Get the x, y coordinate's relative to a mouseclick in Dojo/Javascript

I have a image that has a dojo touch event (similar to mouseclick). I want to get the x and y coordinate's relative to the div. Right now I am getting the canvasX and canvasY property. It looks like offsets will solve my problem. How can I get it to work with javascript, or if dojo has some offset functi开发者_如何学编程on?

If I understand the question correctly, you want to get the X,Y which your starting point is the image (not the whole document).

See if this example works for you

<div style="margin-left: 500px; border: 1px black solid;">
    <div style="border: 1px blue solid;">
        <img src="http://ecdn3.hark.com/images/000/000/294/294/original.jpg" 
                onclick="getOffsets(event, this);"/>
    </div>
</div>
<script>
    function getOffsets(event, img)
    {
        var relativeX = event.clientX - img.offsetLeft;
        var relativeY = event.clientY - img.offsetTop;
        alert(relativeX + " " + relativeY);
    }
</script>