class ViewerScene : public QGraphicsScene
{
   Q_OBJECT
public:
  ViewerScene(QWidget* parent = 0, const char* name = 0);
  void setBackgroundPixmap(const QPixmap& pixmap);
  void setRect(const QRect& rect);
  void getRect(QRect& rect);

protected:
  virtual void drawBackground(QPainter* painter, const QRectF& rect);

private:
  QPixmap m_backgroundPixmap;
  QRect m_rect;

void ViewerScene::drawBackground(QPainter* painter, const QRectF & rect)
{
  QRect sourceRect(0, 0, m_backgroundPixmap.width(),
  m_backgroundPixmap.height());
  painter->drawPixmap(m_rect, m_backgroundPixmap, sourceRect);
  QGraphicsScene::drawBackground(painter, rect);
}

QRect r;
scene->getRect(r);
QPoint p = your_QGraphicsView->mapFromScene(r.topLeft());
qDebug() << p;