RF: trying to use output_dtype

matthew-brett · matthew-brett · commit b157b8f6e603 · 2012-06-09T20:36:57.000-07:00
diff --git a/nipy/io/files.py b/nipy/io/files.py
@@ -51,15 +51,15 @@ def load(filename):
     return nifti2nipy(ni_img)
 
 
-def save(img, filename, io_dtype=None):
+def save(img, filename, dtype_from='data'):
     """Write the image to a file.
 
     Parameters
     ----------
     img : An `Image` object
     filename : string
         Should be a valid filename.
-    io_dtype : None or dtype specifier, optional
+    dtype_from : {'data', 'header'} or dtype specifier, optional
         dtype to save data to disk.  Set into header before save as hint for
         output format to chose dtype to save to. Not every format supports every
         dtype, so some values of this parameter will raise errors.  The default
@@ -127,11 +127,17 @@ def save(img, filename, io_dtype=None):
         saver = nib.spm2analyze.save
     else:
         raise ValueError('Cannot save file type "%s"' % ftype)
+    dtype_from_str = isinstance(dtype_from, basestring)
+    if dtype_from_str and dtype_from == 'header':
+        saver(ni_img, filename)
+        return img
     # Set output dtype if possible
     hdr = ni_img.get_header()
-    # Set io dtype if possible
-    if not io_dtype is None:
-        hdr.set_data_dtype(io_dtype)
+    if dtype_from_str and dtype_from == 'data':
+        io_dtype = img.get_data().dtype
+    else:
+        io_dtype = dtype_from
+    hdr.set_data_dtype(io_dtype)
     # make new image
     saver(ni_img, filename)
     return img
diff --git a/nipy/io/tests/test_image_io.py b/nipy/io/tests/test_image_io.py
@@ -84,12 +84,12 @@ def randimg_in2out(rng, in_dtype, out_dtype, name):
     data = data.astype(in_dtype)
     img = Image(data, AfT('kji', 'zxy', np.eye(4)))
     # The io_dtype won't be visible until the image is loaded
-    newimg = save_image(img, name, io_dtype=out_dtype)
+    newimg = save_image(img, name, dtype_from=out_dtype)
     return newimg.get_data(), data
 
 
 def test_scaling_io_dtype():
-    # Does io_dtype get set?
+    # Does data dtype get set?
     # Is scaling correctly applied?
     rng = np.random.RandomState(19660520) # VBD
     ulp1_f32 = np.finfo(np.float32).eps
@@ -125,6 +125,11 @@ def test_scaling_io_dtype():
         del img
 
 
+def test_from_data():
+    # Default data dtype comes from data
+    pass
+
+
 def test_header_roundtrip():
     img = load_image(anatfile)
     hdr = img.metadata['header']
