/* components/My_bg/index.wxss */
.box-bg-image {
    position: fixed;
    width: 100vw;
    height: 100vh;
    top: 0;
    left: 0;
    z-index: -9999;
}

.box-bg-image>image {
    width: 100%;
    height: 100%;
    z-index: -9999;
}