Abstract
One of the concepts of lossless universal pattern-matching coding, i. e. coding via copying, is applied to multi-dimensional lossy coding. This application produces an instantaneous-decision coding algorithm based on the concept of coding via copying for low-rate irreversible image compression. Previously proposed instantaneous-decision coding algorithms employ multiple-coding modes, and adaptively choose the proper coding mode for a given input subblock instantly without any delay by using threshold logic based on waveform distortion. This adaptive selection of the coding mode is not optimal because the current selection of the coding mode affects the future behavior of the encoder. To enhance coding-mode selection adaptability, a delayed-decision mechanism known as an (M, L) algorithm is introduced, and a new delayed-decision coding algorithm is developed based on the concept of coding via copying. At low coding rates of less than 0.5 bit/pixel, the delayed-decision mechanism improves coding performance by approximately 2-3 dB, and can compress still images more efficiently than existing discrete cosine transform coding.
