jquery bg image resizer

jquery bg image resizer

<script>
$(document).ready(resizebg);
$(window).resize(resizebg);
function resizebg() {
	var w,h,x,y;
	var ratio = 4/3;
	x = $(window).width();
	y = $(window).height();
	var constrain = x/y > ratio ? 'w' : 'h';
	if(constrain=='w') {
		w = x;
		h = Math.round(x*.75);
	} else if(constrain=='h') {
		w = Math.round(y*1.333);
		h = y;
	}
	$('#bg').css({ 'width': w+'px', 'height': h+'px'});
}
</script>
<style>
#bg { position:absolute; bottom:0; right:0; z-index:0; }
</style>