var flag=false;  
function DrawImage(ImgD, ImgW, ImgH)
{
	var Alt = arguments[3]?arguments[3]:'';
	//alert(Alt);
	var image=new Image();  
    image.src=ImgD.src;  
    if(image.width>0 && image.height>0)
	{
		flag=true;  
		if(image.width/image.height>= ImgW/ImgH)
		{  
			if(image.width>ImgW)
			{
				ImgD.width=ImgW;  
				ImgD.height=(image.height*ImgW)/image.width;  
			}
			else
			{
				ImgD.width=image.width;      
				ImgD.height=image.height;  
			}
			if (Alt=='')
			{
				ImgD.alt="实际图片大小为"+image.width+"×"+image.height;  
			}
		}
		else
		{
			if(image.height>ImgH)
			{
				ImgD.height=ImgH;
				ImgD.width=(image.width*ImgH)/image.height;            
			}
			else
			{  
				ImgD.width=image.width;      
				ImgD.height=image.height;  
			}
			if (Alt=='')
			{
				ImgD.alt="实际图片大小为"+image.width+"×"+image.height;  
			}
		}
	}  
}