public function setWatermark(Container $watermark)
{
$watermark->setParent($this);
$watermark->setAttribute('vertical-align', self::VERTICAL_ALIGN_MIDDLE);
$watermark->setHeight($this->getHeight());
$watermark->setWidth($this->getWidth());
$watermark->setBoundary(clone $this->getBoundary());
$this->watermark = $watermark;
}
