pub fn ras_axes(affine: &[f64; 16]) -> [usize; 3]Expand description
Which volume axis each of R, A, S runs along — lab2im’s get_ras_axes.
Returns [axis_of_R, axis_of_A, axis_of_S]. A degenerate affine that maps two world axes
onto the same volume axis is repaired by reassigning the last duplicate to whichever volume
axis is otherwise unused, so the result is always a permutation.