全屏背景图片的实现
.swper{
background-image: url(./img/bg.jpg);
width:100%;
height:100%;/*父级高不为100%请使用100vh*/
zoom: 1;
background-color: #fff;
background-repeat: no-repeat;
background-size: cover;
-webkit-background-size: cover;
-o-background-size: cover;
background-position: center 0;
}