像微信朋友圈一样，添加图片的时候，等比例正方形显示在列表中，如何让图片根据宽高来自适应显示在页面上呢？示例如下：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width,user-scalable=no,target-densitydpi=device-dpi" />
<style type="text/css">
.figure-list{
margin: 0;
padding: 0;
}
.figure-list:after{
content: "";
display: block;
clear: both;
height: 0;
overflow: hidden;
visibility: hidden;
}
.figure-list li{
list-style: none;
float: left;
width: 23.5%;
margin: 0 2% 2% 0;
}
.figure-list figure{
border: 1px solid #000;
position: relative;
width: 100%;
height: 0;
overflow: hidden;
margin: 0;
padding-bottom: 100%; /* 关键就在这里 */
background-position: center;
background-repeat: no-repeat;
background-size: cover;
}
.figure-list figure a{
display: block;
position: absolute;
width: 100%;
top: 0;
bottom: 0;
}
</style>
<ul class="figure-list">
<li>
<figure style="background-image:url(1.png)">
<a href="#"></a>
</figure>
</li>
<li>
<figure style="background-image:url(2.png)">
<a href="#"></a>
</figure>
</li>
<li>
<figure style="background-image:url(3.png)">
<a href="#"></a>
</figure>
</li>
<li>
<figure style="background-image:url(4.png)">
<a href="#"></a>
</figure>
</li>
<li>
<figure style="background-image:url(5.png)">
<a href="#"></a>
</figure>
</li>
<li>
<figure style="background-image:url(6.png)">
<a href="#"></a>
</figure>
</li>
</ul>
</html>