A BITPLANE TREE WEIGHTING METHOD FOR LOSSLESS COMPRESSION OF GRAY-SCALE IMAGES

A Bitplane Tree Weighting (BTW) method with arithmetic coding is propo sed for lossless coding of gray scale images, which are represented wi th multiple bitplanes. A bitplane tree, in the same way as the context tree in the CTW method, is used to derive a weighted coding probabili ty distribution for arithmetic coding with the first order Markov mode l. It is shown that the proposed method can attain better compression ratio than known schemes with MDL criterion. Furthermore, the BTW meth od can be extended to a high order Markov model by combining the BTW w ith the CTW or with prediction. The performance of these modified meth ods is also evaluated. It is shown that they attain better compression ratio than the original BTW method without increasing memory size and coding time, and they can beat the lossless JPEG coding.