html to canvas does not screenshot the background

So, I got this code to screenshot the page when I click a square:

$  ("#empty").click(function(){          html2canvas(document.body).then(function(canvas) {         document.body.appendChild(canvas);             });         }) 

but the screen I got does not include the background (I set an image as background). The background in the screenshot is white, like it wasn’t there.