3 Image Enhancement 3.5.2非线性（排序）平滑滤波器 Smoothing Nonlinear Filters(Ranking Filter) √中值滤波器(Median Filter):抑制噪声的同时又能很好地保持图像的边缘 √中值滤波器(median filter):R=median{zklk=1,2,,nn} The median,,of a set of values is such that half the values in the set are less than or equal to and half are greater than or equal to Example:Given the {21,22,23,24,25,26,27328,29} intensities covered by the mask: {10,20,20,20,15,20,20,25,100} Z1 Zn 3 10 20 20 Rank排序（从小到大） 元4 5 6 20 15 20 {10,15,20,20,20,20,20,25,100} 求中值（第5个数的值） Z7 Z8 Zg 20 25 100 R=mediant=20 Please compute its median value 3 Image Enhancement 3.5.2 非线性(排序)平滑滤波器 Smoothing Nonlinear Filters (Ranking Filter) z1 z2 z3 z4 z5 z6 z7 z8 z9 中值滤波器(Median Filter)：抑制噪声的同时又能很好地保持图像的边缘 中值滤波器(median filter) : R = median{zk |k = 1,2,…, n  n} 10 20 20 20 15 20 20 25 100 The median,, of a set of values is such that half the values in the set are less than or equal to , and half are greater than or equal to . Example：Given the intensities covered by the mask: Please compute its median value 1 2 3 4 5 6 7 8 9 { , , , , , , , , } z z z z z z z z z {10,20,20,20,15,20,20,25,100} ＝ {10,15,20,20,20,20,20,25,100} 求中值(第5个数的值) { } 20 R median z   k Rank排序(从小到大)