$(document).ready(function(){
	var xImg=1800;
	var yImg=1400;
	var rapporto=xImg/yImg;
		

	
	function resize(){
		var xWind=$(window).width();
		var yWind=$(window).height();
		var rapportoAttuale= xWind/yWind;
		
		if(rapporto<=rapportoAttuale){
			$('img.bg').css({width:'100%', height:'auto'});
		}else{
			$('img.bg').css({width:'auto', height:'100%'});
		}
		
	}
	

	$(window).bind('resize', function() {
		resize();
	});
	
	resize();

});