ffttest.m

由上述实验过程的图像变化可知

   I = imread('lena1.bmp');
   data=zeros(8,8);
   J=fft2(I);K=fftshift(J);
   for m=1:256
       for n=1:256
    
%           distance=sqrt((m-128)^2+(n-128)^2);
        
 %          if distance>100
  %              K(m,n)=0;
  %        end
           
       end
   end
   JJ=ifftshift(K);
   R=ifft2(JJ);
      
    imshow(abs(R),[])
   % imshow(log(abs(K)),[])