function AutoSize(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;
     }
     //ImgD.alt="ԭʼ³ß´ç:¿í" + image.width+",¸ß"+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;
     }
     }
    }
}