In the present invention, an image determination processing unit detects an image characteristic for each pixel in cyan image data of image data subjected to a registration shift correction by one pixel by use of a profile characteristic. Each set of characteristic determination result information A to C is stored in a determination result storing unit, and a decoder determines whether or not to perform a registration shift correction less than one pixel according to the information A to C. For magenta, yellow, or black, an image edge simple determination processing unit and a screen image simple determination processing unit for each color detect the image characteristic for each pixel in a simplified manner. According to this detected characteristic determination result information, it is determined whether or not to perform the registration shift correction less than one pixel for magenta, yellow, or black.