Java implementation of OpenCV Hough Circle Transform.

JavaObject Oriented ProgrammingProgramming

You can detect circles in a given image using the Hough circle transform. You can apply Hough Circle transform using the HoughCircles() method, this method accept the following parameters −

  • A Mat object representing the input image.

  • A Mat object to store the output vectors of the found circles.

  • An integers variables representing the detection method.

  • Two double variables representing an inverse ratio of the accumulator resolution to the image resolution and minimum distance between the centers of the detected circles.


import org.opencv.core.Core;
import org.opencv.core.Mat;
import org.opencv.core.Point;
import org.opencv.core.Scalar;
import org.opencv.highgui.HighGui;
import org.opencv.imgcodecs.Imgcodecs;
import org.opencv.imgproc.Imgproc;
import java.awt.Image;
import java.awt.image.BufferedImage;
import javafx.application.Application;
import javafx.embed.swing.SwingFXUtils;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.image.ImageView;
import javafx.scene.image.WritableImage;
import javafx.stage.Stage;
public class HoughCircleTransform extends Application {
   public void start(Stage stage) throws IOException {
      //Loading the OpenCV core library
      System.loadLibrary( Core.NATIVE_LIBRARY_NAME );
      String file ="D:\Images\compass.jpg";
      Mat src = Imgcodecs.imread(file);
      //Converting the image to Gray
      Mat gray = new Mat();
      Imgproc.cvtColor(src, gray, Imgproc.COLOR_RGBA2GRAY);
      //Blurring the image
      Mat blur = new Mat();
      Imgproc.medianBlur(gray, blur, 5);
      //Detecting the Hough Circles
      Mat circles = new Mat();
      Imgproc.HoughCircles(blur, circles, Imgproc.HOUGH_GRADIENT, Math.PI/180, 150);
      for (int i = 0; i < circles.cols(); i++ ) {
         double[] data = circles.get(0, i);
         Point center = new Point(Math.round(data[0]), Math.round(data[1]));
         // circle center, center, 1, new Scalar(0, 0, 255), 3, 8, 0 );
         // circle outline
         int radius = (int) Math.round(data[2]);, center, radius, new Scalar(0,0,255), 3, 8, 0 );
      //Converting matrix to JavaFX writable image
      Image img = HighGui.toBufferedImage(src);
      WritableImage writableImage= SwingFXUtils.toFXImage((BufferedImage) img, null);  
      //Setting the image view
      ImageView imageView = new ImageView(writableImage);
      //Setting the Scene object
      Group root = new Group(imageView);
      Scene scene = new Scene(root, 595, 400);
      stage.setTitle("Hough Circle Transform");
   public static void main(String args[]) {

Input Image


On executing, the above produces the following output −

Updated on 13-Apr-2020 10:55:03