flash as中为动态蒙版添加动画效果

import mx.transitions.Tween;
import mx.transitions.easing.*;
var mclListener:Object = new Object();
mclListener.onLoadInit = function(target_mc:MovieClip) {
    target_mc._visible = false;
    // 在舞台上将图像居中。
    target_mc._x = (Stage.width - target_mc._width) / 2;
    target_mc._y = (Stage.height - target_mc._height) / 2;
    var maskClip:MovieClip = target_mc.createEmptyMovieClip("mask_mc", 20);
    with (maskClip) {
        // 绘制与加载的图像大小相同的遮罩。
        beginFill(0xFF00FF, 100);
        moveTo(0, 0);
        lineTo(target_mc._width, 0);
        lineTo(target_mc._width, target_mc._height);
        lineTo(0, target_mc._height);
        lineTo(0, 0);
        endFill();
    }
    target_mc.setMask(maskClip);
    target_mc._visible = true;
    var mask_tween:Tween = new Tween(maskClip, "_yscale", Strong.easeOut, 0, 100, 2, true);
};
this.createEmptyMovieClip("img_mc", 10);
var img_mcl:MovieClipLoader = new MovieClipLoader();
img_mcl.addListener(mclListener);
img_mcl.loadClip("/images/image1.jpg", img_mc);