《数字图像处理 Digital Image Processing》课件 Digital Image Fundamentals[精品].pptVIP

Define distance function: For pixels p, q, and z, with coordinates (x,y), (s,t), and (v,w), respectively, D is a distance function or metric if 1) D(p,q) ≥ 0 (D(p,q) = 0 iff p = q), 2) D(p,q) = D(q,p), and 3) D(p,z) ≤ D(p,q) + D(q,z). Distance measures Lecture 3: Chapter 2: Digital Image Fundamentals 1. The Euclidean distance between p and q is defined as: Different ways of measuring distance Using this method, the pixels having a distance less than or equal to some value r from (x,y) are the points contained in a disk of radius r centered at (x,y). p q Lecture 3: Chapter 2: Digital Image Fundamentals 2. The D4 distance (also called city block distance) between p and q is defined as: Using this method, the pixels having a D4 distance from (x,y) less than or equal to some value r form a diamond centered at (x,y). For example, the pixels with D4 distance ≤ 2 from (x,y) form the following contours of constant distance: The pixels with D4 = 1 are the 4-neighbors of (x,y). 2 2 1 1 2 2 1 0 2 2 2 1 2 D4 distance Different ways of measuring distance con’t Lecture 3: Chapter 2: Digital Image Fundamentals 3. The D8 distance (also called chessboard distance) between p and q is defined as: D8(p,q) = max( x-s , y-t ) 2 2 2 2 2 2 1 1 1 2 2 1 0 1 2 2 1 1 1 2 2 2 2 2 2 D8 distance Different ways of measuring distance con’t The pixels with D8 = 1 are the 8-neighbors of (x,y). Lecture 3: Chapter 2: Digital Image Fundamentals 4. The Dm distance between two points is defined as the shortest m-path between the points. In this case, the distance between two pixels will depend on the values of the pixels along the path, as well as the values of their neighbors. Let’s see the following example: Different ways of measuring distance con’t Lecture 3: Chapter 2: Digital Image Fundamentals p2 p p1 p4 p3 Assume that p, p2, and p4 have value 1 and that p1 and p3 can have a value 0 or 1. For V = {1}, solve for Dm distance between p and p4. Solution: If p1 and p3 are 0, then Dm is 2. If