The present invention is structured in such a manner that, when multivalued pixel data which constitutes a multivalued image are supplied, a predetermined number of interpolated pixel data are generated and inserted between the supplied and successive pixels. At this time, the gradient of each of the interpolated pixels is calculated and determined in accordance with the gradient of the supplied neighboring multivalued pixels. Thus, the image is recorded on a recording medium in accordance with image data including the interpolated pixel. As a result, print information processed so as to be printed by a low resolution printer can be printed with the same size and high quality as when printed by a high resolution printer according to the present invention.