1. A computer-readable medium having stored thereon a plurality of sequences of instructions for converting a resolution based on a model generated through statistical processing of multiple images, the plurality of sequences of instructions including sequences of instructions, which, when executed by a processor, cause the processor to perform the steps of: receiving an input image having a resolution; reducing the resolution of the input image to conform to a first model resolution of a first prepared model; calculating a characteristic parameter of the reduced input image; and applying the calculated characteristic parameter to a second prepared model that has a second model resolution, the second model resolution being higher than the first model resolution.