How does Basecamp crop uploaded user images into a circle?

Question

Does 37signals manipulate the image on the server side? Or do they use javascript to center and crop the user's image on the client-side?

Answer 1

It's happening client side with the border-radius CSS rules (in a todo's comment section):

img.avatar {
  -webkit-border-radius: 100px;
  -moz-border-radius: 100px;
  border-radius: 100px;
}