模板匹配课件学习.pptVIP

* Template Matching * Agenda Template Matching Definition and Method Bi-Level Image Gray-Level Image Matlab Example Gray-Level Template Matching Machine Vision Example * Definition Technique used in classifying objects. Template Matching techniques compare portions of images against one another. Sample image may be used to recognize similar objects in source image. * Definition, cont. If standard deviation of the template image compared to the source image is small enough, template matching may be used. Templates are most often used to identify printed characters, numbers, and other small, simple objects. * Method x,y Template Image Input Image I(x,y) O(x,y) Output Image x,y Correlation The matching process moves the template image to all possible positions in a larger source image and computes a numerical index that indicates how well the template matches the image in that position. Match is done on a pixel-by-pixel basis. * Bi-Level Image TM Template is a small image, usually a bi-level image. Find template in source image, with a Yes/No approach. Template Source * Grey-Level Image TM When using template-matching scheme on grey-level image it is unreasonable to expect a perfect match of the grey levels. Instead of yes/no match at each pixel, the difference in level should be used. Template Source Image * Euclidean Distance Let I be a gray level image and g be a gray-value template of size n?m. In this formula (r,c) denotes the top left corner of template g. * Correlation Correlation is a measure of the degree to which two variables agree, not necessary in actual value but in general behavior. The two variables are the corresponding pixel values in two images, template and source. * Grey-LevelCorrelation Formula x is the template gray level image x is the average grey level in the template image y is the source image section y is the average grey level in the source image N is the number of pixels in the section image (N= template image size = columns * rows)