<div class="picture">
  <img src="https://loremflickr.com/640/480/building" alt="building" width="640" height="480">
  </div>

				* {
					box-sizing: border-box;
				}
				html, body {
					margin: 0;
					padding: 0;
				}
				.picture {
					height: 100vh;
					outline: red dotted 1px;
				}
				.picture img {
					object-fit: contain;
					height: 100%;
					width: 100%;
				}