Combining Gray coding and JBIG for lossless image compression

An important international standardization effort has been made for still image compression. Two standards have been elaborated, namely, the IS 10918 or more commonly the JPEG (Joint Photographic image Expert Group) for continuous-tone images and the IS 11544 or JBIG (Joint Bi-level Image expert Group) for black-white images. Though JPEG has a lossless operation mode, it addresses mainly lossy compression. We report that some gain in the lossless compression ratio can be obtained by representing the original image with a Gray code, separating the bit plane and applying the JBIG standard. A gain of 15% to 22% is achieved by the Gray code with respect to the usual binary code. Some results obtained with a general data compression algorithm, namely, the GZIP (which is based on an Lempel, Ziv, Storer and Szymanski method cascaded with an adaptive Huffman coding) combined with Gray coding and bit plane separation are also presented