JQuery 图片延迟加载并等比缩放插件

(function($){
$.fn.zoom = function(settings){
//一些默认配置；
settings = $.extend({
height:0,
width:0,
loading:"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);