# HoughCircles cannot detect circles in this image

I am trying to detect circles in my image that contain a circle of dots, but unfortunately I cannot do this. I am using opencv HoughTransform and I cannot find the parameters that make this work.

```
src = imread("encoded.jpg",1);
/// Convert it to gray
cvtColor(src, src_gray, CV_BGR2GRAY);
vector<Vec3f> circles;
/// Apply the Hough Transform to find the circles
HoughCircles(src_gray, circles, CV_HOUGH_GRADIENT, 1, 10,
100, 30, 1, 30 // change the last two parameters
// (min_radius & max_radius) to detect larger circles
);
/// Draw the circles detected
for (size_t i = 0; i < circles.size(); i++)
{
cout << "Positive" << endl;
Point center(cvRound(circles[i][0]), cvRound(circles[i][1]));
int radius = cvRound(circles[i][2]);
// circle center
circle(src, center, 3, Scalar(0, 255, 0), -1, 8, 0);
// circle outline
circle(src, center, radius, Scalar(0, 0, 255), 3, 8, 0);
}
/// Show your results
namedWindow("Hough Circle Transform Demo", CV_WINDOW_AUTOSIZE);
imshow("Hough Circle Transform Demo", src_gray);
waitKey(0);
```

Why can't HoughCircles detect circles in this image? It seems to work with other simpler images like PCB.

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