img-responsive class bootstrap code example
Example 1: image responsive bootstrap 4
<img class="img-fluid" src="" alt=""> //This will make your image responsive
Example 2: img class bootstrap
<!-- Circuler Image -->
<img src="cinqueterre.jpg" class="img-circle" alt="Cinque Terre">
<!-- Image With some border-raduis property -->
<img src="cinqueterre.jpg" class="img-rounded" alt="Cinque Terre">
<!-- Image like thumbnail -->
<img src="cinqueterre.jpg" class="img-thumbnail" alt="Cinque Terre">