INTERNATIONAL ITU-T STANDARD STILL IMAGE COMPRESSION TECHNIQUES FOR GROUP 3 & GROUP 4 CODED IMAGES -- A SURVEY

This overview focuses on comparison of Lossless, Lossy and nearlossless compression capabilities of the international standard algorithms for still image compression known as MH, MR, MMR, JPEG, JBIG and JBIG2 for Facsimile transmission. This paper describes the variuos coding schemes standardized by ITU-T (formerly CCITT) for bi-level, multi level, half-tone, Gray and continous tone images and discusses the compression variations due to differences in data. The CCITT classifies the apparatus for facsimile transmission into four groups. With the arrival of the Internet, facsimile transmission has changed as well, given the wide range of rates and “apparatus” used for digital communication, the focus is more on protocols than on apparatus. The newer recommendations from the ITU-T provide standards for compression that are more or less independent of apparatus. The CCITT (now ITU-T) has issued a number of recommendations based on the speed requirements at a given time. The compression schemes described in the ITU-T recommendations based on apparatus are T.4 includes Modified Huffman (MH), Modified Read (MR),T.6 Modified Modified read (MMR),T.81 Joint photographic expert group (JPEG),T.82 Joint Bi-level image group (JBIG) and independent of apparatus is T.88 (JBIG2). In this study a comparison of all the above algorithms are addressed, As a rule of thumb it can be concluded that MH achieve compression ratio of 7:1, MR gives 10:1,MMR gives15:1,JBIG gives 18:1,JBIG2 21:1 or more for JBIG2 visually lossless it acheives compression near to 100.