Encoder and decoder

A decoder comprising:

• first memory means for storing a code including such information on at least a to-be-transformed region and a transformation method that an error of a transformed image signal with reference to a to-be-coded image signal has a value less than a predetermined value, and a mean value of the pixels of a to-be-coded region, said transformed image signal being obtained by transforming a to-be-transformed image signal in accordance with a predetermined transformation method;
• designation signal outputting means for transforming the code read out from the first memory means to a to-be-transformed region designation signal and a transformation method designation signal, and outputting the transformed signals;
• second memory means for storing the to-be-transformed region image signal and outputting the to-be-transformed region image signal within the to-be-transformed region designated by the to-be-transformed region image designation signal;
• transforming means for transforming the to-be-transformed region image signal by means of the transformation method designation signal, outputting the transformation image signal, having the transformation image signal stored in said second memory means as the to-be-transformed region image signal, and repeating transformation until the to-be-transformed image signal is converged;
• and
• a circuit for correcting the transformation image signal by the mean value of the to-be-coded region and outputting the corrected transformation image signal as a decoded signal.