Usage: nbtopo filein.pgm connex <PP|P|M|MM> fileout.pgm
Description: For each point p of the input grayscale image, compute the connectivity number T++, T+, T- or T-- according to the given option (resp. PP, P, M, MM). Refs: [BEC97, CBB01].
Types supported: byte 2D, byte 3D
Category: topogray