Add image_like function for generic SpatialImage

Author: effigies

nibabel/__init__.py

@@ -58,6 +58,7 @@
 from .freesurfer import MGHImage
 from .funcs import (squeeze_image, concat_images, four_to_three,
                     as_closest_canonical)
+from .spatialimages import image_like
 from .orientations import (io_orientation, orientation_affine,
                            flip_axis, OrientationError,
                            apply_orientation, aff2axcodes)

nibabel/spatialimages.py

@@ -872,3 +872,11 @@ def __getitem__(self):
         raise TypeError("Cannot slice image objects; consider slicing image "
                         "array data with `img.dataobj[slice]` or "
                         "`img.get_data()[slice]`")
+
+
+def image_like(img, data):
+    ''' Create new SpatialImage with metadata of `img`, and data
+    contained in `data`.
+    '''
+    return img.__class__(data, img.affine, img.header.copy(),
+                         extra=img.extra.copy())

nibabel/tests/test_spatialimages.py

@@ -13,7 +13,7 @@
 import numpy as np
 
 from ..spatialimages import (Header, SpatialImage, HeaderDataError,
-                             ImageDataError)
+                             ImageDataError, image_like)
 
 from unittest import TestCase
 
@@ -382,3 +382,13 @@ def test_load_mmap(self):
                 # Check invalid values raise error
                 assert_raises(ValueError, func, param1, mmap='rw')
                 assert_raises(ValueError, func, param1, mmap='r+')
+
+
+def test_image_like():
+    zeros = SpatialImage(np.zeros((2, 3, 4)), np.eye(4))
+    ones = image_like(zeros, np.ones((2, 3, 4)))
+
+    assert np.all(ones.dataobj != zeros.dataobj)
+    assert np.all(ones.affine == zeros.affine)
+    assert ones.header == zeros.header
+    assert ones.extra == zeros.extra