Apply suggestions from code review

Co-authored-by: Chris Markiewicz <[email protected]>

Author: oesteban

niworkflows/utils/images.py

@@ -7,7 +7,7 @@ def rotation2canonical(img):
     """Calculate the rotation w.r.t. cardinal axes of input image."""
     img = nb.as_closest_canonical(img)
     newaff = np.diag(img.header.get_zooms()[:3])
-    r = newaff @ np.linalg.inv(img.affine[:3, :3])
+    r = newaff @ np.linalg.pinv(img.affine[:3, :3])
     if np.allclose(r, np.eye(3)):
         return None
     return r
@@ -20,8 +20,7 @@ def rotate_affine(img, rot=None):
 
     img = nb.as_closest_canonical(img)
     affine = np.eye(4)
-    affine[:3, :3] = rot @ img.affine[:3, :3]
-    affine[:3, 3] = rot @ img.affine[:3, 3]
+    affine[:3] = rot @ img.affine[:3]
     return img.__class__(img.dataobj, affine, img.header)