OpenCV  4.10.0-dev
Open Source Computer Vision
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An example using the Hough circle detector

using namespace cv;
using namespace std;
int main(int argc, char** argv)
const char* filename = argc >=2 ? argv[1] : "smarties.png";
// Loads an image
Mat src = imread( samples::findFile( filename ), IMREAD_COLOR );
// Check if image is loaded fine
printf(" Error opening image\n");
printf(" Program Arguments: [image_name -- default %s] \n", filename);
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);
n-dimensional dense array class
Definition mat.hpp:812
bool empty() const
Returns true if the array has no elements.
int rows
the number of rows and columns or (-1, -1) when the matrix has more than 2 dimensions
Definition mat.hpp:2138
int main(int argc, char *argv[])
Definition highgui_qt.cpp:3
"black box" representation of the file storage associated with a file on disk.
Definition core.hpp:102
STL namespace.