A unified lossless coding scheme for gray-level, bi-level and compound images

A unified source coding method is highly desired for many systems that deal with images diversifying from 1 bit/pel bilevel documents to SHD (Super High Definition) images of 12 bit/pel for each color component, and progressive coding that allows images to be reconstructed with increasing pixel accuracy or spatial resolution is essential for many applications including World Wide Web, medical image archive. digital library, pre-press and quick look applications. In this paper, we propose a unified continuous-tone and bi-level image coding method with pyramidal and progressive transmission feature. Hierarchical structure is constructed by interlacing subsampling, and each hierarchy is encoded by DPCM combined with reduced Markov model. Simulation results show that the proposed method is a little inferior than JBIG for hi-level image coding but can achieve better lossless compression ratio for gray-level image coding than CREW! in which wavelet transform is exploited to construct hierarchical structure.