Untitled

<div><img src="http://placehold.it/250x150" alt=""></div>

<div><img src="http://placehold.it/150x250" alt=""></div>

div {

  width: 100px;

  height: 100px;

  background-color: red;

  margin-bottom: 40px;

  line-height: 100px;

  text-align: center;

}

img {

  max-width: 100%;

  max-height: 100%;

  vertical-align: middle;

}