Explain OpenCV Distance Transformation using java Example

The distance transform, in general, is a derived representation of a digital image. In this operation, the gray level intensities of the points inside the foreground regions are changed to distance their respective distances from the closest 0 value (boundary).

The distanceTransform() method of the Imgproc class applies Distance Transform on the given image, this method accepts −

  • Two Mat objects representing the source and destination images.

  • An integer variable representing the type of the distance transformation to be applied.

  • An integer value representing the mask size to be used.


import java.awt.Image;
import java.awt.image.BufferedImage;
import java.io.IOException;
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;
import org.opencv.core.Core;
import org.opencv.core.Mat;
import org.opencv.highgui.HighGui;
import org.opencv.imgcodecs.Imgcodecs;
import org.opencv.imgproc.Imgproc;
public class DistanceTransform extends Application {
   public void start(Stage stage) throws IOException {
      //Loading the OpenCV core library
      System.loadLibrary( Core.NATIVE_LIBRARY_NAME );
      //Reading the Image from the file and storing it in to a Matrix object
      String file ="D://images//boy.jpg";
      Mat src = Imgcodecs.imread(file, Imgcodecs.IMREAD_GRAYSCALE);
      //Creating an empty matrix to store the results
      Mat dst = new Mat();
      Mat binary = new Mat();
      //Converting the gray scale image to binary image
      Imgproc.threshold(src, binary, 100, 255, Imgproc.THRESH_BINARY);
      //Applying distance transform
      Imgproc.distanceTransform(binary, dst, Imgproc.DIST_C, 3);
      Core.convertScaleAbs( dst, dst );
      //Converting matrix to JavaFX writable image
      Image img = HighGui.toBufferedImage(dst);
      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("Distance Transform");
   public static void main(String args[]) {

Input Image


On executing, the above program generates the following windows −

Updated on: 13-Apr-2020


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