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

#ifndef MYLABEL_H#define MYLABEL_H#include <QLabel>#include <QPoint>#include <QColor>#include <QPaintEvent>#include <QImage>#include <QPixmap>class myLabel : public QLabel{    //Q_OBJECTpublic:    myLabel();    //~myLabel();    //绘制线条    virtual void paintEvent(QPaintEvent *event) override;    //鼠标按下    void mousePressEvent(QMouseEvent *e);    //鼠标移动    void mouseMoveEvent(QMouseEvent *e);    //鼠标抬起    void mouseReleaseEvent(QMouseEvent *e);    //设置所画线条属性    void setLineColor(const QColor lineColor);    void setLineSize(const int lineSize);    //得到画线的起点和终点    QPoint getStartPoint();    QPoint getEndPoint();    void clear();private:    QPoint lineStartPoint;          //画线起点    QPoint lineEndPoint;            //画线终点    QColor lineColor;               //线条颜色    int lineSize;                  //5种线型    bool isPressed;};#endif // MYLABEL_H

myLabel.cpp

#include "myLabel.h"#include <QPen>#include<QPainter>myLabel::myLabel(){    this->lineStartPoint = QPoint(0,0);    this->lineEndPoint = QPoint(0,0);    this->lineColor = QColor(Qt::black);    this->lineSize = 3;}//绘制线条void myLabel::paintEvent(QPaintEvent *event){    QLabel::paintEvent(event);//必须有，才能让背景图片显示出来    QPainter painter(this);    QPen pen;    pen.setColor(lineColor);    pen.setWidth(lineSize);    painter.setPen(pen);    painter.drawLine(lineStartPoint,lineEndPoint);}//鼠标按下void myLabel::mousePressEvent(QMouseEvent *e){    lineStartPoint = e->pos();    lineEndPoint = e->pos();    //在图片上绘制    isPressed = true;}//鼠标移动void myLabel::mouseMoveEvent(QMouseEvent *e){    if(isPressed)    {        lineEndPoint=e->pos();        update();    }}//鼠标抬起void myLabel::mouseReleaseEvent(QMouseEvent *e){    isPressed=false;    update();}void myLabel::setLineColor(const QColor lineColor){    this->lineColor = lineColor;}void myLabel::setLineSize(const int lineSize){    this->lineSize = lineSize;}QPoint myLabel::getStartPoint(){    return lineStartPoint;}QPoint myLabel::getEndPoint(){    return lineEndPoint;}void myLabel::clear(){    lineStartPoint = QPoint(0,0);    lineEndPoint = QPoint(0,0);    update();}