import flash.geom.Rectangle;
import flash.geom.Point;

var bmd:BitmapData;
var bmd2:BitmapData;
var bm:Bitmap;
var loader:Loader=new Loader();

var W:int;
var H:int;

var outerColor:uint;
var innerColor:uint;

loader.load(new URLRequest("shape.jpg"));
loader.contentLoaderInfo.addEventListener(Event.COMPLETE,loadComplete);
addEventListener(MouseEvent.MOUSE_MOVE, mouseMoveHandler);


function loadComplete(e:Event)
{
	W = e.target.content.width;
	H = e.target.content.height;

	bmd=new BitmapData(W,H);
	bm=new Bitmap(bmd);
	mcHolder.addChild(bm);
	bmd.draw(e.target.content);

	outerColor = bmd.getPixel(10,10);
	innerColor = bmd.getPixel(W/2,H/2);

	bmd2 = bmd.clone();
}

function mouseMoveHandler(event:MouseEvent):void
{
	var outerAlpha:uint = 0xff * mouseY / height;
	var innerAlpha:uint = 0xff - outerAlpha;

	outerAlpha <<= 24;
	innerAlpha <<= 24;

	var replaceOuterColor:uint = (outerColor & 0x00ffffff) | outerAlpha;
	var replaceInnerColor:uint = (innerColor & 0x00ffffff) | innerAlpha;

	var rect:Rectangle = new Rectangle(0,0,W,H);
	var point:Point = new Point(0,0);

	// Just comparing blue component : this will depend on image colors
	var compareMask:uint = 0x000000ff;
	bmd.threshold(bmd2, rect, point, "<", 0x80, replaceInnerColor, compareMask);
	bmd.threshold(bmd2, rect, point, ">", 0x80, replaceOuterColor, compareMask);
}