(reposted from image-sig@python.org) By some odd reason, I wrote a PCX encoder for PIL this weekend. While PCX uses a simple run-length encoding scheme, it still produced files that were much smaller than the "uncompressed by legal reasons" GIF files you get from the current version of PIL. Anyway, when my good friend the mad scientist heard about this, he asked me why I didn't use run-length encoding also for the GIF files (while run-length en- coding often gives smaller files, it's not even remotely similar to the patented LZW algorithm) After some experimentation, I've managed to write a new GIF encoder which uses run-length encoding (this wasn't exactly trivial ;-). this gives files that are typically 30%-50% of the size generated by earlier versions (ranging from exactly the same size as before, down to files that are actually smaller than the corresponding GIF files...) But I need your help in testing this on a larger sample of GIF files and GIF readers. If you have some time to spare, and a PIL 1.0b1 build within reach, you can grab the "patch" from: http://www.pythonware.com/madscientist/gif-990208.zip replace libImaging/Gif.h and libImaging/GifEncode.c with the versions in this file, and rebuild. You can then use the checkgif.py script on a bunch of existing GIF files to make sure it works on your data. If you have some extra time to spare, you could also try loading GIF files generated by this encoder with whatever GIF-reading software you have. Report your findings to me (I'm not on this list). If I don't hear anything at all, or if I only hear positive things, this will go into the next PIL release. Cheers /F fredrik@pythonware.com http://www.pythonware.com