OPT: smaller offset to crop around sc segmentations to adjust for small images (like the testing data)
OPT: smaller offset to crop around sc segmentations to adjust for small images (like the testing data)

Former-commit-id: fc55db016fa73874d8f74c2858d5d55e2827f6f1
Former-commit-id: 3401d383008631e331e91e89214fb9d31ce8dda8
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox