"""
Plot the block mean of an image
================================

An example showing how to use broad-casting to plot the mean of
blocks of an image.
"""

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

f = sp.datasets.face(gray=True)
sx, sy = f.shape
X, Y = np.ogrid[0:sx, 0:sy]

regions = sy//6 * (X//4) + Y//6
block_mean = sp.ndimage.mean(f, labels=regions,
                          index=np.arange(1, regions.max() +1))
block_mean.shape = (sx//4, sy//6)

plt.figure(figsize=(5, 5))
plt.imshow(block_mean, cmap=plt.cm.gray)
plt.axis('off')

plt.show()