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

2019 年 11 月 11 日
笔记

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