imagepreviewpanel.java

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package palmsecuresdk.sample.data;

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.beans.*;
import java.io.File;

/** *//**
 * @author matthew
 * 
 */
public class ImagePreviewPanel extends JPanel implements PropertyChangeListener {

    private int width, height;

    private ImageIcon icon;

    private Image image;

    private static final int ACCSIZE = 155;

    private Color bg;

    public ImagePreviewPanel() {
        setPreferredSize(new Dimension(ACCSIZE, -1));
        bg = getBackground();
    }

    public void propertyChange(PropertyChangeEvent e) {
        String propertyName = e.getPropertyName();

        // Make sure we are responding to the right event.
        if (propertyName.equals(JFileChooser.SELECTED_FILE_CHANGED_PROPERTY)) {
            File selection = (File) e.getNewValue();
            String name;

            if (selection == null)
                return;
            else
                name = selection.getAbsolutePath();

            /**//*
             * Make reasonably sure we have an image format that AWT can handle
             * so we don't try to draw something silly.
             */
            if ((name != null) && name.toLowerCase().endsWith(".jpg")
                    || name.toLowerCase().endsWith(".jpeg")
                    || name.toLowerCase().endsWith(".gif")
                    || name.toLowerCase().endsWith(".png")) {
                icon = new ImageIcon(name);
                image = icon.getImage();
                scaleImage();
                repaint();
            }
        }
    }

    private void scaleImage() {
        width = image.getWidth(this);
        height = image.getHeight(this);
        double ratio = 1.0;

        /**//*
         * Determine how to scale the image. Since the accessory can expand
         * vertically make sure we don't go larger than 150 when scaling
         * vertically.
         */
        if (width >= height) {
            ratio = (double) (ACCSIZE - 5) / width;
            width = ACCSIZE - 5;
            height = (int) (height * ratio);
        } else {
            if (getHeight() > 150) {
                ratio = (double) (ACCSIZE - 5) / height;
                height = ACCSIZE - 5;
                width = (int) (width * ratio);
            } else {
                ratio = (double) getHeight() / height;
                height = getHeight();
                width = (int) (width * ratio);
            }
        }

        image = image.getScaledInstance(width, height, Image.SCALE_DEFAULT);
    }

    public void paintComponent(Graphics g) {
        g.setColor(bg);

        /**//*
         * If we don't do this, we will end up with garbage from previous images
         * if they have larger sizes than the one we are currently drawing.
         * Also, it seems that the file list can paint outside of its rectangle,
         * and will cause odd behavior if we don't clear or fill the rectangle
         * for the accessory before drawing. This might be a bug in
         * JFileChooser.
         */
        g.fillRect(0, 0, ACCSIZE, getHeight());
        g.drawImage(image, getWidth() / 2 - width / 2 + 5, getHeight() / 2
                - height / 2, this);
    }

    /** *//**
     * @param args
     */
    public static void main(String[] args) {
        JFileChooser chooser = new JFileChooser();
        ImagePreviewPanel preview = new ImagePreviewPanel();
        chooser.setAccessory(preview);
        chooser.addPropertyChangeListener(preview);
        chooser.showOpenDialog(null);

    }

}