<div class="box"> <img src="img/2222.jpg" /> </div>
.box {
position: relative;
width: 100%;
height: 0;
padding-bottom: 100%;
}
.box img {
position: absolute;
top: 0;
left: 0;
width: 100%;
height: 100%;
}
原文：https://www.cnblogs.com/qqing/p/9066608.html