how to draw a circle in video - c++

Question

im trying to draw a circle in a video from my webcam i using this function
cv::circle(cap,points(1,0),3,cv::Scalar(255,255,255),-1);
i found it in a document but i don't know why its't work i edit my code many time but its still give my error that's my full code i using opencv3
#include <opencv2/opencv.hpp>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <vector>
#include <iostream>
#include <sstream>
#include <opencv2/video/background_segm.hpp>
#include <opencv2/video/background_segm.hpp>
using namespace cv;
using namespace std;
int main()
{
VideoCapture cap(0); // open the video file for reading
if ( !cap.isOpened() ) // if not success, exit program
{
cout << "Cannot open the video file" << endl;
return -1;
}
//cap.set(CV_CAP_PROP_POS_MSEC, 300); //start the video at 300ms
double fps = cap.get(CV_CAP_PROP_FPS); //get the frames per seconds of the video
cout << "Frame per seconds : " << fps << endl;
namedWindow("MyVideo",CV_WINDOW_AUTOSIZE); //create a window called "MyVideo"
while(1)
{
Mat frame;
bool bSuccess = cap.read(frame); // read a new frame from video
if (!bSuccess) //if not success, break loop
{
cout << "Cannot read the frame from video file" << endl;
break;
}
imshow("MyVideo", frame); //show the frame in "MyVideo" window
cv::circle(cap,points(1,0),3,cv::Scalar(255,255,255),-1);
if(waitKey(30) == 27) //wait for 'esc' key press for 30 ms. If 'esc' key is pressed, break loop
{
cout << "esc key is pressed by user" << endl;
break;
}
}
return 0;
}

Answer 1

circle accepts a Mat object, not a VideoCapture object. So you need to draw the circle on frame.
Also you need to show the image after you actually draw the circle.
So replace the imshow / circle part of your code with:
...
cv::circle(frame, points(1,0), 3, cv::Scalar(255,255,255), -1);
imshow("MyVideo", frame);
...