Fig. 4.

Schematic showing how the ordering process works. (A) An example image showing the pixelated binary skeleton. (B) The initial “disordered” trace in which coordinates are listed in ascending order based on the x-coordinate. Note how this trace does not follow the contours of the molecule. (C) The ordered trace that now follows the direction of the underlying molecule. (D) Diagrammatic representation of the angular search algorithm used to select the next point in the trace when multiple candidates are available. The point P_i is the reference point, and the reference angle is calculated using the vector between points P_i-4 and P_i. To distinguish between the candidate points, P_j, P_k and P_l, the angle between each candidate point and the reference point P_i-4 is calculated. The candidate point with the vector angle most similar to that between P_i and P_i-4 is accepted as the next point in the trace.