(function($) {

    $.backstretch = function(src, options, callback) {
        var settings = {
            centeredX: true, 
            centeredY: true,
            speed: 0
        },
        rootElement = ("onorientationchange" in window) ? $(document) : $(window), 
        imgRatio, bgImg, bgWidth, bgHeight, bgOffset, bgCSS;
        
        if(options && typeof options == "object") $.extend(settings, options);
        $(document).ready(_init);
  
        return this;
    
        function _init() {
            if(src) {
                var container = $("<div />").attr("id", "backstretch")
                                            .css({left: 0, top: 0, position: "fixed", overflow: "hidden", zIndex: -9999}),
                    img = $("<img />").css({position: "relative", display: "none"})
                                      .bind("load", function(e) {                                          
                                          var self = $(this);
                                          imgRatio = $(e.target).width() / $(e.target).height();
    
                                          _adjustBG(function() {
                                              self.fadeIn(settings.speed, function(){
                                                  if(typeof callback == "function") callback();
                                              });
                                          });
                                      })
                                      .appendTo(container);
                  
                $("body").prepend(container);
                img.attr("src", src);
                $(window).resize(_adjustBG);
            }
        }
            
        function _adjustBG(fn) {
            try {
                bgCSS = {left: 0, top: 0}
                bgWidth = rootElement.width();
                bgHeight = bgWidth / imgRatio;

                if(bgHeight >= rootElement.height()) {
                    bgOffset = (bgHeight - rootElement.height()) /2;
                    if(settings.centeredY) $.extend(bgCSS, {top: "-" + bgOffset + "px"});
                } else {
                    bgHeight = rootElement.height();
                    bgWidth = bgHeight * imgRatio;
                    bgOffset = (bgWidth - rootElement.width()) / 2;
                    if(settings.centeredX) $.extend(bgCSS, {left: "-" + bgOffset + "px"});
                }

                $("#backstretch img").width( bgWidth ).height( bgHeight ).css(bgCSS);
            } catch(err) {
            }
            if (typeof fn == "function") fn();
        }
    };
  
})(jQuery);