Qt--在显示视频的Label上画矩形

左手的ㄟ右手 2023-07-13 04:25 48阅读 0赞

1、实现方法：需重写Label的鼠标事件和绘图事件

2、工程代码如下：

mylabel.h

#ifndef MyLabel_H
    #define MyLabel_H
    
    #include <QLabel>
    #include <QPoint>
    #include <QPainter>
    #include <QColor>
    #include <QPaintEvent>
    #include <QPen>
    #include<QPainter>
    #include <QWidget>
    
    #include <QDebug>
    #include <QMouseEvent>
    
    #include <QPixmap>
    
    class MyLabel : public QLabel
    { 
        //Q_OBJECT
    public:
        explicit MyLabel(QWidget *parent = 0);
        ~MyLabel();
        
    protected:
        void paintEvent(QPaintEvent *event);    //绘制矩形
        void mousePressEvent(QMouseEvent *e);   //鼠标按下
        void mouseMoveEvent(QMouseEvent *e);    //鼠标移动
        void mouseReleaseEvent(QMouseEvent *e); //鼠标抬起
    
    private:
        QPoint m_rectStartPoint;
        QPoint m_rectEndPoint;
    };
    
    #endif // MyLabel_H

mylabe.cpp

#include "mylabel.h"
    
    MyLabel::MyLabel(QWidget *parent /*= 0*/ ) : QLabel(parent)
    { 
    
    }
    
    //鼠标按下
    void MyLabel::mousePressEvent(QMouseEvent *e)
    { 
        m_rectStartPoint = e->pos();
    }
    
    //鼠标移动
    void MyLabel::mouseMoveEvent(QMouseEvent *e)
    { 
        m_rectEndPoint = e->pos();
    }
    
    //鼠标抬起
    void MyLabel::mouseReleaseEvent(QMouseEvent *e)
    { 
    
    }
    
    //绘图
    void MyLabel::paintEvent(QPaintEvent *event)
    { 
        QLabel::paintEvent(event);      //先调用父类的paintEvent为了显示'背景'!!!
        QPainter painter(this);
    
        painter.setPen(QPen(Qt::green, 2));
        if (m_rectStartPoint != m_rectEndPoint)
        { 
            painter.drawRect(QRect(m_rectStartPoint, m_rectEndPoint));
        }
    }
    
    //
    MyLabel::~MyLabel()
    { 
    
    }

main.cpp

#include "mywidget.h"
    #include <QApplication>
    
    int main(int argc, char *argv[])
    { 
        QApplication a(argc, argv);
        MyWidget w;
        w.show();
    
        return a.exec();
    }

mywidget.h

#ifndef MYWIDGET_H
    #define MYWIDGET_H
    
    #include <QWidget>
    #include <QTimer>
    #include "mylabel1.h"
    
    #include "opencv2/opencv.hpp"
    #include "opencv2/imgproc/imgproc.hpp"
    #include "opencv2/highgui/highgui.hpp"
    #include "opencv2/videoio/videoio.hpp"
    
    using namespace cv;
    
    namespace Ui { 
    class MyWidget;
    }
    
    class MyWidget : public QWidget
    { 
        Q_OBJECT
    
    public:
        explicit MyWidget(QWidget *parent = 0);
        ~MyWidget();
    
        QImage mat2QImage(cv::Mat cvImg);
        QImage ScaleImage2Label(QImage qImage, QLabel* qLabel);
    
    private slots:
        void readFrame();
    
    private:
        Ui::MyWidget *ui;
    
        QTimer *timer;
        Mat frame;
        VideoCapture cap;
    
        MyLabel *label;
    };
    
    #endif // MYWIDGET_H

mywidget.cpp

#include "mywidget.h"
    #include "ui_mywidget.h"
    
    MyWidget::MyWidget(QWidget *parent) :
        QWidget(parent),
        ui(new Ui::MyWidget)
    { 
        ui->setupUi(this);
    
        label = new MyLabel;
        label->setStyleSheet("border:2px solid;border-color:blue");
        ui->horizontalLayout->addWidget(label);
        timer = new QTimer(this);
    
        timer->start(10);
    
        connect(timer, SIGNAL(timeout()), this, SLOT(readFrame()));
    
        cap.open(1);
    }
    
    
    void MyWidget::readFrame()
    { 
       cap >> frame;
    
       if(frame.empty())
       { 
            qDebug()<<"frame is empty";
            cap.release();
       }
    
       QImage img = ScaleImage2Label( mat2QImage(frame), label );
       label->setAlignment(Qt::AlignCenter);
       label->setPixmap(QPixmap::fromImage(img));
    }
    
    QImage MyWidget::ScaleImage2Label(QImage qImage, QLabel* qLabel)
    { 
        QImage qScaledImage;
        QSize qImageSize = qImage.size();
        QSize qLabelSize = qLabel->size();
    
        double dWidthRatio = 1.0*qImageSize.width() / qLabelSize.width();
        double dHeightRatio = 1.0*qImageSize.height() / qLabelSize.height();
        if (dWidthRatio > dHeightRatio)
        { 
            qScaledImage = qImage.scaledToWidth(qLabelSize.width());
        } else { 
            qScaledImage = qImage.scaledToHeight(qLabelSize.height());
        }
        return qScaledImage;
    }
    
    
    QImage MyWidget::mat2QImage(cv::Mat cvImg)
    { 
        QImage qImg;
    
        if (cvImg.channels() == 3)                             //3 channels color image
        { 
            cv::cvtColor(cvImg, cvImg, CV_BGR2RGB);
            qImg = QImage((const unsigned char*)(cvImg.data),
                          cvImg.cols, cvImg.rows,
                          cvImg.cols*cvImg.channels(),
                          QImage::Format_RGB888);
        }
    
        else if (cvImg.channels() == 1)                    //grayscale image
        { 
            qImg = QImage((const unsigned char*)(cvImg.data),
                          cvImg.cols, cvImg.rows,
                          cvImg.cols*cvImg.channels(),
                          QImage::Format_Indexed8);
        }
    
        else
        { 
            qImg = QImage((const unsigned char*)(cvImg.data),
                          cvImg.cols, cvImg.rows,
                          cvImg.cols*cvImg.channels(),
                          QImage::Format_RGB888);
        }
    
        return qImg;
    }
    
    MyWidget::~MyWidget()
    { 
        delete ui;
    }

3、效果  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjcwNDA5MA_size_16_color_FFFFFF_t_70]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjcwNDA5MA_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20200310203457819.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjcwNDA5MA==,size_16,color_FFFFFF,t_70