基于Qt框架实现绘图软件的功能

一、项目架构设计

1. 模块划分

// 核心类关系图
+-------------------+       +-------------------+       +-------------------+
|   MainWindow      | →→→→→ |   GraphicsScene   | →→→→→ |   CustomGraphicsItem |
| - 工具栏/菜单     |       | - 图形管理        |       | - 图形基类        |
| - 状态栏          |       | - 坐标转换        |       | - 属性存储        |
+-------------------+       +-------------------+       +-------------------+

2. 关键类设计

// 自定义图形基类
class CustomGraphicsItem : public QGraphicsItem {
public:
    enum ItemType { RECT, ELLIPSE, LINE, TEXT };
    
    CustomGraphicsItem(ItemType type, QGraphicsItem *parent = nullptr);
    QRectF boundingRect() const override;
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) override;
    
    // 属性设置接口
    void setColor(const QColor &color);
    void setRotationAngle(qreal angle);
    void setScaleFactor(qreal factor);
    
protected:
    void mousePressEvent(QGraphicsSceneMouseEvent *event) override;
    void mouseMoveEvent(QGraphicsSceneMouseEvent *event) override;
    void mouseReleaseEvent(QGraphicsSceneMouseEvent *event) override;
    
private:
    ItemType m_type;
    QColor m_color;
    qreal m_rotation;
    qreal m_scale;
    QPointF m_startPos;
};

---

二、核心功能实现

1. 图形绘制模块

// 自定义矩形绘制
CustomGraphicsRectItem::CustomGraphicsRectItem(QGraphicsItem *parent)
    : QGraphicsRectItem(-50, -50, 100, 50, parent), m_type(RECT) {
    setFlag(ItemIsMovable | ItemIsSelectable);
    setAcceptHoverEvents(true);
}

// 绘制事件处理
void CustomGraphicsRectItem::paint(QPainter *painter, 
                                  const QStyleOptionGraphicsItem *option, 
                                  QWidget *widget) {
    painter->setPen(Qt::black);
    painter->setBrush(QBrush(m_color));
    painter->drawRect(rect());
    
    // 绘制控制点（缩放手柄）
    QPainterPath handles;
    handles.addEllipse(rect().adjusted(0,0,-5,-5).topLeft(), 5,5);
    handles.addEllipse(rect().adjusted(0,0,-5,-5).topRight(), 5,5);
    painter->drawPath(handles);
}

2. 缩放与旋转实现

// 视图缩放（支持鼠标滚轮）
void GraphicsView::wheelEvent(QWheelEvent *event) {
    if(event->angleDelta().y() > 0) {
        scale(1.1, 1.1);  // 放大
    } else {
        scale(0.9, 0.9);  // 缩小
    }
}

// 图形旋转（按住Ctrl+拖动）
void CustomGraphicsItem::mousePressEvent(QGraphicsSceneMouseEvent *event) {
    if(event->modifiers() == Qt::ControlModifier) {
        m_startPos = event->scenePos();
    } else {
        QGraphicsItem::mousePressEvent(event);
    }
}

void CustomGraphicsItem::mouseMoveEvent(QGraphicsSceneMouseEvent *event) {
    if(event->modifiers() == Qt::ControlModifier) {
        qreal delta = (event->scenePos() - m_startPos).manhattanLength();
        setRotation(rotation() + delta / 2);  // 每像素旋转0.5度
        m_startPos = event->scenePos();
    } else {
        QGraphicsItem::mouseMoveEvent(event);
    }
}

---

三、交互功能实现

1. 图形选择与操作

// 多选处理
void MainWindow::keyPressEvent(QKeyEvent *event) {
    if(event->key() == Qt::Key_Control) {
        view->setDragMode(QGraphicsView::RubberBandDrag);
    }
}

// 组合操作
void MainWindow::onGroupAction() {
    QList<QGraphicsItem *> selected = scene->selectedItems();
    if(selected.size() < 2) return;
    
    QGraphicsItemGroup *group = new QGraphicsItemGroup;
    for(auto item : selected) {
        group->addToGroup(item);
    }
    scene->addItem(group);
}

// 反选功能
void MainWindow::onInvertSelection() {
    QList<QGraphicsItem *> allItems = scene->items();
    for(auto item : allItems) {
        item->setSelected(!item->isSelected());
    }
}

---

四、界面设计

1. 工具栏配置

// 创建工具栏
QToolBar *toolbar = addToolBar("绘图工具");

// 添加绘图按钮
QAction *rectAction = new QAction(QIcon(":/icons/rect.png"), "矩形", this);
connect(rectAction, &QAction::triggered, [=]{
    scene->addItem(new CustomGraphicsRectItem);
});

// 添加缩放控件
QSpinBox *zoomSpinBox = new QSpinBox;
zoomSpinBox->setRange(10, 400);
zoomSpinBox->setValue(100);
connect(zoomSpinBox, QOverload<int>::of(&QSpinBox::valueChanged), [=](int val){
    view->setTransform(QTransform::fromScale(val/100.0, val/100.0));
});
toolbar->addWidget(zoomSpinBox);

---

五、性能优化方案

1. 双缓冲绘图

// 在自定义图形项中启用双缓冲
void CustomGraphicsItem::paint(QPainter *painter, ...) {
    painter->setRenderHint(QPainter::Antialiasing);
    painter->setRenderHint(QPainter::SmoothPixmapTransform);
    // ... 绘制逻辑
}

2. 批量更新

// 启用场景批量更新
void MainWindow::batchUpdate() {
    scene->blockSignals(true);
    scene->prepareGeometryChange();
    // 执行多个图形操作
    scene->blockSignals(false);
    scene->update();
}

---

六、扩展功能实现

1. 文件操作

// 保存为SVG格式
void MainWindow::onSaveSvg() {
    QSvgGenerator generator;
    generator.setFileName("drawing.svg");
    generator.setSize(QSize(800,600));
    QPainter painter(&generator);
    scene->render(painter);
}

// 导入图像
void MainWindow::onImportImage() {
    QString fileName = QFileDialog::getOpenFileName(this, "导入图片", "", "Images (*.png *.jpg)");
    if(!fileName.isEmpty()) {
        QGraphicsPixmapItem *item = new QGraphicsPixmapItem(QPixmap(fileName));
        scene->addItem(item);
    }
}

---

七、调试技巧

1. 坐标系调试

// 在状态栏显示坐标
void MainWindow::mouseMoveEvent(QMouseEvent *event) {
    QPointF scenePos = view->mapToScene(event->pos());
    statusBar()->showMessage(QString("Scene: (%1, %2)").arg(scenePos.x()).arg(scenePos.y()));
}

2. 性能监控

// 绘制耗时统计
QElapsedTimer timer;
timer.start();
// ... 绘制操作
qDebug() << "绘制耗时:" << timer.elapsed() << "ms";

参考代码 qt 绘图软件，实现简单图形的绘制，缩放等功能 www.youwenfan.com/contentcnj/69827.html

八、完整工程结构

DrawingApp/
├── Src/
│   ├── main.cpp
│   ├── mainwindow.cpp
│   ├── graphicsview.cpp
│   └── customitem.cpp
├── Inc/
│   ├── mainwindow.h
│   ├── graphicsview.h
│   └── customitem.h
├── Res/
│   ├── icons/          # 图标资源
│   └── styles/         # 样式表
└── CMakeLists.txt

---

九、关键技术点

1. 图形变换矩阵

   使用QTransform实现复合变换：

   QTransform transform;
   transform.translate(100, 100);  // 平移
   transform.rotate(45);           // 旋转
   transform.scale(2, 2);          // 缩放
   item->setTransform(transform);
   

2. 事件过滤器

   实现全局快捷键：

   qApp->installEventFilter(this);
   
   bool MainWindow::eventFilter(QObject *obj, QEvent *event) {
       if(event->type() == QEvent::KeyPress) {
           QKeyEvent *keyEvent = static_cast<QKeyEvent*>(event);
           if(keyEvent->key() == Qt::Key_Z) {
               // 撤销操作
               return true;
           }
       }
       return QMainWindow::eventFilter(obj, event);
   }