img垂直居中div - css样式

参考： https://www.jianshu.com/p/f1b570eabe33

html:

<div class="showImg" style="text-align:center"><img src="xxx" /></div>

css:

        .showImg img {
            max-width:100%;
            overflow:auto;
            margin:auto;
            position:absolute;
            top:0;
            left:0;
            bottom:0;
            right:0;
        }