img.background-index {
  width: 100%;
  height: 100%;
  position: relative;
  display: block;
  object-fit: cover;
  object-position: 30% center;
}

div.background-index {
    height: 50vh;
    overflow: hidden;
    top: 0;
    left: 0;
    animation-name: OU;
    animation-duration: 0.9s;
}