alpha_pen(const etl::generic_pen<Color, ColorAccumulator>& pen, const Color::value_type &a = 1, const _BlendFunc &func = _BlendFunc()):
etl::alpha_pen< etl::generic_pen<Color, ColorAccumulator>, Color::value_type, _BlendFunc >(pen,a,func)
{ }
alpha_pen(const etl::generic_pen<Color, ColorAccumulator>& pen, const Color::value_type &a = 1, const _BlendFunc &func = _BlendFunc()):
etl::alpha_pen< etl::generic_pen<Color, ColorAccumulator>, Color::value_type, _BlendFunc >(pen,a,func)
{ }