基于MATLAB实现的DCT变换进行噪声估计的功能，代码已经实现过了，可用哦+使用说明文档.rar

% The mean of DCT high-frequency conefficients method % let A be the imput image; % let An be the imput image conbined with the gaussian noise; % use the dctmtx(I) to compute the 2D-DCT and the formula DCT=I*P*I'; % C1,C2,C3 the coding styles is C, which is the disadvantage in version 0.1 % $anthor: chencan $version:0.1 A=imread('lena.bmp');%读入图像信息，显示为3维； figure,imshow(A) An=imnoise(A,'gaussian',0,(20/255)^2);% 学会imnoise函数的使用方法; figure,imshow(An) An=double(An);%此句必不可少，转化为double精度 % compute the DCT of each block in C I=dctmtx(8); for p=1:8:505 for q=1:8:505 P=An(p:p+7,q:q+7); K=I*P*I'; C(p:p+7,q:q+7)=K; end end k=1.0061426171829178 N=4096;%number of blocks in C %Obtain all coefficients at position[6,7] r=1; for p=1:8:505 for q=1:8:505 temp=C(p:p+7,q:q+7); C1(r)=temp(6,7); r=r+1; end end %Obtain all coefficients at position[7,6] r=1; for p=1:8:505 for q=1:8:505 temp=C(p:p+7,q:q+7); C2(r)=temp(7,6); r=r+1; end end % Obtain all coefficients at position[7,7] r=1; for p=1:8:505 for q=1:8:505 temp=C(p:p+7,q:q+7); C3(r)=temp(7,7); r=r+1; end end test1=var(C1); test2=var(C2); test3=var(C3); result=sqrt((test1+test2+test3)/3)*k;