flash加载外部图片等比缩放类(as3)

以下为引用的内容：

/*
  等比缩放
  as1984 - qq:38657783
  20091221
  请注意包路径，我的as包都放在tools目录下。所以包的路径是 tools
  如果你的路径不一样，请注意修改
*/
package tools
{
    public class imgzoom {
       
        // 变量声明
        private var isZoom:Boolean;//是否缩放
        private var srcWidth:Number;//原始宽
        private var srcHeight:Number;//原始高
        private var maxWidth:Number;//限制宽
        private var maxHeight:Number;//限制高
        private var newWidth:Number;//新宽
        private var newHeight:Number;//新高
       
        public function imgzoom(srcWidth:Number,srcHeight:Number,maxWidth:Number,maxHeight:Number):
void
        {
            this.srcWidth=srcWidth;//获得原始宽度
            this.srcHeight=srcHeight;//获得原始高度
            this.maxWidth=maxWidth;//获得限定宽度
            this.maxHeight=maxHeight;//获得限定高度
            if(this.srcWidth>0 && this.srcWidth>0){//检查图片高度是否正常
                this.isZoom=true;//高宽正常，执行缩放处理
            }else{
                this.isZoom=false;//不正常，返回0
            }
            conductimg();//执行缩放算法
        }
        public function width():Number{//返回处理后的宽度，精确到2个小数点
            return Number(this.newWidth.toFixed(2));
        }
        public function height():Number{//返回处理后的高度，精确到2个小数点
            return Number(this.newHeight.toFixed(2));
        }
        private function conductimg():void{
            if(this.isZoom){//如果高宽正常，开始计算
                if(this.srcWidth/this.srcHeight>=this.maxWidth/this.maxHeight){
                                       //比较高宽比例，确定以宽或者是高为基准进行计算。
                    if(this.srcWidth>this.maxWidth){//以宽为基准开始计算，
                                                //当宽度大于限定宽度，开始缩放
                        this.newWidth=this.maxWidth;
                        this.newHeight=(this.srcHeight*this.maxWidth)/this.srcWidth
                    }else{
                                                //当宽度小于限定宽度，直接返回原始数值。
                        this.newWidth=this.srcWidth;
                        this.newHeight=this.srcHeight;
                    }
                }else{
                    if(this.srcHeight>this.maxHeight){//以高为基准，进行计算
                                                //当高度大于限定高度，开始缩放。
                        this.newHeight=this.maxHeight;
                        this.newWidth=(this.srcWidth*this.maxHeight)/this.srcHeight
                    }else{
                                                //当高度小于限定高度，直接返回原始数值。
                        this.newWidth=this.srcWidth;
                        this.newHeight=this.srcHeight;
                    }
                }
            }else{//不正常，返回0
                this.newWidth=0;
                this.newHeight=0;
            }
        }
    }
}

以下为引用的内容：

import tools.imgzoom;
函数 当加载完毕时{
                        var t:Sprite=new Sprite();
            var w:Number=685;//限定的宽度
            var h:Number=450;//限定的高度
                        var t:Sprite=new Sprite();//造个东西准备装图片
            var myZoom:imgzoom=new imgzoom(e.target.content.width,e.target.content.height,w,h);//实例化算法
            e.target.content.width=myZoom.width();//把加载过来的东西宽度弄了
            e.target.content.height=myZoom.height();//把加载过来的东西高度弄了
            t.addChild(e.target.content);//加入t的显示列表
           
}

以下为引用的内容：

              public static function getZoomDraw(targetisplayObject, tarW:int, tarH:int,full:Boolean=true):BitmapData {
                     //获取显示对象矩形范围
                     var rect:Rectangle = target.getBounds(target);
                     //计算出应当缩放的比例
                     var perw = tarW / rect.width;
                     var perh = tarH / rect.height;
                     var scale = full?((perw <= perh)?perwerh)(perw <= perh)?perherw);
                     //计算缩放后与规定尺寸之间的偏移量
                     var offerW = (tarW - rect.width * scale) / 2;
                     var offerH = (tarH - rect.height * scale) / 2;
                     //开始绘制快照（这里透明参数是false,是方便观察效果，实际应用可改为true)
                     var bmd:BitmapData = new BitmapData(tarW, tarH, false, 0);
                     var matrix:Matrix = new Matrix();
                     matrix.scale(scale, scale);
                     matrix.translate( offerW, offerH);
                     bmd.draw(target, matrix);
                     //如果是bitmap对象，释放位图资源
                     if (target is Bitmap)   (target as Bitmap).bitmapData.dispose();
                     //返回截图数据
                     return bmd;
              }