multiplier_rgba
for_each_pixel(multiplier_rgba<color_type, order_type>::premultiply);
for_each_pixel(multiplier_rgba<color_type, order_type>::demultiply);
for_each_pixel(multiplier_rgba<color_type, order_type>::premultiply);
for_each_pixel(multiplier_rgba<color_type, order_type>::demultiply);