Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!mcsun!ukc!icdoc!mvax.cc.ic.ac.uk!sunb!dds From: dds@sunb.cc.ic.ac.uk (Diomidis Spinellis) Newsgroups: comp.graphics Subject: Re: Compression of multi-bit images Keywords: delta modulation compression Message-ID: <1990Jun6.215749.21647@cc.ic.ac.uk> Date: 6 Jun 90 21:57:49 GMT References: <8099@b11.ingr.com> Sender: news@cc.ic.ac.uk (USENET News System) Reply-To: dds@cc.ic.ac.uk (Diomidis Spinellis) Organization: Imperial College Computer Center, London, UK Lines: 30 In article spencer@eecs.umich.edu (Spencer W. Thomas) writes: >Lossless methods: >A popular method is LZW (Lempel-Ziv-Welch) as found in the Unix 'compress' >program. [...] > >Simple Huffman (adaptive or otherwise (the Unix 'pack' program) may do [...] Some time ago I implemented a compress / uncompress set of programs for a face server project that was going on here, based on delta modulation. The compressed file contains the difference of each byte from the previous one, coded in a single nibble. I tried the delta modulation programs, compress and pack on a 256 * 256 * 8 gray scale picture of me. These are the results: Original 65536 /bin/pack 59660 /usr/ucb/compress 53510 ./deltac 40489 I can post the programs if there is demand. Diomidis -- Diomidis Spinellis Internet: dds@cc.ic.ac.uk Department of Computing UUCP: ...!ukc!iccc!dds Imperial College JANET: dds@uk.ac.ic.cc London SW7 2BZ #include "/dev/tty"