Draw dot on image using jQuery

I have the following code to track where a user clicks on an image:

 <img src="images/test.jpg" id="testimg" />

    <script type="text/javascript">
        $("#testimg").click(function (ev) {
            mouseX = ev.pageX;
            mouseY = ev.pageY
            alert(mouseX + ' ' + mouseY);
        })

    </script>

What I would like to do is, when the user clicks on the image, I want to draw a dot at the X,Y coordinates of the click.

Can someone give me some advice on how this can be done?