[Qt学习笔记]Qt实现多摄像头的识别、显示、截图、分辨率帧率设置等功能

前言

项目中需要使用USB 的免驱摄像头进行采集图像，一般这种USB的摄像头直接可以使用Qt中的QCamera获取图像及相关各种操作，这里基于QCamera来实现摄像头的显示和抓图的基本功能。

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一、功能介绍和成果展示

多摄像头的信息获取、显示和抓图功能

• CameraInfo遍历设备获取多摄像头信息
• 获取摄像头的分辨率和最大帧率，并进行选择设置

• 实现单张抓图和连续抓拍功能
  

  二、实现流程

  1.配置工作

  首先要在Pro文件中加入multimedia模块，如下
  
  在ui中把图像视频显示的widget提升为QVideoWidget
  

  2.遍历摄像头设备

  调用QCameraInfo来获取可用的摄像头设备列表

    cameras = QCameraInfo::availableCameras();//获取可用摄像头设备列表
    int index = cameras.size();
    for(int i=0;icmb_CameraName->addItem(cameras.at(i).description());
    }

  3.获取摄像头支持的分辨率和最大帧率

  获取摄像头的参数并填入UI控件中

  void MainWindow::SetFrameResolution()
  {
    mResSize.clear();
    mResSize = m_camera->supportedViewfinderResolutions();
    ui->cmb_Resolution->clear();
    int i=0;
    foreach (QSize msize, mResSize) {
        qDebug()<cmb_Resolution->addItem(QString::number(msize.width(),10)+"*"+QString::number(msize.height(),10), i++);
    }  //摄像头支持分辨率打印
    ui->cmb_Resolution->setCurrentIndex(0);
  
    mMaxFrame.clear();
    int j;
    for(j=0;j< m_camera->supportedViewfinderFrameRateRanges().length();j++)
    {
        qreal frameRates = m_camera->supportedViewfinderFrameRateRanges().at(j).maximumFrameRate;
        mMaxFrame.append(frameRates);
        ui->cmb_MaxFrameRate->addItem(QString::number(frameRates));
    }
    ui->cmb_MaxFrameRate->setCurrentIndex(j-1);
  }

  4.显示视频和抓图操作

  显示视频时可以把捕捉模式设置为静态帧或视频，目前这两种看起来显示效果没差别，如果有大佬知道可以评论告知区别；

    m_camera = new QCamera(this);//初始化摄像头设备
    m_camera->setCaptureMode(QCamera::CaptureStillImage);//设置捕捉模式为静态帧
  //    m_camera->setCaptureMode(QCamera::CaptureVideo);//设置捕捉模式为视频
    m_camera->setViewfinder(ui->widgetCamera);//设置 摄像头画面的显示位置
    image_capture = new QCameraImageCapture(m_camera);
    m_camera->start();//开启摄像头
  
    connect(image_capture, SIGNAL(imageCaptured(int, QImage)), this, SLOT(processCapturedImage(int, QImage)));
    timer_image_capture = new QTimer(this);
    connect(timer_image_capture,&QTimer::timeout,this,&MainWindow::captureImage);
    SetFrameResolution();

  三、功能实现代码

  mainwindow.h

  #ifndef MAINWINDOW_H
  #define MAINWINDOW_H
  
  #include 
  #include 
  #include 
  #include 
  #include 
  #include 
  #include 
  
  namespace Ui {
  class MainWindow;
  }
  
  class MainWindow : public QMainWindow
  {
    Q_OBJECT
    
  public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();
    
  private slots:
    //    void on_btnCameraCtrl_clicked();
    
    void on_btnSnap_clicked();
    
    void on_btnVedio_clicked();
    
    void processCapturedImage(int request_id, const QImage &img);
    void captureImage();
    
    void on_cmb_CameraName_activated(int index);
    
    void on_cmb_Resolution_activated(int index);
    
    void on_cmb_MaxFrameRate_activated(int index);
    
  private:
    Ui::MainWindow *ui;
    QList cameras;
    QCamera* m_camera;//摄像头设备
    QCameraImageCapture* image_capture;
    QTimer *timer_image_capture;//图像抓图
    
    QList mResSize = {};//分辨率List
    QList mMaxFrame = {};//最大帧率
    QTimer *myTimer;//状态栏时间显示
    //相机状态标志量参数
    QLabel * m_status1;
    QLabel * m_status2;
    QLabel * m_status3;
    
    void initCamera();
    void initForm();
    void SetFrameResolution();
    void UpdateCameraStatus();
  };
  
  #endif // MAINWINDOW_H
  

  mainwindow.cpp

  #pragma execution_character_set("utf-8")
  #include "mainwindow.h"
  #include "ui_mainwindow.h"
  
  MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
  {
    ui->setupUi(this);
    this->initCamera();
    this->initForm();
  
  
  }
  
  MainWindow::~MainWindow()
  {
    delete ui;
  }
  
  void MainWindow::initCamera()
  {
    cameras = QCameraInfo::availableCameras();//获取可用摄像头设备列表
    int index = cameras.size();
    for(int i=0;icmb_CameraName->addItem(cameras.at(i).description());
    }
  
    m_camera = new QCamera(this);//初始化摄像头设备
    m_camera->setCaptureMode(QCamera::CaptureStillImage);//设置捕捉模式为静态帧
  //    m_camera->setCaptureMode(QCamera::CaptureVideo);//设置捕捉模式为视频
    m_camera->setViewfinder(ui->widgetCamera);//设置 摄像头画面的显示位置
    image_capture = new QCameraImageCapture(m_camera);
    m_camera->start();//开启摄像头
  
    connect(image_capture, SIGNAL(imageCaptured(int, QImage)), this, SLOT(processCapturedImage(int, QImage)));
    timer_image_capture = new QTimer(this);
    connect(timer_image_capture,&QTimer::timeout,this,&MainWindow::captureImage);
    SetFrameResolution();
  }
  
  void MainWindow::initForm()
  {
    myTimer=new QTimer(this);
    myTimer->start(1000);
    QLabel * btn = new QLabel(this);
    connect(myTimer , &QTimer::timeout, [=](){
        QDateTime Date_Time =QDateTime::currentDateTime();
        QString Time_system = Date_Time.toString("yyyy-MM-dd hh:mm:ss ddd");
        btn->setText(Time_system);
    });
  //    statusBar()->setStyleSheet(QString("QStatusBar::item{border: 2px}"));
    statusBar()->setSizeGripEnabled(false);
    ui->statusBar->addPermanentWidget(btn);
    m_status1 = new QLabel(this);
    m_status1->setGeometry(2,2,18,18);
    m_status2 = new QLabel(this);
    m_status3 = new QLabel(this);
    UpdateCameraStatus();
  }
  
  void MainWindow::UpdateCameraStatus()
  {
    QString curCamName = ui->cmb_CameraName->currentText();
    QString curCamFrame = ui->cmb_MaxFrameRate->currentText();
    QString curCamRes = ui->cmb_Resolution->currentText();
    m_status1->setText("摄像头："+curCamName);
    ui->statusBar->addWidget(m_status1);
    m_status2->setText("帧率："+curCamFrame);
    ui->statusBar->addWidget(m_status2);
    m_status3->setText("分辨率："+curCamRes);
    ui->statusBar->addWidget(m_status3);
  }
  
  void MainWindow::on_btnSnap_clicked()
  {
    image_capture->capture();
  }
  
  void MainWindow::on_btnVedio_clicked()
  {
    int Intervalue = ui->spinBox->value();
    timer_image_capture->setInterval(Intervalue);
    timer_image_capture->start();
  }
  
  void MainWindow::processCapturedImage(int request_id, const QImage &img)
  {
    QImage scaledImage = img.scaled(ui->label->size(),
                                    Qt::KeepAspectRatio,
                                    Qt::SmoothTransformation);
    ui->label->setPixmap(QPixmap::fromImage(scaledImage));
  }
  
  void MainWindow::captureImage()
  {
    image_capture->capture();
  }
  
  void MainWindow::on_cmb_CameraName_activated(int index)
  {
    index = ui->cmb_CameraName->currentIndex();
    qDebug()<<"Index"<< index <<": "<< ui->cmb_CameraName->currentText();
    if(m_camera->isAvailable())
    {
        m_camera->stop();
        delete m_camera;
    }
  
    m_camera = new QCamera(cameras[index]);
    m_camera->setCaptureMode(QCamera::CaptureStillImage);
    m_camera->setViewfinder(ui->widgetCamera);
    image_capture = new QCameraImageCapture(m_camera);
    m_camera->start();
    connect(image_capture, SIGNAL(imageCaptured(int, QImage)), this, SLOT(processCapturedImage(int, QImage)));
    SetFrameResolution();
        UpdateCameraStatus();
  }
  
  void MainWindow::SetFrameResolution()
  {
    mResSize.clear();
    mResSize = m_camera->supportedViewfinderResolutions();
    ui->cmb_Resolution->clear();
    int i=0;
    foreach (QSize msize, mResSize) {
        qDebug()<cmb_Resolution->addItem(QString::number(msize.width(),10)+"*"+QString::number(msize.height(),10), i++);
    }  //摄像头支持分辨率打印
    ui->cmb_Resolution->setCurrentIndex(0);
  
    mMaxFrame.clear();
    int j;
    for(j=0;j< m_camera->supportedViewfinderFrameRateRanges().length();j++)
    {
        qreal frameRates = m_camera->supportedViewfinderFrameRateRanges().at(j).maximumFrameRate;
        mMaxFrame.append(frameRates);
        ui->cmb_MaxFrameRate->addItem(QString::number(frameRates));
    }
    ui->cmb_MaxFrameRate->setCurrentIndex(j-1);
  }
  
  void MainWindow::on_cmb_Resolution_activated(int index)
  {
    index = ui->cmb_Resolution->currentIndex();
    qDebug()<<"Index"<< index <<": "<< ui->cmb_Resolution->currentText();
    qDebug()<<"mResSize:"<setViewfinderSettings(set);
    UpdateCameraStatus();
  }
  
  void MainWindow::on_cmb_MaxFrameRate_activated(int index)
  {
    index = ui->cmb_MaxFrameRate->currentIndex();
    //设置摄像头最大帧率
    QCameraViewfinderSettings set;
    set.setMaximumFrameRate(mMaxFrame[index]);
    m_camera->setViewfinderSettings(set);
    UpdateCameraStatus();
  }
  

  四、源码下载

  源码下载：多摄像头显示源码

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总结

这里实现了多个相机的视频显示、参数设置和抓图操作，也可以在初始化中使用QList来初始化所有的摄像头并用控件显示，这样就可以同时显示所有摄像头的视频。但是也有部分功能需要进一步研究优化

• 1.使用QCameraImageCapture类发送的capture的信号，系统会默认保存抓取的图像保存到电脑默认路径，一般在C盘下图片这个文件夹下，如果连续采图会导致本地缓存爆炸增长
• 2.在实际项目中，一般要采集到图像进行图像操作后再显示，不是单独去实现视频显示，这里需要使用QAbstractVideoSurface捕获视频帧，进行图像处理后再使用QPainter画到显示控件。