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基于QGraphicsView、QGraphicsScene、自定义QGraphicsItem的小demo(正矩形、旋转矩形及圆形)_item->move(qpointf(rect.right(), rect.top() + rect

作者：你好赵伟 | 2024-02-16 07:18:09

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item->move(qpointf(rect.right(), rect.top() + rect.height() / 2));

网上有很多关于这三个的资料，这方面的功能不做过多的描述，仅仅将在做小Demo过程中遇到的问题做下记录，下面是Demo的界面图：

Demo的初衷是不想每次使用QGraphicsView和QGraphicsScene都重写，可以直接拿来使用，后来慢慢加了一些图形项，因为其实是为了熟悉QGpaphicsXX，所以目前只加了3种（正矩形，旋转矩形、圆），刚好这个Demo也练习了一种设计模式——工厂模式，现在就讲些步骤及遇到的问题（只贴关键的代码，整体代码看最后下载链接）：

一、以鼠标为中心进行缩放

QGraphicsView和QGraphicsScene(后面简称View和Scene)都是要重写的，这一部分我主要放在View中实现，主要重写滚轮事件 wheelEvent(QWheelEvent * event)，代码（部分）如下：

  1. void MyGraphicsView::wheelEvent(QWheelEvent * event)
  2. {
  3. 	if (this->scene()->items().size() == 0)
  4. 		return;
  5. 	QPointF curPoint = event->pos();
  6. 	QPointF scenePos = this->mapToScene(QPoint(curPoint.x(), curPoint.y()));
  7.  
  8. 	qreal viewWidth = viewport()->width();
  9. 	qreal viewHeight = viewport()->height();
  10.  
  11. 	qreal hScale = curPoint.x() / viewWidth;
  12. 	qreal vScale = curPoint.y() / viewHeight;
  13.  
  14. 	int wheelDeltaValue = event->delta();
  15. 	// 当前放缩倍数;
  16. 	qreal scaleFactor = this->matrix().m11();
  17. 	if ((scaleFactor < 0.4 && wheelDeltaValue<0)||(scaleFactor>50 &&wheelDeltaValue>0))
  18. 		return;
  19.  
  20. 	wheelDeltaValue > 0 ? scale(1.2, 1.2) : scale(1.0/1.2, 1.0/1.2);
  21. 	// 将scene坐标转换为放大缩小后的坐标;
  22. 	QPointF viewPoint = this->matrix().map(scenePos);
  23. 	this->horizontalScrollBar()->setValue(int(viewPoint.x() - viewWidth * hScale ));
  24. 	this->verticalScrollBar()->setValue(int(viewPoint.y() - viewHeight * vScale ));
  25.  
  26. 	update();
  27. }

这段代码其实是通过控制ScrollBar来达到目的，但是其实可以不需要这么做，只需要在构造函数中设置属性即可，构造函数如下：

  1. MyGraphicsView::MyGraphicsView(QWidget *parent)
  2. 	: QGraphicsView(parent)
  3. {
  4. 	setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff); // 去掉滚动条
  5. 	setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
  6. 	setViewportUpdateMode(QGraphicsView::FullViewportUpdate);
  7. 	setRenderHints(QPainter::Antialiasing);
  8.  
  9. 	/*以鼠标中心进行缩放*/
  10. 	setMouseTracking(true);        
  11. 	setTransformationAnchor(QGraphicsView::AnchorUnderMouse);
  12. 	setResizeAnchor(QGraphicsView::AnchorUnderMouse);
  13. 	/********************/
  14.  
  15. }

构造函数中的后三句才是重点。之所以还留着滚轮事件中ScrollBar->setValue()是发现在放大过程中放大到一定程度，加载进去的图片就“消失”。

注：在Scene中要设置SceneRect的大小，尽量大，具体看后面附带的代码下载链接；

二、绘制不随窗口变化大小的背景

Demo带有棋盘格的背景，实现是重写View的drawBackground(QPainter * painter, const QRectF & rect)；

  1. void MyGraphicsView::drawBackground(QPainter * painter, const QRectF & rect)
  2. {
  3. 	//绘制背景
  4. 	int wid = this->geometry().width();
  5. 	int hei = this->geometry().height();
  6. 	m_ptCenter = this->mapToScene(wid / 2, hei / 2);
  7. 	QPixmap pix(wid, hei);
  8. 	QPainter pter(&pix);
  9. 	QColor clr_white(Qt::white);
  10. 	QColor clr_gray(240, 240, 240, 240);
  11. 	int spacing = 15;
  12. 	QColor useColor;
  13. 	for (int i = 0; i <= floor(wid / spacing); i++)
  14. 	{
  15. 		for (int j = 0; j <= floor(hei/ spacing); j++)
  16. 		{
  17. 			useColor = ((i + j) % 2 == 0 ? clr_white : clr_gray);
  18. 			pter.fillRect(i*spacing, j*spacing, spacing, spacing, useColor);
  19. 		}
  20. 	}
  21. 	painter->drawImage(rect, pix.toImage());
  22. }

三、加载自定义图像Item

自定义图像item其实就是继承QGraphicsItem,由于代码里加了很多图形item，只显示部分；

  1. QRectF MyGraphicsImageItem::boundingRect() const
  2. {
  3. 	return QRectF(-m_Pixmap.width() / 2, -m_Pixmap.height() / 2, m_Pixmap.width(), m_Pixmap.height());
  4. }
  5.  
  6. void MyGraphicsImageItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
  7. {
  8. 	Q_UNUSED(option);
  9. 	Q_UNUSED(widget);
  10. 	QPen pen = painter->pen();
  11. 	pen.setWidth(0);
  12. 	pen.setStyle(Qt::SolidLine);
  13. 	pen.setColor(QColor(0, 255, 255, 100));
  14. 	painter->setPen(pen);
  15. 	painter->setBrush(QColor(0, 0, 255, 100));
  16. 	painter->drawPixmap(-m_Pixmap.width() / 2, -m_Pixmap.height() / 2, m_Pixmap);
  17. }

四、在图像Item上绘制图形item

1、图形边缘控制点

边缘控制点其实也是自定义的Item,定义为MyCornerItem,该Item不随视图的缩放而缩放，需要更新移动后item的位置：

  1. #pragma once
  2. #ifndef MY_CORNER_ITEM_H
  3. #define MY_CORNER_ITEM_H
  4.  
  5. #include <QAbstractGraphicsShapeItem>
  6. #include <QGraphicsSceneHoverEvent>
  7. #include <QPainter>
  8. #include <QCursor>
  9. #include <QGraphicsItem>
  10.  
  11. enum CustomType {
  12. 	TypeImage = 65536 + 1,
  13. 	TypeCorner = 65536 + 2,
  14. 	TypeRect,
  15. 	TypeRotateRect,
  16. 	TypeCircle
  17. };
  18.  
  19. constexpr int CORNER_SIZE = 3;
  20.  
  21. enum SelectionHandleState
  22. {
  23. 	SelectionHandleOff,
  24. 	SelectionHandleInactive,
  25. 	SelectionHandleActive
  26. };
  27.  
  28. enum CornerDirction    //鼠标经过时的形状
  29. {
  30. 	None = 0,
  31. 	LeftTop,
  32. 	Top,
  33. 	RightTop,
  34. 	Right,
  35. 	RightBottom,
  36. 	Bottom,
  37. 	LeftBottom,
  38. 	Left,
  39. 	Rotation,           //旋转
  40. };
  41.  
  42. class MyCornerItem : public QAbstractGraphicsShapeItem
  43. {
  44. 	/*Q_OBJECT*/
  45.  
  46. public:
  47. 	explicit MyCornerItem(QGraphicsItem *parent, QPointF point, CornerDirction dir, bool control = false);
  48. 	virtual ~MyCornerItem() {};
  49. 	bool hitTest(const QPointF &point);
  50. 	CornerDirction getDir() const { return m_Dir; }
  51. 	void setState(SelectionHandleState state);
  52. 	void move(QPointF point);
  53. 	void cornerTranslate(QPointF point);
  54. 	inline void setSelectState(bool bState) { m_bSelect = bState; }
  55. 	inline bool getSelectState() { return m_bSelect; }
  56. 	inline QPointF getPointCenter() { return m_point; }
  57.  
  58. 	virtual int type() const { return TypeCorner; }
  59.  
  60. private:
  61. 	QBrush m_brush;
  62. 	QPointF m_point;
  63. 	CornerDirction m_Dir;
  64. 	SelectionHandleState m_State;
  65. 	QCursor m_RotateCursor;  //旋转图标
  66. 	double m_scaleFactor;
  67. 	bool m_bSelect;   //对由多个点组成的图形，点击被选中的标志
  68. 	QPointF m_ptPress, m_ptMove;
  69.  
  70. protected:
  71. 	virtual QRectF boundingRect() const override;
  72. 	virtual void hoverEnterEvent(QGraphicsSceneHoverEvent *event) override;
  73. 	virtual void hoverLeaveEvent(QGraphicsSceneHoverEvent *event) override;
  74. 	virtual void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = 0) Q_DECL_OVERRIDE;
  75. 	virtual void mousePressEvent(QGraphicsSceneMouseEvent* event) override;
  76. 	virtual void mouseMoveEvent(QGraphicsSceneMouseEvent* event) override;
  77. 	virtual void mouseReleaseEvent(QGraphicsSceneMouseEvent *event) override;
  78.  
  79.  
  80. };
  81.  
  82. #endif
  1. #include "MyCornerItem.h"
  2. #include <QDebug>
  3.  
  4. MyCornerItem::MyCornerItem(QGraphicsItem * parent, QPointF point, CornerDirction dir, bool control)
  5. 	:QAbstractGraphicsShapeItem(parent)
  6. 	, m_point(point)
  7. 	,m_Dir(dir)
  8. {
  9. 	setAcceptHoverEvents(true);
  10. 	QPixmap pixRotate = QPixmap("Resources\\icon\\rotate.png");
  11. 	m_RotateCursor = QCursor(pixRotate); 
  12. 	m_scaleFactor = 1;
  13. 	m_bSelect = false;
  14. 	m_brush = QBrush(Qt::white);
  15. }
  16.  
  17. void MyCornerItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
  18. {
  19. 	Q_UNUSED(option);     //这个宏是用来把不用到的参数注掉的功能
  20. 	Q_UNUSED(widget);
  21. 	m_scaleFactor = painter->matrix().m11();
  22. 	painter->save();
  23. 	QPen pen;
  24. 	pen.setWidth(0);
  25. 	pen.setStyle(Qt::SolidLine);
  26. 	painter->setPen(pen);
  27. 	painter->setBrush(m_brush);
  28. 	painter->setRenderHint(QPainter::Antialiasing, false);  //不开反走样
  29. 	painter->drawEllipse(m_point, CORNER_SIZE/ m_scaleFactor, CORNER_SIZE/ m_scaleFactor);
  30. 	painter->restore();
  31. }
  32.  
  33. bool MyCornerItem::hitTest(const QPointF & point)
  34. {
  35. 	//QPointF pt = mapFromScene(point);
  36. 	return boundingRect().contains(point);
  37. }
  38.  
  39. void MyCornerItem::setState(SelectionHandleState state)
  40. {
  41. 	if (state == m_State)
  42. 		return;
  43. 	switch (state) {
  44. 	case SelectionHandleOff:
  45. 		hide();
  46. 		break;
  47. 	case SelectionHandleInactive:
  48. 	case SelectionHandleActive:
  49. 		show();
  50. 		break;
  51. 	}
  52. 	m_State = state;
  53. }
  54.  
  55. void MyCornerItem::move(QPointF point)
  56. {
  57. 	if (point == m_point)
  58. 		return;
  59. 	//moveBy(0, 0);
  60. 	m_point = point;
  61. 	update();
  62. }
  63.  
  64. void MyCornerItem::cornerTranslate(QPointF point)
  65. {
  66. 	QPointF local = point + boundingRect().topLeft();
  67. 	QRectF delta = QRectF(local, boundingRect().size());
  68. 	prepareGeometryChange();
  69. 	m_point = delta.center();
  70. 	update();
  71. }
  72.  
  73. QRectF MyCornerItem::boundingRect() const
  74. {
  75. 	double centerX = m_point.x() - CORNER_SIZE * 2 / m_scaleFactor / 2;
  76. 	double centerY = m_point.y() - CORNER_SIZE * 2 / m_scaleFactor / 2;
  77. 	return QRectF(centerX, centerY, CORNER_SIZE * 2 / m_scaleFactor, CORNER_SIZE * 2 / m_scaleFactor);
  78. }
  79.  
  80. void MyCornerItem::mousePressEvent(QGraphicsSceneMouseEvent * event)
  81. {
  82. 	if (event->button() == Qt::LeftButton)
  83. 	{
  84. 		m_ptPress = event->scenePos();
  85. 		m_ptMove = event->scenePos();
  86. 		m_bSelect = true;
  87. 	}
  88. }
  89.  
  90. void MyCornerItem::mouseMoveEvent(QGraphicsSceneMouseEvent* event)
  91. {
  92. 	if (event->buttons()&Qt::LeftButton)
  93. 	{
  94. 		m_ptMove = event->scenePos();
  95. 		QPointF pt = mapFromScene(m_ptMove) - mapFromScene(m_ptPress);
  96. 		m_ptPress = event->scenePos();
  97. 		cornerTranslate(pt);
  98. 	}
  99. 	QGraphicsItem::mouseMoveEvent(event);
  100.  
  101. }
  102.  
  103. void MyCornerItem::mouseReleaseEvent(QGraphicsSceneMouseEvent * event)
  104. {
  105. 	/*if (event->button() == Qt::LeftButton)
  106. 	{
  107. 		m_ptMove = event->scenePos();
  108. 		QPointF pt = mapFromScene(m_ptMove) - mapFromScene(m_ptPress);
  109. 		m_ptPress = event->scenePos();
  110. 		cornerTranslate(pt);
  111. 	}
  112. 	QGraphicsItem::mouseReleaseEvent(event);*/
  113. }
  114.  
  115. void MyCornerItem::hoverEnterEvent(QGraphicsSceneHoverEvent * event)
  116. {
  117. 	switch (m_Dir)
  118. 	{
  119. 	case LeftTop:
  120. 	case RightBottom:
  121. 		setCursor(Qt::SizeFDiagCursor);
  122. 		break;
  123. 	case LeftBottom:
  124. 	case RightTop:
  125. 		setCursor(Qt::SizeBDiagCursor);
  126. 		break;
  127. 	case Top:
  128. 	case Bottom:
  129. 		setCursor(Qt::SizeVerCursor);
  130. 		break;
  131. 	case Left:
  132. 	case Right:
  133. 		setCursor(Qt::SizeHorCursor);
  134. 		break;
  135. 	case Rotation:
  136. 		setCursor(m_RotateCursor);
  137. 		break;
  138. 	default:
  139. 		setCursor(Qt::ArrowCursor);
  140. 		break;
  141. 	}
  142. 	m_brush = QBrush(Qt::green);
  143. 	update();
  144. 	QGraphicsItem::hoverEnterEvent(event);
  145. }
  146.  
  147. void MyCornerItem::hoverLeaveEvent(QGraphicsSceneHoverEvent * event)
  148. {
  149. 	m_bSelect = false;
  150. 	m_brush = QBrush(Qt::white);
  151. 	update();
  152. 	QGraphicsItem::hoverLeaveEvent(event);
  153. }
  154.

2、图形基类及工厂

图形基类继承QGraphicsItem，以组合的方式声明边缘点QList<MyCornerItem*> m_HandlesList，主要实现item移动，左键双击改变z值，右双击可以改变颜色

  1. #ifndef MY_CUSTOMDRAWITEM_H
  2. #define MY_CUSTOMDRAWITEM_H
  3.  
  4. #include <QGraphicsItem>
  5. #include "MyCornerItem.h"
  6. #include <QPainterPath>
  7. #include <QColorDialog>
  8. #include <QDebug>
  9.  
  10. /*  需要使用的定义及相关函数  */
  11. constexpr double PI = 3.1415926;
  12.  
  13. template <typename T>    //T 为QPointF 或QPoint
  14. double Distance(T p1, T p2)
  15. {
  16. 	return std::sqrt(std::pow(p1.x() - p2.x(), 2) + std::pow(p1.y() - p2.y(), 2));
  17. }
  18.  
  19.  
  20. class QGraphicsItem;
  21. /**图形基类**/
  22. class CustomItemBase : public QGraphicsItem
  23. {
  24. public:
  25. 	CustomItemBase(QGraphicsItem *parent = nullptr)
  26. 	{
  27. 		setFlags(QGraphicsItem::ItemIsMovable | QGraphicsItem::ItemIsSelectable | QGraphicsItem::ItemSendsGeometryChanges);
  28. 		this->setAcceptHoverEvents(true);
  29. 		m_bUseDoubleClick = true;
  30. 		m_brush = QBrush(QColor(0, 0, 255, 100));
  31. 	}
  32. 	virtual ~CustomItemBase() {};
  33.  
  34. 	void SetState(SelectionHandleState state);
  35. 	bool isCornerSelected(int &index);
  36.  
  37. 	void itemAtImage2Move(QPointF point)
  38. 	{
  39. 		move(point);
  40. 	}
  41.  
  42. 	virtual int type() const = 0;
  43. 	virtual void move(QPointF point) = 0;  //平移
  44. 	virtual void updateShape() = 0;    //拖动corner后要更新形状
  45. 	virtual void updateConnerPos() = 0;   //移动后更新所有corner的位置
  46. 	virtual QPainterPath shape() const = 0;
  47. protected:
  48. 	virtual QRectF boundingRect() const = 0;
  49. 	virtual QVariant itemChange(GraphicsItemChange change, const QVariant &value);
  50. 	virtual void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) = 0;
  51. 	virtual void mousePressEvent(QGraphicsSceneMouseEvent* event) override;
  52. 	virtual void mouseMoveEvent(QGraphicsSceneMouseEvent* event) override;
  53. 	virtual void mouseReleaseEvent(QGraphicsSceneMouseEvent *event) override;
  54. 	virtual void mouseDoubleClickEvent(QGraphicsSceneMouseEvent *event) override;
  55. 	
  56. public:
  57. 	QRectF m_rect;    //外接矩形
  58. 	QList<MyCornerItem*> m_HandlesList;
  59. 	QPointF m_ptPress,m_ptMove;
  60. 	QBrush m_brush;
  61. 	bool m_bUseDoubleClick;
  62. };
  63.  
  64. class CustomItemBaseFactory
  65. {
  66. public:
  67. 	virtual ~CustomItemBaseFactory() {}
  68. 	virtual CustomItemBase* CreateCustomItem(QVector<QPointF> vecPoint) = 0;
  69. 	virtual void DrawOnPaint(QPainter* painter, QVector<QPointF> vecPoint) = 0;
  70. 	virtual int NeedClickCount() 
  71. 	{ return --m_nClickCnt; }    //图形需要几步完成
  72.  
  73. 	int m_nClickCnt;
  74. 	inline int GetNeedCnt() { return m_nNeedCnt; }
  75.  
  76. protected:
  77. 	int m_nNeedCnt;    //不变
  78. };
  1. #include "MyCustomDrawItem.h"
  2. #include <QGraphicsScene>
  3. #include <QDebug>
  4.  
  5. /************************************************************************/
  6. /*                图形基类相关函数                                     */
  7. /*    左双击改变Z值，右双击改变颜色                                     */
  8. /************************************************************************/
  9. void CustomItemBase::SetState(SelectionHandleState state)
  10. {
  11. 	for (auto item: m_HandlesList)
  12. 		item->setState(state);
  13. }
  14.  
  15. bool CustomItemBase::isCornerSelected(int & index)
  16. {
  17. 	bool bSelect = false;
  18. 	index = 0;
  19. 	for (auto item : m_HandlesList)
  20. 	{
  21. 		if (item->getSelectState())
  22. 		{
  23. 			bSelect = true;
  24. 			break;
  25. 		}
  26. 		index++;
  27. 	}
  28. 	return bSelect;
  29. }
  30.  
  31. QVariant CustomItemBase::itemChange(GraphicsItemChange change, const QVariant & value)
  32. {
  33. 	if (change == QGraphicsItem::ItemSelectedHasChanged)
  34. 	{
  35. 		qDebug() << "Item Selected:" << value.toString();
  36. 		SetState(value.toBool() ? SelectionHandleActive : SelectionHandleOff);
  37. 	}
  38. 	else if (change == QGraphicsItem::ItemRotationHasChanged)
  39. 	{
  40. 		qDebug() << "Item Rotation Changed:" << value.toString();
  41. 	}
  42. 	else if (change == QGraphicsItem::ItemTransformOriginPointHasChanged)
  43. 	{
  44. 		qDebug() << "ItemTransformOriginPointHasChanged:" << value.toPointF();
  45. 	}
  46. 	return QGraphicsItem::itemChange(change, value);
  47. }
  48.  
  49. void CustomItemBase::mousePressEvent(QGraphicsSceneMouseEvent * event)
  50. {
  51. 	if (event->button() == Qt::LeftButton)
  52. 	{
  53. 		m_ptPress = event->scenePos();
  54. 		m_ptMove = event->scenePos();
  55. 		for (auto corner:m_HandlesList)
  56. 		{
  57. 			corner->setZValue(this->zValue());
  58. 		}
  59. 	}
  60. 	QGraphicsItem::mousePressEvent(event);
  61. }
  62.  
  63. void CustomItemBase::mouseMoveEvent(QGraphicsSceneMouseEvent * event)
  64. {
  65. 	if (event->buttons() & Qt::LeftButton)
  66. 	{
  67. 		int index = 0;
  68. 		if (!isCornerSelected(index))
  69. 		{
  70. 			m_ptMove = event->scenePos();
  71. 			QPointF pt = mapFromScene(m_ptMove) - mapFromScene(m_ptPress);
  72. 			m_ptPress = event->scenePos();
  73. 			move(pt);
  74. 		}
  75. 		update();
  76. 	}
  77. }
  78.  
  79. void CustomItemBase::mouseReleaseEvent(QGraphicsSceneMouseEvent * event)
  80. {
  81. 	if (event->button() == Qt::LeftButton)
  82. 	{
  83. 		for (auto item : m_HandlesList)
  84. 		{
  85. 			item->setSelectState(false);
  86. 		}
  87. 		QGraphicsItem::mouseReleaseEvent(event);
  88. 	}
  89. }
  90.  
  91. void CustomItemBase::mouseDoubleClickEvent(QGraphicsSceneMouseEvent * event)
  92. {
  93. 	if (event->button() == Qt::RightButton)
  94. 	{
  95. 		if (m_bUseDoubleClick)
  96. 		{
  97. 			QColorDialog dlg;
  98. 			if (dlg.exec() == QDialog::Accepted)
  99. 			{
  100. 				QColor color = dlg.selectedColor();
  101. 				color.setAlpha(100);
  102. 				m_brush = QBrush(color);
  103. 			}
  104. 		}
  105. 	}
  106. }

至于为什么还要加个“工厂”，主要就是要加入一个图形，如果以switch的方式分别new出相关的类，这样不便于后续添加其他图形，使用工厂模式就解决了该问题。图形有自己的工厂，使用的时候只要传入相应的工厂指针就好了【不知道该模式的话自行补】。下面仅展示正矩形和圆的实现：

  1. /**************矩形******************/
  2. class CustomRectItem :public CustomItemBase
  3. {
  4. public:
  5. 	CustomRectItem(QRectF &rect, QGraphicsItem *parent = nullptr);
  6.  
  7. 	virtual int type() const { return TypeRect; }
  8.  
  9. 	virtual void move(QPointF point);
  10. 	virtual void updateShape(); //一个corner改变则进行一次更新
  11. 	virtual void updateConnerPos();
  12. 	virtual QPainterPath shape() const;
  13.  
  14. protected:
  15. 	virtual QRectF boundingRect() const;
  16. 	virtual void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
  17.  
  18. };
  19.  
  20. class CustomRectItemFactory : public CustomItemBaseFactory
  21. {
  22. public:
  23. 	CustomRectItemFactory()
  24. 	{
  25. 		m_nClickCnt = 1;
  26. 		m_nNeedCnt = 1;
  27. 	}
  28. 	virtual CustomItemBase* CreateCustomItem(QVector<QPointF> vecPoint)
  29. 	{
  30. 		return new CustomRectItem(QRectF(vecPoint.at(0), vecPoint.at(1)));
  31. 	}
  32. 	virtual void DrawOnPaint(QPainter* painter, QVector<QPointF> vecPoint)
  33. 	{
  34. 		painter->drawRect(QRectF(vecPoint.at(0), vecPoint.at(1)));
  35. 	}
  36. };
  37.  
  38. /**************圆**************/
  39. class CustomCircleItem :public CustomItemBase
  40. {
  41. public:
  42. 	CustomCircleItem(QPointF center, double radius, QGraphicsItem *parent = nullptr);
  43.  
  44. 	virtual int type() const { return TypeCircle; }
  45.  
  46. 	virtual void move(QPointF point);  //平移
  47. 	virtual void updateShape();
  48. 	virtual void updateConnerPos();   //移动后更新所有corner的位置
  49. 	virtual QPainterPath shape() const;
  50.  
  51. protected:
  52. 	virtual QRectF boundingRect() const;
  53. 	virtual void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
  54.  
  55. };
  56.  
  57. class CustomCircleItemFactory : public CustomItemBaseFactory
  58. {
  59. public:
  60. 	CustomCircleItemFactory()
  61. 	{
  62. 		m_nClickCnt = 1;
  63. 		m_nNeedCnt = 1;
  64. 	}
  65. 	virtual CustomItemBase* CreateCustomItem(QVector<QPointF> vecPoint)
  66. 	{
  67. 		double dRadius = Distance(vecPoint.at(0), vecPoint.at(1));
  68. 		return new CustomCircleItem(vecPoint.at(0), dRadius);
  69. 	}
  70. 	virtual void DrawOnPaint(QPainter* painter, QVector<QPointF> vecPoint)
  71. 	{
  72. 		double radius = Distance(vecPoint.at(0), vecPoint.at(1));
  73. 		painter->drawEllipse(vecPoint.at(0), radius, radius);
  74. 	}
  75. };
  1. /************************************************************************/
  2. /*    图形子类函数实现                                                  */
  3.  /*   1、 正矩形                                                    */
  4. /************************************************************************/
  5. CustomRectItem::CustomRectItem(QRectF & rect, QGraphicsItem * parent)
  6. {
  7. 	m_rect = rect;
  8. 	m_HandlesList.clear();
  9. 	const int num = 8;
  10. 	QPointF point[num] = { QPointF((rect.left() + rect.right()) / 2,rect.bottom()),QPointF(rect.left(),rect.bottom()),
  11. 						 QPointF(rect.left(),(rect.top() + rect.bottom()) / 2) ,QPointF(rect.left(),rect.top()),
  12. 						 QPointF((rect.left() + rect.right()) / 2,rect.top()),QPointF(rect.right(),rect.top()),
  13. 						QPointF(rect.right(),(rect.top() + rect.bottom()) / 2),QPointF(rect.right(),rect.bottom())};
  14. 	CornerDirction dir[num] = { Bottom,LeftBottom ,Left,LeftTop ,Top , RightTop, Right,RightBottom };
  15. 	for (int i = 0; i < num; i++)
  16. 	{
  17. 		MyCornerItem* corner = new MyCornerItem(this, point[i], dir[i]);
  18. 		m_HandlesList.push_back(corner);
  19. 	}
  20. }
  21.  
  22. void CustomRectItem::paint(QPainter * painter, const QStyleOptionGraphicsItem * option, QWidget * widget)
  23. {
  24. 	Q_UNUSED(option);
  25. 	Q_UNUSED(widget);
  26. 	QPen pen = painter->pen();
  27. 	pen.setWidth(0);
  28. 	pen.setColor(QColor(0, 255, 255, 100));
  29. 	painter->setPen(pen);
  30. 	painter->setBrush(m_brush);
  31.  
  32. 	updateShape();
  33. 	painter->drawRect(m_rect);
  34. }
  35.  
  36. void CustomRectItem::updateShape()
  37. {
  38. 	int index = 0;
  39. 	if (isCornerSelected(index))
  40. 	{
  41. 		QRectF rect = m_rect;
  42. 		CornerDirction dir = m_HandlesList[index]->getDir();
  43. 		switch (dir)
  44. 		{
  45. 		case Top:
  46. 			rect.setTop(m_HandlesList[index]->getPointCenter().y());
  47. 			break;
  48. 		case Right:
  49. 			rect.setRight(m_HandlesList[index]->getPointCenter().x());
  50. 			break;
  51. 		case Bottom:
  52. 			rect.setBottom(m_HandlesList[index]->getPointCenter().y());
  53. 			break;
  54. 		case Left:
  55. 			rect.setLeft(m_HandlesList[index]->getPointCenter().x());
  56. 			break;
  57. 		case LeftTop:
  58. 			rect.setTopLeft(m_HandlesList[index]->getPointCenter());
  59. 			break;
  60. 		case LeftBottom:
  61. 			rect.setBottomLeft(m_HandlesList[index]->getPointCenter());
  62. 			break;
  63. 		case RightTop:
  64. 			rect.setTopRight(m_HandlesList[index]->getPointCenter());
  65. 			break;
  66. 		case RightBottom:
  67. 			rect.setBottomRight(m_HandlesList[index]->getPointCenter());
  68. 			break;
  69. 		default:
  70. 			break;
  71. 		}
  72. 		prepareGeometryChange();
  73. 		m_rect = rect;
  74. 		updateConnerPos();
  75. 	}
  76. }
  77.  
  78. QPainterPath CustomRectItem::shape() const
  79. {
  80. 	QPainterPath path;
  81. 	path.addRect(boundingRect());
  82. 	return path;
  83. }
  84.  
  85. void CustomRectItem::move(QPointF point)
  86. {
  87. 	QPointF local = point + m_rect.topLeft();
  88. 	QRectF delta = QRectF(local, m_rect.size());
  89. 	prepareGeometryChange();
  90. 	m_rect = delta;
  91. 	updateConnerPos();
  92. }
  93.  
  94. void CustomRectItem::updateConnerPos()
  95. {
  96. 	const QRectF rect = m_rect;
  97. 	for (auto item : m_HandlesList)
  98. 	{
  99. 		CornerDirction dir = item->getDir();
  100. 		switch (dir)
  101. 		{
  102. 		case Top:
  103. 			item->move((rect.topLeft()+rect.topRight())/2);
  104. 			break;
  105. 		case Right:
  106. 			item->move((rect.topRight()+ rect.bottomRight())/2);
  107. 			break;
  108. 		case Bottom:
  109. 			item->move((rect.bottomLeft()+ rect.bottomRight())/2);
  110. 			break;
  111. 		case Left:
  112. 			item->move((rect.topLeft()+ rect.bottomLeft())/2);
  113. 			break;
  114. 		case LeftTop:
  115. 			item->move(rect.topLeft());
  116. 			break;
  117. 		case LeftBottom:
  118. 			item->move(rect.bottomLeft());
  119. 			break;
  120. 		case RightTop:
  121. 			item->move(rect.topRight());
  122. 			break;
  123. 		case RightBottom:
  124. 			item->move(rect.bottomRight());
  125. 			break;
  126. 		}
  127. 	}
  128. }
  129.  
  130. QRectF CustomRectItem::boundingRect() const
  131. {
  132. 	return m_rect;
  133. }

圆形实现也类似，只要理解了正矩形，圆形也一样。

因为所有的图形类都是在图像上画的，所以在图像Item中声明CustomItemBaseFactory* m_itemFactory;  使用的话就简单贴下代码 [具体请看下载链接的代码]：

m_rectFactory = new CustomRectItemFactory;

m_Scene->m_ImageItem->m_itemFactory = m_rectFactory;

总结

因为只是练习的demo，所以在完成正矩形，旋转矩形和圆形这三个图像就不在继续了，这里只是做个Mark，后面想继续在继续完善。

下载链接地址：

QtAppTest220104.zip-C/C++文档类资源-CSDN下载

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