ie8下背景图片平铺问题

IE9+及其他浏览器实现背景图片平铺可能需要一个属性就可以background-size:100%/cover;

但是ie8下background-size是不兼容的，因此我们需要用到滤镜，来解决背景图片拉伸问题。

仅需如下代码：

filter: progid:DXImageTransform.Microsoft.AlphaImageLoader(
src='../img/news/news-banner.png',
sizingMethod='scale');
-ms-filter: progid:DXImageTransform.Microsoft.AlphaImageLoader(
src='../img/news/news-banner.png',
sizingMethod='scale');

eg:

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width,initial-scale=1,user-scalable=no">
  <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />
  <meta name="renderer" content="webkit" />
  <title>投影仪－新闻中心</title>
  <style type="text/css">
  *{margin: 0;padding: 0;}
    .news-banner{
        width:100%;
        height:225px;
        background-position:50%;
        background-size:cover;
        background-repeat: no-repeat;
        background-image:url(news-banner.png);
        filter: progid:DXImageTransform.Microsoft.AlphaImageLoader(
        src='news-banner.png',
        sizingMethod='scale');
        -ms-filter: progid:DXImageTransform.Microsoft.AlphaImageLoader(
        src='news-banner.png',
        sizingMethod='scale');
    }
  </style>
</head>
<body>
  <div class="news-banner">
  </div>
</body>
</html>