export default function ( hexColor , lightness ) { let hex = String ( hexColor ) . replace ( /[^0-9a-f]/gi , '' ) ; if ( hex . length < 6 ) { hex = hex . replace ( /(.)/g , '$1$1' ) ; } const lum = lightness || 0 ; let rgb = '#' ; let c ; for ( let i = 0 ; i < 3 ; ++ i ) { c = parseInt ( hex . substr ( i * 2 , 2 ) , 16 ) ; c = Math . round ( Math . min ( Math . max ( 0 , c + c * lum ) , 255 ) ) . toString ( 16 ) ; rgb += ( '00' + c ) . substr ( c . length ) ; } return rgb ; }