此方法用来图片缩放不变形的处理

* @param  elementid    元素id
* @param  iwidth       设定的宽度
* @param  iheight      设定的高度
* @param  flag         不同的方式，0为没有，1为表TD，2为INPUT
* @exemple
*/
function DrawImage(elementid,iwidth,iheight,flag){
var e = document.getElementById(elementid);
if(e != null){
var ImgD = e.getElementsByTagName("IMG");
for(var i=0;i0 && this.height>0){
     if(this.width/this.height >= this.iwidth/this.iheight){
      if(this.width > this.iwidth){
       this.c_IMG.width = this.iwidth;
       this.c_IMG.height = (this.height*this.iwidth)/this.width;
      }else{
       this.c_IMG.width = this.width;
       this.c_IMG.height=this.height;
      }
     }else{
      if(this.height > this.iheight){
       this.c_IMG.height=this.iheight;
       this.c_IMG.width=(this.width*this.iheight)/this.height;
      }else{
       this.c_IMG.width = this.width;
       this.c_IMG.height = this.height;
      }
     }
     this.c_IMG.alt = this.c_IMG.width+"×"+this.c_IMG.height; 
    }
   
   }
   image.src = ImgD[i].src;
}
  }
}