close all;
close all;
clc;
img=zeros(100,100);
img(20:80,40:60)=1;
subplot(1,3,1);imshow(img);%产生图像
f=fft2(img);
magnitude=log(1+abs(f));
subplot(1,3,2);imshow(magnitude,[]);%进行傅里叶变换，产生频谱图
img1=zeros(100,100);
for x=1:100
for y=1:100
img1(x,y)=(-1)^(x+y)*img(x,y);
end
end
f=fft2(img1);
magnitude1=log(1+abs(f));
subplot(1,3,3);imshow(magnitude1,[]);
