"""
Image manipulation and NumPy arrays
====================================

This example shows how to do image manipulation using common NumPy arrays
tricks.

"""

import numpy as np
import scipy as sp
import matplotlib.pyplot as plt

face = sp.datasets.face(gray=True)
face[10:13, 20:23]
face[100:120] = 255

lx, ly = face.shape
X, Y = np.ogrid[0:lx, 0:ly]
mask = (X - lx/2)**2 + (Y - ly/2)**2 > lx*ly/4
face[mask] = 0
face[range(400), range(400)] = 255

plt.figure(figsize=(3, 3))
plt.axes([0, 0, 1, 1])
plt.imshow(face, cmap=plt.cm.gray)
plt.axis('off')

plt.show()