egret简单的刮刮乐效果

private createGameScene1(): void {

var bg = new egret.Shape();
bg.graphics.beginFill(0x0000FF);
bg.graphics.drawRect(0, 0, 480, 800);
bg.graphics.endFill();
this.addChild(bg);

var container: egret.DisplayObjectContainer = new egret.DisplayObjectContainer();
container.width = 300;
container.height = 300;
this.addChild(container);

var shape: egret.Bitmap = new egret.Bitmap();
shape.texture = RES.getRes("bg_jpg");
shape.width = 480;
shape.height = 800;
container.addChild(shape);

this.mask1 = new egret.Shape();
container.addChild(this.mask1);
shape.mask = this.mask1;

this.touchEnabled = true;
this.addEventListener(egret.TouchEvent.TOUCH_MOVE, this.fill, this);
}

private fill(event: egret.TouchEvent) {
this.mask1.graphics.beginFill(0x00FF00);
this.mask1.graphics.drawCircle(event.stageX, event.stageY, 30);
this.mask1.graphics.endFill();
this.mask1.alpha = 0;
// this.mask1.blendMode = egret.BlendMode.ERASE;
}