text: from __future__ import print_function
  import matplotlib.pyplot as plt
  import numpy as np
  import matplotlib.cbook as cbook
  
  w, h = 512, 512
  
  datafile = cbook.get_sample_data('ct.raw.gz', asfileobj=True)
  s = datafile.read()
  A = np.fromstring(s, np.uint16).astype(float)
  A *= 1.0 / max(A)
  A.shape = w, h
  
  extent = (0, 25, 0, 25)
  im = plt.imshow(A, cmap=plt.cm.hot, origin='upper', extent=extent)
  
  markers = [(15.9, 14.5), (16.8, 15)]
  x, y = zip(*markers)
  plt.plot(x, y, 'o')
  
  plt.title('CT density')
  
  plt.show()
  