Binary Patent Image Retrieval Using the Hierarchical Oriented Gradient Histogram

To confirm the ingenuity of a patent, the drawings appeared in the patent document play a great role in the comparison of similar patent and can further combine with text-based image retrieval for accurate search. Considerable work has been done in image retrieval using shape, color and texture information. However, patent images are usually binary with complex shapes, no color and little texture information, thus little effort has been made specifically for patents. In this paper, we proposed a novel method named the hierarchical oriented gradient histogram, which extracts the local and global gradient distribution of the image. It can be used in binary patent images which are very complex and cannot be easily segmented into shapes. Experiments on a public database demonstrated that the proposed algorithm could get higher accuracy than other state-of-the-art approaches. Because the dimension of feature of an image is less than 200, our method can be utilized for patent image retrieval in real-time.