AJAX, ASHX, IMAGE

Hello,

I create dynamic image (.png). 

It takes  10-15 sec. 

I would like to add busy indicator, but I could not make second part work.

Server side is the same, or I have to change it?

I could not find right example.

//first - works
    function Refresh() 
    {
        document.getElementById("Image").src = "ViewHandler.ashx";
        document.getElementById("Image").style.visibility = 'visible';
    }
-----------------------------------------------------
//second - doesn't work
    function Refresh() 
    {
        spinner.style.display = 'inline';

        var url = "ViewHandler.ashx";
        xmlHttp = GetXmlHttpObject(OnComplete);
        xmlHttp.open("GET", url, true);
        xmlHttp.send(null);
    }

    function OnComplete() 
    {
        if (xmlHttp.readyState == 4 || xmlHttp.readyState == "complete") 
        {
            document.getElementById("Image").src = xmlHttp.responseText;
            document.getElementById("Image").style.visibility = 'visible';

            spinner.style.display = 'none';
        }
    }