Anti-aliased Euclidean distance transform
http://webstaff.itn.liu.se/~stegu/edtaa/

Copyright (C) 2009 Stefan Gustavson (stefan.gustavson@gmail.com)

This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 3 of the License, or (at your
option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

The GNU General Public License is available on <http://www.gnu.org/licenses/>.