javascript – 滚动时导致滞后的大背景图像

我正在构建的网站有4个大的背景图像,占用了用户浏览器的整个高度和宽度.它们被实现为CSS背景div.问题是,当在较大的屏幕尺寸上滚动时,它非常滞后且不连贯.当用户按下按钮时,这些图像之间的滚动是通过 JavaScript自动完成的,所以这是我网站核心功能的一部分,我必须找到一种方法来防止延迟.

到目前为止,我已经尝试通过JS预加载图像并将图像从PNG转换为JPEG(增加压缩并降低质量)服务器端.这些都没有奏效.

图像的最小高度可以是630像素.如何在部分之间滚动时防止延迟？

这是我的代码：

CSS：

body { height: 100%; margin: 0px; font-family: HelveticaNeue,Helvetica,Arial,sans-serif; }

 .area { height: 630px; border: 0px solid red; background: repeat-x; margin-bottom: 0px; }

 a { text-decoration: none; }
 h1,h2,h3,h4,h5,h6 { font-family: Av,sans-serif; color: #292E37; font-weight: lighter; }

 #top { position: fixed; width: 100%; height: 10%; background: #292E37; box-shadow: inset 0px -1px 5px #000; z-index: 1000; }
 #navigation { float: right; height: 100%; }
 #bottom { width: 100%; position: fixed; bottom: 0px; padding: 10px; background: #292E37; box-shadow: inset 0px 1px 5px #000; text-shadow: 0px 1px 0px #000; color: #fff; }
 #sceneSelection { top: 20%; position: fixed; padding: 10px; }
 #info { margin-top: 50px; margin-bottom: 50px; }
 .box { margin-top: 50px; padding: 75px; background: #292E37; box-shadow: inset 0px 1px 5px #000; text-shadow: 0px 1px 0px #000; color: #fff; }

 .nav { position: relative; top: 38%; height: 100%; margin-right: 35px; display: inline-block;  color: #fff; text-shadow: 0px 1px #000; }
 .nav:hover { color: #EA5555; }

 .nimage { float: left; width: 16px; height: 16px; position: relative; top: 5%; left: -20%; }
 .home { background: url(site_images/icons/nav/home.png); }
 .pricing { background: url(site_images/icons/nav/pricing.png); }
 .features { background: url(site_images/icons/nav/features.png); }
 .blog { background: url(site_images/icons/nav/blog.png); }
 .contact { background: url(site_images/icons/nav/contact.png); }
 .about { background: url(site_images/icons/nav/us.png); }

 .logo { font-size: 2em; text-shadow: 0px 1px #000; padding-top: 10px;  padding-left: 15px; color: #EA5555; font-family: Av,sans-serif; }
 .red { color: #EA5555; }
 .white { color: #fff; text-shadow: 0px 1px 0px #000; font-weight: bold; }
 .dark { color: #202020; }

 .center { text-align: center; }
 .left { text-align: left; }
 .right { text-align: right; }

 .larger { font-size: 1.25em; }


 .buttoni { -webkit-border-radius: 2px; -moz-border-radius: 0px; border-radius: 4px; background: #ddd; display: block; color: #ccc; font-size: 14pt; height: 50px; text-align: right; margin: 10px; cursor: pointer; color: #505050; }
 .buttoni:hover { background: #EA5555; color: #fff; }

 .btext { padding: 15px; position: relative; top: 25%; }

 .groundi { background: url(ground_button.png); }
 .skyi { background: url(sky_button.png); }
 .stratospherei { background: url(stratosphere_button.png); }
 .spacei { background: url(space_button.png); }

 .image { height: 50px; width: 50px; float: left; border-top-left-radius: 5px; border-bottom-left-radius: 5px; }

 li { color: #EA5555; }
 li span { color: #505050; }

HTML：

<div class="space area" id="a4">

  </div>
  <div class="stratosphere area" id="a3">

  </div>
  <div class="sky area" id="a2">

  </div>
  <div class="ground area" id="a1">

  </div>

JavaScript的：

function scroll_to(id,speed,margin) {
         $('html,body').animate({
           scrollTop: $('#' + id).offset().top - margin
         },speed);
       }

function match_height() {
         var heights = [11,630,693,756,819,882,945,1008,1071,1134,1197,1260,1323,1386,1449,1512,1575,1638,1701,1764,1827,1890,1953,2016,2079,2142,2205,2268,2331,2394,2457,2520];

           var browsery = $(window).height();


           var i = 0;

           while(browsery > heights[i]) {
             i++;
           }

           var h = heights[i];

           $(".area").css("height",h + "px");
           $(".area").css("width","100%");

           $(".ground").css("background","url(scenes/ground/" + h + ".png)");

           $(".sky").css("background","url(scenes/sky/" + h + ".png)");
           $(".stratosphere").css("background","url(scenes/stratosphere/" + h + ".png)");

           $(".space").css("background","url(scenes/space/" + h + ".png)");


       }

       match_height();

       var pos = 0;

       $(".buttoni").click(function() {
         var id = $(this).attr("id");

         if(pos != id) {
           scroll_to("a" + id,2000,0);
         }

         pos = id;
       });

function getScrollerSelector() {
    var $body = $("<body/>");
    $body.scrollTop(1);
    return $body.scrollTop() == 1 ? "body" : "html";
}

.scrolldown.scrollto-a2 #a1,.scrolldown.scrollto-a3 #a1,.scrolldown.scrollto-a3 #a2,.scrolldown.scrollfrom-a3 #a4,.scrolldown.scrollfrom-a2 #a4,.scrolldown.scrollfrom-a2 #a3,.scrollup.scrollto-a3 #a4,.scrollup.scrollto-a2 #a4,.scrollup.scrollto-a2 #a3,.scrollup.scrollfrom-a2 #a1,.scrollup.scrollfrom-a3 #a1,.scrollup.scrollfrom-a3 #a2
    { background: none; }

function scroll_to(id,margin) {
    var currentScrollTop = window.pageYOffset || document.documentElement.scrollTop || document.body.scrollTop;
    var scrollTop = $('#' + id).offset().top - margin;
    var direction = scrollTop > currentScrollTop ? "down" : "up";
    $("body").addClass("scroll"+direction + " scrollto-"+id + " scrollfrom-"+getScrollFrom(direction));
    $( scrollerSelector ).animate({
             scrollTop: scrollTop
        },{
             //easing: 'linear',duration: speed,complete: function() {
                 $("body").removeClass("scrollup scrolldown scrollto-a1 scrollto-a2 scrollto-a3 scrollto-a4 scrollfrom-a1 scrollfrom-a2 scrollfrom-a3 scrollfrom-a4");                     
             }
         }
     );
}