javascript - 大背景图像导致滚动时滞后

Question

我正在构建的网站有 4 个大背景图像，它们占据了用户浏览器的整个高度和宽度。它们作为 CSS 背景 div 实现。问题是，在较大的屏幕尺寸上滚动时，它非常滞后和不稳定。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，因此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。这些都不起作用。

图像的最小高度可以是 630 像素。在各部分之间滚动时如何防止延迟？

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, Helvetica, Arial, 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, Helvetica, Arial, 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:

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;
       });

Answer 1

OP,

对于支持 3d 变换的浏览器，例如:-webkit-transform，您可以尝试以下操作:

your.div { -webkit-transform: translate3d(0,0,1px); }

可能看起来不太像，但执行上述操作会导致相关的 div 进行硬件加速。

如果您遇到任何闪烁问题(已知它们在某些情况下会出现)，以下内容应该可以解决您的问题:

your.div { 
    -webkit-transform: translate3d(0,0,1px); 
    -webkit-backface-visibility: hidden;
}

通过大卫沃尔什 - http://davidwalsh.name/translate3d

The use of translate3d pushes CSS animations into hardware acceleration. Even if you're looking to do a basic 2d translation, use translate3d for more power! If your animation is still flickering after switching to the transform above, you can use a few little-known CSS properties to try to fix the problem

希望对您有所帮助。