背景图片切换核心代码

base.js

/*! Backstretch - v2.0.3 - 2012-11-30
* http://srobbin.com/jquery-plugins/backstretch/
* Copyright (c) 2012 Scott Robbin; Licensed MIT */
(function(e,t,n){"use strict";e.fn.backstretch=function(r,s){return(r===n||r.length===0)&&e.error("No images were supplied for Backstretch"),e(t).scrollTop()===0&&t.scrollTo(0,0),this.each(function(){var t=e(this),n=t.data("backstretch");n&&(s=e.extend(n.options,s),n.destroy(!0)),n=new i(this,r,s),t.data("backstretch",n)})},e.backstretch=function(t,n){return e("body").backstretch(t,n).data("backstretch")},e.expr[":"].backstretch=function(t){return e(t).data("backstretch")!==n},e.fn.backstretch.defaults={centeredX:!0,centeredY:!0,duration:5e3,fade:0};var r={wrap:{left:0,top:0,overflow:"hidden",margin:0,padding:0,height:"100%",width:"100%",zIndex:-999999},img:{position:"absolute",display:"none",margin:0,padding:0,border:"none",width:"auto",height:"auto",maxWidth:"none",zIndex:-999999}},i=function(n,i,o){this.options=e.extend({},e.fn.backstretch.defaults,o||{}),this.images=e.isArray(i)?i:[i],e.each(this.images,function(){e("<img />")[0].src=this}),this.isBody=n===document.body,this.$container=e(n),this.$wrap=e('<div class="backstretch"></div>').css(r.wrap).appendTo(this.$container),this.$root=this.isBody?s?e(t):e(document):this.$container;if(!this.isBody){var u=this.$container.css("position"),a=this.$container.css("zIndex");this.$container.css({position:u==="static"?"relative":u,zIndex:a==="auto"?0:a,background:"none"}),this.$wrap.css({zIndex:-999998})}this.$wrap.css({position:this.isBody&&s?"fixed":"absolute"}),this.index=0,this.show(this.index),e(t).on("resize.backstretch",e.proxy(this.resize,this)).on("orientationchange.backstretch",e.proxy(function(){this.isBody&&t.pageYOffset===0&&(t.scrollTo(0,1),this.resize())},this))};i.prototype={resize:function(){try{var e={left:0,top:0},n=this.isBody?this.$root.width():this.$root.innerWidth(),r=n,i=this.isBody?t.innerHeight?t.innerHeight:this.$root.height():this.$root.innerHeight(),s=r/this.$img.data("ratio"),o;s>=i?(o=(s-i)/2,this.options.centeredY&&(e.top="-"+o+"px")):(s=i,r=s*this.$img.data("ratio"),o=(r-n)/2,this.options.centeredX&&(e.left="-"+o+"px")),this.$wrap.css({width:n,height:i}).find("img:not(.deleteable)").css({width:r,height:s}).css(e)}catch(u){}return this},show:function(t){if(Math.abs(t)>this.images.length-1)return;this.index=t;var n=this,i=n.$wrap.find("img").addClass("deleteable"),s=e.Event("backstretch.show",{relatedTarget:n.$container[0]});return clearInterval(n.interval),n.$img=e("<img />").css(r.img).bind("load",function(t){var r=this.width||e(t.target).width(),o=this.height||e(t.target).height();e(this).data("ratio",r/o),e(this).fadeIn(n.options.speed||n.options.fade,function(){i.remove(),n.paused||n.cycle(),n.$container.trigger(s,n)}),n.resize()}).appendTo(n.$wrap),n.$img.attr("src",n.images[t]),n},next:function(){return this.show(this.index<this.images.length-1?this.index+1:0)},prev:function(){return this.show(this.index===0?this.images.length-1:this.index-1)},pause:function(){return this.paused=!0,this},resume:function(){return this.paused=!1,this.next(),this},cycle:function(){return this.images.length>1&&(clearInterval(this.interval),this.interval=setInterval(e.proxy(function(){this.paused||this.next()},this),this.options.duration)),this},destroy:function(n){e(t).off("resize.backstretch orientationchange.backstretch"),clearInterval(this.interval),n||this.$wrap.remove(),this.$container.removeData("backstretch")}};var s=function(){var e=navigator.userAgent,n=navigator.platform,r=e.match(/AppleWebKit\/([0-9]+)/),i=!!r&&r[1],s=e.match(/Fennec\/([0-9]+)/),o=!!s&&s[1],u=e.match(/Opera Mobi\/([0-9]+)/),a=!!u&&u[1],f=e.match(/MSIE ([0-9]+)/),l=!!f&&f[1];return!((n.indexOf("iPhone")>-1||n.indexOf("iPad")>-1||n.indexOf("iPod")>-1)&&i&&i<534||t.operamini&&{}.toString.call(t.operamini)==="[object OperaMini]"||u&&a<7458||e.indexOf("Android")>-1&&i&&i<533||o&&o<6||"palmGetResource"in t&&i&&i<534||e.indexOf("MeeGo")>-1&&e.indexOf("NokiaBrowser/8.5.0")>-1||l&&l<=6)}()})(jQuery,window);