[devel] Enhance pngvalid, correct an error in gray_to_rgb, correct doc error.

CHANGES

@@ -3204,6 +3204,7 @@ Version 1.5.1beta08 [January 23, 2011]
     skipping of unread data (e.g., if the reader marks a chunk to be skipped.)
 
 Version 1.5.1beta09 [January 23, 2011]
+Subject: [PATCH] Enhance pngvalid, correct an error in gray_to_rgb, correct doc error.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
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Makefile.am

@@ -120,7 +120,8 @@ pngvalid.o pngtest.o: pnglibconf.h
 
 SYMBOL_CFLAGS = -DPNGLIB_LIBNAME='PNG@PNGLIB_MAJOR@@PNGLIB_MINOR@_0'\
 		-DPNGLIB_VERSION='@PNGLIB_VERSION@'\
-		-DSYMBOL_PREFIX='$(SYMBOL_PREFIX)'
+		-DSYMBOL_PREFIX='$(SYMBOL_PREFIX)'\
+		-DPNG_NO_USE_READ_MACROS
 
 .dfn.out:
 	rm -f $@ dfn.c dfn?.out

Makefile.in

@@ -357,7 +357,8 @@ config.sub configure depcomp install-sh ltmain.sh missing
 SUFFIXES = .chk .dfn .out
 SYMBOL_CFLAGS = -DPNGLIB_LIBNAME='PNG@PNGLIB_MAJOR@@PNGLIB_MINOR@_0'\
 		-DPNGLIB_VERSION='@PNGLIB_VERSION@'\
-		-DSYMBOL_PREFIX='$(SYMBOL_PREFIX)'
+		-DSYMBOL_PREFIX='$(SYMBOL_PREFIX)'\
+		-DPNG_NO_USE_READ_MACROS
 
 all: config.h
 	$(MAKE) $(AM_MAKEFLAGS) all-am

libpng-manual.txt

@@ -1341,16 +1341,12 @@ Copyright (c) 1998-01-04 Charles Poynton <poynton at inforamp.net>
 
     Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
 
-Libpng approximates this with
+Libpng approximates this integers scaled by 32768:
 
-    Y = 0.21268 * R    + 0.7151 * G    + 0.07217 * B
-
-which can be expressed with integers as
-
-    Y = (6969 * R + 23434 * G + 2365 * B)/32768
+    Y = (6968 * R + 23434 * G + 2366 * B)/32768
 
 The calculation is done in a linear colorspace, if the image gamma
-is known.
+can be determined.
 
 If you have a grayscale and you are using png_set_expand_depth(),
 png_set_expand(), or png_set_gray_to_rgb to change to truecolor or to

png.h

@@ -1067,7 +1067,9 @@ PNG_EXPORT(30, void, png_set_bgr, (png_structp png_ptr));
 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
 /* Expand the grayscale to 24-bit RGB if necessary. */
 PNG_EXPORT(31, void, png_set_gray_to_rgb, (png_structp png_ptr));
+#endif
 
+#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
 /* Reduce RGB to grayscale. */
 PNG_FP_EXPORT(32, void, png_set_rgb_to_gray, (png_structp png_ptr,
     int error_action, double red, double green));
@@ -2203,31 +2205,6 @@ PNG_EXPORT(216, png_uint_32, png_get_io_chunk_type,
      (png_uint_32)32767) / (png_uint_32)65535L)
 #endif /* PNG_READ_COMPOSITE_NODIV_SUPPORTED */
 
-#ifdef PNG_USE_READ_MACROS
-/* Inline macros to do direct reads of bytes from the input buffer.
- * The png_get_int_32() routine assumes we are using two's complement
- * format for negative values, which is almost certainly true.
- */
-#  define png_get_uint_32(buf) \
-     (((png_uint_32)(*(buf)) << 24) + \
-      ((png_uint_32)(*((buf) + 1)) << 16) + \
-      ((png_uint_32)(*((buf) + 2)) << 8) + \
-      ((png_uint_32)(*((buf) + 3))))
-
-   /* From libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the
-    * function) incorrectly returned a value of type png_uint_32.
-    */
-#  define png_get_uint_16(buf) \
-     ((png_uint_16) \
-      (((unsigned int)(*(buf)) << 8) + \
-       ((unsigned int)(*((buf) + 1)))))
-
-#  define png_get_int_32(buf) \
-     ((png_int_32)((*(buf) & 0x80) \
-      ? -((png_int_32)((png_get_uint_32(buf) ^ 0xffffffffL) + 1)) \
-      : (png_int_32)png_get_uint_32(buf)))
-#endif
-
 #ifdef PNG_READ_INT_FUNCTIONS_SUPPORTED
 PNG_EXPORT(201, png_uint_32, png_get_uint_32, (png_const_bytep buf));
 PNG_EXPORT(202, png_uint_16, png_get_uint_16, (png_const_bytep buf));
@@ -2255,6 +2232,31 @@ PNG_EXPORT(207, void, png_save_uint_16, (png_bytep buf, unsigned int i));
 /* No png_save_int_16 -- may be added if there's a real need for it. */
 #endif
 
+#ifdef PNG_USE_READ_MACROS
+/* Inline macros to do direct reads of bytes from the input buffer.
+ * The png_get_int_32() routine assumes we are using two's complement
+ * format for negative values, which is almost certainly true.
+ */
+#  define png_get_uint_32(buf) \
+     (((png_uint_32)(*(buf)) << 24) + \
+      ((png_uint_32)(*((buf) + 1)) << 16) + \
+      ((png_uint_32)(*((buf) + 2)) << 8) + \
+      ((png_uint_32)(*((buf) + 3))))
+
+   /* From libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the
+    * function) incorrectly returned a value of type png_uint_32.
+    */
+#  define png_get_uint_16(buf) \
+     ((png_uint_16) \
+      (((unsigned int)(*(buf)) << 8) + \
+       ((unsigned int)(*((buf) + 1)))))
+
+#  define png_get_int_32(buf) \
+     ((png_int_32)((*(buf) & 0x80) \
+      ? -((png_int_32)((png_get_uint_32(buf) ^ 0xffffffffL) + 1)) \
+      : (png_int_32)png_get_uint_32(buf)))
+#endif
+
 /* Maintainer: Put new public prototypes here ^, in libpng.3, and project
  * defs
  */

pngrtran.c

@@ -692,8 +692,13 @@ png_set_gray_to_rgb(png_structp png_ptr)
 {
    png_debug(1, "in png_set_gray_to_rgb");
 
-   png_ptr->transformations |= PNG_GRAY_TO_RGB;
-   png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
+   if (png_ptr != NULL)
+   {
+      /* Because rgb must be 8 bits or more: */
+      png_set_expand_gray_1_2_4_to_8(png_ptr);
+      png_ptr->transformations |= PNG_GRAY_TO_RGB;
+      png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
+   }
 }
 #endif