Add optional data parameter to from_image, call from_image from image_like

Author: effigies

nibabel/spatialimages.py

@@ -847,7 +847,7 @@ def instance_to_filename(klass, img, filename):
         img.to_filename(filename)
 
     @classmethod
-    def from_image(klass, img):
+    def from_image(klass, img, data=None):
         ''' Class method to create new instance of own class from `img`
 
         Parameters
@@ -861,7 +861,7 @@ def from_image(klass, img):
         cimg : ``spatialimage`` instance
            Image, of our own class
         '''
-        return klass(img.dataobj,
+        return klass(img.dataobj if data is None else data,
                      img.affine,
                      klass.header_class.from_header(img.header),
                      extra=img.extra.copy())
@@ -878,5 +878,4 @@ 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())
+    return img.from_image(img, data)