css图片等比列放大

<style>
.cli{
width: 400px;
height: 400px;
overflow: hidden;
position: relative; }
.cli img{
position: absolute;
margin: auto;
min-height: 100%;
min-width: 100%;
left: -100%;
right: -100%;
top: -100%;
bottom: -100%;
}
</style>

<div  class="cli" style="background: green;">
<img src="images/11.jpg">
</div>