This paper proposes a new lossless coding scheme for color still images using adaptive color transformation and minimum-rate predictors. First, RGB signals are converted into three components utilizing a lossless color transformation technique of the ladder network type, and these components are encoded separately by the same coding method. In order to improve coding efficiency, the scheme partitions a color image into square blocks composed of 8*8 pels, and classifies these blocks into 16 classes. Then not only the linear predictors but coefficients of the color transformation are optimized individually in each class so that the total coding rate of the three components can have a minimum. Simulation results indicate that the proposed coding scheme is superior to the conventional scheme, which utilizes the color transformation used in JPEG2000, for many kinds of color images in terms of a coding rate.
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