matlab中ordfilt2函数（统计排序滤波函数）

https://blog.youkuaiyun.com/yi_tech_blog/article/details/53932153

aa=imread('timg.jpg');
aa=rgb2gray(aa);
imshow(aa);
title('原图');
g=imnoise(aa,'salt & pepper');
figure();
imshow(g);
title('salt noise');
Y=ordfilt2(g,5,ones(3,3));
figure();
imshow(Y);
title('中值滤波');
Y=ordfilt2(g,1,ones(3,3));
figure();
imshow(Y);
title('最小值滤波');
Y=ordfilt2(g,9,ones(3,3));
figure();
imshow(Y);
title('最大值滤波');