www.pudn.com > MatlabSIFT.zip > fit_paraboloid.m

function [yctr,xctr] = fit_paraboloid(data) 
 
%Create Solution Matrix 
[yp,xp] = meshgrid(-1:1,-1:1); 
yp=yp(:); xp=xp(:); 
 
M=zeros(9,6); 
for i=1:length(yp) 
    x=xp(i); y=yp(i); 
    M(i,:) = [x^2 y^2 x*y x y 1]; 
end 
 
g = data'; 
g = g(:); 
 
cf = inv(M'*M)*M'*g; 
a=cf(1); b=cf(2); c=cf(3); d=cf(4); e=cf(5); 
xctr = (-2*b*d+e*c)/(4*a*b-c*c); 
yctr = (-2*a*e-d*c)/(4*a*b-c*c); 
 
%A = [a c/2; c/2 b]; 
%[u,s,v] = svd(A);