• matplotlib 1.5.3, python 3.5.1, macos.

I have a grayscale image:

But plt.inshow displays a wrong image (clearly, it differs from the origin one):

 from PIL import Image
 import matplotlib.pyplot as plt
 import matplotlib.cm as cm
 img = Image.open('...')
 plt.imshow(image, cmap=cm.gray)

I have tried Display image as grayscale using matplotlib, but it dose not work still.

My question is: how to display grayscale image correctly using pyplot?