Background-image-overlay scss.css

#bg {
  background: url("~assets/img/bg-img.jpg") no-repeat center center fixed;
  -webkit-background-size: cover;
  -moz-background-size: cover;
  -o-background-size: cover;
  background-size: cover;
  position: relative;
  background-color: grey;

  &:before {
    content: "";
    position: absolute;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;

    background-image: linear-gradient(to bottom right, #000000, #000000);
    opacity: 0.4;
  }
}