title: Rotate 2D points using openCV and python
body: <p>I am using <code>cv2.getRotationMatrix2D</code> to get a 2x3 matrix to rotate a source image. This works fine. Now i have several 2D coordinates, which represent points in the unrotated image. 
  Can I use the same matrix to rotate the indiviual points and if yes, how?
  If i understood correcty, I should be able to multiply the matrix with the (x,y)-coordinates, but no matter which combination of matrix and points I try, I never get simple x and y coordinates as a result.</p>
  
  <p>Thanks for your help!</p>
  
  <p>Edit:</p>
  
  <p>the rotation matrix is</p>
  
  <pre><code>[[  9.24630834e-01   3.80864571e-01   1.52747702e-01]
   [ -3.80864571e-01   9.24630834e-01   1.57068951e+02]]
  </code></pre>
  
  <p>What I am doing so far:</p>
  
  <pre><code>point = np.array([marker.x, marker.y, 1])
  transform = rot_matrix * point.T
  print transform
  </code></pre>
  
  <p>But this does not give me a 2x1 matrix as it should, but: </p>
  
  <pre><code>[[  2.10815830e+02   7.92198307e+01   1.52747702e-01]
   [ -8.68371221e+01   1.92323213e+02   1.57068951e+02]]
  </code></pre>