Updated shading example to show new styles and added exmaple DEM from…

… SRTM data
matplotlib · jenshnielsen · Sep 29, 2014 · Jul 21, 2014 · Jul 21, 2014 · Jul 21, 2014
commit ed5cd76d231a8279633bde02e6549350c005fa82
diff --git a/examples/pylab_examples/shading_example.py b/examples/pylab_examples/shading_example.py
@@ -1,28 +1,49 @@
 import numpy as np
 import matplotlib.pyplot as plt
 from matplotlib.colors import LightSource
+from matplotlib import cbook
 
-# example showing how to make shaded relief plots 
+# Example showing how to make shaded relief plots 
 # like Mathematica
 # (http://reference.wolfram.com/mathematica/ref/ReliefPlot.html)
 # or Generic Mapping Tools
 # (http://gmt.soest.hawaii.edu/gmt/doc/gmt/html/GMT_Docs/node145.html)
 
-# test data
-X,Y=np.mgrid[-5:5:0.05,-5:5:0.05]
-Z=np.sqrt(X**2+Y**2)+np.sin(X**2+Y**2)
-# create light source object.
-ls = LightSource(azdeg=0,altdeg=65)
-# shade data, creating an rgb array.
-rgb = ls.shade(Z,plt.cm.copper)
-# plot un-shaded and shaded images.
-plt.figure(figsize=(12,5))
-plt.subplot(121)
-plt.imshow(Z,cmap=plt.cm.copper)
-plt.title('imshow')
-plt.xticks([]); plt.yticks([])
-plt.subplot(122)
-plt.imshow(rgb)
-plt.title('imshow with shading')
-plt.xticks([]); plt.yticks([])
-plt.show()
+def main():
+    # Test data
+    x, y = np.mgrid[-5:5:0.05, -5:5:0.05]
+    z = 5 * (np.sqrt(x**2 + y**2) + np.sin(x**2 + y**2))
+    fig = compare(z, plt.cm.copper)
+    fig.suptitle('HSV Blending Looks Best with Smooth Surfaces', y=0.95)
+
+    dem = np.load(cbook.get_sample_data('jacksboro_fault_dem.npz'))
+    fig = compare(dem['elevation'], plt.cm.gist_earth, ve=0.05)
+    fig.suptitle('Overlay Blending Looks Best with Rough Surfaces', y=0.95)
+
+    plt.show()
+
+def compare(z, cmap, ve=1):
+    # Create subplots and hide ticks
+    fig, axes = plt.subplots(ncols=2, nrows=2)
+    for ax in axes.flat:
+        ax.set(xticks=[], yticks=[])
+
+    # Illuminate the scene from the northwest
+    ls = LightSource(azdeg=315, altdeg=45)
+
+    axes[0,0].imshow(z, cmap=cmap)
+    axes[0,0].set(xlabel='Colormapped Data')
+
+    axes[0,1].imshow(ls.hillshade(z, vert_exag=ve), cmap='gray')
+    axes[0,1].set(xlabel='Illumination Intensity')
+
+    axes[1,0].imshow(ls.shade(z, cmap=cmap, vert_exag=ve, blend_mode='hsv'))
+    axes[1,0].set(xlabel='Blend Mode: "hsv" (default)')
+
+    axes[1,1].imshow(ls.shade(z, cmap=cmap, vert_exag=ve, blend_mode='overlay'))
+    axes[1,1].set(xlabel='Blend Mode: "overlay"')
+
+    return fig
+
+if __name__ == '__main__':
+    main()
diff --git a/lib/matplotlib/mpl-data/sample_data/jacksboro_fault_dem.npz b/lib/matplotlib/mpl-data/sample_data/jacksboro_fault_dem.npz