You stated you want circular crops from recangles. This may not be able to be done with the 3 popular bootstrap classes (img-rounded; img-circle; img-polaroid)
You may want to write a custom CSS class using border-radius where you have more control. If you want it more circular just increase the radius.
.CattoBorderRadius_x000D_
{_x000D_
border-radius: 25px;_x000D_
}
_x000D_
<img class="img-responsive CattoBorderRadius" src="http://placekitten.com/g/200/200" />
_x000D_
Fiddle URL: http://jsfiddle.net/ccatto/LyxEb/
I know this may not be the perfect radius but I think your answer will use a custom css class. Hope this helps.