Matching of distorted central symmetry image—An application to seal impression collation
Haruo Takeda, Kuniaki Tabata, Toshihiro Hananoi · Systems and Computers in Japan · 1987
Abstract This paper considers the pattern matching of images in which, originally, the boundary has central symmetry which is made incomplete by defects and noises. A detection method for the centroid of symmetry is proposed. In the proposed method, the boundary is rotated by 180° to match itself (self‐matching of the boundary), thereby detecting the centroid by utilizing all position information of the pixels on the boundary. When the defects are assumed, methods such as tracing cannot be applied directly to the extraction of the boundary, and a simple scheme is employed which scans the image in parallel to the coordinate axis. The effect of the spurious information produced by the scanning is eliminated by using the histogram as the measure of the boundary matching. The effect of the missing information is eliminated by superposing the histogram, which is obtained by scanning in the direction perpendicular to the original scanning, to the original histogram. The proposed method is applied to collation of seal impressions. It was verified that the positioning is performed within the error of one pixel for the ordinary defect of the impression frame and the partial defect of the frame due to the noise by background and fibrous padding material. It was also verified that a processing with practically sufficient speed can be realized. The proposed method will also be applied effectively to the positioning of the images with partial central symmetry, such as a circular component with a protrusion.