Check if a background image is loaded, Responsive Edition

[Escorcege]

I have set a background image to the body tag (large pic) and I want to fade it in once loaded (since the image is large, it would roll in when loading).I have seen this answer that basically uses a hidden img tag and leverage the browser cache: http://stackoverflow.com/questions/5057990/how-can-i-check-if-a-background-image-is-loadedThanks,