//
// another example of the Java AWT, showing loading and display of
//	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.image.* ;
import java.io.* ;

//
// a ColorSep object is a DrawingFrame that obtains an image from a
//	file (GIF and JPEG formats are supported), and then displays
//	four versions of it, the original and three colored-filtered
//	versions.
//
class ColorSep extends DrawingFrame {

	private Image img ;
	private Image redImg, greenImg, blueImg ;
	private int imgWidth, imgHeight ;

	ColorSep(String imageFile) {
		super("ColorSep") ;

		// start loading image.
		img = getToolkit().getImage(imageFile) ;
		System.out.println("loading image ....") ;

		// wait for completion.
		waitForImage(img) ;
		System.out.println("done") ;

		// get size of loaded image and use to set
		//	initial size (big enough for four copies).
		imgWidth = img.getWidth(this) ;
		imgHeight = img.getHeight(this) ;

		setDrawingSize(new Dimension(2*imgWidth, 2*imgHeight)) ;

		// create filtered images
		redImg = createImage(
			new FilteredImageSource(img.getSource(),
				new ColorMaskFilter(Color.red))) ;
		greenImg = createImage(
			new FilteredImageSource(img.getSource(),
				new ColorMaskFilter(Color.green))) ;
		blueImg = createImage(
			new FilteredImageSource(img.getSource(),
				new ColorMaskFilter(Color.blue))) ;

		show() ;
	}

	// waits for image to finish loading.
	private void waitForImage(Image im) {
		MediaTracker tracker = new MediaTracker(this) ;
		// add desired image to list of things the
		//	MediaTracker is tracking, with id = 0.
		tracker.addImage(im, 0) ;
		try {
			// wait for loading of image we just
			//	added to MediaTracker's list.
			tracker.waitForID(0) ;
		} catch(InterruptedException e) { }
	}

	// creates onscreen image by scaling image from file.
	public void paint(Graphics g) {

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

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

		// draw original image and three filtered versions.
		g.drawImage(img, 0, 0, this) ;
		g.drawImage(redImg, imgWidth, 0, this) ;
		g.drawImage(greenImg, 0, imgHeight, this) ;
		g.drawImage(blueImg, imgWidth, imgHeight, this) ;
	}

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

	//
	// ---- main ---------------------------------------------------
	//
	// command-line argument:  file from which to load image.
	//
	public static void main(String[] args) {

		if (args.length < 1) {
			System.out.println("Argument is filename") ;
			System.exit(-1) ;
		}

		File f = new File(args[0]) ;
		if (!f.exists() || !f.canRead()) {
			System.out.println("Filename not found") ;
			System.exit(-1) ;
		}

		ColorSep s = new ColorSep(args[0]) ;
	}
}

//
// a ColorMaskFilter object filters pixel data, multiplying its
//	red, green, and blue components by the corresponding 
//	components of the mask.
//
class ColorMaskFilter extends RGBImageFilter {
	private Color msk ;

	ColorMaskFilter(Color mask) {
		msk = mask ;
		canFilterIndexColorModel = true ;
	}

	public int filterRGB(int x, int y, int pixel) {
		return (255 << 24) |
			((redPart(pixel) * msk.getRed()/255) << 16) |
			((greenPart(pixel) * msk.getGreen()/255) << 8) |
			((bluePart(pixel) * msk.getBlue()/255)) ;
	}

	private int redPart(int pixel) {
		return (pixel & 0xff0000) >> 16 ;
	}

	private int greenPart(int pixel) {
		return (pixel & 0xff00) >> 8 ;
	}

	private int bluePart(int pixel) {
		return (pixel & 0xff) ;
	}
}