Use background-size: cover; to cover the entire element, while maintaining the aspect ratio:
.background-1,
.background-2,
.background-3 {
/* Set the background image, size, and position. */
background-image: url('//via.placeholder.com/350x150');
background-size: cover;
background-position: center;
/* Or, use the background shortcut. */
background: url('//via.placeholder.com/350x150') center/cover;
margin: 20px;
border: 1px solid rgba(0, 0, 0, 0.3);
}
.background-1 {
width: 300px;
height: 200px;
}
.background-2 {
width: 200px;
height: 50px;
}
.background-3 {
width: 100px;
height: 200px;
}
<div class="background-1"></div>
<div class="background-2"></div>
<div class="background-3"></div>
If you want to display the entire image, while maintaining the aspect ratio, use background-size: contain; instead:
.background-1,
.background-2,
.background-3 {
/* Set the background image, size, position, repeat, and color. */
background-image: url('//via.placeholder.com/350x150');
background-size: contain;
background-position: center;
background-repeat: no-repeat;
background-color: #fbfbfb;
/* Or, use the background shortcut. */
background: #fbfbfb url('//via.placeholder.com/350x150') no-repeat center/contain;
margin: 20px;
border: 1px solid rgba(0, 0, 0, 0.3);
}
.background-1 {
width: 300px;
height: 200px;
}
.background-2 {
width: 200px;
height: 50px;
}
.background-3 {
width: 100px;
height: 200px;
}
<div class="background-1"></div>
<div class="background-2"></div>
<div class="background-3"></div>