How to fit the image inside the bootstrap div?

I am using the div like below

<div class="col-sm-6 col-md-6 col-lg-4">
<img src="images/dummy_image.png" class="img-responsive">
</div>

User will upload any kind of image. So i need to fit the image inside the div it means i need to cover the full div using image..I am using bootstrap please advise.