+ $previewcontent->rect($llx - 20, $lly + $ury, 20, 20); # upper left
+ $previewcontent->rect($llx + $urx, $lly + $ury, 20, 20); # upper right
+ $previewcontent->rect($llx - 20, $lly - 20, 20, 20); # lower left
+ $previewcontent->rect($llx + $urx, $lly - 20, 20, 20); # lower right