METHOD FOR CODING STEPWISE REVERSIBLE IMAGE SIGNAL, METHOD FOR DECODING, CODER, DECODER AND RECORDING MEDIUM FOR ITS CODING AND DECODING PROGRAM

摘要

PROBLEM TO BE SOLVED: To provide a method for coding stepwise reversible image signal by which supplement information is attached to a bit stream generated by an irreversible coding system so as to obtain the same image signal as an original image signal and the code amount of the supplement information can be reduced. SOLUTION: An inverse orthogonal transform value just before integer processing that is a final stage to obtain a decoded pixel value is used for a decoded image signal used for generating a supplement information code attached to an irreversible bit stream 10. Furthermore, in the case of obtaining the same image signal as the original image signal from a stepwise reversible bit stream, a real value not subjected to an integer processing just after inverse orthogonal transform is used for a decoded image signal resulting from decoding the irreversible bit stream.