/*	Date: 10/05/96  File is: AlphaBlend.java  Release: 1.0
 *	Last Modified: 12/19/96 by: abb@nuccard.eushc.org
 *	Copyright (c) Andrew B. Barclay 1996. All rights reserved.
 */

// I like to know what I'm importing for sanity checks.
import java.applet.Applet ;
import java.awt.image.FilteredImageSource ;
import java.awt.Color ;
import java.awt.Dimension ;
import java.awt.Event ;
import java.awt.Graphics ;
import java.awt.Image ;

// Classes that I've added:
import AlphaFilter ;

public class AlphaBlend extends Applet {
    Image srcim1, srcim2 ;
    Image alphaim ;
    int alpha ;
    int thresh ;

    int lastx, lasty ;
    int dx, dy ;

    Dimension dim1, dim2 ;
    Image osim ;
    Graphics osgr ;

    public String getAppletInfo() {
	return "Alpha Blending Applet by Andrew Barclay" ;
    }

    /* ============================================================
     * Initializing stuff:
     */
    public void init() {
	String param ;
	param = getParameter("src1") ;
	srcim1 = getImage( getDocumentBase(), param ) ;
	param = getParameter("src2") ;
	srcim2 = getImage( getDocumentBase(), param ) ;

	// Parse the alpha (converted from percentage).
	param = getParameter( "alpha" ) ;
	alpha = (int)( 0.5 + (255.0/100.0)*
		Double.valueOf( param ).doubleValue() ) ;

	// Parse the threshold
	param = getParameter( "thresh" ) ;
	if( param != null ) {
	    thresh = (int)( 0.5 + (255.0/100.0)*
		    Double.valueOf( param ).doubleValue() ) ;
	} else {
	    thresh = 0 ;
	}

	setBackground( Color.black ) ;
    }

    // Public methods for JavaScript control.
    public synchronized void setAlpha( double pct ) {
	alpha = (int)( 0.5 + (255.0/100.0)*pct ) ;
	if( alphaim != null ) {
	    // conserve resources
	    alphaim.flush() ;
	}
	alphaim = null ;
	repaint() ;
    }

    public synchronized void setThreshold( double pct ) {
	thresh = (int)( 0.5 + (255.0/100.0)*pct ) ;
	if( alphaim != null ) {
	    // conserve resources
	    alphaim.flush() ;
	}
	alphaim = null ;
	repaint() ;
    }

    /* ============================================================
     * Painting.
     */

    public void update( Graphics gr ) {
	paint( gr ) ;
    }

    public void paint( Graphics gr ) {
	if( alphaim == null ) {
	    alphaim = filterImage( srcim2, alpha, thresh ) ;
	}

	int winwidth = size().width ;
	int winheight = size().height ;

	if( osim == null ) {
	    int w1 = srcim1.getWidth( this ) ;
	    int h1 = srcim1.getHeight( this ) ;
	    int w2 = alphaim.getWidth( this ) ;
	    int h2 = alphaim.getHeight( this ) ;

	    /*
	     * Drawing the offscreen image with no zoom and
	     * then zooming it to the screen makes this really,
	     * really slow.  Offscreen image must be same size
	     * as onscreen for best speed.
	     */
	    if( w1 > -1 && h1 > -1 && w2 > -1 && h2 > -1 ) {
		// Size to largest image dimensions.
		int maxw = Math.max( w1, w2 ) ;
		int maxh = Math.max( h1, h2 ) ;

		dim1 = new Dimension(
		    (maxw * winwidth)/w1, (maxh * winheight)/h1
		) ;
		dim2 = new Dimension(
		    (maxw * winwidth)/w2, (maxh * winheight)/h2
		) ;

		osim = createImage( winwidth, winheight ) ;
		osgr = osim.getGraphics() ;

		gr.clearRect( 0, 0, 30, 100 ) ;
		gr.setColor( Color.red ) ;
		gr.drawString( "Got width and height.",
			10, 20 ) ;
	    } else {
		gr.clearRect( 0, 0, 30, 100 ) ;
		gr.setColor( Color.red ) ;
		gr.drawString( "Waiting on width and height...",
			10, 20 ) ;
	    }

	    repaint( 100 ) ;
	} else {
	    osgr.drawImage( srcim1, 0, 0,
			dim1.width, dim1.height, this ) ;
	    osgr.drawImage( alphaim, dx, dy,
			dim2.width, dim2.height, this ) ;
	    gr.drawImage( osim, 0, 0, winwidth, winheight, this ) ;

	    gr.setColor( Color.cyan ) ;
	    gr.drawString( "dx="+dx+", dy="+dy, 10, 20 ) ;
	}
    }

    Image filterImage( Image srcim, int alpha, int threshold ) {
	AlphaFilter filter = new AlphaFilter( alpha, threshold ) ;
	return createImage( 
	    new FilteredImageSource( srcim.getSource(), filter )
	) ;
    }

    /* ============================================================
     * Event handling.
     */

    public boolean mouseDown( Event evt, int x, int y ) {
	lastx = x ;
	lasty = y ;
	return true ;
    }

    public boolean mouseDrag( Event evt, int x, int y ) {
	dx += x-lastx ;
	dy += y-lasty ;
	lastx = x ;
	lasty = y ;
	repaint( 100 ) ;
	return true ;
    }

    public boolean keyDown( Event evt, int key ) {
	boolean ret = false ;
	switch( key ) {
	    case Event.UP:
	    case 'k':
		dy-- ;
		repaint( 100 ) ;
		return true ;
	    case Event.DOWN:
	    case 'j':
		dy++ ;
		repaint( 100 ) ;
		return true ;
	    case Event.LEFT:
	    case 'h':
		dx-- ;
		repaint( 100 ) ;
		return true ;
	    case Event.RIGHT:
	    case 'l':
		dx++ ;
		repaint( 100 ) ;
		return true ;
	    default:
		System.out.println( "keyDown: key = "+key ) ;
		return false ;
	}
    }

}