[master] Imported from libpng-1.2.41beta08.tar

libpng.3

@@ -1703,6 +1703,15 @@ images) is fully transparent, with
 
     png_set_invert_alpha(png_ptr);
 
+The PNG format only supports pixels with postmultiplied alpha.
+If you want to replace the pixels, after reading them, with pixels
+that have premultiplied color samples, you can do this with
+
+    png_set_premultiply_alpha(png_ptr);
+
+If you do this, any input with a tRNS chunk will be expanded to
+have an alpha channel.
+
 PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as
 they can, resulting in, for example, 8 pixels per byte for 1 bit
 files.  This code expands to 1 pixel per byte without changing the
@@ -3756,6 +3765,70 @@ selection of assembler code features:
 We replaced all of these functions with simple stubs in libpng-1.2.20,
 when the Intel assembler code was removed due to a licensing issue.
 
+These macros are deprecated:
+
+    PNG_READ_TRANSFORMS_NOT_SUPPORTED
+    PNG_PROGRESSIVE_READ_NOT_SUPPORTED
+    PNG_NO_SEQUENTIAL_READ_SUPPORTED
+    PNG_WRITE_TRANSFORMS_NOT_SUPPORTED
+    PNG_READ_ANCILLARY_CHUNKS_NOT_SUPPORTED
+    PNG_WRITE_ANCILLARY_CHUNKS_NOT_SUPPORTED
+
+They have been replaced, respectively, by:
+
+    PNG_NO_READ_TRANSFORMS
+    PNG_NO_PROGRESSIVE_READ
+    PNG_NO_SEQUENTIAL_READ
+    PNG_NO_WRITE_TRANSFORMS
+    PNG_NO_READ_ANCILLARY_CHUNKS
+    PNG_NO_WRITE_ANCILLARY_CHUNKS
+
+PNG_MAX_UINT was replaced with PNG_UINT_31_MAX.  It has been
+deprecated since libpng-1.0.16 and libpng-1.2.6.
+
+The function
+    png_check_sig(sig, num)
+was replaced with
+    !png_sig_cmp(sig, 0, num)
+It has been deprecated since libpng-0.90.
+
+The function
+    png_set_gray_1_2_4_to_8()
+which also expands tRNS to alpha was replaced with
+    png_set_expand_gray_1_2_4_to_8()
+which does not. It has been deprecated since libpng-1.0.18 and 1.2.9.
+
+Functions png_set_benign_errors(), png_benign_error(), and
+png_chunk_benign_error() were added.
+
+Support for setting the maximum amount of memory that the application
+will allocate for reading chunks was added, as a security measure.
+The functions png_set_chunk_cache_max() and png_get_chunk_cache_max()
+were added to the library.
+
+We implemented support for I/O states. Added png_ptr member io_state, and
+functions png_get_io_chunk_name() and png_get_io_state() in pngget.c
+
+The png_calloc() function was added and is used in place of
+of "png_malloc(); png_memset();" except in the case in png_read_png()
+where the array consists of pointers; in this case a "for" loop is used
+after the png_malloc() to set the pointers to NULL.
+
+We added PNG_TRANSFORM_GRAY_TO_RGB to the available high-level
+input transforms.
+
+We added the png_set_premultiply_alpha and
+png_do_read_premultiply_alpha() functions.
+
+The call to png_do_chop() in pngrtran.c, which reduces 16-bit input
+files to 8-bit bit depth, was relocated ahead of the building
+of gamma tables.  This allows us to build 8-bit tables instead
+of 16-bit tables, when only 8-bit tables are needed. This avoids 
+wasting some computing resources when the application has called
+the png_set_strip_16() function and encounters a 16-bit PNG file.
+
+Checking for and reporting of errors in the IHDR chunk is more thorough.
+
 .SH IX.  (Omitted)
 .SH X. Detecting libpng