Merge pull request #279 from nipy/fix/finalize-270

FIX: Respect singleton 4th-D

Author: oesteban

nitransforms/resampling.py

@@ -234,6 +234,7 @@ def apply(
     if isinstance(spatialimage, (str, Path)):
         spatialimage = _nbload(str(spatialimage))
 
+    singleton_4d = spatialimage.ndim == 4 and spatialimage.shape[-1] == 1
     spatialimage = squeeze_image(spatialimage)
 
     # Avoid opening the data array just yet
@@ -370,7 +371,8 @@ def apply(
             with suppress(ValueError):
                 resampled = np.squeeze(resampled, axis=3)
 
-        moved = spatialimage.__class__(resampled, _ref.affine, hdr)
+        moved = spatialimage.__class__(
+            resampled[..., None] if singleton_4d else resampled, _ref.affine, hdr)
         return moved
 
     output_dtype = output_dtype or input_dtype

nitransforms/tests/test_resampling.py

@@ -56,8 +56,13 @@ def test_apply_singleton_time_dimension():
 
     data = np.reshape(np.arange(27, dtype=np.uint8), (3, 3, 3, 1))
     nii = nb.Nifti1Image(data, np.eye(4))
-    xfm = nitl.Affine(np.eye(4), reference=nii)
-    apply(xfm, nii)
+    ref = nb.Nifti1Image(np.zeros((4, 4, 4)), np.eye(4))
+    xfm = nitl.Affine(np.eye(4), reference=ref)
+    movednii = apply(xfm, nii)
+    assert movednii.shape == ref.shape + (1, )
+
+    movednii = apply(xfm, nii, reference=ref)
+    assert movednii.shape == ref.shape + (1, )
 
 
 @pytest.mark.parametrize(