title: TypeError: <unknown> is not a numpy array in cv2.calcOpticalFlowPyrLK()
body: <p>I'm trying to make an LK tracker in OpenCV 2.3.1 with python bindings. When I do</p>
  
  <pre><code>calcOpticalFlowPyrLK(img1, img2,
                     template_pt, target_pt, status, err, 
                     (win_size_lk, win_size_lk), 0, TERM_CRITERIA_EPS, 
                     (TERM_CRITERIA_EPS | TERM_CRITERIA_COUNT, 10, 0.03), eig)
  </code></pre>
  
  <p>I'm getting </p>
  
  <p><strong>TypeError:  is not a numpy array</strong></p>
  
  <p>where</p>
  
  <pre><code>img1, img2 - iplimage
  template_pt, target_pt - A List consisting of tuples with two integers eg. [(120,140),(300,400),..]
  win_size_lk = 10
  eig = 0.001
  status = ""
  err = None
  </code></pre>
  
  <p>More info about cv2.calcOpticalFlowPyrLK() is given here</p>
  
  <p><a href="http://opencv.itseez.com/modules/video/doc/motion_analysis_and_object_tracking.html?highlight=opticalflow#cv.CalcOpticalFlowPyrLK" rel="nofollow">http://opencv.itseez.com/modules/video/doc/motion_analysis_and_object_tracking.html?highlight=opticalflow#cv.CalcOpticalFlowPyrLK</a></p>
  
  <p>When I set</p>
  
  <pre><code>eig = np.array([(0.0,1.0),(1.0,0.0)])
  </code></pre>
  
  <p>It gives me the following error</p>
  
  <p><strong>TypeError: only length-1 arrays can be converted to Python scalars</strong></p>
  
  <p>What could be the problem here ?</p>