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
