QT中QGraphicsItem 获取点坐标的几种方法

// 假设 item 是你的 QGraphicsEllipseItem 指针
if (QGraphicsEllipseItem* pointItem = qgraphicsitem_cast<QGraphicsEllipseItem*>(item)) {
    // 获取图元中心点在场景中的坐标
    QPointF scenePos = pointItem->scenePos();
    
    // 或者获取包围矩形的中心
    QRectF rect = pointItem->rect();
    QPointF centerInItem = rect.center();
    QPointF centerInScene = pointItem->mapToScene(centerInItem);
    
    qDebug() << "场景坐标:" << scenePos;
    qDebug() << "精确中心坐标:" << centerInScene;
}

QMap<int, QGraphicsEllipseItem*> pointMap; // 你的点图元容器

// 遍历获取所有点坐标
for (auto it = pointMap.constBegin(); it != pointMap.constEnd(); ++it) {
    int id = it.key();
    QGraphicsEllipseItem* item = it.value();
    
    QPointF scenePos = item->scenePos();
    QRectF rect = item->rect();
    QPointF center = item->mapToScene(rect.center());
    
    qDebug() << "点ID:" << id << "场景坐标:" << center;
    
    // 如果需要视图坐标（像素坐标）
    QPoint viewPos = mGraphicsView->mapFromScene(center);
    qDebug() << "视图坐标:" << viewPos;
}

// 在场景子类中重写鼠标事件
void MyGraphicsScene::mousePressEvent(QGraphicsSceneMouseEvent* event) {
    QGraphicsScene::mousePressEvent(event); // 先让基类处理选择逻辑
    
    // 获取点击位置的图元
    QGraphicsItem* item = itemAt(event->scenePos(), QTransform());
    
    if (item && (item->type() == QGraphicsEllipseItem::Type)) {
        QGraphicsEllipseItem* ellipse = static_cast<QGraphicsEllipseItem*>(item);
        QPointF center = ellipse->mapToScene(ellipse->rect().center());
        qDebug() << "点击了点图元，中心坐标:" << center;
    }
}

// 获取当前选中的所有点图元坐标
QList<QPointF> getSelectedPointsCoordinates() {
    QList<QPointF> coordinates;
    
    foreach (QGraphicsItem* item, mScene->selectedItems()) {
        if (item->type() == QGraphicsEllipseItem::Type) {
            QGraphicsEllipseItem* ellipse = static_cast<QGraphicsEllipseItem*>(item);
            coordinates.append(ellipse->mapToScene(ellipse->rect().center()));
        }
    }
    
    return coordinates;
}

// 局部坐标 → 场景坐标
QPointF scenePos = item->mapToScene(localPos);

// 场景坐标 → 视图坐标
QPoint viewPos = graphicsView->mapFromScene(scenePos);

// 视图坐标 → 场景坐标
QPointF scenePos = graphicsView->mapToScene(viewPos);