Patent ID: 8818103

Claim:
An image retrieval method comprising: a step of extracting at least one query feature vector from a query image on which a subject of the image retrieval is captured, the query feature vector representing a local feature of the query image; a step of accessing an image data base in which a plurality of reference images are stored previously, each reference image being stored in conjunction with learning images generated therefrom and reference feature vectors representing local features of the reference image and the learning images; a comparing step of comparing the query feature vector with the reference feature vectors stored in conjunction with each reference image using an approximate nearest neighbor search to find a reference feature vector approximately nearest to the query feature vector; and a selecting step of selecting a reference image with which the found reference feature vector is stored in conjunction from the reference images as a retrieval result wherein: each learning image is generated by adding a defocus and/or a motion-blur effect likely to occur on capturing the subject to each reference image, one of the reference feature vectors is extracted from each reference image using a scale-space approach and another of the reference feature vectors is extracted from each learning image corresponding to the reference image using the scale-space approach, the query feature vector is extracted from the query image using the scale-space approach, and the comparing step repeats the comparison of the query feature vector with each reference feature vector using plural degrees of approximation in order from rough to close corresponding to a processing load in order from light to heavy, respectively, the selecting step makes the comparing step repeated to perform the comparison until a basis to determine the retrieval result is provided, and each of the above steps is executed by a computer.