Progressive Transmission of Two-Tone Images

A technique is proposed for transmitting two-tone images in a progression of stages. In the first stage, information is transmitted to allow a crude reproduction of the picture. In the following stages, the quality of the received picture is improved until a copy identical to the original is obtained. The proposed technique uses a modification of the two-dimensional code recommended by the CCITT for transmission of facsimile. The main features of the coding scheme are as follows. 1) A crude version of the image is obtained after approximately 10-20 percent of the total transmission time. A good version, with half the resolution in both the horizontal and vertical directions, is obtained after 50 percent of the total transmission time. 2) Compatibility with the CCITT codes for transmission of facsimile. 3) Total transmission time is only about 20 percent larger than the time required for nonprogressive transmission using the CCITT codes.