1. An image processor which uses a plurality of sample images acquired by capturing an image of an object from a plurality of directions to extract one or more partial images having high consistency with one of said sample images from an input image that includes one or more images of the object, comprising: a first computing means for applying orthogonal transformation to each of said sample image based on a normalized orthogonal system composed of predetermined elements, and determining a component group composed of components on each element of said normalized orthogonal system; means for selecting partial images corresponding to a plurality of predetermined areas in said input image respectively from said input image as comparison target images; means for selecting a part of elements from the elements constituting said normalized orthogonal system and creating a partial normalized orthogonal system composed of said part of selected elements; second computing means for determining for each of the comparison target images a partial component group composed of components on each element of said partial normalized orthogonal system by performing orthogonal transformation on said comparison target images based on said partial normalized orthogonal system; means for extracting a comparison target image having high consistency with one of said sample images as an extracted image, by comparison and collation between said partial component groups that were determined for said comparison target images respectively, and partial component groups composed of components corresponding to the respective elements of said partial normalized orthogonal system among the component groups determined for said sample images; means for selecting a plurality of partial images near each of said extracted images in said input image as new comparison target images; and means for creating a new partial normalized orthogonal system of which the number of elements is the same as or more than those of said partial normalized orthogonal system, wherein a partial image is extracted from said plurality of new comparison target images by using said second computing means and said extraction means for said plurality of new comparison target images and said new partial normalized orthogonal system.