matlab练习程序，图像加噪，各种滤波

cl;
img=imread(\'3.17.tif\');
imgn=imnoise(img,\'salt & pepper\',0.02);
[m n]=size(img);
%h=fspecial(\'average\',[3 3]);    %   3*3的均值滤波
%imgn1=imfilter(imgn,h,\'replicate\');
%imgn=medfilt2(imgn,[3 3]);     %    3*3的中值滤波
%%%%自己编写3*3均值滤波
%{
tem=0;
for i=2:1:m-1
    for j=2:1:n-1     
        for p=i-1:1:i+1
            for q=j-1:1:j+1
                tem=tem+double(imgn(p,q));
            end
        end
        tem=tem/9;
        imgn(i,j)=tem;
        tem=0;
    end
end
%}
%%%%自己编写3*3中值滤波
%{
s=zeros(1,9);
for i=2:1:m-1
    for j=2:1:n-1     
        he=1;
        for p=i-1:1:i+1
            for q=j-1:1:j+1            
                s(he)=imgn(p,q);
                he=he+1;               
            end
        end
        s=sort(s);
        imgn(i,j)=s(5);
    end
end
%}
imshow(imgn)