Lossless image compression via bit-plane separation and multilayer context tree modeling

Color separation and highly optimized context tree mod- eling for binary layers have provided the best compression results for color map images that consist of highly complex spatial struc- tures but only a relatively few number of colors. We explore whether this kind of approach works on photographic and palette images as well. The main difficulty is that these images can have a much higher number of colors, and it is therefore much more difficult to exploit spatial dependencies via binary layers. The original contribu- tions of this work include: 1. the application of context-tree-based compression (previously designed for map images) to natural and color palette images; 2. the consideration of four different methods for bit-plane separation; and 3. Extension of the two-layer context to a multilayer context for better utilization of the crosslayer correla- tions. The proposed combination is extensively compared to state of the art lossless image compression methods. © 2006 SPIE and