Bit-Plane Analysis and Contexts Combining of JPEG2000 Contexts for On-Board Satellite Image Compression

This paper studies the performance of the ZC contexts in JPEG2000. A quality criterion based on the mutual information is introduced. According to this criterion, there exist ZC contexts which are not effective in any bit-plane. They can thus be merged with others without significant loss of the compression efficiency. Since the contextual conditional probabilities strongly depend on the bit-planes, an adaptation of the contexts to the bit-planes is also proposed. First, an optimal context quantizer is used on each bit-planes, then a simple greedy entropy minimization procedure allows to combine the ZC contexts in JPEG2000. The results are compared with a global combination of JPEG2000 ZC contexts. Tests have been performed on a real satellite image data base. With only four ZC contexts, the PSNR is less than 0.01 dB lower than the PSNR with the nine ZC contexts.