中值滤波，去噪

实验原理：中值滤波器是将领域内像素灰度的中值代替该像素的值,对处理脉冲噪声(椒盐噪声)非常有效。为了对一幅图像上的某个点进行中值滤波处理，必须先将掩模内欲求的像素及其领域的像素值排序，确定出中值，主要功能是使拥有不同灰度的点看起来更接近于它的邻近值。-Median filtering and denoising

Test principle: median filter is to field pixel gray value instead of the pixel value, to deal with impulse noise (salt and pepper noise) is very effective. To a certain point in an image processing median filtering, must first to mask the desires of the pixel and the pixel values in the field of sorting, determine the median, the main function is to make with a different point of gray looks closer to its adjacent values.