Detecting color clipping and added control over clipping_colors

holoviews/plotting/mpl/element.py

@@ -1,4 +1,4 @@
-import math
+import math, copy
 
 from matplotlib import ticker
 from matplotlib import colors
@@ -497,8 +497,10 @@ class ColorbarPlot(ElementPlot):
     colorbar = param.Boolean(default=False, doc="""
         Whether to draw a colorbar.""")
 
-    cbar_width = param.Number(default=0.05, doc="""
-        Width of the colorbar as a fraction of the main plot""")
+    clipping_colors = param.Dict(default={'NaN': ('w', 1)}, doc="""
+        Dictionary to specify colors for clipped values, allows setting
+        color for NaN values and for values above and below the min and
+        max value.""")
 
     cbar_padding = param.Number(default=0.01, doc="""
         Padding between colorbar and other plots.""")
@@ -510,11 +512,18 @@ class ColorbarPlot(ElementPlot):
         set to None default matplotlib ticking behavior is
         applied.""")
 
+    cbar_width = param.Number(default=0.05, doc="""
+        Width of the colorbar as a fraction of the main plot""")
+
     symmetric = param.Boolean(default=False, doc="""
         Whether to make the colormap symmetric around zero.""")
 
     _colorbars = {}
 
+    def __init__(self, *args, **kwargs):
+        super(ColorbarPlot, self).__init__(*args, **kwargs)
+        self._cbar_extend = 'neither'
+
     def _adjust_cbar(self, cbar, label, dim):
         noalpha = math.floor(self.style[self.cyclic_index].get('alpha', 1)) == 1
         if (cbar.solids and noalpha):
@@ -571,7 +580,7 @@ def _draw_colorbar(self, artist, element, dim=None):
             scaled_w = w*width
             cax = fig.add_axes([l+w+padding+(scaled_w+padding+w*0.15)*offset,
                                 b, scaled_w, h])
-            cbar = plt.colorbar(artist, cax=cax)
+            cbar = plt.colorbar(artist, cax=cax, extend=self._cbar_extend)
             self._adjust_cbar(cbar, label, dim)
             self.handles['cax'] = cax
             self.handles['cbar'] = cbar
@@ -608,6 +617,27 @@ def _norm_kwargs(self, element, ranges, opts, vdim):
         opts['vmin'] = clim[0]
         opts['vmax'] = clim[1]
 
+        # Check whether the colorbar should indicate clipping
+        el_min, el_max = element.range(vdim)
+        if el_min < opts['vmin'] and el_max > opts['vmax']:
+            self._cbar_extend = 'both'
+        elif el_min < opts['vmin']:
+            self._cbar_extend = 'min'
+        elif el_max > opts['vmax']:
+            self._cbar_extend = 'max'
+
+        # Define special out-of-range colors on colormap
+        cmap_name = opts.pop('cmap', None)
+        cmap = copy.copy(plt.cm.get_cmap('gray' if cmap_name is None else cmap_name))
+        if 'max' in self.clipping_colors:
+            cmap.set_over(*util.wrap_tuple(self.clipping_colors['max']))
+        if 'min' in self.clipping_colors:
+            cmap.set_under(*util.wrap_tuple(self.clipping_colors['min']))
+        if 'NaN' in self.clipping_colors:
+            cmap.set_bad(*util.wrap_tuple(self.clipping_colors['NaN']))
+        opts['cmap'] = cmap
+
+
 
 class LegendPlot(ElementPlot):
 

holoviews/plotting/mpl/raster.py

@@ -155,10 +155,8 @@ def get_data(self, element, ranges, style):
         _, style, axis_kwargs = super(HeatMapPlot, self).get_data(element, ranges, style)
         data = element.raster
         data = np.ma.array(data, mask=np.logical_not(np.isfinite(data)))
-        cmap_name = style.pop('cmap', None)
-        cmap = copy.copy(plt.cm.get_cmap('gray' if cmap_name is None else cmap_name))
-        cmap.set_bad('w', 1.)
-        style['cmap'] = cmap
+        vdim = element.vdims[0]
+        self._norm_kwargs(element, ranges, style, vdim)
         style['annotations'] = self._annotate_values(element)
         return [data], style, axis_kwargs