How to use an alpha channel image on a gtk window to do a pixmap

gistfile1.php

	/**
	 * public function set_image
	 *
	 * sets a background image for the splash screen
	 *
	 * @param string $image absolute path to splash background
	 * @return void
	 */
	public function set_image($image)
	{
		$pixbuf = GdkPixbuf::new_from_file($image);
		list($pixmap, $mask) = $pixbuf->render_pixmap_and_mask();
		list($width, $height) = $pixmap->get_size();
		$this->set_app_paintable(true);
		$this->set_size_request($width, $height);
		$this->realize();
		if($mask instanceof GdkPixmap)
		{
			$this->shape_combine_mask($mask, 0, 0);
		}
		$this->window->set_back_pixmap($pixmap, false);
		return;
	}