Add contrib/pngminim/preader files

(README, gather.sh, makefile.std, and pngusr.h)

contrib/pngminim/preader/README

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+This demonstrates the use of PNG_USER_CONFIG and pngusr.h
+
+To build a minimal read-only progressive decoder with X display, run
+    gather.sh  # to collect needed files from pngminus, libpng, and zlib
+    make -f makefile.std
+ 

contrib/pngminim/preader/gather.sh

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+cp ../../gregbook/rpng2-x.c ../../gregbook/readpng2.[ch] .
+cp ../../gregbook/COPYING ../../gregbook/LICENSE .
+cp ../../../*.h .
+cp ../../../*.c .
+rm example.c pnggccrd.c pngvcrd.c pngtest.c pngw*.c
+# change the following 2 lines if zlib is somewhere else
+cp ../../../../zlib/*.h .
+cp ../../../../zlib/*.c .
+rm minigzip.c example.c compress.c deflate.c 

contrib/pngminim/preader/makefile.std

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+# Makefile for PngMinus (rpng2)
+# Linux / Unix
+
+#CC=cc
+CC=gcc
+LD=$(CC)
+
+RM=rm -f
+
+#XINC = -I/usr/include			# old-style, stock X distributions
+#XLIB = -L/usr/lib/X11 -lX11		#  (including SGI IRIX)
+
+#XINC = -I/usr/openwin/include		# Sun workstations (OpenWindows)
+#XLIB = -L/usr/openwin/lib -lX11
+
+XINC = -I/usr/X11R6/include		# new X distributions (X.org, etc.)
+XLIB = -L/usr/X11R6/lib -lX11
+#XLIB = -L/usr/X11R6/lib64 -lX11	# e.g., Red Hat on AMD64
+
+#XINC = -I/usr/local/include   		# FreeBSD
+#XLIB = -L/usr/local/lib -lX11
+
+#LIBS = $(XLIB)
+LIBS = $(XLIB) -lm                      #platforms that need libm
+
+CFLAGS=-DPNG_USER_CONFIG -DNO_GZCOMPRESS -DNO_GZIP \
+       -DdeflateParams\(a,b,c\)=Z_OK -I. $(XINC) -O1
+
+C=.c
+O=.o
+L=.a
+E=
+
+ZOBJS  = adler32$(O) crc32$(O) gzio$(O) \
+	 infback$(O) inffast$(O) inflate$(O) inftrees$(O) \
+	 trees$(O) uncompr$(O) zutil$(O)
+
+OBJS  = rpng2-x$(O) readpng2$(O) png$(O) pngerror$(O) pngget$(O) pngmem$(O) \
+	pngpread$(O) pngread$(O) pngrio$(O) pngrtran$(O) pngrutil$(O) \
+	pngset$(O) pngtrans$(O)  $(ZOBJS)
+
+# implicit make rules -------------------------------------------------------
+
+.c$(O): png.h pngconf.h readpng2.h pngusr.h zlib.h
+	$(CC) -c $(CFLAGS) $<
+
+# dependencies
+
+all: rpng2-x$(E)
+
+rpng2-x$(E): $(OBJS)
+	$(LD) -o rpng2-x$(E) $(OBJS) $(LIBS)
+	strip rpng2-x$(E)
+
+clean:
+	$(RM) rpng2-x$(O)
+	$(RM) rpng2-x$(E)
+	$(RM) $(OBJS)
+
+# End of makefile for rpng2-x

contrib/pngminim/preader/pngusr.h

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+/* minrdpngconf.h: headers to make a minimal png-read-only library
+ * For conditions of distribution and use, see copyright notice in png.h
+ * Copyright (c) 2007 Glenn Randers-Pehrson
+ * Derived from pngcrush.h, Copyright 1998-2007, Glenn Randers-Pehrson
+ */
+
+#ifndef MINRDPNGCONF_H
+#define MINRDPNGCONF_H
+
+#define PNG_NO_GLOBAL_ARRAYS
+
+#define PNG_NO_WARNINGS
+#define png_warning(s1,s2) ""
+#define png_chunk_warning(s1,s2) ""
+#define PNG_NO_ERROR_TEXT
+#define png_error(s1,s2) png_err(s1)
+#define png_chunk_error(s1,s2) png_err(s1)
+
+#define PNG_NO_ASSEMBLER_CODE
+#define PNG_NO_OPTIMIZED_CODE
+#define PNG_NO_READ_DITHER
+#define PNG_NO_READ_INVERT
+#define PNG_NO_READ_SHIFT
+#define PNG_NO_READ_PACK
+#define PNG_NO_READ_PACKSWAP
+#define PNG_NO_READ_FILLER
+#define PNG_NO_READ_SWAP_ALPHA
+#define PNG_NO_READ_INVERT_ALPHA
+#define PNG_NO_READ_RGB_TO_GRAY
+#define PNG_NO_READ_USER_TRANSFORM
+#define PNG_NO_READ_cHRM
+#define PNG_NO_READ_hIST
+#define PNG_NO_READ_iCCP
+#define PNG_NO_READ_pCAL
+#define PNG_NO_READ_pHYs
+#define PNG_NO_READ_sBIT
+#define PNG_NO_READ_sCAL
+#define PNG_NO_READ_sPLT
+#define PNG_NO_READ_TEXT
+#define PNG_NO_READ_tIME
+#define PNG_NO_READ_UNKNOWN_CHUNKS
+#define PNG_NO_READ_USER_CHUNKS
+#define PNG_NO_READ_EMPTY_PLTE
+#define PNG_NO_READ_OPT_PLTE
+#define PNG_NO_READ_STRIP_ALPHA
+#define PNG_NO_READ_oFFs
+#define PNG_NO_WARN_UNINITIALIZED_ROW
+
+#define PNG_NO_WRITE_SUPPORTED
+
+#define PNG_NO_INFO_IMAGE
+#define PNG_NO_USER_MEM
+#define PNG_NO_FIXED_POINT_SUPPORTED
+#define PNG_NO_MNG_FEATURES
+#define PNG_NO_USER_TRANSFORM_PTR
+#define PNG_NO_HANDLE_AS_UNKNOWN
+#define PNG_NO_CONSOLE_IO
+#define PNG_NO_ZALLOC_ZERO
+#define PNG_NO_ERROR_NUMBERS
+#define PNG_NO_EASY_ACCESS
+
+#endif /* MINRDPNGCONF_H */