var flag=false;   //¿ØÖÆСͼ
function DrawImage(ImgD,maxwidth,maxheight)
{  
   var image=new Image(); 
   image.src=ImgD.src;  
   if(image.width>0 && image.height>0)
   {  
    flag=true;  
    if(image.width/image.height>=maxwidth/maxheight)
    {  
     if(image.width>maxwidth)
     {    
         ImgD.width=maxwidth;  
         ImgD.height=(image.height*maxwidth)/image.width;  
     }
     else
     {  
         ImgD.width=image.width;    
         ImgD.height=image.height;  
     }  
    }  
    else
    {  
     if(image.height>maxheight)
     {    
         ImgD.height=maxheight;  
         ImgD.width=(image.width*maxheight)/image.height;       
     }
     else
     {  
         ImgD.width=image.width;    
         ImgD.height=image.height;  
     }  
    }  
   }  
}