import numpy as np

import matplotlib.pyplot as plt
from matplotlib.patches import Circle

image = np.random.random((10,10))
c = Circle((5., 5.), 3.)

fig = plt.figure()
ax = fig.add_subplot(1,1,1)
ax.imshow(image, interpolation='nearest', vmin=-2., vmax=3.)
ax.add_patch(c)
fig.savefig('nearest.png')

fig = plt.figure()
ax = fig.add_subplot(1,1,1)
ax.imshow(image, vmin=-2., vmax=3.)
ax.add_patch(c)
fig.savefig('default.png')