% 園形圖二維離散付氏變換幅度譜偽彩色顯示  s086
I86=zeros(256,256);
I860=zeros(256,256);
for i=1:256
    for j=1:256
        d=sqrt((i-128)^2+(j-128)^2);
        if d<6
          I86(i,j)=1;
        end
        if d<12
          I860(i,j)=1;
        end
    end
end
I861=fft2(I86);
I862=fft2(I860);
subplot(1,2,1),imshow(log(abs(I861)),[]),colormap(jet(64));
subplot(1,2,2),imshow(log(abs(I862)),[]),colormap(jet(64))