使用方法：

$(".viewArea img").zoom({height:74,width:103});

 

(function($){

    $.fn.zoom = function(settings){

                //一些默认配置；

                settings = $.extend({

                    height:0,

                    width:0,

                    loading:"http://www.dadachina.com/images/lightbox-ico-loading.gif"

                    },settings);

                    

                var images = this;

                $(images).hide();

                var loadding = new Image();

                loadding.className="loadding"

                loadding.src = settings.loading;

                $(images).after(loadding);    

                

                //预加载

                var preLoad = function($this){

                    var img = new Image();

                    img.src = $this.src;

                    if (img.complete) { 

                        processImg.call($this);

                        return;

                    }

                    //$this.src = loadding.src;//会导致获取错误的尺寸

                    img.onload = function(){

                        //$this.src = this.src; //会导致获取错误的尺寸

                        

                        processImg.call($this);

                        img.onload=function(){};

                    } 

                }

                

                //计算图片尺寸；

                function processImg(){

                        //if(settings.height===0||settings.width ===0) return;

                        var m = this.height-settings.height;

                        var n = this.width - settings.width;

                        if(m>n)                        

                            this.height = this.height>settings.height ? settings.height : 

this.height;

                        else

                            this.width = this.width >settings.width ? settings.width : 

this.width;

                        $(this).next(".loadding").remove()

                        $(this).show();

                }

                

                return $(images).each(function(){

                    preLoad(this);

                });                

        }

})(jQuery);