OPT: correct binarization
OPT: correct binarization

Former-commit-id: 6febcf3cd6a3714c9500a55cae70c7caa09fccd4
Former-commit-id: a3b6ca1d5913cb08ca084c24b203d9f8bc5e5c0f
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox