Lossless Compression of Textual Images: A Study on Indic Script Documents

This paper presents a method for lossless compression of Indian language textual images. The study is an extension of the previously developed pattern matching and substitution (PM&S)-based method for lossy compression of similar images. Here an efficient method for residue coding is proposed and its performance is compared with CCITT Gr-IV and JBIG. A set of 20 text images for two most popular Indic scripts, namely Devanagari (Hindi) and Bengali, is used in the experiment. It is noted that the best results is achieved by PM&S-based approach followed by LZW-based residue coding. This combined scheme gives lossless compression ratio of about 37.9