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

function v = interp(img,xc,yc) 
 
 
       px = floor(xc); 
       py = floor(yc); 
       alpha = xc-px; 
       beta = yc-py; 
 
       nw = img(py,px); 
       ne = img(py,px+1); 
       sw = img(py+1,px); 
       se = img(py+1,px+1); 
        
       v = (1-alpha)*(1-beta)*nw + ...  %interpolate 
              (1-alpha)*beta*sw + ... 
              alpha*(1-beta)*ne + ... 
              alpha*beta*se;