IMAGE MATCHING APPARATUS

To provide an image matching apparatus that realizes a new method for comparing two images which differ in sizes and orientations. In an image recognition system, for each of two plane images on which two-dimensional orthogonal wavelet decomposition has been performed, a two-dimensional feature information generating unit detects large spatial gradients in the horizontal and vertical directions of the plane image and expresses the spatial gradients as two-dimensional vectors that are present in spatial positions of the plane image. Next, a three-dimensional vector generating unit uses one of the spatial positions and a direction of a two-dimensional vector present in the spatial position respectively as a reference point and a reference direction, to express the other two-dimensional vectors using three-dimensional vectors which are each made up of a magnitude component and two angle components. Lastly, a judging unit compares a group of three-dimensional vectors generated for one plane image with a group of three-dimensional vectors generated for the other plane image, to judge whether the two plane images match.