I=imread('i.bmp');
X=double(I);
[row,col]=size(X);
for u=1:col
I2(:,u)=fft(X(:,u));% 得到圖象X的某一(u)列數(shù)據(jù)
end
for v=1:row
I3(v,:)=fft(I2(v,:));
end 
I4=fftshift(I3);
RR=real(I4);
II=imag(I4);
C=sqrt(RR.^2+II.^2);
C=(C-min(min(C)))/(max(max(C))-min(min(C)))*255;
figure;
imshow(C)