Rapid Algorithm of Template Matching Based on Integral Image
基于积分图像的快速模板匹配

In face detection, it is needed to normalize grayscale distribution of image windows before template matching, and that the grayscale average and variance must be computed before grayscale distribution normalization. Based on integral image, the square integral image is proposed and used to realize a rapid algorithm for calculating grayscale average and variance of image windows, and the calculating speed is independent of the windows' size. With this rapid algorithm and transformation of some formulas, such as approximately formulas for computing grayscale distribution normalization, formulas for computing the correlation coefficient and average deviation, and leaving out some needless processes such as copying windows and conversion of windows' grayscale value, the template matching is sped up. Experimental results of face detection demonstrate the efficiency of this rapid algorithm for template matching.