Abstract: The value of the pixel at the same position of each of the training input image as well as a plurality of training feature images is inputted into the discrimination device, which learns in such a way as to reduce the error between the output value obtained from the discrimination device and the value of the pixel at the aforementioned pixel position in the training output image. At the time of enhancement processing, the feature image is produced from the image to be processed, and the values of the pixels of these images at the same position are inputted into the discrimination device, thereby outputting the enhanced image wherein the value outputted from this discrimination device is set as the value of the pixel at the aforementioned pixel position.