宽度自适应情况下图片等比缩放，超出部分裁切

<div class="banner" style="background-image: url('./img/apply-avatar.png')"></div>

scss代码：

.banner {
    width: 100%;
    height: 0;
    @include px2rem(padding-bottom, 440px);
    overflow: hidden;
    background-position: center center;
    background-repeat: no-repeat;
    -webkit-background-size: cover;
    -moz-background-size: cover;
    background-size: cover;
  }