Coding parameter optimization for the block truncation coding of still pictures

Block truncation coding is a highly efficient compression coding for the natural picture. It is useful in reducing the cost for storage and transmission of full-color still pictures, such as those in the picture data base and the videotex. In the application of the highly efficient compression coding to the practical system, it is required to adjust the coding complexity and the picture quality, according to the cost and quality of the service provided by the system. From such a viewpoint, this paper discusses the control of the coding parameters, which determine the coding condition, and then the optimization of the coding parameters, to arrive at the coding complexity and the picture quality to meet the requirement. First, the traditional adaptive block truncation coding is extended to improve the coding efficiency and to expand the realizable range of coding complexity and picture quality. Then the control of coding is discussed which determines the coding parameter values in an adaptive and automatic way, according to the required picture quality and the property of the object picture in the considered system, to arrive at the desired quality. It is shown that it is possible to realize the coding with the desired quality simply by specifying SNR, independently of the property of the object picture.