Coordinates Versus Sequential Facsimile

The purpose of this paper is to quantitatively evaluate the improvement that can be obtained, in the coding of graphics, by using more sophisticated encoding schemes than run-length. These schemes are now well within the reach of today's technology. In the broad class of encoders by coordinates, three isoentropic encoding schemes are considered: 1) encoding of isolated points, 2) encoding of unidimensional patterns, 3) encoding of two-dimensional patterns. Although the three systems are all conceptually straightforward, they require an increasing complexity of encoding-decoding operations. This complexity is balanced, however, by a larger compression factor for the more complex schemes. The results obtained with these encoding schemes are finally compared to those of a run-length coding scheme for the case of a first-order Markov model of the source.