Image encoder and image decoder, image encoding method and image decoding method, image encoding program and image decoding program, and computer readable recording medium recorded with image encoding program and computer readable recording medium recorded with image decoding program

Abstract

An image encoder including: a predicted-image generating unit that generates a predicted image in accordance with a plurality of prediction modes indicating predicted-image generating methods; a prediction-mode judging unit that evaluates prediction efficiency of a predicted image outputted from the predicted-image generating unit to judge a predetermined prediction mode; and an encoding unit that subjects an output of the prediction-mode judging unit to variable-length encoding. The prediction-mode judging unit judges, on the basis of a predetermined control signal, which one of a common prediction mode and a separate prediction mode is used for respective color components forming the input image signal, and multiplexes information on the control signal on a bit stream, multiplexes, when the common prediction mode is used, common prediction mode information on the bit stream, and multiplexes, when the common prediction mode is not used, prediction mode information for each of the color components on the bit stream.