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.

Example

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);       imageView.setX(10);       imageView.setY(10);       imageView.setFitWidth(575);       imageView.setPreserveRatio(true);       //Setting the Scene object       Group root = new Group(imageView);       Scene scene = new Scene(root, 595, 400);       stage.setTitle("Distance Transform");       stage.setScene(scene);       stage.show();    }    public static void main(String args[]) {       launch(args);    } }

Input Image

Output

On executing, the above program generates the following windows −