Qt事件过滤实现点击图片的放大和缩小

#ifndef EVENTFILTER_H
#define EVENTFILTER_H
#include <QLabel>
#include <QImage>
#include <QDialog>

class EventFilter : public QDialog
{
    Q_OBJECT

public:
    EventFilter(QWidget *parent = nullptr,Qt::WindowFlags f=0);
    ~EventFilter();
public slots:
    bool eventFilter(QObject *watched, QEvent *event) override;
private:
    QLabel *m_label1;       //显示图片1
    QLabel *m_label2;       //显示图片2
    QLabel *m_label3;       //显示图片3
    QLabel *m_stateLabel;   //用于显示按下、松开的是哪一张图片
    QImage m_image1;
    QImage m_image2;
    QImage m_image3;

};
#endif // EVENTFILTER_H

EventFilter::EventFilter(QWidget *parent,Qt::WindowFlags f)
    : QDialog(parent,f)
{
    setWindowTitle("事件过滤");
    m_label1=new QLabel;
    m_label2=new QLabel;
    m_label3=new QLabel;
    m_stateLabel=new QLabel(QString("鼠标按下标志"));
    m_stateLabel->setAlignment(Qt::AlignHCenter);    //设置标签居中显示
    //加载图片
    m_image1.load(QString("../fly1.png")); //图片存在默认Debug目录的上一级目录
    m_image2.load(QString("../fly2.png"));
    m_image3.load(QString("../fly3.png"));

    //给标签设置图片
    m_label1->setPixmap(QPixmap::fromImage(m_image1));
    m_label2->setPixmap(QPixmap::fromImage(m_image2));
    m_label3->setPixmap(QPixmap::fromImage(m_image3));

    //设置水平布局、垂直布局
    QHBoxLayout *hLayout=new QHBoxLayout;
    hLayout->addWidget(m_label1);
    hLayout->addWidget(m_label2);
    hLayout->addWidget(m_label3);

    QVBoxLayout *mainLayout=new QVBoxLayout(this);
    mainLayout->addLayout(hLayout);
    mainLayout->addWidget(m_stateLabel);

    resize(m_image2.width()*3,m_image2.height()*2);//调整窗口的大小

    //给图片标签安装事件过滤，指定当前窗体对象为监视事件的对象
    m_label1->installEventFilter(this);
    m_label2->installEventFilter(this);
    m_label3->installEventFilter(this);


}

//重写事件过滤槽函数，watched为被监视对象
bool EventFilter::eventFilter(QObject *watched, QEvent *event)
{
    QMatrix matrix;
    QImage tempImage;//保存放大过后的图片
    matrix.scale(2.0,2.0);//放大两倍
    if(watched==m_label1){
        //事件类型是鼠标按下事件
        if(event->type()==QEvent::MouseButtonPress){
            QMouseEvent *mouseEvent=reinterpret_cast<QMouseEvent*>(event);
            if(mouseEvent->button()==Qt::LeftButton){
                m_stateLabel->setText("鼠标左键按下图片1");
            }else if(mouseEvent->button()==Qt::MidButton){
                m_stateLabel->setText("鼠标中键按下图片1");
            }else if(mouseEvent->button()==Qt::RightButton){
                m_stateLabel->setText("鼠标右键按下图片1");
        }
            //转换图片的比例
            tempImage=m_image1.transformed(matrix);
            m_label1->setPixmap(QPixmap::fromImage(tempImage));

        }
        //鼠标松开事件
        if(event->type()==QEvent::MouseButtonRelease){
            m_stateLabel->setText("鼠标松开图片1");
            m_label1->setPixmap(QPixmap::fromImage(m_image1));//鼠标松开返回本身图片的大小
        }
    }
    //m_label2、m_label2的处理过程同m_label1相同
    else if(watched==m_label2){
        if(event->type()==QEvent::MouseButtonPress){
            QMouseEvent *e=reinterpret_cast<QMouseEvent*>(event);
            if(e->buttons()&Qt::LeftButton){
                m_stateLabel->setText("鼠标左键按下图片2");
            }else if(e->buttons()&Qt::MidButton){
                m_stateLabel->setText("鼠标中键按下图片2");
            }else if(e->buttons()&Qt::RightButton){
                m_stateLabel->setText("鼠标右键按下图片2");
            }
            tempImage=m_image2.transformed(matrix);
            m_label2->setPixmap(QPixmap::fromImage(tempImage));
        }
        if(event->type()==QEvent::MouseButtonRelease){
            m_stateLabel->setText("鼠标松开图片2");
            m_label2->setPixmap(QPixmap::fromImage(m_image2));
        }
    }
    else if(watched==m_label3){
        if(event->type()==QEvent::MouseButtonPress){
            QMouseEvent *e=reinterpret_cast<QMouseEvent*>(event);
            if(e->buttons()&Qt::LeftButton){
                m_stateLabel->setText("鼠标左键按下图片3");
            }else if(e->buttons()&Qt::MidButton){
                m_stateLabel->setText("鼠标中键按下图片3");
            }else if(e->buttons()&Qt::RightButton){
                m_stateLabel->setText("鼠标右键按下图片3");
            }
            tempImage=m_image3.transformed(matrix);
            m_label3->setPixmap(QPixmap::fromImage(tempImage));
        }
        if(event->type()==QEvent::MouseButtonRelease){
            m_stateLabel->setText("鼠标松开图片3");
            m_label3->setPixmap(QPixmap::fromImage(m_image3));
        }
    }
    //事件交给上层对话框进行处理
    return QDialog::eventFilter(watched,event);
}