1. An apparatus for generating image feature data from an image of interest for which the image feature data is generated, said apparatus comprising: rectangular area generating means for generating a rectangular area which contains said image of interest, each side of said rectangular area adjoining at least one point of said image of interest; rectangular image generating means for padding an average color of said image of interest into an area which does not include said image of interest, said area being within the rectangular area generated by said rectangular area generating means, to generate a rectangular image; and image feature data generating means for generating frequency-domain feature data for the rectangular image generated by said rectangular image generating means.