Make grid accept alpha rcParam

Default grid.alpha is 1.0

Author: dmcdougall

lib/matplotlib/axis.py

@@ -412,6 +412,7 @@ def _get_gridline(self):
                    color=rcParams['grid.color'],
                    linestyle=rcParams['grid.linestyle'],
                    linewidth=rcParams['grid.linewidth'],
+                   alpha=rcParams['grid.alpha'],
                    )
         l.set_transform(self.axes.get_xaxis_transform(which='grid'))
         l.get_path()._interpolation_steps = GRIDLINE_INTERPOLATION_STEPS
@@ -550,6 +551,7 @@ def _get_gridline(self):
                     color=rcParams['grid.color'],
                     linestyle=rcParams['grid.linestyle'],
                     linewidth=rcParams['grid.linewidth'],
+                    alpha=rcParams['grid.alpha'],
                     )
 
         l.set_transform(self.axes.get_yaxis_transform(which='grid'))

lib/matplotlib/rcsetup.py

@@ -539,6 +539,7 @@ def __call__(self, s):
     'grid.color'       : ['k', validate_color],       # grid color
     'grid.linestyle'   : [':', str],       # dotted
     'grid.linewidth'   : [0.5, validate_float],     # in points
+    'grid.alpha'       : [1.0, validate_float],
 
 
     # figure props