[mcj]利用opencv打开本地摄像头

#include <opencv2/opencv.hpp>   
using namespace cv;
int main()
{
       VideoCapture capture(0);
       Mat frame;
       while (capture.isOpened())
       {
              capture >> frame;
              imshow("capture", frame);
              if (cvWaitKey(10) == 27)  //cvWaitKey的参数相当于多少ms一帧，现在是40ms一帧，1s25帧
                     break;                //按ESC就退出
       }
       return 0;
}