css实现图片垂直居中

1、行高 == 高度：已知图片的高宽

<div style="text-align: center;  500px;height:200px; line-height:200px; border: green solid 1px;">
   <img alt="" src="https://www.baidu.com/img/baidu_jgylogo3.gif" style="display: inline-block; vertical-align: middle;" />
</div>

2、display:table display:table-cell：不兼容IE6/IE7

<div style="text-align: center;  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>

3、绝对定位：已知图片的高宽

<div style=" 500px;height:200px; position: relative; border: green solid 1px;">
    <img alt="" src="https://www.baidu.com/img/baidu_jgylogo3.gif" style=" 120px; height: 40px;position: absolute; left:50%; top: 50%; margin-left: -60px;margin-top: -20px;" />
</div>

4、flex布局：h5端可用

<style type="text/css">
    .ui-flex {
        display: -webkit-box !important;
        display: -webkit-flex !important;
        display: -ms-flexbox !important;
        display: flex !important;
        -webkit-flex-wrap: wrap;
        -ms-flex-wrap: wrap;
        flex-wrap: wrap
    }

    .ui-flex, .ui-flex *, .ui-flex :after, .ui-flex :before {
        box-sizing: border-box
    }

    .ui-flex.justify-center {
        -webkit-box-pack: center;
        -webkit-justify-content: center;
        -ms-flex-pack: center;
        justify-content: center
    }
    .ui-flex.center {
        -webkit-box-pack: center;
        -webkit-justify-content: center;
        -ms-flex-pack: center;
        justify-content: center;
        -webkit-box-align: center;
        -webkit-align-items: center;
        -ms-flex-align: center;
        align-items: center
    }
</style>

<div class="ui-flex justify-center center" style="border: green solid 1px;  500px; height: 200px;">
    <div class="cell">
    <img alt="" src="https://www.baidu.com/img/baidu_jgylogo3.gif" style="" />
    </div>
</div>