使用Qt显示摄像头图像

1、在*.pro文件中添加多媒体模块

QT += multimedia multimediawidgets

2、使用QCamera`和`QCameraViewfinder实现捕捉和显示摄像头图像

2.1 头文件mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QCamera>

class QCamera;
class QCameraInfo;
class QCameraViewfinder;

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

private:
    Ui::MainWindow *ui;

    QCamera *m_camera;
    QCameraViewfinder *m_viewfinder;
};
#endif // MAINWINDOW_H

2.2 源文件mainwindow.cpp

#include <QCameraInfo>
#include <QCameraViewfinder>
#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    m_viewfinder = new QCameraViewfinder();
    m_viewfinder->setStyleSheet(tr("background-color:black"));
    m_viewfinder->setAspectRatioMode(Qt::AspectRatioMode::IgnoreAspectRatio);
    m_viewfinder->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);

    m_camera = new QCamera(QCameraInfo::defaultCamera());
    m_camera->setViewfinder(m_viewfinder);
    m_camera->start();

    setCentralWidget(m_viewfinder);
}

MainWindow::~MainWindow()
{
    delete ui;
    delete m_camera;
}