移动端背景图片无法居中显示的情况

    main{
        height: calc(100vh);
        background-image: url(../assets/image/background.png) ; //图片导入
	background-size: 100% 100%;背景尺寸
        100vw;
	background-clip:content-box;  裁切背景图片 到content (border-box|padding-box|content-box)
    }