使用OpenCV库操作摄像头拍照、调节参数和视频录制

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

解决方法：

编解码器得问题，cv::VideoWrite查阅相关资料发现其只支持固定的几个格式，其中就包括avi。

入坑二：录制视频奔溃

原因：

因为初始设置摄像头的宽高（400 x 400），根据测试推断摄像头会默认给最接近初始化设置的分辨率，但是却不是直接是设置的（400 x 400）而是返回了最接近的分辨率（320 x 240），除非设置的分辨率正好是摄像头本身支持。

所以设置分辨率是需要摄像头硬件支持。

解决方法：

进一步验证同时解决该问题