Histogram equalization on an image in OpenCV using Java.

JavaObject Oriented ProgrammingProgramming

The histogram of an image shows the frequency of pixels’ intensity values. In an image histogram, the X-axis shows the gray level intensities and the Y-axis shows the frequency of these intensities and improves the contrast of an image.

The equalizeHist() method of the Imgproc method accepts to Mat objects representing the source and destination images, equalizes the histogram of the source matrix and receives it in the destination matrix.

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 HistogramEquilization extends Application {
   public void start(Stage stage) throws IOException {
      //Loading the OpenCV core library
      System.loadLibrary( Core.NATIVE_LIBRARY_NAME );
      String file ="D:\\Images\\win2.jpg";
      Mat src = Imgcodecs.imread(file, Imgcodecs.IMREAD_GRAYSCALE);
      //Creating an empty matrices to store the destination image.
      Mat dst = new Mat(src.rows(), src.cols(), src.type());
      //Detecting the edges
      Imgproc.equalizeHist(src, 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("Histogram Equilization Example");
      stage.setScene(scene);
      stage.show();
   }
   public static void main(String args[]) {
      launch(args);
   }
}

Input Image

Output

On executing, the above produces the following output −

raja
Published on 13-Apr-2020 10:57:24
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