| OpenCV 3.4.3 Open Source Computer Vision

samples/cpp/tutorial_code/ImgTrans/houghcircles.cpp

An example using the Hough circle detector

#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui.hpp"
#include "opencv2/imgproc.hpp"
using namespace cv;
using namespace std;
int main(int argc, char** argv)
{
const char* filename = argc >=2 ? argv[1] : "../data/smarties.png";
// Loads an image
Mat src = imread( filename, IMREAD_COLOR );
// Check if image is loaded fine
if(src.empty()){
printf(" Error opening image\n");
printf(" Program Arguments: [image_name -- default %s] \n", filename);
return -1;
}
Mat gray;
cvtColor(src, gray, COLOR_BGR2GRAY);
medianBlur(gray, gray, 5);
vector<Vec3f> circles;
HoughCircles(gray, circles, HOUGH_GRADIENT, 1,
gray.rows/16, // change this value to detect circles with different distances to each other
100, 30, 1, 30 // change the last two parameters
// (min_radius & max_radius) to detect larger circles
);
for( size_t i = 0; i < circles.size(); i++ )
{
Vec3i c = circles[i];
Point center = Point(c[0], c[1]);
// circle center
circle( src, center, 1, Scalar(0,100,100), 3, LINE_AA);
// circle outline
int radius = c[2];
circle( src, center, radius, Scalar(255,0,255), 3, LINE_AA);
}
imshow("detected circles", src);
waitKey();
return 0;
}