(function($) {

            $.fn.fullBg = function(){

                var bgImg = $(this);

    

                bgImg.addClass('fullBg');

    

                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'

                        });

                    } else {

                        bgImg.css({

                            width: widthdiff+'px',

                            height: winheight+'px'

                        });

                    }

                }

                resizeImg();

                $(window).resize(function() {

                    resizeImg();

                });

            };

        })(jQuery)

    

        jQuery(function($) {

            $("#background").fullBg();

        });