css keep aspect ratio image

1img {
2    display: block;
3    max-width: 100%;
4    max-height: 100%;
5    width: auto;
6    height: auto;
7}

1img {
2  object-fit: cover;
3  width: 100px;
4  height:100px;
5}

1/* Simply add width without height,
2aspect ratio will be maintained 
3and height will be calculated accordingly*/
4
5img {
6  width: 100px;
7}

1.image-full {
2    background: url(...some image...) no-repeat;
3    background-size: cover;
4    background-position: center center;
5}
6

1Don't set height AND width. Use one or the other and the correct aspect ratio will be maintained.