JavaFX + ImageIO: Convert PNG file to JPG

This example show how to choose PNG file using JavaFX FileChooser, open with ImageIO (actually any supported image format), and save in JPG using ImageIO.

package javafximagefilechooser;

import java.awt.Color;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javafx.application.Application;
import javafx.embed.swing.SwingFXUtils;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.Menu;
import javafx.scene.control.MenuBar;
import javafx.scene.control.MenuItem;
import javafx.scene.image.ImageView;
import javafx.scene.layout.StackPane;
import javafx.scene.layout.VBox;
import javafx.stage.FileChooser;
import javafx.stage.Stage;
import javax.imageio.ImageIO;

/**
 *
 * @web http://java-buddy.blogspot.com
 */
public class JavaFXImageFileChooser extends Application {

    @Override
    public void start(Stage primaryStage) {
        
        final FileChooser fileChooser = new FileChooser();
        final Button openButton = new Button("Open Image");

        openButton.setOnAction(
            new EventHandler<ActionEvent>() {
                @Override
                public void handle(final ActionEvent e) {
                    setExtFilters(fileChooser);
                    File file = fileChooser.showOpenDialog(primaryStage);
                    if (file != null) {
                        openNewImageWindow(file);
                    }
                }
            });

        StackPane root = new StackPane();
        root.getChildren().add(openButton);
        
        Scene scene = new Scene(root, 400, 150);
        
        primaryStage.setTitle("java-buddy.blogspot.com");
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
    
    private void setExtFilters(FileChooser chooser){
        chooser.getExtensionFilters().addAll(
                new FileChooser.ExtensionFilter("All Images", "*.*"),
                new FileChooser.ExtensionFilter("PNG", "*.png")
        );
    }
    
    private void openNewImageWindow(File file){
        Stage secondStage = new Stage();
        
        MenuBar menuBar = new MenuBar();
        Menu menuFile = new Menu("File");
        MenuItem menuItem_Save = new MenuItem("Save Image");
        menuFile.getItems().addAll(menuItem_Save);
        menuBar.getMenus().addAll(menuFile);
        
        Label name = new Label(file.getAbsolutePath());
        
        BufferedImage bufferedImage = null;
        try {
            bufferedImage = ImageIO.read(file);
        } catch (IOException ex) {
            Logger.getLogger(JavaFXImageFileChooser.class.getName()).log(Level.SEVERE, null, ex);
        }

        ImageView imageView = new ImageView();

        final BufferedImage imageToWrite = 
            new BufferedImage(
                bufferedImage.getWidth(),
                bufferedImage.getHeight(),
                BufferedImage.TYPE_INT_RGB);

        imageToWrite.createGraphics().drawImage(bufferedImage, 0, 0, Color.WHITE, null);
        
        menuItem_Save.setOnAction(new EventHandler<ActionEvent>() {

            @Override
            public void handle(ActionEvent event) {
                FileChooser fileChooser = new FileChooser();
                fileChooser.setTitle("Save Image");
                
                File file = fileChooser.showSaveDialog(secondStage);
                
                if (file != null) {
                    try {
                        ImageIO.write(imageToWrite, "jpg", file);
                    } catch (IOException ex) {
                        Logger.getLogger(
                            JavaFXImageFileChooser.class.getName()).log(Level.SEVERE, null, ex);
                    }
                }
            }
        });

        final VBox vbox = new VBox();
        vbox.setAlignment(Pos.CENTER);
        vbox.setSpacing(10);
        vbox.setPadding(new Insets(0, 10, 0, 10));
        vbox.getChildren().addAll(name, imageView);
        
        imageView.setFitHeight(400);
        imageView.setPreserveRatio(true);
        imageView.setImage(SwingFXUtils.toFXImage(bufferedImage, null));
        imageView.setSmooth(true);
        imageView.setCache(true);
        
        Scene scene = new Scene(new VBox(), 400, 350);
        ((VBox)scene.getRoot()).getChildren().addAll(menuBar, vbox);
        
        secondStage.setTitle(file.getName());
        secondStage.setScene(scene);
        secondStage.show();
    }
    
}

To list ImageIO supported read/write file format on your system

Example to list suffixes, format names and MIME types of supported image format on your system, by ImageIO, for read and write.

package javasupportedimageformat;

import javax.imageio.ImageIO;

/**
 *
 * @web http://java-buddy.blogspot.com
 */
public class JavaSupportedImageFormat {

    public static void main(String[] args) {
        
        //reader support
        System.out.println("ImageIO reader supported file suffixes:");
        String readerFileSuffixes[] = ImageIO.getReaderFileSuffixes();
        for(String f : readerFileSuffixes){
            System.out.println(f);
        }
        System.out.println();
        
        System.out.println("ImageIO reader supported format names:");
        String readerFormatNames[] = ImageIO.getReaderFormatNames();
        for(String f : readerFormatNames){
            System.out.println(f);
        }
        System.out.println();
        
        System.out.println("ImageIO reader supported MIME types:");
        String readerMIMETypes[] = ImageIO.getReaderMIMETypes();
        for(String f : readerMIMETypes){
            System.out.println(f);
        }
        System.out.println();
        
        //writer support
        System.out.println("ImageIO writer supported file suffixes:");
        String writerFileSuffixes[] = ImageIO.getWriterFileSuffixes();
        for(String f : writerFileSuffixes){
            System.out.println(f);
        }
        System.out.println();
        
        System.out.println("ImageIO writer supported format names:");
        String writerFormatNames[] = ImageIO.getWriterFormatNames();
        for(String f : writerFormatNames){
            System.out.println(f);
        }
        System.out.println();
        
        System.out.println("ImageIO writer supported MIME types:");
        String writerMIMETypes[] = ImageIO.getWriterMIMETypes();
        for(String f : writerMIMETypes){
            System.out.println(f);
        }
        System.out.println();
    }
    
}