.frame {
  height: 400px; /*can be anything*/
  width: 400px; /*can be anything*/
  display: inline-block;
  vertical-align: top; /*not required*/
  border: 10px solid white; /*not required*/
  position: relative;
}

.image {
  max-height: 100%;
  max-width: 100%;
  width: auto;
  height: auto;
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
  margin: auto;
}

/* everything below is not required */
.frame span {
  font-family: arial, sans-serif;
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  text-align: center;
  color: white;
  background: rgba(0,0,0,0.4);
  font-size: 12px;
}