title: opencv Saddle point detection 2d image, exclude non saddle corners
body: <p>What is the best way to find only saddle points in 2d image? seems like all the corner algos in opencv return saddles and corners alike.</p>
  <p>i am in the process of a heuristic solution, but hope there are better ways</p>
  <p>Note: i originally asked the question on opencv forum, but reposting here due to lack of response.</p>