Added *vmin* and *vmax* arguments to LightSource.shade

Author: joferkington

examples/specialty_plots/advanced_hillshading.py

@@ -40,7 +40,7 @@ def avoid_outliers():
     ax1.imshow(rgb)
     ax1.set_title('Full range of data')
 
-    rgb = ls.shade(z, plt.cm.copper, norm=Normalize(-10, 10)) # Note the norm!!
+    rgb = ls.shade(z, plt.cm.copper, vmin=-10, vmax=10)
     ax2.imshow(rgb)
     ax2.set_title('Manually set range')
 

lib/matplotlib/colors.py

@@ -1574,8 +1574,8 @@ def hillshade(self, elevation, vert_exag=1, dx=1, dy=1, fraction=1.):
 
         return intensity
 
-    def shade(self, data, cmap, norm=None, blend_mode='hsv',
-              vert_exag=1, dx=1, dy=1, fraction=1, **kwargs):
+    def shade(self, data, cmap, norm=None, blend_mode='hsv', vmin=None,
+              vmax=None, vert_exag=1, dx=1, dy=1, fraction=1, **kwargs):
         """
         Combine colormapped data values with an illumination intensity map
         (a.k.a.  "hillshade") of the values.
@@ -1603,6 +1603,14 @@ def shade(self, data, cmap, norm=None, blend_mode='hsv',
             array (also 0 to 1).  (Call signature `func(rgb, illum, **kwargs)`)
             Additional kwargs supplied to this function will be passed on to
             the *blend_mode* function.
+        vmin : scalar or None, optional
+            The minimum value used in colormapping *data*. If *None* the
+            minimum value in *data* is used. If *norm* is specified, then this
+            argument will be ignored.
+        vmax : scalar or None, optional
+            The maximum value used in colormapping *data*. If *None* the
+            maximum value in *data* is used. If *norm* is specified, then this
+            argument will be ignored.
         vert_exag : number, optional
             The amount to exaggerate the elevation values by when calculating
             illumination. This can be used either to correct for differences in
@@ -1626,8 +1634,12 @@ def shade(self, data, cmap, norm=None, blend_mode='hsv',
         rgba : ndarray
             An MxNx4 array of floats ranging between 0-1.
         """
+        if vmin is None:
+            vmin = data.min()
+        if vmax is None:
+            vmax = data.max()
         if norm is None:
-            norm = Normalize(vmin=data.min(), vmax=data.max())
+            norm = Normalize(vmin=vmin, vmax=vmax)
 
         rgb0 = cmap(norm(data))
         rgb1 = self.shade_rgb(rgb0, elevation=data, blend_mode=blend_mode,