enh: return radians unless degrees=True

Author: oesteban

nibabel/affines.py

@@ -299,7 +299,7 @@ def voxel_sizes(affine):
     return np.sqrt(np.sum(top_left ** 2, axis=0))
 
 
-def obliquity(affine):
+def obliquity(affine, degrees=False):
     r"""
     Estimate the obliquity an affine's axes represent, in degrees from plumb.
 
@@ -309,4 +309,7 @@ def obliquity(affine):
     """
     vs = voxel_sizes(affine)
     fig_merit = (affine[:-1, :-1] / vs[np.newaxis, ...]).max(axis=1).min()
-    return abs(acos(fig_merit) * 180 / PI)
+    radians = abs(acos(fig_merit))
+    if not degrees:
+        return radians
+    return radians * 180 / PI

nibabel/tests/test_affines.py

@@ -187,4 +187,4 @@ def test_obliquity():
     R = from_matvec(euler2mat(x=0.09, y=0.001, z=0.001), [0.0, 0.0, 0.0])
     oblique = R.dot(aligned)
     assert_almost_equal(obliquity(aligned), 0.0)
-    assert_almost_equal(obliquity(oblique), 5.1569948883)
+    assert_almost_equal(obliquity(oblique, degrees=True), 5.1569948883)