注意,要在ui界面上放置一个“Vertical Layout”控件,调整到合适大小
头文件

#include <QtWidgets/QMainWindow>  
#include <QPaintEvent>
#include <QTimer>
#include <QPainter>
#include <QPixmap>
#include <QLabel>
#include <QImage>
#include <opencv.hpp>
#include "ui_mainwindow.h"
using namespace cv;
class mainwindow : public QMainWindow
{
Q_OBJECT

public:
mainwindow(QWidget *parent = 0);
~mainwindow();
public slots:
void updateImage();
private:

QTimer theTimer;
Mat srcImage;
VideoCapture videoCap;
QLabel *imageLabel;

Ui::mainwindowClass ui;

protected:
void paintEvent(QPaintEvent *e);
};

源文件

mainwindow::mainwindow(QWidget *parent)  
: QMainWindow(parent)
{
ui.setupUi(this);
connect(&theTimer, &QTimer::timeout, this, &mainwindow::updateImage);
//从摄像头捕获视频
if(videoCap.open(0))
{
srcImage = Mat::zeros(videoCap.get(CV_CAP_PROP_FRAME_HEIGHT), videoCap.get(CV_CAP_PROP_FRAME_WIDTH), CV_8UC3);
theTimer.start(33);
}
//设置显示视频用的Label
imageLabel = new QLabel(this);
ui.verticalLayout->addWidget(imageLabel);
}

mainwindow::~mainwindow()
{

}

void mainwindow::paintEvent(QPaintEvent *e)
{
//显示方法一
QPainter painter(this);
QImage image1 = QImage((uchar*)(srcImage.data), srcImage.cols, srcImage.rows, QImage::Format_RGB888);
painter.drawImage(QPoint(20,20), image1);
//显示方法二
QImage image2 = QImage((uchar*)(srcImage.data), srcImage.cols, srcImage.rows, QImage::Format_RGB888);
imageLabel->setPixmap(QPixmap::fromImage(image2));
imageLabel->resize(image2.size());
imageLabel->show();
}

void mainwindow::updateImage()
{
videoCap>>srcImage;
if(srcImage.data)
{
cvtColor(srcImage, srcImage, CV_BGR2RGB);//Qt中支持的是RGB图像, OpenCV中支持的是BGR
this->update(); //发送刷新消息
}
}