video capture card (webcam like) with OpenCV

I want to use video capture card to capture my screen display, and process the image by OpenCV/C++.

I have heard that there's some video capture card which is webcam like.(i.e. I can get the screen display by VideoCapture in OpenCV.)

Can someone tell me which video capture card should I buy?

Thanks !!!

I do not know if there some way to achieve that directly using OpenCV. However, a simple workaround could be like this:

1. Using this software you can create new webcam that stream your screen: https://sparkosoft.com/how-to-stream-desktop-as-webcam-video

2. Using OpenCV you can start capture the stream using this code:

   cv::VideoCapture cap;
   if(!cap.open(0)) // Use the new webcam Id instead of 0
       return 0;
   while(true){
         cv::Mat frame;
         cap >> frame;
         if(frame.empty()) break;
         cv::imshow("Screen", frame);
         if( waitKey(10) == 27 ) break;
   }
   return 0;