.. _pylab_examples-image_masked:

pylab_examples example code: image_masked.py
============================================



.. plot:: /home/mdboom/Work/builds/matplotlib/doc/mpl_examples/pylab_examples/image_masked.py

::

    #!/usr/bin/env python
    '''imshow with masked array input and out-of-range colors.
    
        The second subplot illustrates the use of BoundaryNorm to
        get a filled contour effect.
    '''
    
    from pylab import *
    from numpy import ma
    import matplotlib.colors as colors
    
    delta = 0.025
    x = y = arange(-3.0, 3.0, delta)
    X, Y = meshgrid(x, y)
    Z1 = bivariate_normal(X, Y, 1.0, 1.0, 0.0, 0.0)
    Z2 = bivariate_normal(X, Y, 1.5, 0.5, 1, 1)
    Z = 10 * (Z2-Z1)  # difference of Gaussians
    
    # Set up a colormap:
    palette = cm.gray
    palette.set_over('r', 1.0)
    palette.set_under('g', 1.0)
    palette.set_bad('b', 1.0)
    # Alternatively, we could use
    # palette.set_bad(alpha = 0.0)
    # to make the bad region transparent.  This is the default.
    # If you comment out all the palette.set* lines, you will see
    # all the defaults; under and over will be colored with the
    # first and last colors in the palette, respectively.
    Zm = ma.masked_where(Z > 1.2, Z)
    
    # By setting vmin and vmax in the norm, we establish the
    # range to which the regular palette color scale is applied.
    # Anything above that range is colored based on palette.set_over, etc.
    
    subplot(1,2,1)
    im = imshow(Zm, interpolation='bilinear',
        cmap=palette,
        norm = colors.Normalize(vmin = -1.0, vmax = 1.0, clip = False),
        origin='lower', extent=[-3,3,-3,3])
    title('Green=low, Red=high, Blue=bad')
    colorbar(im, extend='both', orientation='horizontal', shrink=0.8)
    
    subplot(1,2,2)
    im = imshow(Zm, interpolation='nearest',
        cmap=palette,
        norm = colors.BoundaryNorm([-1, -0.5, -0.2, 0, 0.2, 0.5, 1],
                            ncolors=256, clip = False),
        origin='lower', extent=[-3,3,-3,3])
    title('With BoundaryNorm')
    colorbar(im, extend='both', spacing='proportional',
                    orientation='horizontal', shrink=0.8)
    
    show()
    
    

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