//图片按比例缩放 
	var flag=false; 
	function DrawImage(ImgD,iwidth,iheight)
	{ 
		var image=new Image(); 
		//var iwidth = 800;  //定义允许图片宽度 
		//var iheight = 550;  //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; 
			} 
		} 
	}