function imgresize(id,newwidth,newheight)
{
	 var resizeWidth,resizeHeight;
	 resizeWidth=240;//最大宽度
	 resizeHeight=240;//最大高度
	  if (newheight>resizeHeight)
	 	{newwidth=newwidth*(resizeHeight/newheight);
		 newheight=newheight*(resizeHeight/newheight);}
	  if (newwidth>resizeWidth)	
	  	{newheight=newheight*(resizeWidth/newwidth);
		newwidth=newwidth*(resizeWidth/newwidth);}
	document.getElementById(id).width=newwidth;
	document.getElementById(id).height=newheight;
}