I’m working for a customer to create a Bootstrap 3 theme from scratch, since I’ve to create a kind of portfolio-like page with some thumbnails I needed to apply the Bootstrap’s CSS class
img-thumbnail to all the images.
It took some time but the action is possible and take few steps, it assume that you are using a custom image style type to display your image(s):
1. In your
template.php file you need to define a new override function like this: