Correction for eliminating deformations of an image to be output from an image apparatus is executed while suppressing the processing load on the host computer side. A host computer acquires deformation information used to designate read addresses according to deformations of a scan line from a laser beam printer. A CPU (1) of the laser beam printer generates read addresses according to the deformation information to read out image data from a RAM, and transmits the readout image data to the laser beam printer. The laser beam printer (0) forms an image based on the image data received from the host computer (3000).