A fast double difference based image encoding algorithm

A fast encoding algorithm that reduces the number of quantizer levels without introducing gray-scale contouring is presented. The algorithm uses entropy to determine the most advantageous difference mapping technique and the number of bits per pixel used to encode an image. In general, the double difference was found to be the most efficient difference mapping with bit rates on the order of 3 bits pixel in the one-dimensional case and 1.5 bits/pixel in the two-dimensional case. The performance of the algorithm is compared to that of the discrete cosine transform (DCT) in terms of the root mean square criterion, subjective testing, compression ratio, and speed