title: geometry of QGraphicsRectItem
body: <p>I have a qgraphicsRectItem drawn on a qgraphicsScene. With mouse events, it's being moved over the scene, resized and repositioned, ie, select the item, mousePress and mouseMove. How can I get the geometry of that qgraphicsRectItem boundingRect, pos wrt scene on mouseReleaseEvent?
  There's a image on scene, and a boundingrect of qgraphicsRectItem is drawn on the scene, then i need to get qrect for cropping that portion of image within the bounding rect. </p>