import numpy as np
import pylab
import matplotlib.cm as cm
import Image
f = pylab.figure()
for n, fname in enumerate(('1.png', '2.png')):
    image = Image.open(fname).convert('L')
arr = np.asarray(image)
f.add_subplot(2, 1, n)
pylab.imshow(arr, cmap=cm.Greys_r)
pylab.title('Double image')
pylab.show()
display two png images simultaneously using pylab