matplotlib.image:Clipping input data to the valid range for imshow with RGB data ([0..1] for floats or [0..255] for integers). code example

Example: Clipping input data to the valid range for imshow with RGB data ([0..1] for floats or [0..255] for integers)

np.array(img,np.int32)
or 
If you want to show it, you can use img/255