//方式一
#container{
position:relative;
}
#center{
position:absolute;
width:100px;
height:100px;
top:50%;
left:50%;
transform: translate(-50%,-50%);
//margin:-50% 0 0 -50%
}
//方式二
#container{
display:flex;
justify-content:center;
align-items:center;
}
//方式三
#container{
text-align: center;
width: 500px;
height:200px;
ine-height:200px;
}
#center{
display: inline-block;
vertical-align: middle;
}
//方式四 //使用display:table实现(不兼容ie6/7)
<div style="text-align: center; width: 500px;height:200px; display: table;border: green solid 1px;">
<span style="display: table-cell; vertical-align: middle; ">
<img alt="" src="https://www.baidu.com/img/baidu_jgylogo3.gif" style="display: inline- block;" />
</span>
</div>
//方式五 任意父级高度的垂直居中,自适应居中(也可以用伪元素替代span标签)
<div style="height:200px;text-align:center;">
<img src="../../images/zhuyin.png" alt="" style="vertical:middle">
<span style="display:inline-block;height:100%;vertical-align:middle;font-size:0;"></span>
</div>