如何在QGraphicsItem的可移动区域周围绘制一个边界矩形？

huangapple
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英文:

How to draw a bounding rect around movable area of QGraphicsItem?

问题

我创建了一个自定义的QGraphicsItem，并重写了paint函数来绘制图像，这个图像是ghost.png，是一个具有复杂边界的角色，可以通过点击图像的下/上/左/右四个边来移动。

我理解这是因为boundingRect的设置，我将其设置得更大，因为我需要绘制其他内容，比如文本、生命值条等等...

如何保持较大的boundingRect，同时限制只有在图像上点击时才能移动图像？

我的类：

  1. class DrawImage : public QGraphicsItem
  2. {
  3. public:
  4.     DrawImage();
  5.     
  6. protected:
  7.     QRectF boundingRect() const override;
  8.     void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) override;
  9. };

我的定义：

  1. DrawImage::DrawImage()
  2. {
  3.     setFlag(ItemIsMovable);
  4. }
  6. QRectF DrawImage::boundingRect() const
  7. {
  8.     return QRectF(0, 0, 100, 200);
  9. }
  11. void DrawImage::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
  12. {
  13.     auto ghost = QImage("ghost.png");
  14.     painter->drawImage(QRect(0, 0, 100, 100), ghost);
  15. }
英文:

I made a custom QGraphicsItem and I am overriding the paint function to draw image which is ghost.png, a character that has a complex boundary, and can be moved by clicking on lower/upper/ left/right side of the image.

I understand this is happening because of the boundingRect, I am setting it larger because I need to draw something else, for example: text, health bar, etc...

How can I keep a larger boundingrect and also limit the image to move only if clicked on the image.

My class :

  1. class DrawImage : public QGraphicsItem
  2. {
  3. public:
  4.     DrawImage();
  6. protected:
  7.     QRectF boundingRect() const override;
  8.     void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) override;
  9. };

My Definition :

  1. DrawImage::DrawImage()
  2. {
  3.     setFlag(ItemIsMovable);
  4. }
  6. QRectF DrawImage::boundingRect() const
  7. {
  8.     return QRectF(0, 0, 100, 200);
  9. }
  11. void DrawImage::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
  12. {
  13.     auto ghost = QImage(":ghost.png");
  14.     painter->drawImage(QRect(0, 0, 100, 100), ghost);
  15. }

答案1

得分: 2

musicamante 说道：

>重写 [QGraphicsItem::]shape。

以下是如何使你的 QGraphicsPixmapItem 仅在点击其 pixmap 时可移动，并在其周围有一个 boundingRect 的示例：

  1. class DrawImage : public QGraphicsItem
  2. {
  3. public:
  4.     DrawImage()
  5.     {
  6.         setFlag(ItemIsMovable);
  7.     }
  9. protected:
  10.     QRectF boundingRect() const override
  11.     {
  12.         return QRectF(0, 0, 100, 200);
  13.     }
  15.     void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) override
  16.     {
  17.         auto greenBall = QPixmap("green.svg");
  18.         QRect rect = boundingRect().toRect();
  20.         // 你可以调整 pixmap 的绘制位置
  21.         // 我选择了 bounding rect 的上半部分
  22.         rect.adjust(0,0,0,-rect.height()/2);
  23.         painter->drawPixmap(rect, greenBall);
  25.         // 为了可见性，我绘制了整个 bounding rect
  26.         painter->setPen(Qt::green);
  27.         painter->drawRect(boundingRect());
  28.     }
  30.     QPainterPath shape() const
  31.     {
  32.         // 这里你可以指定用户点击哪个区域移动对象
  33.         auto greenBall = QPixmap("green.svg");
  34.         QRect rect = boundingRect().toRect();
  35.         
  36.         // 确保它与你绘制 pixmap 的区域相同
  37.         rect.adjust(0,0,0,-rect.height()/2);
  38.         QPainterPath path;
  39.         // 将其添加为你想要的形状，我选择了绿色圆圈的椭圆形状
  40.         path.addEllipse(rect);
  41.         return path;
  42.     }
  43. };

这是结果图：

如何在QGraphicsItem的可移动区域周围绘制一个边界矩形？

查看源代码以获取更多详细信息：

英文:

musicamante said:

>Override [QGraphicsItem::]shape.

Here's how you can make your QGraphicsPixmapItem moveable only when clicked on its pixmap, and have a boundingRect around it:

  1. class DrawImage : public QGraphicsItem
  2. {
  3. public:
  4.     DrawImage()
  5.     {
  6.         setFlag(ItemIsMovable);
  7.     }
  9. protected:
  10.     QRectF boundingRect() const override
  11.     {
  12.         return QRectF(0, 0, 100, 200);
  13.     }
  15.     void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) override
  16.     {
  17.         auto greenBall = QPixmap(":green.svg");
  18.         QRect rect = boundingRect().toRect();
  20.         //You can adjust where your pixmap is drawn
  21.         //I chose the upper part of the bounding rect
  22.         rect.adjust(0,0,0,-rect.height()/2);
  23.         painter->drawPixmap(rect, greenBall);
  25.         //I'm drawing the full bounding rect just to make it visible
  26.         painter->setPen(Qt::green);
  27.         painter->drawRect(boundingRect());
  28.     }
  30.     QPainterPath shape() const
  31.     {
  32.         //this is where you sepecify which area of your object allows the user to move it when clicked
  33.         auto greenBall = QPixmap(":green.svg");
  34.         QRect rect = boundingRect().toRect();
  35.         
  36.         //Make sure it is the same area where you're drawing your pixmap
  37.         rect.adjust(0,0,0,-rect.height()/2);
  38.         QPainterPath path;
  39.         //add it as the shape you want, I chose an ellipse for the green circle
  40.         path.addEllipse(rect);
  41.         return path;
  42.     }
  43. };

Here's the result:

如何在QGraphicsItem的可移动区域周围绘制一个边界矩形？

See the source code for more details:

huangapple
  • 本文由 发表于 2023年6月12日 02:03:10
  • 转载请务必保留本文链接：https://go.coder-hub.com/76451832.html
  • c++
  • qgraphicsitem
  • qpixmap
  • qt
  • qt6
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