Function resample_labels_onto 

pub fn resample_labels_onto<T: Copy + PartialEq + Default>(
    labels: &[T],
    src_dims: (usize, usize, usize),
    src_affine: &[f64; 16],
    dst_dims: (usize, usize, usize),
    dst_affine: &[f64; 16],
) -> Result<Vec<T>, InputError>

Resample a label image (a segmentation, a parcellation) from one grid onto another.

Each destination voxel takes the label with the largest total trilinear weight among the eight source voxels around it: equivalently, each label’s indicator is interpolated linearly and the largest wins. Ties go to the nearest voxel’s label. Outside the source the output is T::default() (0, background).

The output only ever holds labels that are in the input. Trilinear interpolation (resample_onto) would invent values between label ids at every boundary; plain nearest neighbour does not, but on a rotated grid it takes whichever single voxel the rounding lands on, so boundaries come out staircased and a structure one or two voxels thick can be dropped or doubled depending on where the grids happen to line up. The vote moves each boundary to where the interpolated label fraction crosses one half, as a linearly interpolated mask thresholded at 0.5 would, and costs the same eight lookups as trilinear interpolation. On the identity mapping it returns the input unchanged.

Works for any label type: u8/u16/u32 ids, or integer-valued f64 as read from a NIfTI.

Errors

If labels is not src_dims in size, or the source affine is singular.