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The results of a computer simulation of an image transmission system are reported. A reduction in the total number of bits required to describe a picture by a factor of 4 to 23 is possible as compared with 6-bit PCM. In this system an image is treated as a two-dimensional signal of the spatial coordinates x and y. The large changes in brightness in a picture occur at the edges of objects and are accentuated by the visual system. The edge points can be isolated by the gradient or Laplacian operator. The fact that these edge points lie along connected contours in two dimensions is used to code the location and characteristics of each point efficiently. Two-dimensional reconstruction filters are derived to synthesize the high frequency picture from the decoded edge information. A two-dimensional low-pass or out-of-focus picture is also formed which can be transmitted with a relatively small number of bits. After a possible accentuation to make the picture appear "sharper," the "synthetic highs" signal is added to the low-pass picture to yield the final output.
D.N. Graham (Sun,) studied this question.