The technique of the present invention carries out specific image processing that emphasizes articulation of display with a varying degree of emphasis for respective sites of an image projected by a projector. A typical example of such image processing is sharpness adjustment. The degree of emphasis in sharpness adjustment at each site is specified, based on an elevation angle of the projector and a focalized position of the projected image. The technique of the invention thus readily prevents deterioration of the image quality due to out-of-focus state of the projected image.