function   DrawImage(ImgD,widht,height){ 
      var   flag=false;
      var   image=new   Image(); 
      var   iwidth   =   widht;     //定义允许图片宽度 
      var   iheight   =  height;     //定义允许图片高度 
      image.src=ImgD.src; 
      if(image.width> 0&&image.height> 0){ 
        flag=true; 
        if(image.width/image.height>=iwidth/iheight){ 
          if(image.width> iwidth){     
          ImgD.width=iwidth; 
          ImgD.height=(image.height*iwidth)/image.width; 
          }else{ 
          ImgD.width=image.width;     
          ImgD.height=image.height; 
          } 
          //ImgD.alt=image.width+ "× "+image.height; 
          } 
        else{ 
          if(image.height> iheight){     
          ImgD.height=iheight; 
          ImgD.width=(image.width*iheight)/image.height;           
          }else{ 
          ImgD.width=image.width;     
          ImgD.height=image.height; 
          } 
          //ImgD.alt=image.width+ "× "+image.height; 
          } 
        } 
}