Pre-processing technique for block coding of graphics

This paper describes an irrelevance reduction pre-processing technique which increases the efficiency of a subsequent block code. The proposed method subdivides the image into blocks of 3×3 (5×5) picture elements. The aim is to substitute each block with a prototype pattern out of a reduced pattern set in such a way that occuring picture impairments are limited to a minimum. The substitution method is examined and the attained compression ratios are compared with a very efficient run length code. Its simplicity and its high compression ratio makes the proposed method suitable for real time applications.