How to stretch image

Question

Hi
I am using the following method to resize an image, but when the new width and height do not maintain the aspect ratio of the image, the image doesn't stretch to the new size, but rather fills the background with black.
I would like to change the method to stretch the image if the new coords do not maintain the image's aspect ratio.
Also, how would I add support for saving the resized image as a GIF?
Kind regards
Peter
public static void resizeImage(String filename, int newWidth, int newHeight)
     try
          BufferedImage input = ImageIO.read(new File(filename));
          BufferedImage output = new BufferedImage(newWidth, newHeight, BufferedImage.TYPE_INT_RGB);
          double scale = (double)Math.max(newWidth,newHeight)/(double)input.getHeight(null);
          if (input.getWidth(null) > input.getHeight(null)) {
               scale = (double)Math.max(newWidth,newHeight)/(double)input.getWidth(null);
          // Set the scale.
          AffineTransform tx = new AffineTransform();
          if (scale < 1.0d)
          tx.scale(scale, scale);
          // Paint image.
          Graphics2D g2d = output.createGraphics();
          g2d.drawImage(input, tx, null);
          g2d.dispose();
          //TODO: Add support for GIF.
          ImageIO.write(output,MiscUtils.extractFileExt(filename),new File(filename));
     catch(IOException e)
          e.printStackTrace();
}

Answer 1

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.awt.image.BufferedImage;
import java.io.*;
import java.net.*;
import java.text.*;
import javax.imageio.ImageIO;
import javax.swing.*;
import javax.swing.event.*;
public class ImageScaling
    public static void main(String[] args)
        JFrame f = new JFrame("Image Scaling");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        BufferedImageComponent bic = new BufferedImageComponent();
        ImageSelector selector = new ImageSelector(bic, f);
        ImageAdjustor adjustor = new ImageAdjustor(bic);
        f.setJMenuBar(selector.getMenuBar());
        f.getContentPane().add(bic);
        f.getContentPane().add(adjustor, "South");
        f.setSize(500,350);
        f.setLocation(400,200);
        f.setVisible(true);
        System.out.println(bic.getSize());
* Image component displays scaled image.
class BufferedImageComponent extends JPanel
    URL fileURL;
    BufferedImage image;
    int width, height;
    JLabel label;
    NumberFormat nf;
    boolean centerImage;
    public BufferedImageComponent()
        width = 300;
        height = 200;
        label = new JLabel();
        nf = NumberFormat.getNumberInstance();
        nf.setGroupingUsed(false);
        nf.setMaximumFractionDigits(3);
        centerImage = false;
        setBackground(Color.white);
        setLayout(new GridBagLayout());
        add(label, new GridBagConstraints());
    private void scaleImage(int width, int height)
        BufferedImage scaledImage = new BufferedImage(width, height,
                                            BufferedImage.TYPE_INT_RGB);
        double imageWidth = image.getWidth();
        double imageHeight = image.getHeight();
        // the smaller dimension of image will fill scaledImage
        // allowing the longer dimension to overflow scaledImage
        double wScale = width/imageWidth;
        double hScale = height/imageHeight;
        double scale = Math.max(wScale, hScale);
        double y = (height - scale*imageHeight)/2;
        double x = (width - scale*imageWidth)/2;
        System.out.println("wScale = " + nf.format(wScale) + "\t" +
                           "hScale = " + nf.format(hScale) + "\n" +
                           "scale = " + nf.format(scale) + "\n" +
                           "x = " + nf.format(x) + "\ty = " + nf.format(y) + "\n" +
                           "scaledImageWidth = " + nf.format(scale*imageWidth) + "\t" +
                           "scaledImageHeight = " + nf.format(scale*imageHeight));
        AffineTransform xform = new AffineTransform();
        if(centerImage)
            xform.translate(x,y);
        xform.scale(scale, scale);
        Graphics2D g2 = scaledImage.createGraphics();
        g2.drawImage(image, xform, this);
        g2.dispose();
        label.setIcon(new ImageIcon(scaledImage));
        revalidate();       
        repaint();
    private void loadImage()
        try
            image = ImageIO.read(fileURL);
        catch(IOException ioe)
            System.out.println("IOE: " + ioe.getMessage());
    public void setImage(URL url)
        fileURL = url;
        loadImage();
        scaleImage(width, height);
    public void setCenterFlag(boolean b)
        centerImage = b;
        scaleImage(width, height);
    public void setWidth(int w)
        width = w;
        scaleImage(width, height);
    public void setHeight(int h)
        height = h;
        scaleImage(width, height);
* JSpinners to change the width and height of the image displayed
* in BufferedImageComponent and a JCheckBox that offers a centering option.
* Loaded into south section of content pane in main method.
class ImageAdjustor extends JPanel
    BufferedImageComponent bic;
    public ImageAdjustor(BufferedImageComponent c)
        bic = c;
        SpinnerNumberModel widthModel = new SpinnerNumberModel(300, 50, 400, 10);
        final JSpinner widthSpinner = new JSpinner(widthModel);
        SpinnerNumberModel heightModel = new SpinnerNumberModel(200, 50, 400, 10);
        final JSpinner heightSpinner = new JSpinner(heightModel);
        ChangeListener l = new ChangeListener()
           public void stateChanged(ChangeEvent e)
               JSpinner spinner = (JSpinner)e.getSource();
               int value = ((Integer)spinner.getValue()).intValue();
               if(spinner == widthSpinner)
                   bic.setWidth(value);
               if(spinner == heightSpinner)
                   bic.setHeight(value);
        widthSpinner.addChangeListener(l);
        heightSpinner.addChangeListener(l);
        final JCheckBox centerCheck = new JCheckBox("center");
        centerCheck.addActionListener(new ActionListener()
            public void actionPerformed(ActionEvent e)
                bic.setCenterFlag(centerCheck.isSelected());
        setLayout(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.weightx = 1.0;
        gbc.insets = new Insets(2,2,2,2);
        gbc.anchor = gbc.EAST;
        add(new JLabel("width"), gbc);
        gbc.anchor = gbc.WEST;
        add(widthSpinner, gbc);
        gbc.anchor = gbc.EAST;
        add(new JLabel("height"), gbc);
        gbc.anchor = gbc.WEST;
        add(heightSpinner, gbc);
        gbc.anchor = gbc.CENTER;
        add(centerCheck, gbc);
* JFileChooser used to load images into BufferedImageComponent.
* Accessed through file menu.
class ImageSelector
    BufferedImageComponent bic;
    JFrame frame;
    JFileChooser chooser;
    JMenuBar menuBar;
    public ImageSelector(BufferedImageComponent c, JFrame f)
       bic = c;
       frame = f;
       chooser = new JFileChooser();
       JMenu fileMenu = new JMenu("file");
       final JMenuItem openItem = new JMenuItem("open");
       ActionListener l = new ActionListener()
           public void actionPerformed(ActionEvent e)
               JMenuItem item = (JMenuItem)e.getSource();
               if(item == openItem)
                   openDialog();
        openItem.addActionListener(l);
        fileMenu.add(openItem);
        menuBar = new JMenuBar();
        menuBar.add(fileMenu);
    private void openDialog()
        int returnVal = chooser.showOpenDialog(frame);
        if(returnVal == JFileChooser.APPROVE_OPTION)
            File file = chooser.getSelectedFile();
            if(!isImage(file))
                return;
            try
                URL url = file.toURL();
                bic.setImage(url);
            catch(MalformedURLException mue)
                System.out.println("MUE: " + mue.getMessage());
     * Filters files for jpg and png extensions
    private boolean isImage(File file)
        String extension = file.getPath().toLowerCase();
        if(extension.indexOf("jpg") != -1 || extension.indexOf("png") != -1)
            return true;
        return false;
    public JMenuBar getMenuBar()
        return menuBar;
}