function twentynineteen_hsl_hex( $h, $s, $l, $to_hex = true ) {

  $h /= 360;
  $s /= 100;
  $l /= 100;

  $r = $l;
  $g = $l;
  $b = $l;
  $v = ( $l <= 0.5 ) ? ( $l * ( 1.0 + $s ) ) : ( $l + $s - $l * $s );

  if ( $v > 0 ) {
    $m       = $l + $l - $v;
    $sv      = ( $v - $m ) / $v;
    $h      *= 6.0;
    $sextant = floor( $h );
    $fract   = $h - $sextant;
    $vsf     = $v * $sv * $fract;
    $mid1    = $m + $vsf;
    $mid2    = $v - $vsf;

    switch ( $sextant ) {
      case 0:
        $r = $v;
        $g = $mid1;
        $b = $m;
        break;
      case 1:
        $r = $mid2;
        $g = $v;
        $b = $m;
        break;
      case 2:
        $r = $m;
        $g = $v;
        $b = $mid1;
        break;
      case 3:
        $r = $m;
        $g = $mid2;
        $b = $v;
        break;
      case 4:
        $r = $mid1;
        $g = $m;
        $b = $v;
        break;
      case 5:
        $r = $v;
        $g = $m;
        $b = $mid2;
        break;
    }
  }

  $r = round( $r * 255, 0 );
  $g = round( $g * 255, 0 );
  $b = round( $b * 255, 0 );

  if ( $to_hex ) {

    $r = ( $r < 15 ) ? '0' . dechex( $r ) : dechex( $r );
    $g = ( $g < 15 ) ? '0' . dechex( $g ) : dechex( $g );
    $b = ( $b < 15 ) ? '0' . dechex( $b ) : dechex( $b );

    return "#$r$g$b";

  }

  return "rgb($r, $g, $b)";
}