d=[1 -1 0 0 0 0 0 0 ];
d1=[0 1 -1 0 0 0 0 0];
d2=[0 0 1 -1 0 0 0 0];
d3=[0 0 0 1 -1 0 0 0];
d4=[0 0 0 0 1 -1 0 0];
d5=[0 0 0 0 0 1 -1 0];
d6=[0 0 0 0 0 0 1 -1];
d7=[-1 0 0 0 0 0 0 1];
D = [d;d1;d2;d3;d4;d5;d6;d7];
L =[0 0 0 0 0 0 0 0;
0 0 0 0 0 0 0 0;
0 0 1 1 1 1 0 0;
0 0 1 1 1 1 0 0;
0 0 1 1 1 1 0 0;
0 0 1 1 1 1 0 0;
0 0 0 0 0 0 0 0;
0 0 0 0 0 0 0 0;];
L=L/max(max(L));
S1 = (D*L);
[m,n] = size(S1);
K=(psf2otf([-1;1],[8,8]));
FL=fft2(L);
S2 = K.*FL;
S2 =(real(ifft2(S2)));
S2=S2/max(max(S2));
subplot(121);imagesc(S1);subplot(122);imagesc(S2);