Hierarchical coding method of still pictures with component separation

In the interactive information retrieval system using images with wide areas such as aerial photographs, in general, it is difficult to display the entire image with a sufficient resolution because of the limited number of pixels that can be displayed by the device. Consequently, it is desirable in such a system that an arbitrary subarea of the image can be retrieved and displayed with a high speed. From such a viewpoint, this paper proposes and discusses the hierarchical component separation coding. In the proposed method, the image information is separated into two components such as the gray level and the resolution components in the block truncation code, and the two components are coded hierarchically in regard to the resolution from rough to detailed levels. By this scheme, an arbitrary part of the image can be retrieved and displayed with the specified resolution. An experiment was made by computer simulation, wherein the block truncation code is applied to the proposed code. It is shown that hierarchical representation of the image in regard to the resolution as well as the code compression of one-half to four-fifths can be realized. It is shown also, by applying the proposed coding to the actual image retrieval system that, the code complexity in terminal transmission for the retrieval of the object image can be reduced from one-fifth to one-half the traditional method, leading to a high-speed retrieval and display.