/**
  * Opacity is not applied to layers of this type because each marker has an attribute set with
  * opacity control.
  *
  * @param opacity the current opacity value, which is ignored by this layer.
  */
 @Override
 public void setOpacity(double opacity) {
   super.setOpacity(opacity);
 }
 @Override
 public void setOpacity(double opacity) {
   super.setOpacity(opacity);
   recalculateColors();
 }