png_ptr->pixel_depth,png_ptr->width);
+    png_ptr->info_rowbytes = PNG_ROWBYTES(info_ptr->pixel_depth,
+        png_ptr->width);
+    if (png_ptr->prev_row)
+        memset(png_ptr->prev_row, 0, png_ptr->rowbytes + 1);
+}
+
+#ifdef PNG_PROGRESSIVE_READ_SUPPORTED
+/* same as png_read_reset() but for the progressive reader */
+void /* PRIVATE */
+png_progressive_read_reset(png_structp png_ptr)
+{
+#ifdef PNG_READ_INTERLACING_SUPPORTED
+   /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
+
+   /* Start of interlace block */
+    const int png_pass_start[] = {0, 4, 0, 2, 0, 1, 0};
+
+    /* Offset to next interlace block */
+    const int png_pass_inc[] = {8, 8, 4, 4, 2, 2, 1};
+
+    /* Start of interlace block in the y direction */
+    const int png_pass_ystart[] = {0, 0, 4, 0, 2, 0, 1};
+
+    /* Offset to next interlace block in the y direction */
+    const int png_pass_yinc[] = {8, 8, 8, 4, 4, 2, 2};
+
+    if (png_ptr->interlaced)
+    {
+        if (!(png_ptr->transformations & PNG_INTERLACE))
+            png_ptr->num_rows = (png_ptr->height + png_pass_yinc[0] - 1 -
+                                png_pass_ystart[0]) / png_pass_yinc[0];
+        else
+            png_ptr->num_rows = png_ptr->height;
+
+        png_ptr->iwidth = (png_ptr->width +
+                           png_pass_inc[png_ptr->pass] - 1 -
+                           png_pass_start[png_ptr->pass]) /
+                           png_pass_inc[png_ptr->pass];
+    }
+    else
+#endif /* PNG_READ_INTERLACING_SUPPORTED */
+    {
+        png_ptr->num_rows = png_ptr->height;
+        png_ptr->iwidth = png_ptr->width;
+    }
+    png_ptr->flags &= ~PNG_FLAG_ZSTREAM_ENDED;
+    if (inflateReset(&(png_ptr->zstream)) != Z_OK)
+        png_error(png_ptr, "inflateReset failed");
+    png_ptr->zstream.avail_in = 0;
+    png_ptr->zstream.next_in = 0;
+    png_ptr->zstream.next_out = png_ptr->row_buf;
+    png_ptr->zstream.avail_out = (uInt)PNG_ROWBYTES(png_ptr->pixel_depth,
+        png_ptr->iwidth) + 1;
+}
+#endif /* PNG_PROGRESSIVE_READ_SUPPORTED */
+#endif /* PNG_READ_APNG_SUPPORTED */
 #endif /* READ */
diff --git a/thirdparty/libpng/pngset.c b/thirdparty/libpng/pngset.c
index ec75dbe369..a281db58ae 100644
--- a/thirdparty/libpng/pngset.c
+++ b/thirdparty/libpng/pngset.c
@@ -288,6 +288,11 @@ png_set_IHDR(png_const_structrp png_ptr, png_inforp info_ptr,
    info_ptr->pixel_depth = (png_byte)(info_ptr->channels * info_ptr->bit_depth);
 
    info_ptr->rowbytes = PNG_ROWBYTES(info_ptr->pixel_depth, width);
+
+#ifdef PNG_APNG_SUPPORTED
+   /* for non-animated png. this may be overwritten from an acTL chunk later */
+   info_ptr->num_frames = 1;
+#endif
 }
 
 #ifdef PNG_oFFs_SUPPORTED
@@ -1158,6 +1163,147 @@ png_set_sPLT(png_const_structrp png_ptr,
 }
 #endif /* sPLT */
 
+#ifdef PNG_APNG_SUPPORTED
+png_uint_32 PNGAPI
+png_set_acTL(png_structp png_ptr, png_infop info_ptr,
+    png_uint_32 num_frames, png_uint_32 num_plays)
+{
+    png_debug1(1, "in %s storage function", "acTL");
+
+    if (png_ptr == NULL || info_ptr == NULL)
+    {
+        png_warning(png_ptr,
+                    "Call to png_set_acTL() with NULL png_ptr "
+                    "or info_ptr ignored");
+        return (0);
+    }
+    if (num_frames == 0)
+    {
+        png_warning(png_ptr,
+                    "Ignoring attempt to set acTL with num_frames zero");
+        return (0);
+    }
+    if (num_frames > PNG_UINT_31_MAX)
+    {
+        png_warning(png_ptr,
+                    "Ignoring attempt to set acTL with num_frames > 2^31-1");
+        return (0);
+    }
+    if (num_plays > PNG_UINT_31_MAX)
+    {
+        png_warning(png_ptr,
+                    "Ignoring attempt to set acTL with num_plays "
+                    "> 2^31-1");
+        return (0);
+    }
+
+    info_ptr->num_frames = num_frames;
+    info_ptr->num_plays = num_plays;
+
+    info_ptr->valid |= PNG_INFO_acTL;
+
+    return (1);
+}
+
+/* delay_num and delay_den can hold any 16-bit values including zero */
+png_uint_32 PNGAPI
+png_set_next_frame_fcTL(png_structp png_ptr, png_infop info_ptr,
+    png_uint_32 width, png_uint_32 height,
+    png_uint_32 x_offset, png_uint_32 y_offset,
+    png_uint_16 delay_num, png_uint_16 delay_den,
+    png_byte dispose_op, png_byte blend_op)
+{
+    png_debug1(1, "in %s storage function", "fcTL");
+
+    if (png_ptr == NULL || info_ptr == NULL)
+    {
+        png_warning(png_ptr,
+                    "Call to png_set_fcTL() with NULL png_ptr or info_ptr "
+                    "ignored");
+        return (0);
+    }
+
+    png_ensure_fcTL_is_valid(png_ptr, width, height, x_offset, y_offset,
+                             delay_num, delay_den, dispose_op, blend_op);
+
+    if (blend_op == PNG_BLEND_OP_OVER)
+    {
+        if (!(png_ptr->color_type & PNG_COLOR_MASK_ALPHA) &&
+            !(png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)))
+        {
+          png_warning(png_ptr, "PNG_BLEND_OP_OVER is meaningless "
+                               "and wasteful for opaque images, ignored");
+          blend_op = PNG_BLEND_OP_SOURCE;
+        }
+    }
+
+    info_ptr->next_frame_width = width;
+    info_ptr->next_frame_height = height;
+    info_ptr->next_frame_x_offset = x_offset;
+    info_ptr->next_frame_y_offset = y_offset;
+    info_ptr->next_frame_delay_num = delay_num;
+    info_ptr->next_frame_delay_den = delay_den;
+    info_ptr->next_frame_dispose_op = dispose_op;
+    info_ptr->next_frame_blend_op = blend_op;
+
+    info_ptr->valid |= PNG_INFO_fcTL;
+
+    return (1);
+}
+
+void /* PRIVATE */
+png_ensure_fcTL_is_valid(png_structp png_ptr,
+    png_uint_32 width, png_uint_32 height,
+    png_uint_32 x_offset, png_uint_32 y_offset,
+    png_uint_16 delay_num, png_uint_16 delay_den,
+    png_byte dispose_op, png_byte blend_op)
+{
+    if (width == 0 || width > PNG_UINT_31_MAX)
+        png_error(png_ptr, "invalid width in fcTL (> 2^31-1)");
+    if (height == 0 || height > PNG_UINT_31_MAX)
+        png_error(png_ptr, "invalid height in fcTL (> 2^31-1)");
+    if (x_offset > PNG_UINT_31_MAX)
+        png_error(png_ptr, "invalid x_offset in fcTL (> 2^31-1)");
+    if (y_offset > PNG_UINT_31_MAX)
+        png_error(png_ptr, "invalid y_offset in fcTL (> 2^31-1)");
+    if (width + x_offset > png_ptr->first_frame_width ||
+        height + y_offset > png_ptr->first_frame_height)
+        png_error(png_ptr, "dimensions of a frame are greater than"
+                           "the ones in IHDR");
+
+    if (dispose_op != PNG_DISPOSE_OP_NONE &&
+        dispose_op != PNG_DISPOSE_OP_BACKGROUND &&
+        dispose_op != PNG_DISPOSE_OP_PREVIOUS)
+        png_error(png_ptr, "invalid dispose_op in fcTL");
+
+    if (blend_op != PNG_BLEND_OP_SOURCE &&
+        blend_op != PNG_BLEND_OP_OVER)
+        png_error(png_ptr, "invalid blend_op in fcTL");
+
+    PNG_UNUSED(delay_num)
+    PNG_UNUSED(delay_den)
+}
+
+png_uint_32 PNGAPI
+png_set_first_frame_is_hidden(png_structp png_ptr, png_infop info_ptr,
+                              png_byte is_hidden)
+{
+    png_debug(1, "in png_first_frame_is_hidden()");
+
+    if (png_ptr == NULL)
+        return 0;
+
+    if (is_hidden)
+        png_ptr->apng_flags |= PNG_FIRST_FRAME_HIDDEN;
+    else
+        png_ptr->apng_flags &= ~PNG_FIRST_FRAME_HIDDEN;
+
+    PNG_UNUSED(info_ptr)
+
+    return 1;
+}
+#endif /* PNG_APNG_SUPPORTED */
+
 #ifdef PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED
 static png_byte
 check_location(png_const_structrp png_ptr, int location)
diff --git a/thirdparty/libpng/pngstruct.h b/thirdparty/libpng/pngstruct.h
index 94a6d041ff..2a2236f92e 100644
--- a/thirdparty/libpng/pngstruct.h
+++ b/thirdparty/libpng/pngstruct.h
@@ -1,7 +1,7 @@
 
 /* pngstruct.h - header file for PNG reference library
  *
- * Copyright (c) 2018 Cosmin Truta
+ * Copyright (c) 2018-2019 Cosmin Truta
  * 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.
@@ -228,10 +228,6 @@ 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 */
@@ -396,6 +392,12 @@ struct png_struct_def
    /* deleted in 1.5.5: rgb_to_gray_blue_coeff; */
 #endif
 
+/* New member added in libpng-1.6.36 */
+#if defined(PNG_READ_EXPAND_SUPPORTED) && \
+    defined(PNG_ARM_NEON_IMPLEMENTATION)
+   png_bytep riffled_palette; /* buffer for accelerated palette expansion */
+#endif
+
 /* New member added in libpng-1.0.4 (renamed in 1.0.9) */
 #if defined(PNG_MNG_FEATURES_SUPPORTED)
 /* Changed from png_byte to png_uint_32 at version 1.2.0 */
@@ -407,6 +409,27 @@ struct png_struct_def
    png_byte filter_type;
 #endif
 
+#ifdef PNG_APNG_SUPPORTED
+   png_uint_32 apng_flags;
+   png_uint_32 next_seq_num;         /* next fcTL/fdAT chunk sequence number */
+   png_uint_32 first_frame_width;
+   png_uint_32 first_frame_height;
+
+#ifdef PNG_READ_APNG_SUPPORTED
+   png_uint_32 num_frames_read;      /* incremented after all image data of */
+                                     /* a frame is read */
+#ifdef PNG_PROGRESSIVE_READ_SUPPORTED
+   png_progressive_frame_ptr frame_info_fn; /* frame info read callback */
+   png_progressive_frame_ptr frame_end_fn;  /* frame data read callback */
+#endif
+#endif
+
+#ifdef PNG_WRITE_APNG_SUPPORTED
+   png_uint_32 num_frames_to_write;
+   png_uint_32 num_frames_written;
+#endif
+#endif /* PNG_APNG_SUPPORTED */
+
 /* New members added in libpng-1.2.0 */
 
 /* New members added in libpng-1.0.2 but first enabled by default in 1.2.0 */
diff --git a/thirdparty/libpng/pngwrite.c b/thirdparty/libpng/pngwrite.c
index 160c877d38..5e68032378 100644
--- a/thirdparty/libpng/pngwrite.c
+++ b/thirdparty/libpng/pngwrite.c
@@ -1,7 +1,7 @@
 
 /* pngwrite.c - general routines to write a PNG file
  *
- * Copyright (c) 2018 Cosmin Truta
+ * Copyright (c) 2018-2019 Cosmin Truta
  * 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.
@@ -128,6 +128,10 @@ png_write_info_before_PLTE(png_structrp png_ptr, png_const_inforp info_ptr)
        * the application continues writing the PNG.  So check the 'invalid'
        * flag here too.
        */
+#ifdef PNG_WRITE_APNG_SUPPORTED
+      if (info_ptr->valid & PNG_INFO_acTL)
+         png_write_acTL(png_ptr, info_ptr->num_frames, info_ptr->num_plays);
+#endif
 #ifdef PNG_GAMMA_SUPPORTED
 #  ifdef PNG_WRITE_gAMA_SUPPORTED
       if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) == 0 &&
@@ -370,6 +374,11 @@ png_write_end(png_structrp png_ptr, png_inforp info_ptr)
       png_benign_error(png_ptr, "Wrote palette index exceeding num_palette");
 #endif
 
+#ifdef PNG_WRITE_APNG_SUPPORTED
+   if (png_ptr->num_frames_written != png_ptr->num_frames_to_write)
+      png_error(png_ptr, "Not enough frames written");
+#endif
+
    /* See if user wants us to write information chunks */
    if (info_ptr != NULL)
    {
@@ -948,10 +957,6 @@ 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);
@@ -1465,6 +1470,43 @@ png_write_png(png_structrp png_ptr, png_inforp info_ptr,
 }
 #endif
 
+#ifdef PNG_WRITE_APNG_SUPPORTED
+void PNGAPI
+png_write_frame_head(png_structp png_ptr, png_infop info_ptr,
+    png_bytepp row_pointers, png_uint_32 width, png_uint_32 height,
+    png_uint_32 x_offset, png_uint_32 y_offset,
+    png_uint_16 delay_num, png_uint_16 delay_den, png_byte dispose_op,
+    png_byte blend_op)
+{
+    png_debug(1, "in png_write_frame_head");
+
+    /* there is a chance this has been set after png_write_info was called,
+    * so it would be set but not written. is there a way to be sure? */
+    if (!(info_ptr->valid & PNG_INFO_acTL))
+        png_error(png_ptr, "png_write_frame_head(): acTL not set");
+
+    png_write_reset(png_ptr);
+
+    png_write_reinit(png_ptr, info_ptr, width, height);
+
+    if ( !(png_ptr->num_frames_written == 0 &&
+           (png_ptr->apng_flags & PNG_FIRST_FRAME_HIDDEN) ) )
+        png_write_fcTL(png_ptr, width, height, x_offset, y_offset,
+                       delay_num, delay_den, dispose_op, blend_op);
+
+    PNG_UNUSED(row_pointers)
+}
+
+void PNGAPI
+png_write_frame_tail(png_structp png_ptr, png_infop info_ptr)
+{
+    png_debug(1, "in png_write_frame_tail");
+
+    png_ptr->num_frames_written++;
+
+    PNG_UNUSED(info_ptr)
+}
+#endif /* PNG_WRITE_APNG_SUPPORTED */
 
 #ifdef PNG_SIMPLIFIED_WRITE_SUPPORTED
 /* Initialize the write structure - general purpose utility. */
diff --git a/thirdparty/libpng/pngwutil.c b/thirdparty/libpng/pngwutil.c
index 16345e4c0b..b4809cda6b 100644
--- a/thirdparty/libpng/pngwutil.c
+++ b/thirdparty/libpng/pngwutil.c
@@ -821,6 +821,11 @@ png_write_IHDR(png_structrp png_ptr, png_uint_32 width, png_uint_32 height,
    /* Write the chunk */
    png_write_complete_chunk(png_ptr, png_IHDR, buf, 13);
 
+#ifdef PNG_WRITE_APNG_SUPPORTED
+   png_ptr->first_frame_width = width;
+   png_ptr->first_frame_height = height;
+#endif
+
    if ((png_ptr->do_filter) == PNG_NO_FILTERS)
    {
       if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE ||
@@ -1002,8 +1007,17 @@ png_compress_IDAT(png_structrp png_ptr, png_const_bytep input,
                optimize_cmf(data, png_image_size(png_ptr));
 #endif
 
-         if (size > 0)
-            png_write_complete_chunk(png_ptr, png_IDAT, data, size);
+            if (size > 0)
+#ifdef PNG_WRITE_APNG_SUPPORTED
+            {
+               if (png_ptr->num_frames_written == 0)
+#endif
+               png_write_complete_chunk(png_ptr, png_IDAT, data, size);
+#ifdef PNG_WRITE_APNG_SUPPORTED
+               else
+                  png_write_fdAT(png_ptr, data, size);
+            }
+#endif /* PNG_WRITE_APNG_SUPPORTED */
          png_ptr->mode |= PNG_HAVE_IDAT;
 
          png_ptr->zstream.next_out = data;
@@ -1050,7 +1064,17 @@ png_compress_IDAT(png_structrp png_ptr, png_const_bytep input,
 #endif
 
          if (size > 0)
+#ifdef PNG_WRITE_APNG_SUPPORTED
+         {
+            if (png_ptr->num_frames_written == 0)
+#endif
             png_write_complete_chunk(png_ptr, png_IDAT, data, size);
+#ifdef PNG_WRITE_APNG_SUPPORTED
+            else
+               png_write_fdAT(png_ptr, data, size);
+         }
+#endif /* PNG_WRITE_APNG_SUPPORTED */
+
          png_ptr->zstream.avail_out = 0;
          png_ptr->zstream.next_out = NULL;
          png_ptr->mode |= PNG_HAVE_IDAT | PNG_AFTER_IDAT;
@@ -1885,6 +1909,82 @@ png_write_tIME(png_structrp png_ptr, png_const_timep mod_time)
 }
 #endif
 
+#ifdef PNG_WRITE_APNG_SUPPORTED
+void /* PRIVATE */
+png_write_acTL(png_structp png_ptr,
+    png_uint_32 num_frames, png_uint_32 num_plays)
+{
+    png_byte buf[8];
+
+    png_debug(1, "in png_write_acTL");
+
+    png_ptr->num_frames_to_write = num_frames;
+
+    if (png_ptr->apng_flags & PNG_FIRST_FRAME_HIDDEN)
+        num_frames--;
+
+    png_save_uint_32(buf, num_frames);
+    png_save_uint_32(buf + 4, num_plays);
+
+    png_write_complete_chunk(png_ptr, png_acTL, buf, (png_size_t)8);
+}
+
+void /* PRIVATE */
+png_write_fcTL(png_structp png_ptr, png_uint_32 width, png_uint_32 height,
+    png_uint_32 x_offset, png_uint_32 y_offset,
+    png_uint_16 delay_num, png_uint_16 delay_den, png_byte dispose_op,
+    png_byte blend_op)
+{
+    png_byte buf[26];
+
+    png_debug(1, "in png_write_fcTL");
+
+    if (png_ptr->num_frames_written == 0 && (x_offset != 0 || y_offset != 0))
+        png_error(png_ptr, "x and/or y offset for the first frame aren't 0");
+    if (png_ptr->num_frames_written == 0 &&
+        (width != png_ptr->first_frame_width ||
+         height != png_ptr->first_frame_height))
+        png_error(png_ptr, "width and/or height in the first frame's fcTL "
+                           "don't match the ones in IHDR");
+
+    /* more error checking */
+    png_ensure_fcTL_is_valid(png_ptr, width, height, x_offset, y_offset,
+                             delay_num, delay_den, dispose_op, blend_op);
+
+    png_save_uint_32(buf, png_ptr->next_seq_num);
+    png_save_uint_32(buf + 4, width);
+    png_save_uint_32(buf + 8, height);
+    png_save_uint_32(buf + 12, x_offset);
+    png_save_uint_32(buf + 16, y_offset);
+    png_save_uint_16(buf + 20, delay_num);
+    png_save_uint_16(buf + 22, delay_den);
+    buf[24] = dispose_op;
+    buf[25] = blend_op;
+
+    png_write_complete_chunk(png_ptr, png_fcTL, buf, (png_size_t)26);
+
+    png_ptr->next_seq_num++;
+}
+
+void /* PRIVATE */
+png_write_fdAT(png_structp png_ptr,
+    png_const_bytep data, png_size_t length)
+{
+    png_byte buf[4];
+
+    png_write_chunk_header(png_ptr, png_fdAT, (png_uint_32)(4 + length));
+
+    png_save_uint_32(buf, png_ptr->next_seq_num);
+    png_write_chunk_data(png_ptr, buf, 4);
+
+    png_write_chunk_data(png_ptr, data, length);
+
+    png_write_chunk_end(png_ptr);
+
+    png_ptr->next_seq_num++;
+}
+#endif /* PNG_WRITE_APNG_SUPPORTED */
+
 /* Initializes the row writing capability of libpng */
 void /* PRIVATE */
 png_write_start_row(png_structrp png_ptr)
@@ -2778,4 +2878,39 @@ png_write_filtered_row(png_structrp png_ptr, png_bytep filtered_row,
    }
 #endif /* WRITE_FLUSH */
 }
+
+#ifdef PNG_WRITE_APNG_SUPPORTED
+void /* PRIVATE */
+png_write_reset(png_structp png_ptr)
+{
+    png_ptr->row_number = 0;
+    png_ptr->pass = 0;
+    png_ptr->mode &= ~PNG_HAVE_IDAT;
+}
+
+void /* PRIVATE */
+png_write_reinit(png_structp png_ptr, png_infop info_ptr,
+                 png_uint_32 width, png_uint_32 height)
+{
+    if (png_ptr->num_frames_written == 0 &&
+        (width != png_ptr->first_frame_width ||
+         height != png_ptr->first_frame_height))
+        png_error(png_ptr, "width and/or height in the first frame's fcTL "
+                           "don't match the ones in IHDR");
+    if (width > png_ptr->first_frame_width ||
+        height > png_ptr->first_frame_height)
+        png_error(png_ptr, "width and/or height for a frame greater than"
+                           "the ones in IHDR");
+
+    png_set_IHDR(png_ptr, info_ptr, width, height,
+                 info_ptr->bit_depth, info_ptr->color_type,
+                 info_ptr->interlace_type, info_ptr->compression_type,
+                 info_ptr->filter_type);
+
+    png_ptr->width = width;
+    png_ptr->height = height;
+    png_ptr->rowbytes = PNG_ROWBYTES(png_ptr->pixel_depth, width);
+    png_ptr->usr_width = png_ptr->width;
+}
+#endif /* PNG_WRITE_APNG_SUPPORTED */
 #endif /* WRITE */