% Optical Imaging and Spectroscopy
%
% David J. Brady
% Duke University
% www.opticalimaging.org
%
% figure 8.4
%
% Comparison of transfer functions for MURA codes of various order
%
%
%
snr=10;
hh1=1./(1+snr*ones(128,1));
p=13;
qr=qres(p);
t=zeros(p);
t(2:p,1)=1;
for i=2:p
    for j=2:p
        if qr(i-1)==qr(j-1)
            t(i,j)=1;
        end
    end
end
th=zeros(256);
th(1:p,1:p)=t;
th=1./(1+snr*abs(fftshift(fft2(th))).^2);
t13=th(129:256,128);
p=23;
qr=qres(p);
t=zeros(p);
t(2:p,1)=1;
for i=2:p
    for j=2:p
        if qr(i-1)==qr(j-1)
            t(i,j)=1;
        end
    end
end
th=zeros(256);
th(1:p,1:p)=t;
th=1./(1+snr*abs(fftshift(fft2(th))).^2);
t23=th(129:256,128);
p=41;
qr=qres(p);
t=zeros(p);
t(2:p,1)=1;
for i=2:p
    for j=2:p
        if qr(i-1)==qr(j-1)
            t(i,j)=1;
        end
    end
end
th=zeros(256);
th(1:p,1:p)=t;
th=1./(1+snr*abs(fftshift(fft2(th))).^2);
t41=th(129:256,128);
figure(1);set(gcf,'color','white');
x=linspace(0,1,128);
semilogy(x,t13,'-k',x,t23,'--k',x,t41,'-.k',x,hh1,':k');
legend('p=13','p=23','p=41','p=1');xlabel('Spatial frequency');ylabel('relative error');