Responsive images
Images in Bootstrap are made responsive with .img-fluid. max-width: 100%; and height: auto; are applied to the image so that it scales with the parent element.
<img src="..." class="img-fluid" alt="Responsive image">SVG images and IE 10
In Internet Explorer 10, SVG images with .img-fluid are disproportionately sized. To fix this, add width: 100% \9; where necessary. This fix improperly sizes other image formats, so Bootstrap doesn’t apply it automatically.
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="..." alt="..." class="img-thumbnail">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-left" alt="...">
<img src="..." class="rounded float-right" 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>