OPT: now allow different size of input and output
OPT: now allow different size of input and output

Former-commit-id: e88e229e7adb6cd8c1bcf126ff3b74b4e517b098
Former-commit-id: 6ed736937a302eb8cce496237e22d448e6b740b9
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox