void MainWindow::wheelEvent(QWheelEvent *e)
{
    ui->graphicsView->setTransformationAnchor(QGraphicsView::AnchorUnderMouse);
    double scaleFactor=1.15;
    if(e->delta() > 0)
    {
        ui->graphicsView->scale(scaleFactor,scaleFactor);

    }
    else
    {
        ui->graphicsView->scale(1/scaleFactor,1/scaleFactor);
    }
}