如何在Qt中放大/缩小图像的选定部分？

QImage image;
image.load("path/to/image.png");

QGraphicsScene scene;
QGraphicsView view(&scene);
view.setRenderHints(QPainter::Antialiasing | QPainter::SmoothPixmapTransform);

QPixmap pixmap = QPixmap::fromImage(image);
QGraphicsPixmapItem *item = new QGraphicsPixmapItem(pixmap);
scene.addItem(item);

void MyGraphicsView::mousePressEvent(QMouseEvent *event) {
    // 记录鼠标点击的位置
    startPoint = event->pos();
}

void MyGraphicsView::mouseReleaseEvent(QMouseEvent *event) {
    // 计算鼠标点击的区域
    QRect rect(startPoint, event->pos());

    // 获取选定区域的图像
    QPixmap pixmap = this->grab(rect);

    // 创建一个新的QGraphicsPixmapItem来显示选定区域的图像
    QGraphicsPixmapItem *item = new QGraphicsPixmapItem(pixmap);
    scene.addItem(item);

    // 设置缩放比例
    item->setScale(2.0); // 放大两倍

    // 清除选定区域
    startPoint = QPoint();
}

QMainWindow window;
window.setCentralWidget(&view);
window.show();