css 背景图片自适应全屏

自适应屏幕大小，撑满全屏（图片宽高比会随屏幕宽高比变化）不随着滚动条滚动

.bg{background: url("~@/assets/images/主背景.png");position:fixed;top: 0;left: 0;width:100%;height:100%;min-width: 1000px;z-index:-10;zoom: 1;background-color: #fff;background-repeat: no-repeat;background-size: cover;-webkit-background-size: cover;-o-background-size: cover;background-position: center 0;}