QT中在QLabel显示图片并且利用鼠标点击画线
最近在做在Label上显示图片并且通过鼠标点击画线，在网上查了很多零零散散的东西，收获也多
很多初学者更希望直接贴代码，这样可以模仿来写，我下面直接贴出我的项目中自己写的maLabel类（如果只是实现利用鼠标绘制，重写void paintEvent(QPaintEvent *event);void mousePressEvent(QMouseEvent *e); void mouseMoveEvent(QMouseEvent *e); void mouseReleaseEvent(QMouseEvent *e);即可，其他函数是我项目需求所以多写的，可以忽略）
申明myLabel类，继承QLabel，生成myLabel.h和myLabel.cpp文件
以下为我的代码，供参考。我只是实现了画一条直线，如果要画多条，可以用vector将之前若干条的信息干存下来，每次都绘制
myLabel.h
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#ifndef MYLABEL_H
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#define MYLABEL_H
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#include
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#include
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#include
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#include
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#include
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#include
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class myLabel :
public QLabel
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{
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//Q_OBJECT
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public:
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myLabel();
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//~myLabel();
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//绘制线条
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virtual void paintEvent(QPaintEvent *event) override;
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//鼠标按下
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void mousePressEvent(QMouseEvent *e);
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//鼠标移动
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void mouseMoveEvent(QMouseEvent *e);
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//鼠标抬起
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void mouseReleaseEvent(QMouseEvent *e);
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//设置所画线条属性
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void setLineColor(const QColor lineColor);
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void setLineSize(const int lineSize);
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//得到画线的起点和终点
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QPoint getStartPoint();
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QPoint getEndPoint();
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void clear();
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private:
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QPoint lineStartPoint;
//画线起点
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QPoint lineEndPoint;
//画线终点
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QColor lineColor;
//线条颜色
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int lineSize;
//5种线型
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bool isPressed;
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};
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#endif // MYLABEL_H
myLabel.cpp
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#include "myLabel.h"
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#include
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#include
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myLabel::myLabel()
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{
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this->lineStartPoint = QPoint(
0,
0);
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this->lineEndPoint = QPoint(
0,
0);
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this->lineColor = QColor(Qt::black);
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this->lineSize =
3;
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}
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//绘制线条
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void myLabel::paintEvent(QPaintEvent *event)
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{
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QLabel::paintEvent(event);
//必须有，才能让背景图片显示出来
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QPainter painter(this);
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QPen pen;
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pen.setColor(lineColor);
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pen.setWidth(lineSize);
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painter.setPen(pen);
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painter.drawLine(lineStartPoint,lineEndPoint);
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}
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//鼠标按下
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void myLabel::mousePressEvent(QMouseEvent *e)
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{
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lineStartPoint = e->pos();
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lineEndPoint = e->pos();
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//在图片上绘制
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isPressed =
true;
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}
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//鼠标移动
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void myLabel::mouseMoveEvent(QMouseEvent *e)
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{
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if(isPressed)
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{
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lineEndPoint=e->pos();
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update();
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}
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}
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//鼠标抬起
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void myLabel::mouseReleaseEvent(QMouseEvent *e)
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{
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isPressed=
false;
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update();
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}
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void myLabel::setLineColor(
const QColor lineColor)
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{
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this->lineColor = lineColor;
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}
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void myLabel::setLineSize(
const
int lineSize)
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{
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this->lineSize = lineSize;
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}
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QPoint myLabel::getStartPoint()
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{
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return lineStartPoint;
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}
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QPoint myLabel::getEndPoint()
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{
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return lineEndPoint;
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}
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void myLabel::clear()
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{
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lineStartPoint = QPoint(
0,
0);
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lineEndPoint = QPoint(
0,
0);
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update();
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}
