Update libpng to 1.6.26

18 files changed, 348 insertions, 39 deletions

diff --git a/libpng/scripts/README.txt b/libpng/scripts/README.txt
index f6a9cf38c..71aeebe9a 100644
--- a/libpng/scripts/README.txt
+++ b/libpng/scripts/README.txt
@@ -1,9 +1,9 @@
 
-Makefiles for  libpng version 1.6.17 - March 26, 2015
+Makefiles for  libpng version 1.6.26 - October 20, 2016
 
 pnglibconf.h.prebuilt       =>  Stores configuration settings
  makefile.linux    =>  Linux/ELF makefile
-                       (gcc, creates libpng16.so.16.1.6.17)
+                       (gcc, creates libpng16.so.16.1.6.26)
  makefile.gcc      =>  Generic makefile (gcc, creates static libpng.a)
  makefile.knr      =>  Archaic UNIX Makefile that converts files with
                        ansi2knr (Requires ansi2knr.c from
@@ -33,12 +33,12 @@ pnglibconf.h.prebuilt       =>  Stores configuration settings
  makefile.os2      =>  OS/2 Makefile (gcc and emx, requires libpng.def)
  makefile.sco      =>  For SCO OSr5  ELF and Unixware 7 with Native cc
  makefile.sggcc    =>  Silicon Graphics (gcc,
-                       creates libpng16.so.16.1.6.17)
+                       creates libpng16.so.16.1.6.26)
  makefile.sgi      =>  Silicon Graphics IRIX makefile (cc, creates static lib)
  makefile.solaris  =>  Solaris 2.X makefile (gcc,
-                       creates libpng16.so.16.1.6.17)
+                       creates libpng16.so.16.1.6.26)
  makefile.so9      =>  Solaris 9 makefile (gcc,
-                       creates libpng16.so.16.1.6.17)
+                       creates libpng16.so.16.1.6.26)
  makefile.std      =>  Generic UNIX makefile (cc, creates static libpng.a)
  makefile.sunos    =>  Sun makefile
  makefile.32sunu   =>  Sun Ultra 32-bit makefile
diff --git a/libpng/scripts/def.c b/libpng/scripts/def.c
index 9c88f7743..7f2be6a58 100644
--- a/libpng/scripts/def.c
+++ b/libpng/scripts/def.c
@@ -21,7 +21,7 @@ PNG_DFN "OS2 DESCRIPTION "PNG image compression library""
 PNG_DFN "OS2 CODE PRELOAD MOVEABLE DISCARDABLE"
 PNG_DFN ""
 PNG_DFN "EXPORTS"
-PNG_DFN ";Version 1.6.17"
+PNG_DFN ";Version 1.6.26"
 
 #define PNG_EXPORTA(ordinal, type, name, args, attributes)\
         PNG_DFN "@" SYMBOL_PREFIX "@@" name "@"
diff --git a/libpng/scripts/genchk.cmake.in b/libpng/scripts/genchk.cmake.in
new file mode 100644
index 000000000..ab3b9d746
--- /dev/null
+++ b/libpng/scripts/genchk.cmake.in
@@ -0,0 +1,37 @@
+# genchk.cmake.in
+# Generate .chk from .out with awk (generic), based upon the automake logic.
+
+# Copyright (C) 2016 Glenn Randers-Pehrson
+# Written by Roger Leigh, 2016
+
+# This code is released under the libpng license.
+# For conditions of distribution and use, see the disclaimer
+# and license in png.h
+
+# Variables substituted from CMakeLists.txt
+set(SRCDIR "@CMAKE_CURRENT_SOURCE_DIR@")
+
+set(AWK "@AWK@")
+
+get_filename_component(INPUTEXT "${INPUT}" EXT)
+get_filename_component(OUTPUTEXT "${OUTPUT}" EXT)
+get_filename_component(INPUTBASE "${INPUT}" NAME_WE)
+get_filename_component(OUTPUTBASE "${OUTPUT}" NAME_WE)
+get_filename_component(INPUTDIR "${INPUT}" PATH)
+get_filename_component(OUTPUTDIR "${OUTPUT}" PATH)
+
+if("${INPUTEXT}" STREQUAL ".out" AND "${OUTPUTEXT}" STREQUAL ".chk")
+  # Generate .chk from .out with awk (generic)
+  file(REMOVE "${OUTPUT}" "${OUTPUTDIR}/${OUTPUTBASE}.new")
+  execute_process(COMMAND "${AWK}" -f "${SRCDIR}/scripts/checksym.awk"
+                          "${SRCDIR}/scripts/${INPUTBASE}.def"
+                          "of=${OUTPUTDIR}/${OUTPUTBASE}.new"
+                          "${INPUT}"
+                  RESULT_VARIABLE AWK_FAIL)
+  if(AWK_FAIL)
+    message(FATAL_ERROR "Failed to generate ${OUTPUTDIR}/${OUTPUTBASE}.new")
+  endif()
+  file(RENAME "${OUTPUTDIR}/${OUTPUTBASE}.new" "${OUTPUT}")
+else()
+  message(FATAL_ERROR "Unsupported conversion: ${INPUTEXT} to ${OUTPUTEXT}")
+endif()
diff --git a/libpng/scripts/genout.cmake.in b/libpng/scripts/genout.cmake.in
new file mode 100644
index 000000000..01f12de2f
--- /dev/null
+++ b/libpng/scripts/genout.cmake.in
@@ -0,0 +1,93 @@
+# genout.cmake.in
+# Generate .out from .c with awk (generic), based upon the automake logic.
+
+# Copyright (C) 2016 Glenn Randers-Pehrson
+# Written by Roger Leigh, 2016
+
+# This code is released under the libpng license.
+# For conditions of distribution and use, see the disclaimer
+# and license in png.h
+
+# Variables substituted from CMakeLists.txt
+set(SRCDIR "@CMAKE_CURRENT_SOURCE_DIR@")
+set(BINDIR "@CMAKE_CURRENT_BINARY_DIR@")
+
+set(AWK "@AWK@")
+set(CMAKE_C_COMPILER "@CMAKE_C_COMPILER@")
+set(CMAKE_C_FLAGS @CMAKE_C_FLAGS@)
+set(INCDIR "@CMAKE_CURRENT_BINARY_DIR@")
+set(PNG_PREFIX "@PNG_PREFIX@")
+set(PNGLIB_MAJOR "@PNGLIB_MAJOR@")
+set(PNGLIB_MINOR "@PNGLIB_MINOR@")
+set(PNGLIB_VERSION "@PNGLIB_VERSION@")
+set(ZLIBINCDIR "@ZLIB_INCLUDE_DIR@")
+
+set(PLATFORM_C_FLAGS)
+if(APPLE)
+  set(CMAKE_OSX_ARCHITECTURES "@CMAKE_OSX_ARCHITECTURES@")
+  set(CMAKE_OSX_SYSROOT "@CMAKE_OSX_SYSROOT@")
+  if(CMAKE_OSX_ARCHITECTURES)
+    set(PLATFORM_C_FLAGS ${PLATFORM_C_FLAGS} -arch ${CMAKE_OSX_ARCHITECTURES})
+  endif()
+  if(CMAKE_OSX_SYSROOT)
+    set(PLATFORM_C_FLAGS ${PLATFORM_C_FLAGS} -isysroot ${CMAKE_OSX_SYSROOT})
+  endif()
+endif()
+
+get_filename_component(INPUTEXT "${INPUT}" EXT)
+get_filename_component(OUTPUTEXT "${OUTPUT}" EXT)
+get_filename_component(INPUTBASE "${INPUT}" NAME_WE)
+get_filename_component(OUTPUTBASE "${OUTPUT}" NAME_WE)
+get_filename_component(INPUTDIR "${INPUT}" PATH)
+get_filename_component(OUTPUTDIR "${OUTPUT}" PATH)
+
+if ("${INPUTEXT}" STREQUAL ".c" AND "${OUTPUTEXT}" STREQUAL ".out")
+  get_filename_component(GENDIR "${OUTPUT}" PATH)
+  file(MAKE_DIRECTORY "${GENDIR}")
+
+  file(REMOVE "${OUTPUT}.tf1" "${OUTPUT}.tf2")
+
+  set(INCLUDES "-I${INCDIR}")
+  if(ZLIBINCDIR)
+    foreach(dir ${ZLIBINCDIR})
+      list(APPEND INCLUDES "-I${dir}")
+    endforeach()
+  endif()
+
+  if(PNG_PREFIX)
+    set(PNG_PREFIX_DEF "-DPNG_PREFIX=${PNG_PREFIX}")
+  endif()
+
+  execute_process(COMMAND "${CMAKE_C_COMPILER}" "-E"
+                          ${CMAKE_C_FLAGS}
+                          ${PLATFORM_C_FLAGS}
+                          "-I${SRCDIR}"
+                          "-I${BINDIR}"
+                          ${INCLUDES}
+                          "-DPNGLIB_LIBNAME=PNG${PNGLIB_MAJOR}${PNGLIB_MINOR}_0"
+                          "-DPNGLIB_VERSION=${PNGLIB_VERSION}"
+                          "-DSYMBOL_PREFIX=${SYMBOL_PREFIX}"
+                          "-DPNG_NO_USE_READ_MACROS"
+                          "-DPNG_BUILDING_SYMBOL_TABLE"
+                          ${PNG_PREFIX_DEF}
+                          "${INPUT}"
+                  OUTPUT_FILE "${OUTPUT}.tf1"
+                  WORKING_DIRECTORY "${BINDIR}"
+                  RESULT_VARIABLE CPP_FAIL)
+  if(CPP_FAIL)
+    message(FATAL_ERROR "Failed to generate ${OUTPUT}.tf1")
+  endif()
+
+  execute_process(COMMAND "${AWK}" -f "${SRCDIR}/scripts/dfn.awk"
+                          "out=${OUTPUT}.tf2" "${OUTPUT}.tf1"
+                  WORKING_DIRECTORY "${BINDIR}"
+                  RESULT_VARIABLE AWK_FAIL)
+  if(AWK_FAIL)
+    message(FATAL_ERROR "Failed to generate ${OUTPUT}.tf2")
+  endif()
+
+  file(REMOVE "${OUTPUT}.tf1")
+  file(RENAME "${OUTPUT}.tf2" "${OUTPUT}")
+else()
+  message(FATAL_ERROR "Unsupported conversion: ${INPUTEXT} to ${OUTPUTEXT}")
+endif()
diff --git a/libpng/scripts/gensrc.cmake.in b/libpng/scripts/gensrc.cmake.in
new file mode 100644
index 000000000..f28a62266
--- /dev/null
+++ b/libpng/scripts/gensrc.cmake.in
@@ -0,0 +1,138 @@
+# gensrc.cmake.in
+# Generate source files with awk, based upon the automake logic.
+
+# Copyright (C) 2016 Glenn Randers-Pehrson
+# Written by Roger Leigh, 2016
+
+# This code is released under the libpng license.
+# For conditions of distribution and use, see the disclaimer
+# and license in png.h
+
+# Variables substituted from CMakeLists.txt
+set(SRCDIR "@CMAKE_CURRENT_SOURCE_DIR@")
+set(BINDIR "@CMAKE_CURRENT_BINARY_DIR@")
+
+set(AWK "@AWK@")
+set(DFA_XTRA "@DFA_XTRA@")
+set(PNG_PREFIX "@PNG_PREFIX@")
+set(PNGLIB_VERSION "@PNGLIB_VERSION@")
+
+if("${OUTPUT}" STREQUAL "scripts/pnglibconf.c")
+  # Generate scripts/pnglibconf.c
+
+  file(REMOVE "${BINDIR}/pnglibconf.tf6" "${BINDIR}/pnglibconf.tf7")
+
+  execute_process(COMMAND "${CMAKE_COMMAND}" -E echo "com ${PNGLIB_VERSION} STANDARD API DEFINITION"
+                  COMMAND "${AWK}" -f "${SRCDIR}/scripts/options.awk"
+                          "out=pnglibconf.tf6" "logunsupported=1" "version=search"
+                          "${SRCDIR}/pngconf.h" "-"
+                          "${SRCDIR}/scripts/pnglibconf.dfa"
+                  WORKING_DIRECTORY "${BINDIR}"
+                  RESULT_VARIABLE AWK_FAIL)
+  if(AWK_FAIL)
+    message(FATAL_ERROR "Failed to generate pnglibconf.tf6")
+  endif()
+
+  execute_process(COMMAND "${AWK}" -f "${SRCDIR}/scripts/options.awk"
+                  "out=pnglibconf.tf7" "pnglibconf.tf6"
+                  WORKING_DIRECTORY "${BINDIR}"
+                  RESULT_VARIABLE AWK_FAIL)
+  if(AWK_FAIL)
+    message(FATAL_ERROR "Failed to generate pnglibconf.tf7")
+  endif()
+
+  file(REMOVE "pnglibconf.tf6")
+  file(MAKE_DIRECTORY "${BINDIR}/scripts")
+  file(RENAME "pnglibconf.tf7" "${BINDIR}/scripts/pnglibconf.c")
+
+elseif ("${OUTPUT}" STREQUAL "pnglibconf.c")
+  # Generate pnglibconf.c
+
+  file(REMOVE "${BINDIR}/pnglibconf.tf4" "${BINDIR}/pnglibconf.tf5")
+
+  execute_process(COMMAND "${AWK}" -f "${SRCDIR}/scripts/options.awk"
+                  out=pnglibconf.tf4 version=search
+                  ${SRCDIR}/pngconf.h ${SRCDIR}/scripts/pnglibconf.dfa
+                  ${SRCDIR}/pngusr.dfa ${DFA_XTRA}
+                  WORKING_DIRECTORY "${BINDIR}"
+                  RESULT_VARIABLE AWK_FAIL)
+  if(AWK_FAIL)
+    message(FATAL_ERROR "Failed to generate pnglibconf.tf4")
+  endif()
+
+  execute_process(COMMAND "${AWK}" -f "${SRCDIR}/scripts/options.awk"
+                  out=pnglibconf.tf5 pnglibconf.tf4
+                  WORKING_DIRECTORY "${BINDIR}"
+                  RESULT_VARIABLE AWK_FAIL)
+  if(AWK_FAIL)
+    message(FATAL_ERROR "Failed to generate pnglibconf.tf5")
+  endif()
+
+  file(REMOVE "pnglibconf.tf4")
+  file(MAKE_DIRECTORY "${BINDIR}/scripts")
+  file(RENAME "pnglibconf.tf5" "${BINDIR}/pnglibconf.c")
+
+elseif ("${OUTPUT}" STREQUAL "pnglibconf.h")
+  # Generate pnglibconf.h
+
+  file(REMOVE "${BINDIR}/${OUTPUT}")
+  if(PNG_PREFIX)
+    file(REMOVE "pnglibconf.tf8")
+
+    execute_process(COMMAND "${AWK}" "s==0 && NR>1{print prev}
+                             s==0{prev=\$0}
+                             s==1{print \"#define\", \$1, \"${PNG_PREFIX}\" \$1}
+                             s==2{print \"#define ${PNG_PREFIX}png_\" \$1, \"PNG_\" \$1}
+                             END{print prev}" s=0 pnglibconf.out s=1 "${BINDIR}/scripts/prefix.out"
+                             s=2 "${SRCDIR}/scripts/macro.lst"
+                    OUTPUT_FILE pnglibconf.tf8
+                    RESULT_VARIABLE AWK_FAIL)
+    if(AWK_FAIL)
+      message(FATAL_ERROR "Failed to generate pnglibconf.tf8")
+    endif()
+
+    file(RENAME "pnglibconf.tf8" "${BINDIR}/${OUTPUT}")
+  else()
+    execute_process(COMMAND "${CMAKE_COMMAND}" -E copy "${BINDIR}/pnglibconf.out"
+                                                       "${BINDIR}/${OUTPUT}"
+                    RESULT_VARIABLE COPY_FAIL)
+    if(COPY_FAIL)
+      message(FATAL_ERROR "Failed to create pnglibconf.h")
+    endif()
+  endif()
+
+elseif ("${OUTPUT}" STREQUAL "pngprefix.h")
+  # Generate pngprefix.h
+
+  file(REMOVE "${BINDIR}/${OUTPUT}")
+
+  if(PNG_PREFIX)
+    file(REMOVE "pngprefix.tf1")
+
+    execute_process(COMMAND "${AWK}"
+                            "{print \"#define\", \$1, \"${PNG_PREFIX}\" \$1}"
+                            "${BINDIR}/scripts/intprefix.out"
+                    OUTPUT_FILE "pngprefix.tf1"
+                    RESULT_VARIABLE AWK_FAIL)
+    if(AWK_FAIL)
+      message(FATAL_ERROR "Failed to generate pngprefix.tf1")
+    endif()
+
+    file(RENAME "pngprefix.tf1" "${BINDIR}/${OUTPUT}")
+  else()
+    file(WRITE "${BINDIR}/${OUTPUT}" "/* No libpng symbol prefix configured. */")
+  endif()
+
+elseif("${OUTPUT}" STREQUAL "scripts/pnglibconf.h.prebuilt")
+  # Generate scripts/pnglibconf.h.prebuilt (fails build)
+
+  message(STATUS "Attempting to build scripts/pnglibconf.h.prebuilt")
+  message(STATUS "This is a machine generated file, but if you want to make")
+  message(STATUS "a new one simply build the 'genfiles' target, and copy")
+  message(STATUS "scripts/pnglibconf.out to scripts/pnglibconf.h.prebuilt")
+  message(STATUS "AND set PNG_ZLIB_VERNUM to 0 (you MUST do this)")
+  message(FATAL_ERROR "Stopping build")
+
+else()
+  message(FATAL_ERROR "Unsupported output: ${OUTPUT}")
+endif()
diff --git a/libpng/scripts/libpng-config-head.in b/libpng/scripts/libpng-config-head.in
index d19010df4..b78f9084c 100644
--- a/libpng/scripts/libpng-config-head.in
+++ b/libpng/scripts/libpng-config-head.in
@@ -11,7 +11,7 @@
 
 # Modeled after libxml-config.
 
-version=1.6.17
+version=1.6.26
 prefix=""
 libdir=""
 libs=""
diff --git a/libpng/scripts/libpng.pc.in b/libpng/scripts/libpng.pc.in
index ce61a3e98..7a2cb2b79 100644
--- a/libpng/scripts/libpng.pc.in
+++ b/libpng/scripts/libpng.pc.in
@@ -5,6 +5,6 @@ includedir=@includedir@/libpng16
 
 Name: libpng
 Description: Loads and saves PNG files
-Version: 1.6.17
+Version: 1.6.26
 Libs: -L${libdir} -lpng16
 Cflags: -I${includedir}
diff --git a/libpng/scripts/makefile.cegcc b/libpng/scripts/makefile.cegcc
index cc56297cd..93c123604 100644
--- a/libpng/scripts/makefile.cegcc
+++ b/libpng/scripts/makefile.cegcc
@@ -23,7 +23,7 @@
 
 VERMAJ = 1
 VERMIN = 6
-VERMIC = 17
+VERMIC = 26
 VER = $(VERMAJ).$(VERMIN).$(VERMIC)
 NAME = libpng
 PACKAGE = $(NAME)-$(VER)
diff --git a/libpng/scripts/makefile.linux b/libpng/scripts/makefile.linux
index 86a397f4c..e7347f677 100644
--- a/libpng/scripts/makefile.linux
+++ b/libpng/scripts/makefile.linux
@@ -10,7 +10,7 @@
 # Library name:
 LIBNAME = libpng16
 PNGMAJ = 16
-RELEASE = 17
+RELEASE = 26
 
 # Shared library names:
 LIBSO=$(LIBNAME).so
diff --git a/libpng/scripts/makefile.msys b/libpng/scripts/makefile.msys
index 30595a083..09429ee06 100644
--- a/libpng/scripts/makefile.msys
+++ b/libpng/scripts/makefile.msys
@@ -18,7 +18,7 @@ exec_prefix=$(prefix)
 # Library name:
 LIBNAME = libpng16
 PNGMAJ = 16
-RELEASE = 17
+RELEASE = 26
 
 # Shared library names:
 LIBSO=$(LIBNAME).dll
diff --git a/libpng/scripts/makefile.ne12bsd b/libpng/scripts/makefile.ne12bsd
index d5be81cb7..3d366884a 100644
--- a/libpng/scripts/makefile.ne12bsd
+++ b/libpng/scripts/makefile.ne12bsd
@@ -17,7 +17,7 @@ INCSDIR=${LOCALBASE}/include/libpng16
 
 LIB=	png16
 SHLIB_MAJOR=	0
-SHLIB_MINOR=	1.6.17
+SHLIB_MINOR=	1.6.26
 SRCS=	png.c pngset.c pngget.c pngrutil.c pngtrans.c pngwutil.c \
 	pngread.c pngrio.c pngwio.c pngwrite.c pngrtran.c \
 	pngwtran.c pngmem.c pngerror.c pngpread.c
diff --git a/libpng/scripts/makefile.netbsd b/libpng/scripts/makefile.netbsd
index 58c48844d..8fb2c7633 100644
--- a/libpng/scripts/makefile.netbsd
+++ b/libpng/scripts/makefile.netbsd
@@ -17,7 +17,7 @@ INCSDIR=${LOCALBASE}/include
 
 LIB=	png
 SHLIB_MAJOR=	16
-SHLIB_MINOR=	1.6.17
+SHLIB_MINOR=	1.6.26
 SRCS=	png.c pngset.c pngget.c pngrutil.c pngtrans.c pngwutil.c \
 	pngread.c pngrio.c pngwio.c pngwrite.c pngrtran.c \
 	pngwtran.c pngmem.c pngerror.c pngpread.c
diff --git a/libpng/scripts/makefile.openbsd b/libpng/scripts/makefile.openbsd
index 0ef62a4e4..35b142477 100644
--- a/libpng/scripts/makefile.openbsd
+++ b/libpng/scripts/makefile.openbsd
@@ -11,7 +11,7 @@ LIBDIR=	${PREFIX}/lib
 MANDIR= ${PREFIX}/man/cat
 
 SHLIB_MAJOR=	16
-SHLIB_MINOR=	1.6.17
+SHLIB_MINOR=	1.6.26
 
 LIB=	png
 SRCS=	png.c pngerror.c pngget.c pngmem.c pngpread.c \
diff --git a/libpng/scripts/makefile.sco b/libpng/scripts/makefile.sco
index b9c7c402b..67d84aaac 100644
--- a/libpng/scripts/makefile.sco
+++ b/libpng/scripts/makefile.sco
@@ -1,5 +1,5 @@
 # makefile for SCO OSr5  ELF and Unixware 7 with Native cc
-# Contributed by Mike Hopkirk (hops@sco.com) modified from Makefile.lnx
+# Contributed by Mike Hopkirk (hops at sco.com) modified from Makefile.lnx
 #   force ELF build dynamic linking, SONAME setting in lib and RPATH in app
 # Copyright (C) 2002, 2006, 2010-2014 Glenn Randers-Pehrson
 # Copyright (C) 1998 Greg Roelofs
diff --git a/libpng/scripts/pnglibconf.dfa b/libpng/scripts/pnglibconf.dfa
index e9a82f303..019c06d47 100644
--- a/libpng/scripts/pnglibconf.dfa
+++ b/libpng/scripts/pnglibconf.dfa
@@ -8,7 +8,7 @@ com pnglibconf.h - library build configuration
 com
 version
 com
-com Copyright (c) 1998-2014 Glenn Randers-Pehrson
+com Copyright (c) 1998-2016 Glenn Randers-Pehrson
 com
 com This code is released under the libpng license.
 com For conditions of distribution and use, see the disclaimer
@@ -222,7 +222,7 @@ option SET_OPTION disabled
 #                 with png_set_option
 # ARM_NEON_CHECK: (PNG_ARM_NEON == 1) compile a run-time check to see if Neon
 #                 extensions are supported. This is poorly supported and
-#                 deprectated - use the png_set_option API.
+#                 deprecated - use the png_set_option API.
 setting ARM_NEON_OPT
 option ARM_NEON_API disabled requires ALIGNED_MEMORY enables SET_OPTION,
    sets ARM_NEON_OPT 1
@@ -249,6 +249,17 @@ setting Z_DEFAULT_STRATEGY default @Z_FILTERED
 setting Z_DEFAULT_NOFILTER_STRATEGY default @Z_DEFAULT_STRATEGY
 setting ZLIB_VERNUM default @ZLIB_VERNUM
 
+# Linkage of:
+#
+#  API:      libpng API functions
+#  CALLBACK: internal non-file-local callbacks
+#  FUNCTION: internal non-file-local functions
+#  DATA:     internal non-file-local (const) data
+setting LINKAGE_API default extern
+setting LINKAGE_CALLBACK default extern
+setting LINKAGE_FUNCTION default extern
+setting LINKAGE_DATA default extern
+
 setting TEXT_Z_DEFAULT_COMPRESSION default @Z_DEFAULT_COMPRESSION
 setting TEXT_Z_DEFAULT_STRATEGY default @Z_DEFAULT_STRATEGY
 
@@ -263,12 +274,12 @@ setting DEFAULT_READ_MACROS default 1
 
 option READ_INT_FUNCTIONS requires READ
 
-# The same for write, but these can only be switched off if
-# no writing is required at all - hence the use of an 'enables'
-# not a 'requires' below:
+# The same for write  but these can only be switched off if no writing
+# is required at all - hence the use of a 'disabled', not a 'requires'.
+# If these are needed, they are enabled in the 'WRITE options' section
+# below.
 
 option WRITE_INT_FUNCTIONS disabled
-option WRITE enables WRITE_INT_FUNCTIONS
 
 # Error controls
 #
@@ -479,7 +490,7 @@ option BUILD_GRAYSCALE_PALETTE
 
 # WRITE options
 
-option WRITE
+option WRITE enables WRITE_INT_FUNCTIONS
 
 # Disabling WRITE_16BIT prevents 16-bit PNG files from being
 # generated.
@@ -504,9 +515,7 @@ option WRITE_USER_TRANSFORM requires WRITE_TRANSFORMS
 
 option WRITE_INTERLACING requires WRITE
 
-# The following depends, internally, on WEIGHT_SHIFT and COST_SHIFT
-# where are set below.
-
+# Deprecated, will be removed.
 option WRITE_WEIGHTED_FILTER requires WRITE
 
 option WRITE_FLUSH requires WRITE
@@ -543,6 +552,7 @@ option WRITE_ANCILLARY_CHUNKS requires WRITE
 
 # These options disable *all* the text chunks if turned off
 
+option TEXT disabled
 option READ_TEXT requires READ_ANCILLARY_CHUNKS enables TEXT
 option WRITE_TEXT requires WRITE_ANCILLARY_CHUNKS enables TEXT
 
@@ -657,11 +667,6 @@ setting MAX_GAMMA_8 default 11
 
 setting GAMMA_THRESHOLD_FIXED default 5000
 
-# Scaling factor for filter heuristic weighting calculations
-
-setting WEIGHT_SHIFT default 8
-setting COST_SHIFT default 3
-
 # Precision to use when converting a floating point value to a PNG
 # extension format string in an sCAL chunk (only relevant if the
 # floating point API is enabled)
@@ -869,9 +874,12 @@ option SIMPLIFIED_READ_BGR enables FORMAT_BGR,
 
 # Write:
 option SIMPLIFIED_WRITE,
-   requires WRITE STDIO, SETJMP, WRITE_SWAP, WRITE_PACK,
+   requires WRITE, SETJMP, WRITE_SWAP, WRITE_PACK,
       WRITE_tRNS, WRITE_gAMA, WRITE_sRGB, WRITE_cHRM
 
+# 1.6.22: allow simplified write without stdio support:
+option SIMPLIFIED_WRITE_STDIO requires SIMPLIFIED_WRITE STDIO
+
 option SIMPLIFIED_WRITE_AFIRST enables FORMAT_AFIRST,
    requires SIMPLIFIED_WRITE WRITE_SWAP_ALPHA
 
diff --git a/libpng/scripts/pnglibconf.h.prebuilt b/libpng/scripts/pnglibconf.h.prebuilt
index b4ec3c31e..ba7805ff5 100644
--- a/libpng/scripts/pnglibconf.h.prebuilt
+++ b/libpng/scripts/pnglibconf.h.prebuilt
@@ -1,10 +1,10 @@
-/* libpng 1.6.17 STANDARD API DEFINITION */
+/* libpng 1.6.26 STANDARD API DEFINITION */
 
 /* pnglibconf.h - library build configuration */
 
-/* Libpng version 1.6.17 - March 26, 2015 */
+/* Libpng version 1.6.26 - October 20, 2016 */
 
-/* Copyright (c) 1998-2014 Glenn Randers-Pehrson */
+/* Copyright (c) 1998-2015 Glenn Randers-Pehrson */
 
 /* This code is released under the libpng license. */
 /* For conditions of distribution and use, see the disclaimer */
@@ -101,8 +101,6 @@
 #define PNG_SAVE_UNKNOWN_CHUNKS_SUPPORTED
 #define PNG_SEQUENTIAL_READ_SUPPORTED
 #define PNG_SETJMP_SUPPORTED
-#define PNG_SET_CHUNK_CACHE_LIMIT_SUPPORTED
-#define PNG_SET_CHUNK_MALLOC_LIMIT_SUPPORTED
 #define PNG_SET_OPTION_SUPPORTED
 #define PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
 #define PNG_SET_USER_LIMITS_SUPPORTED
@@ -111,6 +109,7 @@
 #define PNG_SIMPLIFIED_READ_SUPPORTED
 #define PNG_SIMPLIFIED_WRITE_AFIRST_SUPPORTED
 #define PNG_SIMPLIFIED_WRITE_BGR_SUPPORTED
+#define PNG_SIMPLIFIED_WRITE_STDIO_SUPPORTED
 #define PNG_SIMPLIFIED_WRITE_SUPPORTED
 #define PNG_STDIO_SUPPORTED
 #define PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED
@@ -187,11 +186,14 @@
 /* end of options */
 /* settings */
 #define PNG_API_RULE 0
-#define PNG_COST_SHIFT 3
 #define PNG_DEFAULT_READ_MACROS 1
 #define PNG_GAMMA_THRESHOLD_FIXED 5000
 #define PNG_IDAT_READ_SIZE PNG_ZBUF_SIZE
 #define PNG_INFLATE_BUF_SIZE 1024
+#define PNG_LINKAGE_API extern
+#define PNG_LINKAGE_CALLBACK extern
+#define PNG_LINKAGE_DATA extern
+#define PNG_LINKAGE_FUNCTION extern
 #define PNG_MAX_GAMMA_8 11
 #define PNG_QUANTIZE_BLUE_BITS 5
 #define PNG_QUANTIZE_GREEN_BITS 5
@@ -202,7 +204,6 @@
 #define PNG_USER_CHUNK_MALLOC_MAX 8000000
 #define PNG_USER_HEIGHT_MAX 1000000
 #define PNG_USER_WIDTH_MAX 1000000
-#define PNG_WEIGHT_SHIFT 8
 #define PNG_ZBUF_SIZE 8192
 #define PNG_ZLIB_VERNUM 0 /* unknown */
 #define PNG_Z_DEFAULT_COMPRESSION (-1)
diff --git a/libpng/scripts/symbols.def b/libpng/scripts/symbols.def
index 5bdcef20f..612d211ec 100644
--- a/libpng/scripts/symbols.def
+++ b/libpng/scripts/symbols.def
@@ -1,4 +1,4 @@
-;Version 1.6.17
+;Version 1.6.26
 ;--------------------------------------------------------------
 ; LIBPNG symbol list as a Win32 DEF file
 ; Contains all the symbols that can be exported from libpng
@@ -249,3 +249,4 @@ EXPORTS
  png_set_check_for_invalid_index @242
  png_get_palette_max @243
  png_set_option @244
+ png_image_write_to_memory @245
diff --git a/libpng/scripts/test.cmake.in b/libpng/scripts/test.cmake.in
new file mode 100644
index 000000000..fa6a889bb
--- /dev/null
+++ b/libpng/scripts/test.cmake.in
@@ -0,0 +1,31 @@
+# test.cmake.in
+
+# Copyright (C) 2016 Glenn Randers-Pehrson
+# Written by Roger Leigh, 2016
+
+# This code is released under the libpng license.
+# For conditions of distribution and use, see the disclaimer
+# and license in png.h
+
+set(TEST_OPTIONS "@TEST_OPTIONS@")
+set(TEST_FILES "@TEST_FILES@")
+
+foreach(file ${TEST_FILES})
+  file(TO_NATIVE_PATH "${file}" native_file)
+  list(APPEND NATIVE_TEST_FILES "${native_file}")
+endforeach()
+
+# Add the directory containing libpng to the PATH (Windows only)
+if(WIN32)
+  get_filename_component(LIBPNG_DIR "${LIBPNG}" PATH)
+  file(TO_NATIVE_PATH "${LIBPNG_DIR}" LIBPNG_DIR)
+  set(ENV{PATH} "${LIBPNG_DIR};$ENV{PATH}")
+endif()
+
+execute_process(COMMAND "${CMAKE_COMMAND}" -E echo "Running ${TEST_COMMAND}" ${TEST_OPTIONS} ${NATIVE_TEST_FILES})
+
+execute_process(COMMAND "${TEST_COMMAND}" ${TEST_OPTIONS} ${NATIVE_TEST_FILES}
+                RESULT_VARIABLE TEST_STATUS)
+if(TEST_STATUS)
+  message(FATAL_ERROR "Returned failed status ${TEST_STATUS}!")
+endif()