说明：  中值平均滤波法，中值滤波是一种非线性滤波，一般用来处理图像的椒盐噪声。当用来保持边缘同时滤波的要求下，中值滤波要比卷积滤波更加有效。
(Median filter is a nonlinear filtering, usually used for salt and pepper noise image processing. When the filter is used to keep the edge of the filter, the median filter is more effective than the convolution filter.)