import numpy as np
import matplotlib.cm as cm
import matplotlib.pyplot as plt
import matplotlib.cbook as cbook
from matplotlib.path import Path
from matplotlib.patches import PathPatch

delta = 0.02
x = y = np.arange(-3.0, 3.0, delta)
X, Y = np.meshgrid(x, y)
# Z1 = np.cos(X)
# Z2 = np.sin(Y)
# Z = (Z1 - Z2) * 2

Z = np.cos(X)*np.sin(Y)

fig, ax = plt.subplots()


im = ax.imshow(Z, interpolation='nearest',
               origin='lower', extent=[-3, 3, -3, 3],
               vmax=abs(Z).max(), vmin=-abs(Z).max())

plt.show()