(function($) {
  $.fn.fullBg = function(){
  	this.each(function(){
  		var bgImg = $(this);		
	    function resizeImg() {
	      var imgwidth = bgImg.width();
	      var imgheight = bgImg.height();
	 		
	      var winwidth = $(window).width();
	      var winheight = $(window).height();
	 
	      var widthratio = winwidth / imgwidth;
	      var heightratio = winheight / imgheight;
	 
	      var widthdiff = heightratio * imgwidth;
	      var heightdiff = widthratio * imgheight;
	
	      if(heightdiff>winheight) {
	        bgImg.css({
	          width: winwidth+'px',
	          height: heightdiff+'px',
	          top: (winheight - heightdiff)/2 +'px'
	        });
	      } else {
	        bgImg.css({
	          width: widthdiff+'px',
	          height: winheight+'px',
	          left:((winwidth - widthdiff)/2) +'px'
	        });		
	      }
	    } 
		resizeImg();
	    $(window).resize(function() {
	      resizeImg();
	    }); 
	})
  };
})(jQuery)