Lossless hybrid coding scheme for computer cartoon images

Abstract

This paper presents a lossless hybrid coding scheme for compressing computer cartoon images, such as those used in TV cartoon programs and computer games. Such images are usually composed of simple multi-color characters/graphs and complicated full-color backgrounds. The hybrid coding scheme is based on the basic principle of Structure Runlength Coding (SRC) and is combined with prediction coding. It solves two main problems in the conventional methods: that SRC cannot cope with the complicated full-color regions and that predictive DPCM coding cannot efficiently compress the simple multi-color regions. Through an evaluation of entropy, we prove that our hybrid coding scheme is superior to the conventional methods at compressing these computer cartoon images. Compared with an adaptive DPCM coding, our hybrid coding can decrease the entropy by about 1 bit per pixel on average. Compared with SRC, it can decrease the entropy up to 5 bits per pixel in the case of complicated backgrounds. An experimental result shows high compression ratios.