AS3 求Matrix变形后计算显示对象大小的矩形框算法

原文：http://bbs.9ria.com/thread-130511-1-2.html

var wid:int=300;
var hei:int=200;

var m:Matrix=this.transform.matrix;

var lt:Point=new Point(0,0);
var rt:Point=new Point(wid,0);
var lb:Point=new Point(0,hei);
var rb:Point=new Point(wid,hei);

lt=transformPoint(m,lt);
rt=transformPoint(m,rt);
lb=transformPoint(m,lb);
rb=transformPoint(m,rb);

var xmin:Number=Math.min(lt.x,rt.x,lb.x,rb.x);
var ymin:Number=Math.min(lt.y,rt.y,lb.y,rb.y);
var xmax:Number=Math.max(lt.x,rt.x,lb.x,rb.x);
var ymax:Number=Math.max(lt.y,rt.y,lb.y,rb.y);

trace(xmin,ymin,xmax-xmin,ymax-ymin);//104.5107421875 133 197.637939453125 169.17266845703125
trace(this.getBounds(this.parent));//(x=104.5, y=133, w=197.64999999999998, h=169.14999999999998)

function transformPoint(m:Matrix,p:Point):Point{
        //return m.transformPoint(p);
        return new Point(m.a*p.x+m.c*p.y+m.tx,m.b*p.x+m.d*p.y+m.ty);
}