window.setInterval('changeDirtyImage("img#bigImage")', 2000);

$('img.dirtyImage').hover(
    function() {
        changeDirtyImage(this);
    },
    function() {
        changeDirtyImage(this);
    }
);

function changeDirtyImage(selector)
{
    var oldSrc = $(selector).attr('src');
    
    if (oldSrc.substring(oldSrc.length - 10, oldSrc.length - 4) == '-dirty')
    {
        $(selector).attr('src', oldSrc.substring(0, oldSrc.length - 10) + oldSrc.substring(oldSrc.length - 4));
        bBigImageDirty = false;
    }
    else
    {
        $(selector).attr('src', oldSrc.substring(0, oldSrc.length - 4) + '-dirty' + oldSrc.substring(oldSrc.length - 4));
        bBigImageDirty = true;
    }
}