LZW and GIF explained by Steve Blackstock I hope this little document will help enlighten those of you out there who want to know more about the Lempel-Ziv Welch (LZW) compression algorithm, and, specifically, the implementation that GIF uses. Before we start, here's a little terminology, for the purposes of this document: character: a fundamental data element. In normal text files, this is just a single byte. In raster images, which is what we're interested in, it's an index that specifies the ...