function ts=shrink(t,f)% It shrinks an image in a factor f% in each dimension. %	ts = shrink(t,f)% ts may also be complex.% See also: expand.m, blurDn.m% JPM, April 95, Instituto de Optica, CSIC, Madrid.[my,mx]=size(t);T=fftshift(fft2(t))/f^2;Ts=zeros(my/f,mx/f);y1=my/2+2-my/(2*f);y2=my/2+my/(2*f);x1=mx/2+2-mx/(2*f);x2=mx/2+mx/(2*f);Ts(2:my/f,2:mx/f)=T(y1:y2,x1:x2);Ts(1,2:mx/f)=(T(y1-1,x1:x2)+T(y2+1,x1:x2))/2;Ts(2:my/f,1)=(T(y1:y2,x1-1)+T(y1:y2,x2+1))/2;Ts(1,1)=(T(y1-1,x1-1)+T(y1-1,x2+1)+T(y2+1,x1-1)+T(y2+1,x2+1))/4;Ts=fftshift(Ts);ts=ifft2(Ts);if all(imag(t)==0),	ts = real(ts);end