%高斯噪聲下的濾波 


image=imread('F:\sar\speck.tif'); 
[m,n]=size(image); 
image1=imnoise(image,'Gaussian',0,0.002); %加高斯噪聲 
image1=double(image1); %將uint8轉(zhuǎn)換成雙精度 
figure,imagesc(image1),colormap(gray) %顯示濾波前的圖像 

%Sigma濾波 

image2=image1; 

for i=3:m-2 
for j=3:n-2 
temp=image1(i-2:i+2,j-2:j+2); 
q=std(temp(:)); 
max=image1(i,j)+2*q; 
min=image1(i,j)-2*q; 
temp1=zeros(5,5); 
temp2=temp; 
t=0; 
for r=1:5
for s=1:5 
if temp2(r,s)<=max & temp2(r,s)>=min 
temp1(r,s)=temp2(r,s); 
t=t+1; 
else 
temp1(r,s)=0; 
end 
end 
end 
tem=sum(temp1(:))/t; 
image2(i,j)=tem; 
end 
end %