title: Opencv in python: grabcut way too slow. Thinking about cropping an image with mouse first and then using grabcut
body: <p>I am working on using some image processing techniques to extract an object, with python. The code I am following is based on here.
  <a href="https://github.com/Itseez/opencv/blob/master/samples/python2/grabcut.py" rel="nofollow">https://github.com/Itseez/opencv/blob/master/samples/python2/grabcut.py</a></p>
  
  <p>However,the algorithm is waaaay to slow. Therefore what I am thinking is that I first let the user crop a smaller rectangular region of interest, then running the code on grabcut.</p>
  
  <p>I have two questions:</p>
  
  <ol>
  <li>Will this speed up the grabcut process?</li>
  <li>If so, what is the simplest way of letting user draw a rectangle and crop it out? The problem here is the "onmouse" cannot return anything, otherwise I can take advantage of the code already existing to draw the rectangle.</li>
  </ol>
  
  <p>Thanks</p>