Xref: utzoo comp.sys.ibm.pc:49971 comp.graphics:11314 Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!usc!snorkelwacker!bu.edu!nntp-xfer.bu.edu!rosen From: rosen@polar.bu.edu (David B. Rosen) Newsgroups: comp.sys.ibm.pc,comp.graphics Subject: Re: GIF File Format Message-ID: Date: 3 May 90 23:22:24 GMT References: <843@umt.UUCP> Sender: news@bu.edu.bu.edu Followup-To: comp.sys.ibm.pc Organization: Boston University Center for Adaptive Systems Lines: 16 In-reply-to: cs__sjh@umt.UUCP's message of 2 May 90 07:15:11 GMT I don't have the GIF Format, but I know why it's smaller: it's compressed! As I understand it, the GIF file format has LZW (Lempel Ziv Welch) compression (like unix compress) built in. If you use a standard compression utility on your TARGA-16 files, they may end up about the same size as the GIF file (unless TARGA-16 has an internal structure that would make it relatively incompressible on a byte-string basis). LZ algorithms are somewhat subtle, but they rely on the encoder and the decoder each building up the same dictionary of frequently-occuring strings of arbitrary length, where each string is represented as a fixed-size codeword (typically 16 bits or less) in the compressed data stream. -- David B Rosen, Cognitive & Neural Systems rosen@bucasb.bu.edu Center for Adaptive Systems Bitnet: rosen%thalamus@buacca Boston University UUCP: {harvard,uunet}!bu.edu!bucasb!rosen