text: """
  =========================
  Frontpage contour example
  =========================
  
  This example reproduces the frontpage contour example.
  """
  
  import matplotlib.pyplot as plt
  import numpy as np
  from matplotlib import mlab, cm
  
  extent = (-3, 3, -3, 3)
  
  delta = 0.5
  x = np.arange(-3.0, 4.001, delta)
  y = np.arange(-4.0, 3.001, delta)
  X, Y = np.meshgrid(x, y)
  Z1 = mlab.bivariate_normal(X, Y, 1.0, 1.0, 0.0, -0.5)
  Z2 = mlab.bivariate_normal(X, Y, 1.5, 0.5, 1, 1)
  Z = (Z1 - Z2) * 10
  
  levels = np.linspace(-2.0, 1.601, 40)
  norm = cm.colors.Normalize(vmax=abs(Z).max(), vmin=-abs(Z).max())
  
  fig, ax = plt.subplots()
  cset1 = ax.contourf(
      X, Y, Z, levels,
      norm=norm)
  ax.set_xlim(-3, 3)
  ax.set_ylim(-3, 3)
  ax.set_xticks([])
  ax.set_yticks([])
  fig.savefig("contour_frontpage.png", dpi=25)  # results in 160x120 px image
  