Syntax error Altering the brightness and contrast of an image using JavaFX and OpenCV

Altering the brightness and contrast of an image using JavaFX and OpenCV

The convertTo() method of the org.opencv.core.Mat class accepts 4 parameters namely: mat(empty matrix), rtype(integer), alpha(integer), beta(integer), in the same order.

  • To increase the brightness − You need to reduce the beta value from 0 towards -255(keeping alpha value 1).

  • To decrease the brightness − You need to increase the beta value from 0 towards 255(keeping alpha value 1).

  • To increase the contrast − You need to increase the alpha value from 1 towards 100(keeping beta value 0).

  • To decrease the contrast − You need to decrease the alpha value from 1 to 0 (keeping beta value 0).

Example

Following is a JavaFX program with two slide bars to alter the alpha beta values.

import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import javafx.application.Application;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.embed.swing.SwingFXUtils;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.control.Slider;
import javafx.scene.image.ImageView;
import javafx.scene.image.WritableImage;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;
import javax.imageio.ImageIO;
import org.opencv.core.Core;
import org.opencv.core.Mat;
import org.opencv.core.MatOfByte;
import org.opencv.imgcodecs.Imgcodecs;
public class AlphaBetaValuesJavaFX extends Application {
   double contrast = 1;
   private final int rtype = -1;
   double alpha = 1;
   double beta = 0;
   Slider slider1;
   Slider slider2;
   Mat src = null;
   public void start(Stage stage) throws IOException {
      //Loading the OpenCV core library
      System.loadLibrary( Core.NATIVE_LIBRARY_NAME );
      String file ="D:\Image\lamma2.jpg";
      src = Imgcodecs.imread(file);
      WritableImage writableImage = loadImage(src);
      //Setting the image view
      ImageView imageView = new ImageView(writableImage);
      imageView.setX(50);
      imageView.setY(25);
      imageView.setFitHeight(400);
      imageView.setFitWidth(550);
      imageView.setPreserveRatio(true);
      Label label1 = new Label("Alpha value");
      //Setting the slider
      slider1 = new Slider(0.1, 3, 1);
      slider1.setShowTickLabels(true);
      slider1.setShowTickMarks(true);
      slider1.setMajorTickUnit(1);
      slider1.setBlockIncrement(0.05);
      //Setting the label
      Label label2 = new Label();
      Label label3 = new Label("Beta value");
      //Setting the slider
      slider2 = new Slider(-100, 100, 0);
      slider2.setShowTickLabels(true);
      slider2.setShowTickMarks(true);
      slider2.setMajorTickUnit(25);
      slider2.setBlockIncrement(10);
      //Setting the label
      Label label4 = new Label();
      //Listener for the slider
      slider1.valueProperty().addListener(new ChangeListener<Number>() {
         public void changed(ObservableValue <?extends Number>observable, Number oldValue, Number newValue){
            try {
               label2.setText("α-value: " + newValue);
               alpha = newValue.doubleValue();
               Mat dest = new Mat(src.rows(), src.cols(), src.type());
               src.convertTo(dest, rtype, alpha, beta);
               imageView.setImage(loadImage(dest));
            }
            catch(Exception e) {
               System.out.println("");
            }
         }
      });
      slider2.valueProperty().addListener(new ChangeListener<Number>() {
         public void changed(ObservableValue <?extends Number>observable, Number oldValue, Number newValue){
            try {
               label4.setText("β-value: " + newValue);
               beta = newValue.doubleValue();
               Mat dest = new Mat(src.rows(), src.cols(), src.type());
               src.convertTo(dest, rtype, alpha, beta);
               imageView.setImage(loadImage(dest));
            }
            catch(Exception e) {
               System.out.println("");
            }
         }
      });
      //VBox to arrange all the three components
      VBox vbox = new VBox();
      vbox.setPadding(new Insets(20));
      vbox.setSpacing(10);
      vbox.getChildren().addAll(label1, slider1, label2, imageView, label3, slider2, label4);
      //Creating a scene object
      Scene scene = new Scene(vbox, 600, 580);
      stage.setTitle("Loading an image");
      stage.setScene(scene);
      stage.show();
   }
   public WritableImage loadImage(Mat image) throws IOException {
      MatOfByte matOfByte = new MatOfByte();
      Imgcodecs.imencode(".jpg", image, matOfByte);
      //Storing the encoded Mat in a byte array
      byte[] byteArray = matOfByte.toArray();
      //Displaying the image
      InputStream in = new ByteArrayInputStream(byteArray);
      BufferedImage bufImage = ImageIO.read(in);
      System.out.println("Image Loaded");
      WritableImage writableImage = SwingFXUtils.toFXImage(bufImage, null);
      return writableImage;
   }
   public static void main(String args[]) {
      launch(args);
   }
}

Input image 

Output

Updated on: 2020-04-09T08:04:37+05:30

659 Views

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