Development of Encoding System for Continuous Gray Level and Color Images in a Mixed Mode Communication

点击翻译按钮获取中文摘要

The mixed mode communication system which integrates the teletex and the facsimile is considered to be the most useful transmission system from the viewpoint of the transmission efficiency and the quality of received documents. To implement the mixed mode communication system, researches and developments are being carried out extensively in various laboratories. In this system the textual part of a document is transmitted with data codes and the graphic part is transmitted with facsimile codes and the amount of the coded signal can be compared effectively.On the other hand, in proportion to the increase of visual communication demands, the requirements for functions of facsimile are diversified and complicated. Among them, the development of encoding system for the photograph facsimile and color facsimile becomes very important subject. Under this background, in this study, the high compression encoding system with (1) variable size block coding scheme based on block merging and (2) successive clustering and predictive vector quantization, is studied theoretically and experimentally. An experimental model which consists of an input camera, a super personal computer and a display terminal is fabricated and the technical feasibility and usefulness of the coding algorithms are investigated.The experimental results of encoding show that for the continuous tone images, the number of required bits for encoding are 0.43-0.66bits/pel and the S/N of the decoded images are 38.29-34.18dB with the algorithm (1), and with the algorithm (2) those values are 0.5-0.8bits/pel and 30-36dB. This shows that the coding efficiency is increased about 30% compared with the conventional coder. For the colored images, the number of required bits for encoding and the S/N are 0.6-1.02bits/pel and 38.5-33.3dB with the algorithm (1) and 0.3-3.30bits/pel and 34-48.4dB with the algorithm (2).These results categorically prove the usefulness and superiority of the newly developed encoding system.