Qt实用技巧：使用OpenCV库操作摄像头拍照、调节参数和视频录制

OpenCV学堂

发布于 2019-11-11 23:17:40

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发布于 2019-11-11 23:17:40

文章被收录于专栏：贾志刚-OpenCV学堂贾志刚-OpenCV学堂

投稿作者：红模仿_红胖子 研究方向：OpenCV/OpenGL/QT/软硬件结合 博客地址:https://blog.csdn.net/qq21497936 文字编辑：gloomyfish

需求

使用OpenCV做功能，播放摄像头（usb和网络），对摄像头设备进行参数调整（亮度、对比度、饱和度、色调、增益、曝光度）调节，拍照和录像。

原理

使用OpenCV打开摄像头（可打开USB和网路哦摄像头），渲染图像显示，可使用OpenCV属性调整摄像头的各项参数，使用拍照可以将当前图片拍照，使用录像可以从当前时间点开始录像直至停止录像

注意

目前测试，即使PC上有编码器，但是OpenCV存储mat为对应的录像视频文件失败，出现：

录制完视频大小为200多B（基本为0），mp4格式时（查看入坑一）
录制完视频大小为6KB，avi格式时
录制avi传入图像mat，源码内部出现错误宕机

运行效果：

核心代码

打开摄像头代码

bool OpenCVManager::startCapture(int usb, int width, int height)
{
    if(!_pVideoCapture->open(usb))
    {
        qDebug() << __FILE__ << __LINE__ << "Failed to start capture :" << usb;
        return false;
    }
    _width = width;
    _height = height;
    _pVideoCapture->set(CV_CAP_PROP_FRAME_WIDTH, _width);
    _pVideoCapture->set(CV_CAP_PROP_FRAME_HEIGHT, _height);
    _width = _pVideoCapture->get(CV_CAP_PROP_FRAME_WIDTH);
    _height = _pVideoCapture->get(CV_CAP_PROP_FRAME_HEIGHT);
    _pVideoCapture->set(CV_CAP_PROP_FPS, 25);
    _brightness  = _pVideoCapture->get(cv::CAP_PROP_BRIGHTNESS);
    _contrast    = _pVideoCapture->get(cv::CAP_PROP_CONTRAST);
    _saturation  = _pVideoCapture->get(cv::CAP_PROP_SATURATION);
    _hue         = _pVideoCapture->get(cv::CAP_PROP_HUE);
    _gain        = _pVideoCapture->get(cv::CAP_PROP_GAIN);
    _exposure    = _pVideoCapture->get(cv::CAP_PROP_EXPOSURE);
    QTimer::singleShot(0, this, SLOT(slot_captrueFrame()));
    return true;
}

调整属性代码

bool OpenCVManager::getShowProperty() const
{
    return _showProperty;
}

void OpenCVManager::setShowProperty(bool value)
{
    _showProperty = value;
}

double OpenCVManager::getBrightness()
{
    return _brightness;
}

void OpenCVManager::setBrightness(double value)
{
    _brightness = value;
    if(_pVideoCapture)
    {
        _pVideoCapture->set(cv::CAP_PROP_BRIGHTNESS, _brightness);
    }
}

double OpenCVManager::getContrast() const
{
    return _contrast;
}

void OpenCVManager::setContrast(double value)
{
    _contrast = value;
    if(_pVideoCapture)
    {
        _pVideoCapture->set(cv::CAP_PROP_CONTRAST, _contrast);
    }
}

double OpenCVManager::getSaturation() const
{
    return _saturation;
}

void OpenCVManager::setSaturation(double value)
{
    _saturation = value;
    if(_pVideoCapture)
    {
        _pVideoCapture->set(cv::CAP_PROP_SATURATION, _saturation);
    }
}

double OpenCVManager::getHue() const
{
    return _hue;
}

void OpenCVManager::setHue(double value)
{
    _hue = value;
    if(_pVideoCapture)
    {
        _pVideoCapture->set(cv::CAP_PROP_HUE, _hue);
    }
}

double OpenCVManager::getGain() const
{
    return _gain;
}

void OpenCVManager::setGain(double value)
{
    _gain = value;
    if(_pVideoCapture)
    {
        _pVideoCapture->set(cv::CAP_PROP_GAIN, _gain);
    }
}

double OpenCVManager::getExposure() const
{
    return _exposure;
}

void OpenCVManager::setExposure(double value)
{
    _exposure = value;
    if(_pVideoCapture)
    {
        _pVideoCapture->set(cv::CAP_PROP_EXPOSURE, _exposure);
    }
}

拍照代码

void PhotoAndRecordWidget::on_pushButton_photo_clicked()
{
    QString timeStr = QDateTime::currentDateTime().toString("yyyy-MM-hh hh_mm_ss");
    QString dirName = "photos";
    if(!QFile::exists(dirName))
    {
        QDir dir;
        if(!dir.mkdir(dirName))
        {
            ui->label_state->setText("创建文件夹 " + dirName + "失败!!!");
        }
    }
    QString filePath = QString("%1/%2.png").arg(dirName).arg(timeStr);
    if(_image.save(filePath))
    {
        ui->label_state->setText("保存照片至: " + filePath);
    }else{
        ui->label_state->setText("保存照片失败!!!");
    }
}

录像代码

开启录像

void OpenCVManager::startRecord(QString pathFile)
{
    // 多线程处理
    QMetaObject::invokeMethod(this, "slot_startRecord",
                              Qt::DirectConnection, Q_ARG(QString, pathFile));
}
void OpenCVManager::slot_startRecord(QString filePath)
{
    if(_pVideoWrite)
    {
        qDebug() << __FILE__ << __LINE__ << "It's recording!!!";
        return;
    }
    _pVideoWrite = new cv::VideoWriter;
    QString ext = filePath.mid(filePath.lastIndexOf(".") + 1);
    int cvFourcc = 0;
    if(ext == "mpg")
    {
        cvFourcc = CV_FOURCC('D','I','V','X');
        qDebug() << __FILE__ << __LINE__<< ext << "DIVX" << cvFourcc;
    }else if(ext == "avi")
    {
        cvFourcc = CV_FOURCC('M','J','P','G');
        qDebug() << __FILE__ << __LINE__<< ext << "MJPG" << cvFourcc;
    }else if(ext == "mp4")
    {
        // mp4目前录制不成功（可以生成文件，但是打开失败）
//        cvFourcc = CV_FOURCC('M','P','4','2');
        cvFourcc = CV_FOURCC('M','J','P','G');
//        cvFourcc = CV_FOURCC('I', 'Y', 'U', 'V');
        qDebug() << __FILE__ << __LINE__<< ext << "MP42" << cvFourcc;
    }
    _pVideoWrite->open(filePath.toStdString(), cvFourcc, 25, cv::Size(_width, _height));

    _recordFilePath = filePath;
    _recording = true;
}

录像过程

void OpenCVManager::slot_captrueFrame()
{
    if(!_running)
    {
        return;
    }
    if(_pVideoCapture->isOpened())
    {
        cv::Mat mat;
        *_pVideoCapture >> mat;
        if(_showProperty)
        {
            cv::putText(mat, QString("brightness: %1").arg(_brightness).toStdString(),
                        cvPoint(0, 30), cv::FONT_HERSHEY_COMPLEX, 1.0, cv::Scalar(255));
            cv::putText(mat, QString("  contrast: %1").arg(_contrast  ).toStdString(),
                        cvPoint(0, 60), cv::FONT_HERSHEY_COMPLEX, 1.0, cv::Scalar(255));
            cv::putText(mat, QString("saturation: %1").arg(_saturation).toStdString(),
                        cvPoint(0, 90), cv::FONT_HERSHEY_COMPLEX, 1.0, cv::Scalar(255));
            cv::putText(mat, QString("       hue: %1").arg(_hue       ).toStdString(),
                        cvPoint(0, 120), cv::FONT_HERSHEY_COMPLEX, 1.0, cv::Scalar(255));
            cv::putText(mat, QString("      gain: %1").arg(_gain      ).toStdString(),
                        cvPoint(0, 150), cv::FONT_HERSHEY_COMPLEX, 1.0, cv::Scalar(255));
            cv::putText(mat, QString("  exposure: %1").arg(_exposure  ).toStdString(),
                        cvPoint(0, 180), cv::FONT_HERSHEY_COMPLEX, 1.0, cv::Scalar(255));
            cv::putText(mat, QString("press ESC out").toStdString(),
                        cvPoint(0, 210), cv::FONT_HERSHEY_COMPLEX, 1.0, cv::Scalar(255));
        }
        if(_recording)
        {
            _pVideoWrite->write(mat);
        }
        emit signal_captureOneFrame(mat);
        QTimer::singleShot(10, this, SLOT(slot_captrueFrame()));
    }
}

关闭录像

void OpenCVManager::stopRecord()
{
    // 多线程处理
    QMetaObject::invokeMethod(this, "slot_stopRecord", Qt::DirectConnection);
}

void OpenCVManager::slot_stopRecord()
{
    if(_pVideoWrite)
    {
        _recording = false;
        _pVideoWrite->release();
        delete _pVideoWrite;
        _pVideoWrite = 0;
    }
}

入坑记录

入坑一：录制视频保存为空