private function getImageRtfWidth()
    {
        if ($this->_width > 0) {
            return PHPRtfLite_Unit::getUnitInTwips($this->_width);
        }

        $imageWidth = $this->_imageWidth ? $this->_imageWidth : 100;
        if ($this->_height > 0) {
            $imageHeight = $this->_imageHeight ? $this->_imageHeight : 100;
            $width = ($imageWidth / $imageHeight) * $this->_height;
            return PHPRtfLite_Unit::getUnitInTwips($width);
        }

        return PHPRtfLite_Unit::getPointsInTwips($imageWidth);
    }