1. A blood vessel matching apparatus comprising: an input image acquiring unit configured to acquire an input image; a selecting unit configured to select one of a plurality of blood vessel images as a selected blood vessel image, the plurality of blood vessel images being different from each other; a transforming unit configured to transform the input image to transformed input at a first resolution; a first comparing unit configured to compare the transformed input with the selected blood vessel image, transformed at the first resolution; a second comparing unit configured to compare the selected blood vessel image with the input image, the selected blood vessel image and the input image transformed at a second resolution higher than the first resolution, when the selected blood vessel image, transformed at the first resolution, matches the transformed input; and a matching unit configured to determine a match between the input image and the selected blood vessel image based on a result of a comparison by said second comparing unit, wherein said transforming unit is a Hough transform unit that performs image transform processing for transforming points in the input image to patterns of curves based on a distance from a reference position in the input image to the closest point on a straight line passing through the point in the input image and an angle formed by the straight line passing through the reference position and the closest point and a reference axis including the reference position and that transforms linear components in the input image to patterns of the plurality of superimposed curves to generate the transformed input.