Growth point detection

[wpbonelli]

Need to attempt to locate growth points. This would allow estimation of pitcher lengths.

Possibly useful heuristics:

• centroid of convex hull
• dark regions ringed by more or less linear features (assumes pitchers aren't bent/occluded)
• skeletonization, then find root node

It would be much easier to train a neural network for this than for pitcher segmentation, since labeling here involves only one or two point locations per image, rather than painstaking pitcher tracing. Maybe worth a shot too?