中值滤波器%1.该滤波函数用于对图像进行均值滤波作用，
　　%即将一个像元及其邻域中的所有像元的平均值赋给输出图像中的相应的像元，以达到平滑的目的。
　　%2.其中参数impath为图像的路径
　　%3.参数A为滤波模板，A为一个M*N阶矩阵，注意M，N均为奇数，且不大于11。
　　%4.参数output为经过均值滤波后的图像矩阵。
　　%5.该函数采用算法：首先将原始图像矩阵扩充2m行，2n列，并将扩充位补0，(Median filterThis filter function is used to filter the average value of the image,The average of all pixels in a pixel and its neighborhood is assigned to the corresponding pixels in the output image for smoothing.　2. The parameter impath is the image's path 3. Parameter A is a filtering template, A is an M * N matrix, note that M and N are boh odd numbers and not more than 11. The parameter output is the mean filtered image matrix. This function uses the algorithm: first expand the original image matrix by 2m rows and 2n columns, and make the expansion bit complement 0)