img=imread('tushuguan.jpg');
>> figure;imshow(img);
>> img1=imnoise(img,'gaussian');
>> figure;imshow(img1);
>> img2=imnoise(img,'salt & pepper',0.06);
>> figure;imshow(img2);
a=[1/9 1/9 1/9;1/9 1/9 1/9;1/9 1/9 1/9];
>> img3=imfilter(img1,a);
>> figure;imshow(img3);
img4=imfilter(img2,a);
>> figure;imshow(img4);