This invention relates to a technique that prevents an image from falling outside a given range when a printer is controlled to form an image on an arbitrary medium while assuring a margin of a predetermined amount. A host computer shifts an image by only a partial amount of a target margin amount in a predetermined direction within an effective print range of a medium. Furthermore, the host computer controls a printer to form the image by further shifting the image by nearly the remaining amount of the target margin amount so as to form an image within the effective print range. In this way, since the host computer and printer add a margin in two steps, print data can be prevented from falling outside a given range upon processing a binding margin on the printer side.