title: apply the edge detection in an image segmentation
body: <p>I have two questions about snake edge detection.
  The first question is, in openCV there is a function cvSnakeImage(src,points,.......), what does the points parameter mean?</p>
  
  <p>The second questions is: I want to  apply this function on the part surrounded by an edge that I have already made, how can I do this?</p>
  
  <p>This is my code for edge detection:</p>
  
  <pre><code>cvCanny(img_bw, img_canny , thresh, thresh * 50, 3);
  
  cvFindContours(img_canny, contour, &amp;contours, sizeof(CvContour), CV_RETR_TREE,    CV_CHAIN_APPROX_SIMPLE);
  </code></pre>