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1 package ImageAPI;   2 import javax.swing.*;   3 import java.awt.*;   4 import java.awt.event.*;   5 import java.beans.*;   6 import java.io.File;   7   8 /**   9  * @author matthew  10  *  11  */  12 public class ImagePreviewPanel extends JPanel implements PropertyChangeListener {
      13  14     private int width, height;  15  16     private ImageIcon icon;  17  18     private Image image;  19  20     private static final int ACCSIZE = 155;  21  22     private Color bg;  23  24     public ImagePreviewPanel() {
      25         setPreferredSize(new Dimension(ACCSIZE, -1));  26         bg = getBackground();  27     }  28  29     public void propertyChange(PropertyChangeEvent e) {
      30         String propertyName = e.getPropertyName();  31  32         // Make sure we are responding to the right event.  33         if (propertyName.equals(JFileChooser.SELECTED_FILE_CHANGED_PROPERTY)) {
      34             File selection = (File) e.getNewValue();  35             String name;  36  37             if (selection == null)  38                 return;  39             else  40                 name = selection.getAbsolutePath();  41  42             /*  43              * Make reasonably sure we have an image format that AWT can handle  44              * so we don't try to draw something silly.  45              */  46             if ((name != null) && name.toLowerCase().endsWith(".jpg")  47                     || name.toLowerCase().endsWith(".jpeg")  48                     || name.toLowerCase().endsWith(".gif")  49                     || name.toLowerCase().endsWith(".png")) {
      50                 icon = new ImageIcon(name);  51                 image = icon.getImage();  52                 scaleImage();  53                 repaint();  54             }  55         }  56     }  57  58     private void scaleImage() {
      59         width = image.getWidth(this);  60         height = image.getHeight(this);  61         double ratio = 1.0;  62  63         /*  64          * Determine how to scale the image. Since the accessory can expand  65          * vertically make sure we don't go larger than 150 when scaling  66          * vertically.  67          */  68         if (width >= height) {
      69             ratio = (double) (ACCSIZE - 5) / width;  70             width = ACCSIZE - 5;  71             height = (int) (height * ratio);  72         } else {
      73             if (getHeight() > 150) {
      74                 ratio = (double) (ACCSIZE - 5) / height;  75                 height = ACCSIZE - 5;  76                 width = (int) (width * ratio);  77             } else {
      78                 ratio = (double) getHeight() / height;  79                 height = getHeight();  80                 width = (int) (width * ratio);  81             }  82         }  83  84         image = image.getScaledInstance(width, height, Image.SCALE_DEFAULT);  85     }  86  87     public void paintComponent(Graphics g) {
      88         g.setColor(bg);  89  90         /*  91          * If we don't do this, we will end up with garbage from previous images  92          * if they have larger sizes than the one we are currently drawing.  93          * Also, it seems that the file list can paint outside of its rectangle,  94          * and will cause odd behavior if we don't clear or fill the rectangle  95          * for the accessory before drawing. This might be a bug in  96          * JFileChooser.  97          */  98         g.fillRect(0, 0, ACCSIZE, getHeight());  99         g.drawImage(image, getWidth() / 2 - width / 2 + 5, getHeight() / 2 100                 - height / 2, this); 101     } 102 103     /** 104      * @param args 105      */ 106     public static void main(String[] args) {
     107         JFileChooser chooser = new JFileChooser(); 108         ImagePreviewPanel preview = new ImagePreviewPanel(); 109         chooser.setAccessory(preview); 110         chooser.addPropertyChangeListener(preview); 111         chooser.showOpenDialog(null); 112 113     } 114 115 }