IBM Quick Reference Guide - 1992

der Mouse wrote: LZ77 and LZ78 are the two basic families of most low-resource compression schemes. I used those terms specifically because most LZ77 implementations beat most LZ78 implementations. Yes, Terry Welch figured out you don't need to transmit the dictionary in LZ78, but S&S figured out at the same time that LZ78 can be made more efficient than LZ77 if you flag literals with bits (LZSS) instead of trying to encode them. I only write the above because it is *you* who didn't read enough :-) If you want to debate compression we can talk offline; but the simple answer is that the compression scheme used by PNG compresses smaller and decompresses faster than what GIF uses. The alpha channel is barely used, but the ability to have a picture with more than 256 colors is most certainly used. Prior to PNG it was compressed TIFF, which had so many variants (documented and undocumented, little- and big-endian) that it was a real PITA to read one from another program or platform. PNG is uniform across implementations. Web browsers (IE, Mozilla, Opera), graphics manipulation (The Gimp, Photoshop, others), OSS image libraries (ImageMagick, others). ...unless the less complicated can't do the task at all (like going beyond 256 paletted colors). -- Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/ Help our electronic games project: http://www.mobygames.com/ Or check out some trippy MindCandy at http://www.mindcandydvd.com/ A child borne of the home computer wars: http://trixter.wordpress.com/