LOSSLESS IMAGE COMPRESSION BY BLOCK MATCHING

Lossless image compression has often employed techniques quite separat e from those used for text compression or lossy image compression; mos t standards today employ modelling followed by coding (e.g. the JBIG s tandard, the IBM Q-coder, CCITT Group 4). Constantinescu and Storer pr esent a lossy image compression scheme that can be viewed as a general ization of lossless dynamic dictionary compression ('LZ2'-type methods ) to two dimensions with approximate matching; recently, Constantinesc u and Storer have experimented with this approach for lossless hi-leve l image compression with great success, Here we generalize 'LZ1'-type methods (that identify matches in previously seen text) to lossless im age compression. We examine complexity issues and finish by considerin g practical 2-D implementations for bi-level images.