title: Laplacian of Gaussian in openCV, how to find zero crossings?
body: <p>There is Laplacian function in openCV which directly calculate the double derivative. But this doesn't mean I will get the edges right? Because in the output there are many negative values.
  I go through this link and realized that after that also I had to find zero-crossings. I don't get how to find zero crossings. Can somebody help me ?</p>