diff --git a/doc/manual/R-admin.texi b/doc/manual/R-admin.texi
index 522453b4bbe..d748e170bc9 100644
--- a/doc/manual/R-admin.texi
+++ b/doc/manual/R-admin.texi
@@ -991,10 +991,10 @@ You need @code{libpng} and @code{jpeg} sources (available, e.g., from
 Working in the directory @file{@var{R_HOME}/src/gnuwin32/bitmap},
 install the @code{libpng} and @code{jpeg} sources in sub-directories.
 The @code{jpeg} sub-directory for version 7 is named @file{jpeg-7}; if
-you use a different version (e.g.@: @file{jpeg-6b}), edit
-@file{src/gnuwin32/MkRules} and change the definition of @code{JPEGDIR}:
-the names of the @file{libpng} and @file{libtiff} directories can also
-be set there.
+you use a different version (e.g.@: @file{jpeg-6b} or @file{jpeg-8}),
+edit @file{src/gnuwin32/MkRules} and change the definition of
+@code{JPEGDIR}: the names of the @file{libpng} and @file{libtiff}
+directories can also be set there.
 
 Example:
 
diff --git a/src/gnuwin32/MkRules b/src/gnuwin32/MkRules
index 3f921ca2ebe..63b09d46c6a 100644
--- a/src/gnuwin32/MkRules
+++ b/src/gnuwin32/MkRules
@@ -1,6 +1,6 @@
 #-*- Makefile -*-
 ## This file contains tabs: make sure your editor leaves them unchanged.
-## As from R 2.9.0 it is only used when building R itself.
+## As from R 2.9.0 it is only used when building R itself (and not packages)
 
 ## ===== configuration macros for building R  ===============
 
@@ -23,6 +23,8 @@ ATLAS_PATH=/R/ATLAS/lib/WinNT_P4SSE2
 # Support for the ACML and Goto BLASes has been withdrawn: see R-admin.html
 
 # Where does Tcl/Tk live? Spaces allowed.
+# If you alter this you cannot build the installer and will need to set
+# MY_TCLTK to use the package.
 TCL_HOME = $(RHOME)/Tcl
 TCL_VERSION = 85
 
@@ -30,14 +32,15 @@ TCL_VERSION = 85
 # checkout with no modifications).
 # USE_SVNVERSION = YES
 
-# We normally link against DLLs, but this macro forces the use of import libs
-# Needed if using other compilers, including Mingw64
+# We normally link directly against DLLs, 
+# but this macro forces the use of import libs
+# Needed if using other compilers, including _some_ versions of Mingw64
 # USE_IMPLIBS = YES
 
-# Some of the Mingw64 compilers are in fact cross-compilers and have prefixes
+# Some of the 64-bit compilers are in fact cross-compilers and have prefixes
 BINPREF=
 
-# 32- or 64-bit Windows?  For experiments with Mingw64.
+# 32- or 64-bit Windows?  For MinGW-w64.
 WIN=32
 ifeq ($(strip $(WIN)),64)
 USE_IMPLIBS = YES
@@ -58,7 +61,7 @@ ICU_PATH=/sources/icu
 
 ## ====== configuration macros for building installer ===========
 
-# location where Inno Setup 5.[123].x was installed. Spaces allowed.
+# location where Inno Setup 5.3.x was installed. Spaces allowed.
 ISDIR=C:/packages/Inno
 
 ## ====== configuration macros for building MSI installer ===========
@@ -70,14 +73,13 @@ WIXDIR=C:/packages/WiX
 
 ## c99 would force __STRICT_ANSI__ disabling strdup etc, and also alloca
 C99FLAG=-std=gnu99
+## for mingw-runtime <= 3.11
+# C99FLAG=-std=gnu99 -fgnu89-inline
 
 ifeq ($(strip $(BUILD)),GCC4)
 F77=$(BINPREF)gfortran$(GCC4_SUFF)
 FLIBS=-lgfortran
-## for mingw-runtime <= 3.11
-# C99FLAG=-std=gnu99 -fgnu89-inline
-## earlier Rtools needs -sjlj
-## an alternative is -dw2, which currently fails building R.
+## earlier Rtools needs -sjlj; the alternative is -dw2, which fails building R.
 GCC4_SUFF=
 endif
 
diff --git a/src/gnuwin32/bitmap/Makefile b/src/gnuwin32/bitmap/Makefile
index 4dcd8dacbfb..d7b08ab4d76 100644
--- a/src/gnuwin32/bitmap/Makefile
+++ b/src/gnuwin32/bitmap/Makefile
@@ -1,6 +1,6 @@
 ## These can be overridden in MkRules
 
-## must be jpeg-6b or jpeg-7
+## must be jpeg-6b or jpeg-7 or jpeg-8
 JPEGDIR = jpeg-7
 PNGDIR = libpng
 TIFFDIR = libtiff
@@ -23,16 +23,13 @@ buildzlib:
 ## Neither the makefile.{mingw,std} build pnggccrd.c but it is needed if
 ## the compiler defines __MMX__ , which the win64 gcc does.
 ## So we need to explicitly disable it.
+## prefix=foo shuts up a warning
 buildpng:
 	@$(MAKE) CC='$(CC)' \
 	  CFLAGS="-O3 -I../../../extra/zlib -DPNG_NO_MMX_CODE" \
 	  RANLIB=$(RANLIB) ZLIBLIB=../../../extra/zlib -C $(PNGDIR) \
 	  -f scripts/makefile.std libpng.a
 
-# jconfig.h and Makefile obtained running 'CC="gcc -mno-cygwin" ./configure'
-# under CYGWIN. They are here since the configure script doesn't run 
-# (I suspect) using the reduced set of tools we distribute.
-## 2006-01-15 checked under current tools
 buildjpeg: $(JPEGDIR)/jconfig.h Makefile.jpeg
 	$(MAKE) CC='$(CC)' AR='$(AR) rc' RANLIB=$(RANLIB) JPEGDIR=$(JPEGDIR) -C $(JPEGDIR) \
 	  -f ../Makefile.jpeg libjpeg.a
diff --git a/src/gnuwin32/bitmap/Makefile.jpeg b/src/gnuwin32/bitmap/Makefile.jpeg
index c2a2208cfdd..30fe3cbb522 100644
--- a/src/gnuwin32/bitmap/Makefile.jpeg
+++ b/src/gnuwin32/bitmap/Makefile.jpeg
@@ -1,3 +1,11 @@
+#-*- Makefile -*-
+
+## comment from Guido's original version in the 1990's
+# jconfig.h and Makefile obtained running 'CC="gcc -mno-cygwin" ./configure'
+# under CYGWIN. They are here since the configure script doesn't run 
+# (I suspect) using the reduced set of tools we distribute.
+## 2006-01-15 checked under current tools.
+
 CC= gcc
 CFLAGS= -O3 -I.
 
@@ -7,16 +15,7 @@ CFLAGS= -O3 -I.
 SYSDEPMEM= jmemnobs.o
 
 # source files: JPEG library proper
-ifeq ($(strip $(JPEGDIR)),jpeg-7)
-LIBSOURCES= jaricom.c jcapimin.c jcapistd.c jcarith.c jccoefct.c jccolor.c \
-        jcdctmgr.c jchuff.c jcinit.c jcmainct.c jcmarker.c jcmaster.c \
-        jcomapi.c jcparam.c jcprepct.c jcsample.c jctrans.c jdapimin.c \
-        jdapistd.c jdarith.c jdatadst.c jdatasrc.c jdcoefct.c jdcolor.c \
-        jddctmgr.c jdhuff.c jdinput.c jdmainct.c jdmarker.c jdmaster.c \
-        jdmerge.c jdpostct.c jdsample.c jdtrans.c jerror.c jfdctflt.c \
-        jfdctfst.c jfdctint.c jidctflt.c jidctfst.c jidctint.c jquant1.c \
-        jquant2.c jutils.c jmemmgr.c 
-else
+ifeq ($(strip $(JPEGDIR)),jpeg-6b)
 LIBSOURCES= jcapimin.c jcapistd.c jccoefct.c jccolor.c jcdctmgr.c jchuff.c \
         jcinit.c jcmainct.c jcmarker.c jcmaster.c jcomapi.c jcparam.c \
         jcphuff.c jcprepct.c jcsample.c jctrans.c jdapimin.c jdapistd.c \
@@ -25,6 +24,15 @@ LIBSOURCES= jcapimin.c jcapistd.c jccoefct.c jccolor.c jcdctmgr.c jchuff.c \
         jdpostct.c jdsample.c jdtrans.c jerror.c jfdctflt.c jfdctfst.c \
         jfdctint.c jidctflt.c jidctfst.c jidctint.c jidctred.c jquant1.c \
         jquant2.c jutils.c jmemmgr.c
+else
+LIBSOURCES= jaricom.c jcapimin.c jcapistd.c jcarith.c jccoefct.c jccolor.c \
+        jcdctmgr.c jchuff.c jcinit.c jcmainct.c jcmarker.c jcmaster.c \
+        jcomapi.c jcparam.c jcprepct.c jcsample.c jctrans.c jdapimin.c \
+        jdapistd.c jdarith.c jdatadst.c jdatasrc.c jdcoefct.c jdcolor.c \
+        jddctmgr.c jdhuff.c jdinput.c jdmainct.c jdmarker.c jdmaster.c \
+        jdmerge.c jdpostct.c jdsample.c jdtrans.c jerror.c jfdctflt.c \
+        jfdctfst.c jfdctint.c jidctflt.c jidctfst.c jidctint.c jquant1.c \
+        jquant2.c jutils.c jmemmgr.c 
 endif
 
 # These objectfiles are included in libjpeg.a
diff --git a/src/gnuwin32/bitmap/Makefile.tiff b/src/gnuwin32/bitmap/Makefile.tiff
index 3c69e5e9c12..87ede105d0e 100644
--- a/src/gnuwin32/bitmap/Makefile.tiff
+++ b/src/gnuwin32/bitmap/Makefile.tiff
@@ -1,4 +1,5 @@
 #-*- Makefile -*-
+## may be overridden in MkRules
 JPEGDIR = jpeg-7
 include ../../MkRules
 
diff --git a/src/gnuwin32/bitmap/rbitmap.c b/src/gnuwin32/bitmap/rbitmap.c
index b8b2911d307..8341dd21310 100644
--- a/src/gnuwin32/bitmap/rbitmap.c
+++ b/src/gnuwin32/bitmap/rbitmap.c
@@ -65,7 +65,11 @@
 static void my_png_error(png_structp png_ptr, png_const_charp msg)
 {
     R_ShowMessage((char *) msg);
+#if PNG_LIBPNG_VER < 10400
     longjmp(png_ptr->jmpbuf,1);
+#else
+    longjmp(png_jmpbuf(png_ptr),1);
+#endif
 }
 
 static void my_png_warning(png_structp png_ptr, png_const_charp msg)
@@ -115,7 +119,12 @@ int R_SaveAsPng(void  *d, int width, int height,
     /* Set error handling.  REQUIRED if you aren't supplying your own
      * error handling functions in the png_create_write_struct() call.
      */
-    if (setjmp(png_ptr->jmpbuf)) {
+#if PNG_LIBPNG_VER < 10400
+    if (setjmp(png_ptr->jmpbuf))
+#else
+    if (setjmp(png_jmpbuf(png_ptr)))
+#endif
+{    
 	/* If we get here, we had a problem writing the file */
 	free(scanline);
 	png_destroy_write_struct(&png_ptr, &info_ptr);