example_12-02.cpp

// Example 12-2. Using cv::HoughCircles() to return a sequence of circles found in a
// grayscale image

#include <opencv2/opencv.hpp>
#include <iostream>
#include <math.h>

using namespace cv;
using namespace std;

int main(int argc, char** argv) {

  if(argc != 2) {
  cout << "Hough Circle detect\nUsage: " <<argv[0] <<" <imagename>\n" << endl;
  return -1;
  }

  cv::Mat src, image;

  src = cv::imread( argv[1], 1 );
  if( src.empty() ) { cout << "Cannot load " << argv[1] << endl; return -1; }

  cv::cvtColor(src, image, cv::COLOR_BGR2GRAY);
  cv::GaussianBlur(image, image, Size(5,5), 0, 0);

  vector<cv::Vec3f> circles;
  cv::HoughCircles(image, circles, cv::HOUGH_GRADIENT, 2, image.cols/4);

  for( size_t i = 0; i < circles.size(); ++i ) {
    cv::circle(
      src,
      cv::Point(cvRound(circles[i][0]), cvRound(circles[i][1])),
      cvRound(circles[i][2]),
      cv::Scalar(0,0,255),
      2,
      cv::LINE_AA
    );
  }

  cv::imshow( "Hough Circles", src);
  cv::waitKey(0);

  return 0;
}