title: Why the Line (antialiased) function of openCV2 gives different results on CV_16UC1 and CV_8UC1 without overflow
body: <pre><code>themap = cv.CreateMat(8,8,cv.CV_8UC1)
  cv.SetZero(themap)
  cv.Line(themap,(0,0),(7,7),(10),1,cv.CV_AA) #draw a line
  print np.asarray(themap[:,:])
  
  #######output
  [[ 0  0  0  0  0  0  0  0]
   [ 0  0  0  0  0  0  0  0]
   [ 0  2  7  2  0  0  0  0]
   [ 0  0  3 10  3  0  0  0]
   [ 0  0  0  3 10  3  0  0]
   [ 0  0  0  0  2  7  2  0]
   [ 0  0  0  0  0  0  0  0]
   [ 0  0  0  0  0  0  0  0]]
  </code></pre>
  
  <p>However, when I change the image type to <code>cv.CV_16UC1</code>, the result is totally different:</p>
  
  <pre><code>themap = cv.CreateMat(8,8,cv.CV_16UC1)
  cv.SetZero(themap)
  cv.Line(themap,(0,0),(7,7),(10),1,cv.CV_AA) #draw a line
  print np.asarray(themap[:,:])
  
  #######output
  [[10  0  0  0  0  0  0  0]
   [ 0 10  0  0  0  0  0  0]
   [ 0  0 10  0  0  0  0  0]
   [ 0  0  0 10  0  0  0  0]
   [ 0  0  0  0 10  0  0  0]
   [ 0  0  0  0  0 10  0  0]
   [ 0  0  0  0  0  0 10  0]
   [ 0  0  0  0  0  0  0 10]]
  </code></pre>
  
  <p>I'm totally confused by such results. Since the pixel value is only 10, there should not be overflow problems for <code>cv.CV_8UC1</code> image type. Why the results of <code>cv.Line</code> can be so different?</p>
  
  <p>The opencv in installed in <code>/usr/local/Cellar/opencv@2/2.4.13.6_2/lib/python2.7/site-packages/cv.py</code> with <code>brew install opencv@2</code>.</p>