I have an embarrassingly simple question: How can I display an image at double its size without hard coding the width and height attributes? Here's what I tried, but I ended up having to just enter 1000 for width and height. Is something wrong with my function? Thanks!

<img onload="double(self.id);" name="bigPic" id="bigPic" src="album1.jpg" height="1000" width="1000"/>

    function double(id) {
        var img = document.getElementById(id);
        var dblWdth = img.width * 2;
        var dblHt = img.height * 2;

        img.height = dblHt;
        img.width = dblWdth;
    }