title: Drawing true filled circle on an image
body: <p>I have an image which I define like the following:</p>
  
  <p><code>img = np.zeros(474,474)</code></p>
  
  <p>I would like to draw true filled circles and not polygonal approximations of circles on this image at different coordinates as centre and of a fixed radius. For example, I want to draw two circles with centres <code>(100,200)</code> and <code>(150,372)</code> with radius <code>2</code> pixels. What I am expecting is that after plotting the circles, the entries of the original image <code>img</code> should change to all ones where the circle is present. 
  I tried opencv <code>cv.circle</code>module as well as <code>skimage.draw.circle</code> module but they generate some polynomial approximation of circle. 
  I was also trying the following in <code>matplotlib</code> but I don't seem to understand how to plot it on my image <code>img</code>. 
  Any help would be appreciated.</p>
  
  <pre><code>from matplotlib.patches import Circle
  img=np.zeros(474,474)
  fig = plt.figure()
  ax = fig.add_subplot(111)
  centers = [(100,200),(150,372)]
  for i in range(len(centers)):
      Circle((centers[i][0],centers[i][1]), radius= 2)
  </code></pre>