<div class="el"></div>
* {
  box-sizing: border-box;
}
body {
  margin: 0;
  background: linear-gradient(to right, red, blue);
  background-position-x: 0;
  animation: size 3s infinite linear;
}
@keyframes size {
  to {
    background-position-x: 100vw;
  }
}

.el {
  width: 100vw;
  height: 100vh;
  padding: 1rem;

  background-image: url(https://images.unsplash.com/photo-1528287942171-fbe365d1d9ac?ixlib=rb-1.2.1&q=85&fm=jpg&crop=entropy&w=1200&cs=srgb&ixid=eyJhcHBfaWQiOjE0NTg5fQ);
  background-size: cover;
  background-position: center;

  mask-image: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/3/chris-mask.png);
  mask-size: contain;
}

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