protected function _set_stroke_color($color)
    {
        $this->_pdf->setStrokeColor($color);
        $alpha = isset($color["alpha"]) ? $color["alpha"] : 1;
        if ($this->_current_opacity != 1) {
            $alpha *= $this->_current_opacity;
        }
        $this->_set_line_transparency("Normal", $alpha);
    }