OPT: changed centreline to middle vertical line of the image
OPT: changed centreline to middle vertical line of the image

Former-commit-id: b7459deec9973f64404b4bea65d8305828d5362f [formerly 8c8633207fd1d615a8ea2b60e177f98d2010ddef]
Former-commit-id: 57eab3233195e06925b1957ac3cb2236e722ff0e
Former-commit-id: 4aa3b9d8092541cbd056ba67804026cd50da4b14
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox