import java.awt.AWTEvent;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GraphicsEnvironment;
import java.awt.Image;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.RenderingHints;
import java.awt.Toolkit;
import java.awt.event.ComponentAdapter;
import java.awt.event.ComponentEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import java.awt.event.MouseWheelEvent;
import java.awt.event.MouseWheelListener;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.Arrays;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

/**
 * <p>
 * <code>NavigableImagePanel</code> is a lightweight container displaying
 * an image that can be zoomed in and out and panned with ease and simplicity,
 * using an adaptive rendering for high quality display and satisfactory performance.
 * </p>
 * <p>
 * <h3>Image</h3>
 * <p>An image is loaded either via a constructor:</p>
 * <pre>
 * NavigableImagePanel panel = new NavigableImagePanel(image);
 * </pre>
 * or using a setter:
 * <pre>
 * NavigableImagePanel panel = new NavigableImagePanel();
 * panel.setImage(image);
 * </pre>
 * When an image is set, it is initially painted centered in the component, 
 * at the largest possible size, fully visible, with its aspect ratio is preserved. 
 * This is defined as 100% of the image size and its corresponding zoom level is 1.0.
 * </p>
 * <h3>Zooming</h3>
 * <p>
 * Zooming can be controlled interactively, using either the mouse scroll wheel (default)
 * or the mouse two buttons, or programmatically, allowing the programmer to
 * implement other custom zooming methods. If the mouse does not have a scroll wheel,
 * set the zooming device to mouse buttons:
 * <pre>
 * panel.setZoomDevice(ZoomDevice.MOUSE_BUTTON);
 * </pre>
 * The left mouse button works as a toggle switch between zooming in and zooming out 
 * modes, and the right button zooms an image by one increment (default is 20%).
 * You can change the zoom increment value by:
 * <pre>
 * panel.setZoomIncrement(newZoomIncrement);
 * </pre>
 * If you intend to provide programmatic zoom control, set the zoom device to none 
 * to disable both the mouse wheel and buttons for zooming purposes:
 * <pre>
 * panel.setZoomDevice(ZoomDevice.NONE);
 * </pre>
 * and use <code>setZoom()</code> to change the zoom level.
 * </p>
 * <p> 
 * Zooming is always around the point the mouse pointer is currently at, so that
 * this point (called a zooming center) remains stationary ensuring that the area 
 * of an image we are zooming into does not disappear off the screen. The zooming center
 * stays at the same location on the screen and all other points move radially away from
 * it (when zooming in), or towards it (when zooming out). For programmatically
 * controlled zooming the zooming center is either specified when <code>setZoom()</code>
 * is called:
 * <pre>
 * panel.setZoom(newZoomLevel, newZoomingCenter);
 * </pre>
 * or assumed to be the point of an image which is
 * the closest to the center of the panel, if no zooming center is specified:
 * <pre>
 * panel.setZoom(newZoomLevel);
 * </pre>
 * </p>
 * <p>
 * There are no lower or upper zoom level limits.
 * </p> 
 * <h3>Navigation</h3>
 * <p><code>NavigableImagePanel</code> does not use scroll bars for navigation, 
 * but relies on a navigation image located in the upper left corner of the panel. 
 * The navigation image is a small replica of the image displayed in the panel.
 * When you click on any point of the navigation image that part of the image 
 * is displayed in the panel, centered. The navigation image can also be 
 * zoomed in the same way as the main image.</p>
 * <p>In order to adjust the position of an image in the panel, it can be dragged
 * with the mouse, using the left button.
 * </p>
 * <p>For programmatic image navigation, disable the navigation image:
 * <pre>
 * panel.setNavigationImageEnabled(false)
 * </pre>
 * and use <code>getImageOrigin()</code> and
 * <code>setImageOrigin()</code> to move the image around the panel.
 * </p>
 * <h3>Rendering</h3>
 * <p><code>NavigableImagePanel</code> uses the Nearest Neighbor interpolation 
 * for image rendering (default in Java). 
 * When the scaled image becomes larger than the original image, 
 * the Bilinear interpolation is applied, but only to the part
 * of the image which is displayed in the panel. This interpolation change threshold
 * can be controlled by adjusting the value of 
 * <code>HIGH_QUALITY_RENDERING_SCALE_THRESHOLD</code>.</p>
 */
public class NavigableImagePanel extends JPanel {

	/**
	 * <p>Identifies a change to the zoom level.</p>
	 */
	public static final String ZOOM_LEVEL_CHANGED_PROPERTY = "zoomLevel";
	
	/**
	 * <p>Identifies a change to the zoom increment.</p>
	 */
	public static final String ZOOM_INCREMENT_CHANGED_PROPERTY = "zoomIncrement";
	
	/**
	 * <p>Identifies that the image in the panel has changed.</p>
	 */
	public static final String IMAGE_CHANGED_PROPERTY = "image";

	private static final double SCREEN_NAV_IMAGE_FACTOR = 0.15; // 15% of panel's width
	private static final double NAV_IMAGE_FACTOR = 0.3; // 30% of panel's width
	private static final double HIGH_QUALITY_RENDERING_SCALE_THRESHOLD = 1.0;
	private static final Object INTERPOLATION_TYPE = 
		RenderingHints.VALUE_INTERPOLATION_BILINEAR;
	
	private double zoomIncrement = 0.2;
	private double zoomFactor = 1.0 + zoomIncrement;
	private double navZoomFactor = 1.0 + zoomIncrement;
	private BufferedImage image;
	private BufferedImage navigationImage;
	private int navImageWidth;
	private int navImageHeight;
	private double initialScale = 0.0;
	private double scale = 0.0;
	private double navScale = 0.0;
	private int originX = 0;
	private int originY = 0;
	private Point mousePosition;
	private Dimension previousPanelSize;
	private boolean navigationImageEnabled = true;
	private boolean highQualityRenderingEnabled = true;

	private WheelZoomDevice wheelZoomDevice = null;
	private ButtonZoomDevice buttonZoomDevice = null;
	
	/**
	 * <p>Defines zoom devices.</p>
	 */
	public static class ZoomDevice {
		/**
		 * <p>Identifies that the panel does not implement zooming, 
		 * but the component using the panel does (programmatic zooming method).</p>
		 */
		public static final ZoomDevice NONE = new ZoomDevice("none");
		
		/**
		 * <p>Identifies the left and right mouse buttons as the zooming device.</p>
		 */
		public static final ZoomDevice MOUSE_BUTTON = new ZoomDevice("mouseButton");
		
		/**
		 * <p>Identifies the mouse scroll wheel as the zooming device.</p>
		 */
		public static final ZoomDevice MOUSE_WHEEL = new ZoomDevice("mouseWheel");
		
		private String zoomDevice;
		private ZoomDevice(String zoomDevice) {
			this.zoomDevice = zoomDevice;
		}
		public String toString() {
			return zoomDevice;
		}
	}
	
	//This class is required for high precision image coordinates translation.
	private class Coords {
		public double x;
		public double y;
		public Coords(double x, double y) {
			this.x = x;
			this.y = y;
			}
		public int getIntX() {
			return (int)Math.round(x);
		}
		public int getIntY() {
			return (int)Math.round(y);
		}
		public String toString() {
			return "[Coords: x=" + x + ",y=" + y + "]";
		}
	}
	
	private class WheelZoomDevice implements MouseWheelListener {
		public void mouseWheelMoved(MouseWheelEvent e) {
			Point p = e.getPoint();
			boolean zoomIn = (e.getWheelRotation() < 0);
			if (isInNavigationImage(p)) {
				if (zoomIn) {
					navZoomFactor = 1.0 + zoomIncrement;
				} else {
					navZoomFactor = 1.0 - zoomIncrement;
				}
				zoomNavigationImage();
			} else if (isInImage(p)) {
				if (zoomIn) {
					zoomFactor = 1.0 + zoomIncrement;
				} else {
					zoomFactor = 1.0 - zoomIncrement;
				}
				zoomImage();
			}
		}
	}
	
	private class ButtonZoomDevice extends MouseAdapter {
		public void mouseClicked(MouseEvent e) {
			Point p = e.getPoint();
			if (SwingUtilities.isRightMouseButton(e)) {
				if (isInNavigationImage(p)) {
					navZoomFactor = 1.0 - zoomIncrement;
					zoomNavigationImage();
				} else if (isInImage(p)) {
					zoomFactor = 1.0 - zoomIncrement;
					zoomImage();
				}
			} else {
				if (isInNavigationImage(p)) {
					navZoomFactor = 1.0 + zoomIncrement;
					zoomNavigationImage();
				} else if (isInImage(p)) {
					zoomFactor = 1.0 + zoomIncrement;
					zoomImage();
				}
			}
		}		
	}
	
	/**
	 * <p>Creates a new navigable image panel with no default image and 
	 * the mouse scroll wheel as the zooming device.</p>
	 */
	public NavigableImagePanel() {
		setOpaque(false);
		addComponentListener(new ComponentAdapter() {
			public void componentResized(ComponentEvent e) {
				if (scale > 0.0) {
					if (isFullImageInPanel()) {
						centerImage();
					} else if (isImageEdgeInPanel()) {
						scaleOrigin();
					}
					if (isNavigationImageEnabled()) {
						createNavigationImage();
					}
					repaint();
				}
				previousPanelSize = getSize();
			}
		});
		
		addMouseListener(new MouseAdapter() {
			public void mousePressed(MouseEvent e) {
				if (SwingUtilities.isLeftMouseButton(e)) {
					if (isInNavigationImage(e.getPoint())) {
						Point p = e.getPoint();
						displayImageAt(p);
					}
				}
			}
		});
		
		addMouseMotionListener(new MouseMotionListener() {
			public void mouseDragged(MouseEvent e) {
				if (SwingUtilities.isLeftMouseButton(e)
					&& !isInNavigationImage(e.getPoint())) {
					Point p = e.getPoint();
					moveImage(p);
				}
			}
			public void mouseMoved(MouseEvent e) {
				//we need the mouse position so that after zooming
				//that position of the image is maintained
				mousePosition = e.getPoint();
			}
		});

		setZoomDevice(ZoomDevice.MOUSE_WHEEL);
	}
	
	/**
	 * <p>Creates a new navigable image panel with the specified image 
	 * and the mouse scroll wheel as the zooming device.</p>
	 */
	public NavigableImagePanel(BufferedImage image) throws IOException {
		this();
		setImage(image);
	}
	
	private void addWheelZoomDevice() {
		if (wheelZoomDevice == null) {
			wheelZoomDevice = new WheelZoomDevice();
			addMouseWheelListener(wheelZoomDevice);
		}
	}

	private void addButtonZoomDevice() {
		if (buttonZoomDevice == null) {
			buttonZoomDevice = new ButtonZoomDevice();
			addMouseListener(buttonZoomDevice);
		}
	}
	
	private void removeWheelZoomDevice() {
		if (wheelZoomDevice != null) {
			removeMouseWheelListener(wheelZoomDevice);
			wheelZoomDevice = null;
		}	
	}
	
	private void removeButtonZoomDevice() {
		if (buttonZoomDevice != null) {
			removeMouseListener(buttonZoomDevice);
			buttonZoomDevice = null;
		}	
	}
	
	/**
	 * <p>Sets a new zoom device.</p>
	 *
	 * @param newZoomDevice specifies the type of a new zoom device.
	 */
	public void setZoomDevice(ZoomDevice newZoomDevice) {
		if (newZoomDevice == ZoomDevice.NONE) {
			removeWheelZoomDevice();
			removeButtonZoomDevice();
		} else if (newZoomDevice == ZoomDevice.MOUSE_BUTTON) {
			removeWheelZoomDevice();
			addButtonZoomDevice();
		} else if (newZoomDevice == ZoomDevice.MOUSE_WHEEL) {
			removeButtonZoomDevice();
			addWheelZoomDevice();
		}
	}
	
	/**
	 * <p>Gets the current zoom device.</p>
	 */
	public ZoomDevice getZoomDevice() {
		if (buttonZoomDevice != null) {
			return ZoomDevice.MOUSE_BUTTON;
		} else if (wheelZoomDevice != null) {
			return ZoomDevice.MOUSE_WHEEL;
		} else {
			return ZoomDevice.NONE;
		}
	}	
	
	//Called from paintComponent() when a new image is set.
	private void initializeParams() {
		double xScale = (double)getWidth() / image.getWidth();
		double yScale = (double)getHeight() / image.getHeight();
		initialScale = Math.min(xScale, yScale);
		scale = initialScale;
		
		//An image is initially centered
		centerImage();
		if (isNavigationImageEnabled()) {
			createNavigationImage();
		}
	}
	
	//Centers the current image in the panel.
	private void centerImage() {
		originX = (int)(getWidth() - getScreenImageWidth()) / 2;
		originY = (int)(getHeight() - getScreenImageHeight()) / 2;
	}
	
	//Creates and renders the navigation image in the upper let corner of the panel.
	private void createNavigationImage() {
		//We keep the original navigation image larger than initially 
		//displayed to allow for zooming into it without pixellation effect.
		navImageWidth = (int)(getWidth() * NAV_IMAGE_FACTOR);
		navImageHeight = navImageWidth * image.getHeight() / image.getWidth();					
		int scrNavImageWidth = (int)(getWidth() * SCREEN_NAV_IMAGE_FACTOR);
		int scrNavImageHeight = scrNavImageWidth * image.getHeight() / image.getWidth();
		navScale = (double)scrNavImageWidth / navImageWidth;
		navigationImage = new BufferedImage(navImageWidth, navImageHeight, 
			image.getType());
		Graphics g = navigationImage.getGraphics();
		g.drawImage(image, 0, 0, navImageWidth, navImageHeight, null);
	}
	
	/**
	 * <p>Sets an image for display in the panel.</p>
	 *
	 * @param image an image to be set in the panel
	 */
	public void setImage(BufferedImage image) {
		BufferedImage oldImage = this.image;
		this.image = image;
		//Reset scale so that initializeParameters() is called in paintComponent()
		//for the new image.
		scale = 0.0;
		firePropertyChange(IMAGE_CHANGED_PROPERTY, (Image)oldImage, (Image)image);
		repaint();
	}
	
	/**
	 * <p>Tests whether an image uses the standard RGB color space.</p>
	 */
	public static boolean isStandardRGBImage(BufferedImage bImage) {
		return bImage.getColorModel().getColorSpace().isCS_sRGB();
	}
	
	//Converts this panel's coordinates into the original image coordinates
	private Coords panelToImageCoords(Point p) {
		return new Coords((p.x - originX) / scale, (p.y - originY) / scale);
	}

	//Converts the original image coordinates into this panel's coordinates
	private Coords imageToPanelCoords(Coords p) {
		return new Coords((p.x * scale) + originX, (p.y * scale) + originY);
	}

	//Converts the navigation image coordinates into the zoomed image coordinates	
	private Point navToZoomedImageCoords(Point p) {
		int x = p.x * getScreenImageWidth() / getScreenNavImageWidth();
		int y = p.y * getScreenImageHeight() / getScreenNavImageHeight();
		return new Point(x, y);
	}
	
	//The user clicked within the navigation image and this part of the image
	//is displayed in the panel.
	//The clicked point of the image is centered in the panel.
	private void displayImageAt(Point p) {		
		Point scrImagePoint = navToZoomedImageCoords(p);
		originX = -(scrImagePoint.x - getWidth() / 2);
		originY = -(scrImagePoint.y - getHeight() / 2);
		repaint();
	}

	//Tests whether a given point in the panel falls within the image boundaries.	
	private boolean isInImage(Point p) {
		Coords coords = panelToImageCoords(p);
		int x = coords.getIntX();
		int y = coords.getIntY();
		return (x >= 0 && x < image.getWidth() && y >= 0 && y < image.getHeight());
	}
	
	//Tests whether a given point in the panel falls within the navigation image 
	//boundaries.	
	private boolean isInNavigationImage(Point p) {
		return (isNavigationImageEnabled() && p.x < getScreenNavImageWidth() 
			&& p.y < getScreenNavImageHeight());
	}
	
	//Used when the image is resized.
	private boolean isImageEdgeInPanel() {
		if (previousPanelSize == null) {
			return false;
		}
		
		return (originX > 0 && originX < previousPanelSize.width
			|| originY > 0 && originY < previousPanelSize.height);
	}
	
	//Tests whether the image is displayed in its entirety in the panel.
	private boolean isFullImageInPanel() {
		return (originX >= 0 && (originX + getScreenImageWidth()) < getWidth()
				&& originY >= 0 && (originY + getScreenImageHeight()) < getHeight());
	}
	
	/**
	 * <p>Indicates whether the high quality rendering feature is enabled.</p>
	 *
	 * @return true if high quality rendering is enabled, false otherwise.
	 */
	public boolean isHighQualityRenderingEnabled() {
		return highQualityRenderingEnabled;
	}
	
	/**
	 * <p>Enables/disables high quality rendering.</p>
	 *
	 * @param enabled enables/disables high quality rendering
	 */
	public void setHighQualityRenderingEnabled(boolean enabled) {
		highQualityRenderingEnabled = enabled;	
	}

	 //High quality rendering kicks in when when a scaled image is larger 
	 //than the original image. In other words, 
	 //when image decimation stops and interpolation starts.
	private boolean isHighQualityRendering() {
		return (highQualityRenderingEnabled 
			&& scale > HIGH_QUALITY_RENDERING_SCALE_THRESHOLD);
	}
	
	/**
	 * <p>Indicates whether navigation image is enabled.<p>
	 *
	 * @return true when navigation image is enabled, false otherwise.
	 */
	public boolean isNavigationImageEnabled() {
		return navigationImageEnabled;
	}
	
	/**
	 * <p>Enables/disables navigation with the navigation image.</p>
	 * <p>Navigation image should be disabled when custom, programmatic navigation 
	 * is implemented.</p>
	 *
	 * @param enabled true when navigation image is enabled, false otherwise.
	 */
	public void setNavigationImageEnabled(boolean enabled) {
		navigationImageEnabled = enabled;
		repaint();
	}

	//Used when the panel is resized	 
	private void scaleOrigin() {
		originX = originX * getWidth() / previousPanelSize.width;
		originY = originY * getHeight() / previousPanelSize.height;
		repaint();
	}

	//Converts the specified zoom level	to scale.
	private double zoomToScale(double zoom) {
		return initialScale * zoom;
	}
	
	/**
	 * <p>Gets the current zoom level.</p>
	 *
	 * @return the current zoom level
	 */
	public double getZoom() {
		return scale / initialScale;
	}
	
	/**
	 * <p>Sets the zoom level used to display the image.</p>
	 * <p>This method is used in programmatic zooming. The zooming center is 
	 * the point of the image closest to the center of the panel.
	 * After a new zoom level is set the image is repainted.</p>
	 *
	 * @param newZoom the zoom level used to display this panel's image.
	 */
	public void setZoom(double newZoom) {
		Point zoomingCenter = new Point(getWidth() / 2, getHeight() / 2);
		setZoom(newZoom, zoomingCenter);
	}
	
	/**
	 * <p>Sets the zoom level used to display the image, and the zooming center,
	 * around which zooming is done.</p>
	 * <p>This method is used in programmatic zooming. 
	 * After a new zoom level is set the image is repainted.</p>
	 *
	 * @param newZoom the zoom level used to display this panel's image.
	 */
	public void setZoom(double newZoom, Point zoomingCenter) {
		Coords imageP = panelToImageCoords(zoomingCenter);
		if (imageP.x < 0.0) {
			imageP.x = 0.0;
		}
		if (imageP.y < 0.0) {
			imageP.y = 0.0;
		}
		if (imageP.x >= image.getWidth()) {
			imageP.x = image.getWidth() - 1.0;
		}
		if (imageP.y >= image.getHeight()) {
			imageP.y = image.getHeight() - 1.0;
		}
		
		Coords correctedP = imageToPanelCoords(imageP);
		double oldZoom = getZoom();
		scale = zoomToScale(newZoom);
		Coords panelP = imageToPanelCoords(imageP);
		
		originX += (correctedP.getIntX() - (int)panelP.x);
		originY += (correctedP.getIntY() - (int)panelP.y);
		
		firePropertyChange(ZOOM_LEVEL_CHANGED_PROPERTY, new Double(oldZoom),
			new Double(getZoom()));
		
		repaint();
	}
	
	/**
	 * <p>Gets the current zoom increment.</p>
	 *
	 * @return the current zoom increment
	 */
	public double getZoomIncrement() {
		return zoomIncrement;
	}
	
	/**
	 * <p>Sets a new zoom increment value.</p>
	 *
	 * @param newZoomIncrement new zoom increment value
	 */
	public void setZoomIncrement(double newZoomIncrement) {
		double oldZoomIncrement = zoomIncrement;
		zoomIncrement = newZoomIncrement;
		firePropertyChange(ZOOM_INCREMENT_CHANGED_PROPERTY, 
			new Double(oldZoomIncrement), new Double(zoomIncrement));
	}
	
	//Zooms an image in the panel by repainting it at the new zoom level.
	//The current mouse position is the zooming center.
	private void zoomImage() {
		Coords imageP = panelToImageCoords(mousePosition);
		double oldZoom = getZoom();
		scale *= zoomFactor;
		Coords panelP = imageToPanelCoords(imageP);
		
		originX += (mousePosition.x - (int)panelP.x);
		originY += (mousePosition.y - (int)panelP.y);
		
		firePropertyChange(ZOOM_LEVEL_CHANGED_PROPERTY, new Double(oldZoom),
			new Double(getZoom()));
		
		repaint();
	}
	
	//Zooms the navigation image
	private void zoomNavigationImage() {
		navScale *= navZoomFactor;
		repaint();
	}
	
	/**
	 * <p>Gets the image origin.</p>
	 * <p>Image origin is defined as the upper, left corner of the image in
	 * the panel's coordinate system.</p>
	 * @return the point of the upper, left corner of the image in the panel's coordinates
	 * system.
	 */
	public Point getImageOrigin() {
		return new Point(originX, originY);
	}
	
	/**
	 * <p>Sets the image origin.</p>
	 * <p>Image origin is defined as the upper, left corner of the image in
	 * the panel's coordinate system. After a new origin is set, the image is repainted.
	 * This method is used for programmatic image navigation.</p>
	 * @param x the x coordinate of the new image origin
	 * @param y the y coordinate of the new image origin
	 */
	public void setImageOrigin(int x, int y) {
		setImageOrigin(new Point(x, y));
	}
	
	/**
	 * <p>Sets the image origin.</p>
	 * <p>Image origin is defined as the upper, left corner of the image in
	 * the panel's coordinate system. After a new origin is set, the image is repainted.
	 * This method is used for programmatic image navigation.</p>
	 * @param newOrigin the value of a new image origin
	 */
	public void setImageOrigin(Point newOrigin) {
		originX = newOrigin.x;
		originY = newOrigin.y;
		repaint();
	}
	
	//Moves te image (by dragging with the mouse) to a new mouse position p.
	private void moveImage(Point p) {
		int xDelta = p.x - mousePosition.x;
		int yDelta = p.y - mousePosition.y;
		originX += xDelta;
		originY += yDelta;
		mousePosition = p;
		repaint();
	}
	
	//Gets the bounds of the image area currently displayed in the panel (in image
	//coordinates).
	private Rectangle getImageClipBounds() {
		Coords startCoords = panelToImageCoords(new Point(0, 0));
		Coords endCoords = panelToImageCoords(new Point(getWidth() - 1, getHeight() - 1));
		int panelX1 = startCoords.getIntX();
		int panelY1 = startCoords.getIntY();
		int panelX2 = endCoords.getIntX();
		int panelY2 = endCoords.getIntY();
		//No intersection?
		if (panelX1 >= image.getWidth() || panelX2 < 0 || panelY1 >= image.getHeight() || panelY2 < 0) {
			return null;
		}
		
		int x1 = (panelX1 < 0) ? 0 : panelX1;
		int y1 = (panelY1 < 0) ? 0 : panelY1;
		int x2 = (panelX2 >= image.getWidth()) ? image.getWidth() - 1 : panelX2;
		int y2 = (panelY2 >= image.getHeight()) ? image.getHeight() - 1 : panelY2;
		return new Rectangle(x1, y1, x2 - x1 + 1, y2 - y1 + 1);
	}

	/**
	 * Paints the panel and its image at the current zoom level, location, and
	 * interpolation method dependent on the image scale.</p>
	 *
	 * @param g the <code>Graphics</code> context for painting
	 */
	protected void paintComponent(Graphics g) {
		super.paintComponent(g); // Paints the background
		
		if (image == null) {
			return;
		}
		
		if (scale == 0.0) {
			initializeParams();
		}
			
		if (isHighQualityRendering()) {			
			Rectangle rect = getImageClipBounds();
			if (rect == null || rect.width == 0 || rect.height == 0) { // no part of image is displayed in the panel
				return;
			}

			BufferedImage subimage = image.getSubimage(rect.x, rect.y, rect.width, 
				rect.height);
			Graphics2D g2 = (Graphics2D)g;
			g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, INTERPOLATION_TYPE);
			g2.drawImage(subimage, Math.max(0, originX), Math.max(0, originY), 
				Math.min((int)(subimage.getWidth() * scale), getWidth()), 
				Math.min((int)(subimage.getHeight() * scale), getHeight()), null);
		} else {
			g.drawImage(image, originX, originY, getScreenImageWidth(), 
				getScreenImageHeight(), null);
		}
		
		//Draw navigation image
		if (isNavigationImageEnabled()) {
			g.drawImage(navigationImage, 0, 0, getScreenNavImageWidth(),
				getScreenNavImageHeight(), null);
			drawZoomAreaOutline(g);
		}
	}

	//Paints a white outline over the navigation image indicating 
	//the area of the image currently displayed in the panel.
	private void drawZoomAreaOutline(Graphics g) {
		if (isFullImageInPanel()) {
			return;
		}
		
		int x = -originX * getScreenNavImageWidth() / getScreenImageWidth();
		int y = -originY * getScreenNavImageHeight() / getScreenImageHeight();
		int width = getWidth() * getScreenNavImageWidth() / getScreenImageWidth();
		int height = getHeight() * getScreenNavImageHeight() / getScreenImageHeight();
		g.setColor(Color.white);
		g.drawRect(x, y, width, height);
	}
	
	private int getScreenImageWidth() {
		return (int)(scale * image.getWidth());
	}
	
	private int getScreenImageHeight() {
		return (int)(scale * image.getHeight());
	}
	
	private int getScreenNavImageWidth() {
		return (int)(navScale * navImageWidth);
	}
	
	private int getScreenNavImageHeight() {
		return (int)(navScale * navImageHeight);
	}
	
	private static String[] getImageFormatExtensions() {
		String[] names = ImageIO.getReaderFormatNames();
		for(int i = 0; i < names.length; i++) {
			names[i] = names[i].toLowerCase();
		}
		Arrays.sort(names);
		return names;
	}
	
	private static boolean endsWithImageFormatExtension(String name) {
		int dotIndex = name.lastIndexOf(".");
		if (dotIndex == -1) {
			return false;
		}
		
		String extension = name.substring(dotIndex + 1).toLowerCase();
		return (Arrays.binarySearch(getImageFormatExtensions(), extension) >= 0);
	}
	
	public static void main(String[] args) {	
		if (args.length == 0) {
			System.out.println("Usage: java NavigableImagePanel imageFilename");
			System.exit(1);
		}
		
		final String filename = args[0];
		
		SwingUtilities.invokeLater(new Runnable() {
			public void run() {		
				final JFrame frame = new JFrame("Navigable Image Panel");
				frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
				NavigableImagePanel panel = new NavigableImagePanel();
				try {
					final BufferedImage image = ImageIO.read(new File(filename));
					panel.setImage(image);								
				} catch (IOException e) {
					JOptionPane.showMessageDialog(null, e.getMessage(), "", 
						JOptionPane.ERROR_MESSAGE);
					System.exit(1);
				}
				
				frame.getContentPane().add(panel, BorderLayout.CENTER);
				
				GraphicsEnvironment ge = 
					GraphicsEnvironment.getLocalGraphicsEnvironment();
				Rectangle bounds = ge.getMaximumWindowBounds();
				frame.setSize(new Dimension(bounds.width, bounds.height));
				frame.setVisible(true);				
			}
		});
	}
}