IMAGE ENCODER, IMAGE ENCODING METHOD AND RECORDING MEDIUM

摘要

PROBLEM TO BE SOLVED: To provide an image encoder in which reversible compression is performed, high compressibility is obtained and a high-speed image encoding processing is performed for any dither images. SOLUTION: This image encoder is provided with: a prediction means 1 for obtaining the predicted value of a pixel under consideration from already encoded proximate pixels; a prediction error generation means 2 for comparing the predicted value of the pixel under consideration obtained by the prediction means 1 with the actual value of the pixel under consideration and generating the prediction error of the predicted value of the pixel under consideration obtained by the prediction means 1 and the actual value of the pixel under consideration; a first order setting means 3 for setting the order of a prediction probability as the first order for the individual pixels inside a block constituted of a plurality of the pixels; a multi-valued data generating means 4 for ranking all the predication error values of all the pixels inside the block generated by the prediction error generation means 2 by the first order set by the first order setting means 3 and obtaining a single piece of multi-valued data; and an encoding means 5 for encoding the multi-valued data from the multi- valued data generating means 4.