.loading_bg{
    position: fixed;
    top:0;
    left:0;
    width:100%;
    height:100%;
    z-index: 9999;
    background: rgba(0,0,0,0.4);
}
.loading_bg img{
    width: 50px;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
}