javascript - 如何垂直淡出文字，类似于亚马逊的产品描述

Question

我试图将一段文本从第一行的黑色淡化为最后一行的浅灰色。我注意到亚马逊通过他们的产品描述来做到这一点。我尝试查看 CSS 代码，但在那里看不到任何东西，我怀疑它是用 javascript 实现的。

我的问题是：我将如何在我自己的文本块上模拟类似的垂直渐变效果？

Answer 1

这是由http://www.colorzilla.com/gradient-editor/生成的完全跨浏览器的解决方案：

演示：http ://dabblet.com/gist/3511782

CSS：

#container {
    width: 400px; /*width of text box*/
    height: 200px; /*height of text box*/
    border: 2px solid black; /*it needs some kind of border to look good*/
    overflow: hidden; /*necessary to cut off text without scrollbars. alternatively you can use overflow: auto; or overflow: scroll; to show a scrollbar, but you'll have to tweak the #fader box*/
    position: relative; /*positioning so that #fader can be relative to this*/
}
#fader {
    height: 100px; /*from where it starts to fade to where it ends*/
    position: absolute; /*so it can overlap the #container*/
    width: 400px; /*has to be the same as #container*/
    margin-top: 25%; /*position it right at the bottom of the #container*/
    /* IE9 SVG, needs conditional override of 'filter' to 'none' */
    background: url(data:image/svg+xml;base64,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);
    background: -moz-linear-gradient(top,  rgba(255,255,255,0) 0%, rgba(255,255,255,1) 100%); /* FF3.6+ */
    background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,rgba(255,255,255,0)), color-stop(100%,rgba(255,255,255,1))); /* Chrome,Safari4+ */
    background: -webkit-linear-gradient(top,  rgba(255,255,255,0) 0%,rgba(255,255,255,1) 100%); /* Chrome10+,Safari5.1+ */
    background: -o-linear-gradient(top,  rgba(255,255,255,0) 0%,rgba(255,255,255,1) 100%); /* Opera 11.10+ */
    background: -ms-linear-gradient(top,  rgba(255,255,255,0) 0%,rgba(255,255,255,1) 100%); /* IE10+ */
    background: linear-gradient(to bottom,  rgba(255,255,255,0) 0%,rgba(255,255,255,1) 100%); /* W3C */
    filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#00ffffff', endColorstr='#ffffff',GradientType=0 ); /* IE6-8 */
}

HTML：

<div id="container"><div id="fader">&nbsp;</div>
Text goes here
</div>

对于 IE9 支持，您需要在head:

<!--[if gte IE 9]>
  <style type="text/css">
    .gradient {
       filter: none;
    }
  </style>
<![endif]-->

如果您想知道，亚马逊的做法非常相似： http: //pastebin.com/jkq3nbDJ

Answer 2

所以你拥有的是一个绝对定位的 div（.fade-out在我下面的例子中）淡化效果的高度，带有垂直淡入淡出的背景 png 或 css3 渐变。

HTML

<div class="description">
    <p>Text Here</p>
    <div class="fade-out"></div>
</div>

CSS

.description { 
    position: relative;
    width: 100%;
}
.fade-out {
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    z-index: 2;
    height: 30px;
    background: ...
}

Answer 3

有不同的方法可以做到这一点。例如，具有渐变背景的绝对定位的 div 或作为渐变的 png。