Evaluation of lossless compression methods for gray scale document images
A comparative study of lossless compression algorithms is presented. The following algorithms are considered: UNIX compress, gzip, LZW, CCITT Group 3 and Group 4, JBIG, old lossless JPEG, JPEG-LS based on LOCO, CALIC, FELICS, S+P Transform, and PNG. In cases where the algorithm under consideration may only be applied to binary data, the bit planes of the gray scale image are separated, with and without Gray encoding, and the compression is applied to individual bit planes. Testing is done using a set of document images obtained by gray scale scanning of prints of the eight standard CCITT images and a set of nine gray scale pictorial images. The results show that the highest compression is obtained using the CALIC and JPEG-LS algorithms.