function colorLstar ( $col )
        {
#-k     color
#-      Given a color find its L* (perceptual lightness)
#-p     $col    - req   - Hex RGB color (Must be in the form #hhhhhh)
#-p             - ret   - L*
#-c     Myindex response 2019-06-19 on https://stackoverflow.com/questions/596216/formula-to-determine-brightness-of-rgb-color
#-d     2/19/21 - Added

        $Y = colorLuminance ( $col );
        return colorYtoLstar ( $Y );                    # perceived lightness
        }

?>