Transparent background

Hey. Great plugin, thanks!
I changed the code snippet to keep a transparent background. But if the plugin is updated, this code will be lost. Maybe it makes sense to add this code to the plugin?

// create backgound
        $monster = @imagecreatetruecolor(256, 256)
        or die("GD image create failed");
        $color   = imagecolorallocatealpha($monster, 0, 0, 0, 127);
        imagesavealpha($monster, true);
	imagefill($monster,0,0,$color);
        imagefilledrectangle($monster, 0, 0, 256, 256, $color);