figure(1)
clf
a = imread('001.JPG',  'jpeg');
b = a(:,:,2);
imagesc(b);
colormap(gray)

figure(2)
clf
c = fft2(b);
imagesc(abs(fftshift(c)));
colormap(gray)

figure(3)
clf
m = size(c,1); n = size(c,2);
H = ones(m,n);
center_m = round(m/2);
center_n = round(n/2);
H(center_m-20:center_m+20, center_n-20:center_n+20) = zeros(41,41);
d = fftshift(c).*H;
e = ifft2(fftshift(d));
imagesc(abs(e));
colormap(gray)

