[AS3]as3加载外部jpg图片实现等比缩放类源代码实例

每次做相册类的flash的时候，图片加载完毕之后都要写等比缩放的函数来处理加载图片。
今天又遇到了，也不知道哪根筋不对了，弄了十几分钟老是算法有错误。好好的一个美女图片被搞的惨不忍睹。
所以写了这个类 直接放到我的as包里，以后不要再这么麻烦了。
贴一下，能用的朋友就用一用。看不上眼的也不要拍砖啊。下边是代码及注释说明。

/* 
  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 
                                                thisthis.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。 
                                                thisthis.newWidth=this.srcWidth; 
                                                thisthis.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。 
                                                thisthis.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。 
                                                thisthis.newWidth=this.srcWidth; 
                                                thisthis.newHeight=this.srcHeight; 
                                        } 
                                } 
                        }else{//不正常，返回0 
                                this.newWidth=0; 
                                this.newHeight=0; 
                        } 
                } 
        } 
}