title: Automatic calculation of low and high thresholds for the Canny operation in opencv
body: <p>In OpenCV, the low and high thresholds for the canny operator are mandatory:</p>
  <pre><code>cvCanny(input,output,thresh1,thresh2)
  </code></pre>
  <p>In Matlab, there's an option to calculate those automatically:</p>
  <pre><code>edge(input,'canny')
  </code></pre>
  <p>I've looked into Matlab's code for edge, and this is really not straight forward to calculate those automatically.</p>
  <p>Are you aware of any implementation of the canny operator along with automatic threshold calculation for OpenCV?</p>