protected function _set_stroke_colour($colour) {
    $colour[0] = round(255 * $colour[0]);
    $colour[1] = round(255 * $colour[1]);
    $colour[2] = round(255 * $colour[2]);

    if ( is_null($this->_last_stroke_color) || $color != $this->_last_stroke_color ) {
      $this->_pdf->SetDrawColor($color[0],$color[1],$color[2]);
      $this->_last_stroke_color = $color;
    }

  }