Tham khảo tài liệu 'robotics handbook of computer vision algorithms in image algebra part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | EARTHWEB HOME SUBSCRIBE FAQ SITEMAP ft KEY Vi ORD SEARCH GOỈ SM IT Need IT. Find IT. Know IT. Search Tips Handbook of Computer Vision Algorithms in Image Algebra by Gerhard X. Ritter Joseph N. Wilson CRC Press CRC Press LLC ISBN 0849326362 Pub Date 05 01 96 Search this book GO Advanced Search Previous Table of Contents Next Image Algebra Formulation The exact formulation of a discrete correlation of an M X N image n ẽ with a pattern p of size 2m - 1 X 2w - 1 centered at the origin is given by Tt I m 1 For x k y Z X one assumes that a x k y 0. It is also assumed that the pattern size is generally smaller than the sensed image size. Figure illustrates the correlation as expressed by Equation . Figure Computation of the correlation value c x y at a point x y X. To specify template matching in image algebra define an invariant pattern template t corresponding to the pattern p centered at the origin by setting phi - y if - m 1 and n 1 V y n 1 lo otherwise. The unnormalized correlation algorithm is then given by c a t. The following simple computation shows that this agrees with the formulation given by Equation . By definition of the operation we have that 52 9 2-2 tì ec Since t is translation invariant t x ẬU v t 0 0 u -x v - y . Thus Equation can be written as c íờ 53 a tx tO Now t 0 0 u - X V - y 0 unless u -x v -y S t 0 0 or equivalently unless - m -1 d u - X d m - 1 and - w -1 d V - y d n - 1. Changing variables by letting k u - X and ỉ V - y changes Equation to n-1 m I 22 afr M 0 1 0 0 M Sv11 9-2-4 TỊ 1 rn 1 52 52 a y J P M t n 1 fc m i To compute the normalized correlation image c let N denote the neighborhood function defined by N y S ty . The normalized correlation image is then computed as c a@t a@jV . An alternate normalized correlation image is given by the statement c a t a iV ỉ Et o 1 ỉ. Note that t 0 0 is simply the sum of all pixel values of the pattern template at the origin. Comments and .
