一段灰度图像的边缘保持平滑滤波代码。取5×5像素区域，以包含中心点(i,j)的上下左右方向，以及斜45度角方向，中间3×3，总共9个邻域模板，计算其中标准差最小的模板块，取其作为均值滤波的模板。-A gray image edge preserving smoothing filter code. 5* 5 pixel region, to include the center point (I, J) of the vertical and horizontal direction, and the oblique 45 degree angle direction, the middle of the 3 x 3, a total of 9 neighborhood template, and the computation of standard deviation of the template block minimum, take it as the mean filter template.