Hey Robin!
Coincidentally, I was just yesterday going through this paper, "Projection onto the Manifold of Elongated Structures for Accurate Extraction":
Their source code is available here:
I actually don't even know what language they used because I'm travelling and on a crappy connection, so the 65MB package is just chugging along at 33KBps. =P I presume it's C++, based on previous software from that group, but it might be easily wrappable in Cython.
I'm not aware of other options at the moment, sorry!
Juan.