title: Fastest available algorithm for distance transform
body: <p>I am looking for the fastest available algorithm for distance transform. </p>
  
  <p>According to this site <a href="http://homepages.inf.ed.ac.uk/rbf/HIPR2/distance.htm">http://homepages.inf.ed.ac.uk/rbf/HIPR2/distance.htm</a>, it describes: <em>"The distance transform can be calculated much more efficiently using clever algorithms in only two passes (e.g. Rosenfeld and Pfaltz 1968)."</em> </p>
  
  <p>Searching around, I found: <em>"Rosenfeld, A and Pfaltz, J L. 1968. Distance Functions on Digital Pictures. Pattern Recognition, 1, 33-61."</em> </p>
  
  <p>But I believe we should have a better and faster algorithm than the one in 1968 already? In fact, I could not find the source from 1968, so any help is highly appreciated.</p>