javascript 实现双指放大缩小旋转图片

private getTouchDistance():number
{
var _distance:number = 0;
var names = this.touchPoints["names"];
_distance = egret.Point.distance( this.touchPoints[names[names.length-1]],
this.touchPoints[names[names.length-2]]);
return _distance;
}

  private getTouchAngle():number
    {
        var ang:number = 0;
        var names = this.touchPoints["names"];
        var p1:egret.Point = this.touchPoints[names[names.length-1]];
        var p2:egret.Point = this.touchPoints[names[names.length-2]];

        ang = Math.atan2((p1.y-p2.y),(p1.x-p2.x)) / this.c;
        return ang;
    }