Emgu circle detection using a webcam - webcam

Question

I'm trying to write a program that detects a circle when you hold it in front of the webcam. I know how the circle detection works for an image, but I can't figure out how to get it to work with a webcam stream, using the following code:
static class Program
{
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
ImageViewer viewer = new ImageViewer(); //create an image viewer
Capture capture = new Capture(); //create a camera capture
Application.Idle += new EventHandler(delegate(object sender, EventArgs e)
{ //run this until application closed (close button click on image viewer)
Image<Bgr, Byte> image = capture.QueryFrame();
//MemStorage storage = new MemStorage();
//Contour<Point> contours = image.FindContours();
//Contour<Point> currentContour = contours.ApproxPoly(contours.Perimeter * 0.05, storage);
viewer.Image = image; //draw the image obtained from camera
});
viewer.ShowDialog(); //show the image viewer
}
As you can see I've tried using FindContours in the innermost loop but the program just freezes when I try running it, so I commented that particular part out. Can anyone tell me how to implement circle detection using a webcam?

Answer 1

You can use HoughCircle Method for circle detection
Image gray = img.Convert().PyrDown().PyrUp();
Gray cannyThreshold = new Gray(180);
Gray cannyThresholdLinking = new Gray(120);
Gray circleAccumulatorThreshold = new Gray(120);
CircleF[] circles = gray.HoughCircles(
cannyThreshold,
circleAccumulatorThreshold,
5.0, //Resolution of the accumulator used to detect centers of the circles
10.0, //min distance
5, //min radius
0 //max radius
)[0]; //Get the circles from the first channel
See Method HoughCircle