1. An image processing method comprising: a first region determining step of determining a printing region from an original image; a second region determining step of determining a region expanded outward for borderless printing, based on the region determined in said first region determining step; a discrimination step of discriminating whether or not the region determined in said second region determining step exceeds the region of the original image; an extrapolation step of extrapolating, when the result of the discrimination in said discrimination step is affirmative, an image of the surplus region based on an image at end portions of the original image; and a formation step of forming printing data based on the image extrapolated in said extrapolation step and image data of the region determined in said second region determining step.