Simple AS3 moon on water

import flash.display.BitmapData;
import flash.display.Bitmap;
import flash.events.Event;
import flash.geom.Point;
import flash.geom.Rectangle;
import flash.filters.BlurFilter;
import flash.geom.Matrix;
import flash.filters.DisplacementMapFilter;

var w:int = stage.stageWidth/2;
var h:int = stage.stageHeight/2;

var canvas2:BitmapData = new BitmapData(w, h, true, 0x0);
var canvas:BitmapData = new BitmapData(w, h, true, 0x0);
var screen:Bitmap = new Bitmap(canvas);
addChild(screen);
screen.scaleX = screen.scaleY = 2;

var skyCanvas:BitmapData = new BitmapData(w, 76, true, 0xFF000000);
for(var i = 1; i<=30; i++) {
	skyCanvas.setPixel32(Math.random()*w>>0, Math.random()*75>>0, 0xFFFFFFFF);
}
for(var ex = 0; ex<100; ex++) {
	for(var wy = 0; wy<100; wy++) {
		if(Math.sqrt(Math.pow(ex-50, 2)+Math.pow(wy-50, 2))<50) {
			skyCanvas.setPixel32(ex-50+w/2, wy-50+80, 0xFF000000+0x090909*((Math.random()*0x2>>0)*0x4+0x9));
		}
	}
}

var tick:Number = 0;
addEventListener(Event.ENTER_FRAME, ef);
function ef(e:Event) {
	tick = (.2+tick)%1000;
	canvas2.perlinNoise(20, 4, 3, 324, false, true, 1, false, [new Point(tick, -tick/2), new Point(-tick*1.5, tick/1.5), new Point(-tick*2, -tick/2)]);
	canvas2.draw(new blur(), new Matrix(1, 0, 0, .7, 0, 75));
	canvas2.applyFilter(canvas2, new Rectangle(0, 0, w, h), new Point(0, 0), new BlurFilter(2, 2, 1));
	canvas.threshold(canvas2, new Rectangle(0, 0, w, h), new Point(0, 0), "<=", 0x33333333*5, 0xFFFFFFFF, 0x00FFFFFF);
	canvas.threshold(canvas2, new Rectangle(0, 0, w, h), new Point(0, 0), "<=", 0x33333333*4, 0xFF000000+0x101015*8, 0x00FFFFFF);
	canvas.threshold(canvas2, new Rectangle(0, 0, w, h), new Point(0, 0), "<=", 0x33333333*3, 0xFF000000+0x101015*6, 0x00FFFFFF);
	canvas.threshold(canvas2, new Rectangle(0, 0, w, h), new Point(0, 0), "<=", 0x33333333*2, 0xFF000000+0x051015*2, 0x00FFFFFF);
	canvas.threshold(canvas2, new Rectangle(0, 0, w, h), new Point(0, 0), "<=", 0x33333333*1, 0xFF000000+0x051015*0, 0x00FFFFFF);
	canvas.draw(skyCanvas);
}