CODEWITHSUNDEEP
c#opencvcirce
jaebeom lim
jaebeom lim

Reputation: 11

Circle center & radius detection at OpenCV

enter image description here

I want to detect circle center & radius. ( C#, OpenCV2 )

I tried to find it using Canny Edge, Laplace Edge, BinarizerMethod.

I found wrong position and radius.

How can I improve it?

a_circle = new IplImage(src.Size, BitDepth.U8, 3);
Cv.Copy(src, a_circle);

a_gray = new IplImage(src.Size, BitDepth.U8, 1);

Cv.CvtColor(src, a_gray, ColorConversion.BgrToGray);
Cv.Smooth(a_gray, a_gray, SmoothType.Gaussian, 9);

CvMemStorage a_Storage = new CvMemStorage();
CvSeq<CvCircleSegment> circles = Cv.HoughCircles(a_gray, a_Storage, HoughCirclesMethod.Gradient, 1, 100, a_p_edge, a_p_center, 0, 0);

foreach (CvCircleSegment item in circles)
{
    Cv.DrawCircle(a_gray, item.Center, (int)item.Radius, CvColor.White, 3);

    point_radius = (int)item.Radius;
    point_centerX = (int)item.Center.X;
    point_centerY = (int)item.Center.Y;
}

I tried to find it using Canny Edge, Laplace Edge, BinarizerMethod.

How can I find the circle center & radius?

Upvotes: 0

Views: 87

Answers (1)

Alex
Alex

Reputation: 51

The circle can be detected with Hough Circles, but you probably still need to tweak the parameters (dp, param1, param2 etc.) for your image.

Processed Image

See documentation: https://docs.opencv.org/3.4/d4/d70/tutorial_hough_circle.html

using OpenCvSharp;

using Mat originalImageColor = Cv2.ImRead("C:\\circle.png", ImreadModes.Color);
using Mat workerImage = Cv2.ImRead("C:\\circle.png", ImreadModes.Grayscale);

float dp = 0.1f;
int minDistance = 200;
int param1 = 60;
int param2 = 40;
int minRadius = 350;
int maxRadius = 500;

CircleSegment[] results = Cv2.HoughCircles(workerImage, HoughModes.Gradient, dp, minDistance, param1, param2, minRadius, maxRadius);

foreach(var result in results)
{
  Cv2.Circle(originalImageColor, (int)result.Center.X, (int)result.Center.Y, (int)result.Radius, Scalar.Magenta, thickness: 3);
}

Cv2.ImShow("output", originalImageColor);
Cv2.WaitKey();

Upvotes: 1

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