High-speed template matching algorithm using information of contour points

Abstract

Template matching is a useful technique for matching images. This paper proposes a high-speed template matching technique which is effective for images that have sharp contours. The method uses only the image contour parts as one-dimensional templates. Although it can retain fine patterns, the data compression ratio and speed are very high. To improve reliability of matching, gray gradient information and intensity of contour points are used. Also, dilation of contours can reduce several errors due to disturbance of the contour or scaling. The algorithm herein can indicate differences between the template and the target image automatically after the alignment of images. The expanded algorithm applying the sequential similarity detection algorithm (SSDA) method also is discussed. Software simulation proved that the algorithm is 10 or 200 times faster than the conventional template matching technique which uses the cross-correlation estimation between two-dimensional (2-D) template and the target image. This algorithm was applied to special hardware. It can align two 512 × 512 pixels images in 40 ms when the size of the search area is 64 × 64.