OpenCV3.6 實時打開USB 攝像頭 和插網線的網絡攝像頭

//打開USB攝像頭
int OpenCameraWithOpencv::opencvUsvCamera()
{
	VideoCapture cap;
	String videoFile="";

	if (videoFile != "")
	{
		cap.open(videoFile);// read a video file
	}
	else {
		cap.open(0);// read the default caera
	}
	if (!cap.isOpened())// check if we succeeded
	{
		return -1;
	}

	namedWindow("Video", 1);
	while (1)
	{
		Mat frame;
		cap >> frame; // get a new frame from camera
		imshow("Video", frame);
		if (waitKey(30) >= 0) break;
	}

	// Release the camera or video file
	cap.release();
	return 0;


}