> I know from my Windows pixel-based checker that, generally, the PNG > files contain the same image, version after version (there are a few > oddities with some text, which I'm used to). I would have believed > that identical images would only be produced by identical PNG files?
Usually, picture container formats like PNG also contain metadata like the date of image creation or a comment. This makes PNGs different even in case the contained images are identical. Additionally, it's possible that identical images are stored in different formats, for example, a B/W image can be stored either as a 1-bit bitmap or an 8-bit pixmap. However, you could convert PNG images temporarily to the PGM format to compute a hashsum: PGM doesn't have metadata. http://en.wikipedia.org/wiki/Netpbm_format The program to do this is `pngtopnm', probably followed by a call to `pgmtopgm' to assure that B/W images are handled as grayscale images too: pngtopnm image.png \ | pgmtopgm \ | md5sum -b > image.md5 Werner _______________________________________________ lilypond-devel mailing list lilypond-devel@gnu.org https://lists.gnu.org/mailman/listinfo/lilypond-devel
