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Semester 1/Programming 1/Java/examples/projects/chapter13/imageviewer-final/ImagePanel.java

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+import java.awt.*;
+import javax.swing.*;
+import java.awt.image.*;
+
+/**
+ * An ImagePanel is a Swing component that can display an OFImage.
+ * It is constructed as a subclass of JComponent with the added functionality
+ * of setting an OFImage that will be displayed on the surface of this
+ * component.
+ * 
+ * @author Michael Kölling and David J. Barnes.
+ * @version 1.0
+ */
+public class ImagePanel extends JComponent
+{
+    // The current width and height of this panel
+    private int width, height;
+
+    // An internal image buffer that is used for painting. For
+    // actual display, this image buffer is then copied to screen.
+    private OFImage panelImage;
+
+    /**
+     * Create a new, empty ImagePanel.
+     */
+    public ImagePanel()
+    {
+        width = 360;    // arbitrary size for empty panel
+        height = 240;
+        panelImage = null;
+    }
+
+    /**
+     * Set the image that this panel should show.
+     * 
+     * @param image  The image to be displayed.
+     */
+    public void setImage(OFImage image)
+    {
+        if(image != null) {
+            width = image.getWidth();
+            height = image.getHeight();
+            panelImage = image;
+            repaint();
+        }
+    }
+    
+    /**
+     * Clear the image on this panel.
+     */
+    public void clearImage()
+    {
+        Graphics imageGraphics = panelImage.getGraphics();
+        imageGraphics.setColor(Color.LIGHT_GRAY);
+        imageGraphics.fillRect(0, 0, width, height);
+        repaint();
+    }
+    
+    // The following methods are redefinitions of methods
+    // inherited from superclasses.
+    
+    /**
+     * Tell the layout manager how big we would like to be.
+     * (This method gets called by layout managers for placing
+     * the components.)
+     * 
+     * @return The preferred dimension for this component.
+     */
+    public Dimension getPreferredSize()
+    {
+        return new Dimension(width, height);
+    }
+    
+    /**
+     * This component needs to be redisplayed. Copy the internal image 
+     * to screen. (This method gets called by the Swing screen painter 
+     * every time it want this component displayed.)
+     * 
+     * @param g The graphics context that can be used to draw on this component.
+     */
+    public void paintComponent(Graphics g)
+    {
+        Dimension size = getSize();
+        g.clearRect(0, 0, size.width, size.height);
+        if(panelImage != null) {
+            g.drawImage(panelImage, 0, 0, null);
+        }
+    }
+}