Convert your avatar to gray of black/white

Pass your avatar url as url parameter to http://goblak.herokuapp.com.

http://goblak.herokuapp.com/gray?url=http://www.gravatar.com/avatar/c814acfd2c0897d2fc20de6800b76293?s=200

http://goblak.herokuapp.com/bw?url=http://www.gravatar.com/avatar/c814acfd2c0897d2fc20de6800b76293?s=200