An image data generation part 400 generates image data, attaches a tag to the image data, and then outputs the resultant data. A screen processing part 420 carries out a screen process on the image data in accordance with the characteristic indicated by the tag, and outputs the tag to a parameter generation part 428. The parameter generation part 428 adjusts a parameter of a correction process in an image processing part 424 so that a detected misregistration does not interfere with the screen characteristic. The image processing part 424 applies such a correction process as to cancel a detected misregistration in an output image to input image data in accordance with the parameter of the correction process as input. A print processing part 440 controls an apparatus main body 2 to cause it to print corrected image data.