.. _pylab_examples-layer_images:

pylab_examples example code: layer_images.py
============================================



.. plot:: /home/tcaswell/source/my_source/matplotlib/doc/mpl_examples/pylab_examples/layer_images.py

::

    """
    Layer images above one another using alpha blending
    """
    from __future__ import division
    import matplotlib.pyplot as plt
    import numpy as np
    
    
    def func3(x, y):
        return (1 - x/2 + x**5 + y**3)*np.exp(-(x**2 + y**2))
    
    # make these smaller to increase the resolution
    dx, dy = 0.05, 0.05
    
    x = np.arange(-3.0, 3.0, dx)
    y = np.arange(-3.0, 3.0, dy)
    X, Y = np.meshgrid(x, y)
    
    # when layering multiple images, the images need to have the same
    # extent.  This does not mean they need to have the same shape, but
    # they both need to render to the same coordinate system determined by
    # xmin, xmax, ymin, ymax.  Note if you use different interpolations
    # for the images their apparent extent could be different due to
    # interpolation edge effects
    
    
    xmin, xmax, ymin, ymax = np.amin(x), np.amax(x), np.amin(y), np.amax(y)
    extent = xmin, xmax, ymin, ymax
    fig = plt.figure(frameon=False)
    
    Z1 = np.array(([0, 1]*4 + [1, 0]*4)*4)
    Z1.shape = (8, 8)  # chessboard
    im1 = plt.imshow(Z1, cmap=plt.cm.gray, interpolation='nearest',
                     extent=extent)
    plt.hold(True)
    
    Z2 = func3(X, Y)
    
    im2 = plt.imshow(Z2, cmap=plt.cm.jet, alpha=.9, interpolation='bilinear',
                     extent=extent)
    
    plt.show()
    

Keywords: python, matplotlib, pylab, example, codex (see :ref:`how-to-search-examples`)