Images
Documentation and examples for opting images into responsive behavior (so they never become larger than their parent elements) and add lightweight styles to them—all via classes.
Responsive images
Images in Bootstrap are made responsive with .img-fluid. This applies max-width: 100%; and height: auto; to the image so that it scales with the parent element.
<img src="..." class="img-fluid" alt="...">Image thumbnails
In addition to our border-radius utilities, you can use .img-thumbnail to give an image a rounded 1px border appearance.
<img src="..." class="img-thumbnail" alt="...">Aligning images
Align images with the helper float classes or text alignment classes. block-level images can be centered using the .mx-auto margin utility class.
<img src="..." class="rounded float-start" alt="...">
<img src="..." class="rounded float-end" alt="..."><img src="..." class="rounded mx-auto d-block" alt="..."><div class="text-center">
<img src="..." class="rounded" alt="...">
</div>Picture
If you are using the <picture> element to specify multiple <source> elements for a specific <img>, make sure to add the .img-* classes to the <img> and not to the <picture> tag.
?<picture>
<source srcset="..." type="image/svg+xml">
<img src="..." class="img-fluid img-thumbnail" alt="...">
</picture>
Sass
Variables
Variables are available for image thumbnails.
$thumbnail-padding: .25rem;
$thumbnail-bg: $body-bg;
$thumbnail-border-width: $border-width;
$thumbnail-border-color: $gray-300;
$thumbnail-border-radius: $border-radius;
$thumbnail-box-shadow: $box-shadow-sm;