maschera dinamica FlashCS3 AS3

[Ashry]

Salve a tutti, vorrei un' amimazione ,costituita da dei cerchietti posizionati in modo casuale,per far alternare delle immagini, sono riuscita a far comparire le immagini ma non riesco a creare una dissolvenza, nel senso che quando carico la nuova immagine quella vecchia scompare io invece vorrei che restasse sulla stage fino a chè limmagine non è completamente caricata.

ecco il mio codice xml:

<slideshow speed="2">
<image url="images/01.jpg" />
<image url="images/02.jpg" />
<image url="images/03.jpg" />
<image url="images/04.jpg" />
</slideshow> 

e il codice as3:

var my_speed:Number;
var my_total:Number;
var my_xmlList:XMLList;

/*counter*/
var my_playback_counter:Number = 0;

/*creo i contenitori*/
var my_slideshow:Sprite = new Sprite();
var maskContainer:Sprite = new Sprite();
var my_image_slides:Sprite = new Sprite();
var my_preloaders:Sprite = new Sprite();

maskContainer.cacheAsBitmap=true;
my_image_slides.cacheAsBitmap=true;


var my_timer:Timer;

/*carico l'xml*/
var my_xml_loader:URLLoader = new URLLoader();
my_xml_loader.load(new URLRequest("slideshow-data.xml"));
my_xml_loader.addEventListener(Event.COMPLETE, processXML);

function processXML(e:Event):void {

    var my_xml:XML = new XML(e.target.data);
    my_speed=my_xml.@SPEED;
    my_xmlList=my_xml.IMAGE;
    my_total=my_xmlList.length();
    my_xml_loader.removeEventListener(Event.COMPLETE, processXML);
    my_xml_loader = null;
    createContainer();
    callImages(0);

    my_timer = new Timer(my_speed*2000);
    my_timer.addEventListener(TimerEvent.TIMER, timerListener);
    my_timer.start();

}

function createContainer():void {
    addChild(my_slideshow);
    my_slideshow.x=0;
    my_slideshow.addChild(my_image_slides);
    my_image_slides.x = 0;
    my_slideshow.addChild(my_preloaders);
}

function callImages(num:int):void {
    my_image_slides.addChild(maskContainer);

    var timer:Timer=new Timer(40,10);
    timer.addEventListener(TimerEvent.TIMER, timerEvent);
    timer.start();

    var my_url:String = my_xmlList[num].@URL;
    var my_loader = new Loader();
    my_loader.load(new URLRequest(my_url));
    my_loader.contentLoaderInfo.addEventListener(Event.COMPLETE, imageLoaded);

    var preloader_pb:ProgressBar = new ProgressBar();
    preloader_pb.source = my_loader.contentLoaderInfo;
    preloader_pb.x = my_loader.x;
    preloader_pb.y = stage.stageHeight-preloader_pb.height;
    preloader_pb.width =stage.stageWidth;
    my_preloaders.addChild(preloader_pb);

    preloader_pb.addEventListener(Event.COMPLETE, donePb);

}
function imageLoaded(e:Event):void {
    var my_image:Loader = Loader(e.target.loader);
    my_image_slides.addChild(my_image);
    my_image.cacheAsBitmap=true;
    my_image.mask = maskContainer;
}

function donePb(e:Event):void {
    var my_pb:ProgressBar = ProgressBar(e.target);
    my_preloaders.removeChild(my_pb);

}

function timerListener(e:TimerEvent):void {
    removeMaskShape();
    my_playback_counter++;
    if (my_playback_counter == my_total) {
        my_playback_counter =0;
    }
    callImages(my_playback_counter);
}
function hidePrev():void {
    var my_image:Loader=Loader(my_image_slides.getChildAt(0));
    my_image_slides.removeChild(my_image);
}

/*----Gestisco la maschera----*/

function timerEvent(e:TimerEvent):void {

    var maskShape:MaskShape = new MaskShape();
    maskShape.scaleX = 0;
    maskShape.scaleY = 0;

    maskShape.x = Math.random() * stage.stageWidth;
    maskShape.y = Math.random() * stage.stageHeight;

    maskContainer.addChild(maskShape);
    maskShape.alpha=0;
    maskShape.addEventListener(Event.ENTER_FRAME, animateMaskShape);

}

function animateMaskShape(e:Event):void {
    e.target.scaleX += 0.05;
    e.target.scaleY += 0.05;
    e.target.alpha +=0.01;
}

function removeMaskShape():void {

    var count:uint = maskContainer.numChildren;
    //trace(count);
    for (var i:uint=0; i<count; i++) {
        maskContainer.removeChildAt(0);
    }
    //hidePrev();
} 

mi sapete dire dove sbaglio?

Creazie
Ciao