The present invention relates to image processing in which an image resolution of input image data is compared to information of predetermined standard resolution, and the image data is judged to determine whether it includes specific information related to copy protection. Whether or not to perform judging is controlled based on the result of the comparison. Because the control technique of the present invention controls whether or not to perform the judgment based on the result of the c comparison, the control technique according to the invention provides an efficient judging processing, since no judgment is performed on low resolution image data which is not prone to counterfeiting.