FIX: mark the array data as updated to force to_rgba

tacaswell · tacaswell · commit 2bcbe5b67820 · 2017-07-28T17:43:34.000-04:00
closes #8953
diff --git a/lib/matplotlib/collections.py b/lib/matplotlib/collections.py
@@ -711,6 +711,7 @@ def set_alpha(self, alpha):
                 float(alpha)
             except TypeError:
                 raise TypeError('alpha must be a float or None')
+        self.update_dict['array'] = True
         artist.Artist.set_alpha(self, alpha)
         self._set_facecolor(self._original_facecolor)
         self._set_edgecolor(self._original_edgecolor)
