and png_memcmp() macros.

They have not been exported to applications since libpng12.

ignore all unknown chunks and all known chunks except for IHDR, PLTE, tRNS,
IDAT, and IEND.  Previously it only meant ignore all unknown chunks, the
same as num_chunks == 0. Revised png_image_skip_unused_chunks() to
provide a list of chunks to be processed instead of a list of chunks to
ignore.  Revised contrib/gregbook/readpng2.c accordingly.

replacement with png_convert_to_rfc1123_buffer().

palette index.

Some such as PNGAPI begin with "PNG".