//如果有外接攝像頭，則ID為0，內置為1，否則用0就可以表示內置攝像頭   cv::VideoCapture cap(0);    //判斷攝像頭是否打開   if(!cap.isOpened())    {      return -1;    }     cv::Mat myframe;    cv::Mat edges;     bool stop = false;    while(!stop)    {      //獲取當前幀     cap>>myframe;     //轉化為灰度圖      cv::cvtColor(myframe, edges, CV_BGR2GRAY);     //高斯濾波器      cv::GaussianBlur(edges, edges, cv::Size(7,7), 1.5, 1.5);     //Canny算子檢測邊緣      cv::Canny(edges, edges, 0, 30, 3);     //顯示邊緣      cv::imshow("current frame",edges);      if(cv::waitKey(30) >=0)        stop = true;    }    cv::waitKey(0); 

// Open the video file   cv::VideoCapture capture("../images/bike.avi"); // check if video successfully opened if (!capture.isOpened()) return 1;  // Get the frame rate double rate= capture.get(CV_CAP_PROP_FPS);  bool stop(false); cv::Mat frame; // current video frame cv::namedWindow("Extracted Frame");  // Delay between each frame // corresponds to video frame rate int delay= 1000/rate;  //用于設置幀的移動位置。 input_video.set(CV_CAP_PROP_POS_FRAMES,100); // for all frames in video while (!stop) {  // read next frame if any if (!capture.read(frame)) break;   cv::imshow("Extracted Frame",frame);  // introduce a delay // or press key to stop if (cv::waitKey(delay)>=0)  stop= true; }  // Close the video file capture.release();  cv::waitKey();