Save WritableImage to file

To save WritableImage to file, e can use the code:

                    File file = new File("test.png");
                    RenderedImage renderedImage = SwingFXUtils.fromFXImage(writableImage, null);
                    ImageIO.write(
                            renderedImage, 
                            "png",
                            file);

Where we render the image by calling SwingFXUtils.fromFXImage() and write to file by calling ImageIO.write().

Complete example:

Modify the code in last post "Create and adjust Color using hue, saturation, brightness". Add a button to save the image once button clicked.

package testjavafx;

import java.awt.image.BufferedImage;
import java.awt.image.RenderedImage;
import java.io.File;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javafx.application.Application;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.embed.swing.SwingFXUtils;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Slider;
import javafx.scene.control.SliderBuilder;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.image.PixelReader;
import javafx.scene.image.PixelWriter;
import javafx.scene.image.WritableImage;
import javafx.scene.layout.HBox;
import javafx.scene.layout.StackPane;
import javafx.scene.layout.VBox;
import javafx.scene.paint.Color;
import javafx.stage.Stage;
import javax.imageio.ImageIO;

/**
 *
 * @web http://java-buddy.blogspot.com/
 */
public class TestJavaFX extends Application {
    
    PixelReader pixelReader;
    int width, height;
    
    WritableImage writableImage, writableImageHue, writableImageSaturation, writableImageBrightness;
    PixelWriter pixelWriter, pixelWriterHue, pixelWriterSaturation, pixelWriterBrightness;
    ImageView destImageView, imageViewHue, imageViewSaturation, imageViewBrightness;
    
    Slider sliderHue, sliderSaturation, sliderBrightness;
    double adjHue, adjSaturation, adjBrightness;
    
    @Override
    public void start(Stage primaryStage) {
        
        Image image = new Image("http://goo.gl/kYEQl");
        ImageView imageView = new ImageView();
        imageView.setImage(image);
        
        pixelReader = image.getPixelReader();
        width = (int)image.getWidth();
        height = (int)image.getHeight();
        
        //Copy from source to destination pixel by pixel
        writableImage = new WritableImage(width, height);
        pixelWriter = writableImage.getPixelWriter();
        
        writableImageHue = new WritableImage(width, height);
        pixelWriterHue = writableImageHue.getPixelWriter();
        
        writableImageSaturation = new WritableImage(width, height);
        pixelWriterSaturation = writableImageSaturation.getPixelWriter();
        
        writableImageBrightness = new WritableImage(width, height);
        pixelWriterBrightness = writableImageBrightness.getPixelWriter();
        
        destImageView = new ImageView();
        imageViewHue = new ImageView();
        imageViewSaturation = new ImageView();
        imageViewBrightness = new ImageView();
        
        HBox hBox_Image = new HBox();
        hBox_Image.getChildren().addAll(imageView, destImageView);
        
        //Control box for Hue
        sliderHue = SliderBuilder.create()
                .prefWidth(300)
                .min(-360)
                .max(360)
                .majorTickUnit(30)
                .showTickMarks(true)
                .showTickLabels(true)
                .value(0)
                .build();
        sliderHue.valueProperty().addListener(sliderChangeListener);
        HBox hBox_Hue = new HBox();
        hBox_Hue.getChildren().addAll(imageViewHue, sliderHue);
        
        //Control box for Saturation
        sliderSaturation = SliderBuilder.create()
                .prefWidth(300)
                .min(-1)
                .max(1)
                .majorTickUnit(0.2)
                .showTickMarks(true)
                .showTickLabels(true)
                .value(0)
                .build();
        sliderSaturation.valueProperty().addListener(sliderChangeListener);
        HBox hBox_Saturation = new HBox();
        hBox_Saturation.getChildren().addAll(imageViewSaturation, sliderSaturation);
        
        //Control box for Blue
        sliderBrightness = SliderBuilder.create()
                .prefWidth(300)
                .min(-1)
                .max(1)
                .majorTickUnit(0.2)
                .showTickMarks(true)
                .showTickLabels(true)
                .value(0)
                .build();
        sliderBrightness.valueProperty().addListener(sliderChangeListener);
        HBox hBox_Brightness = new HBox();
        hBox_Brightness.getChildren().addAll(imageViewBrightness, sliderBrightness);
        
        Button buttonSave = new Button("Save");
        buttonSave.setOnAction(new EventHandler<ActionEvent>() {

            @Override
            public void handle(ActionEvent event) {
                try {
                    File file = new File("test.png");
                    RenderedImage renderedImage = SwingFXUtils.fromFXImage(writableImage, null);
                    ImageIO.write(
                            renderedImage, 
                            "png",
                            file);
                } catch (IOException ex) {
                    Logger.getLogger(TestJavaFX.class.getName()).log(Level.SEVERE, null, ex);
                }
            }
        });
        
        VBox vBox = new VBox();
        vBox.getChildren().addAll(hBox_Image, 
                hBox_Hue, hBox_Saturation, hBox_Brightness, buttonSave);

        StackPane root = new StackPane();
        root.getChildren().add(vBox);
        Scene scene = new Scene(root, 350, 400);
        primaryStage.setTitle("java-buddy.blogspot.com");
        primaryStage.setScene(scene);
        primaryStage.show();
        
        updateImage();
    }
    
    ChangeListener<Number> sliderChangeListener
            = new ChangeListener<Number>(){

        @Override
        public void changed(ObservableValue<? extends Number> observable, Number oldValue, Number newValue) {
            updateImage();
        }
    };
    
    private void updateImage(){
        adjHue = sliderHue.valueProperty().doubleValue();
        adjSaturation = sliderSaturation.valueProperty().doubleValue();
        adjBrightness = sliderBrightness.valueProperty().doubleValue();
        
        for (int y = 0; y < height; y++){
            for (int x = 0; x < width; x++){
                Color color = pixelReader.getColor(x, y);
                pixelWriter.setColor(x, y, color);
                
                double hue = color.getHue() + adjHue;
                if(hue > 360.0){
                    hue = hue - 360;
                }else if(hue < 0.0){
                    hue = hue + 360.0;
                }
                
                double saturation = color.getSaturation() + adjSaturation;
                if(saturation > 1.0){
                    saturation = 1.0;
                }else if(saturation < 0.0){
                    saturation = 0.0;
                }
                
                double brightness = color.getBrightness() + adjBrightness;
                if(brightness > 1.0){
                    brightness = 1.0;
                }else if(brightness < 0.0){
                    brightness = 0.0;
                }
                
                double opacity = color.getOpacity();
                
                pixelWriterHue.setColor(x, y, new Color(hue/360.0, hue/360.0, hue/360.0, opacity));
                pixelWriterSaturation.setColor(x, y, new Color(saturation, saturation, saturation, opacity));
                pixelWriterBrightness.setColor(x, y, new Color(brightness, brightness, brightness, opacity));
                
                Color newColor = Color.hsb(hue, saturation, brightness, opacity);
                pixelWriter.setColor(x, y, newColor);

            }
        }
        
        imageViewHue.setImage(writableImageHue);
        imageViewSaturation.setImage(writableImageSaturation);
        imageViewBrightness.setImage(writableImageBrightness);
        destImageView.setImage(writableImage);
    }

    public static void main(String[] args) {
        launch(args);
    }
}