//
// another example of the Java AWT, showing creation of an Image
//      an image.
// see class definition for details.
//
// this example is modified from a similar example in chapter 17 of
//      _Exploring Java_ (Niemeyer and Peck).
//
import java.awt.* ;
import java.awt.event.* ;
import java.awt.image.* ;

//
// a ColorPan object is a DrawingFrame that displays an image generated
//	from an array of integers representing RGB color values.  the
//	colors vary across and down the image.  if the window is 
//	resized, the image is scaled to fit.
//
class ColorPan extends DrawingFrame implements ComponentListener {

	private Image img ;
	private int imgWidth, imgHeight ;
	private int pixelData[] ;

        ColorPan(Dimension dims) {
		super("ColorPan") ;
		setDrawingSize(dims) ;
		initializeImage(dims) ;
		addComponentListener(this) ;
		show() ;
	}

	// initializes image -- set img to null (so paint() will
	//	recreate), set width and height, create pixel data.
	private void initializeImage(Dimension dims) {
		img = null ;
		imgWidth = dims.width ;
		imgHeight = dims.height ;
		pixelData = new int [imgWidth * imgHeight] ;
		int i=0 ;
		for (int row = 0 ; row < imgHeight ; row++) {
			int red = (row * 255) / (imgHeight - 1) ;
			for (int col = 0 ; col < imgWidth ; col++) {
				int green = (col * 255) / (imgWidth - 1) ;
				int blue = 128 ;
				int alpha = 255 ;
				pixelData[i++] = (alpha << 24) |
						(red << 16) |
						(green << 8) |
						(blue) ;
			}
		}
	}

	// creates onscreen image from pixel data.
	public void paint(Graphics g) {

		System.out.println("paint called") ;

		if (img == null) {
			System.out.println("creating new image") ;
			img = createImage(
				new MemoryImageSource(
					imgWidth, imgHeight,
					pixelData, 0, imgWidth)) ;
		}

		// position origin to avoid frame borders.
		translateDrawingArea(g) ;

		// draw image.
		g.drawImage(img, 0, 0, this) ;
	}

	// updates onscreen image (no need to clear first, just paint).
	public void update(Graphics g) {
		System.out.println("update called") ;
		paint(g) ;
	}

	// called when component is resized.
	public void componentResized(ComponentEvent e) { 
		System.out.println("componentResized called") ;
		initializeImage(getDrawingSize()) ;
		repaint() ;
	}

	// other methods of ComponentListener interface.
	public void componentHidden(ComponentEvent e) { }
	public void componentMoved(ComponentEvent e) { }
	public void componentShown(ComponentEvent e) { }


	//
	// ---- main ---------------------------------------------------
	//
	// command-line arguments:  initial width, height
	//	(defaults 400, 200)
	//
	public static void main(String[] args) {

		int w = 400 ;
		int h = 200 ;
		if (args.length >= 2) {
			w = Integer.parseInt(args[0]) ;
			h = Integer.parseInt(args[1]) ;
		}

		ColorPan c = new ColorPan(new Dimension(w, h)) ;
	}
}