jQuery.fn.stretchBG=function() {
	var bg = $('#bg_image');
	
	var ratio = 12/7;
	
	bg.css('width', $(window).width() + 'px');
	bg.css('height', ($(window).width() / ratio) + 'px');
	
	var bgheight = bg.css('height').replace('px','');
	
	if (bgheight < $(window).height()) {
		bg.css('height', $(window).height() + 'px');
		bg.css('width', ($(window).height() * ratio) + 'px');
	}

}