ENH: Add dtype argument to Cifti2Image

nibabel/analyze.py

@@ -1020,13 +1020,24 @@ def to_file_map(self, file_map=None, dtype=None):
         inter = hdr['scl_inter'].item() if hdr.has_data_intercept else np.nan
         # Check whether to calculate slope / inter
         scale_me = np.all(np.isnan((slope, inter)))
-        if scale_me:
-            arr_writer = make_array_writer(data,
-                                           out_dtype,
-                                           hdr.has_data_slope,
-                                           hdr.has_data_intercept)
-        else:
-            arr_writer = ArrayWriter(data, out_dtype, check_scaling=False)
+        try:
+            if scale_me:
+                arr_writer = make_array_writer(data,
+                                               out_dtype,
+                                               hdr.has_data_slope,
+                                               hdr.has_data_intercept)
+            else:
+                arr_writer = ArrayWriter(data, out_dtype, check_scaling=False)
+        except WriterError:
+            # Restore any changed consumable values, in case caller catches
+            # Should match cleanup at the end of the method
+            hdr.set_data_offset(offset)
+            hdr.set_data_dtype(data_dtype)
+            if hdr.has_data_slope:
+                hdr['scl_slope'] = slope
+            if hdr.has_data_intercept:
+                hdr['scl_inter'] = inter
+            raise
         hdr_fh, img_fh = self._get_fileholders(file_map)
         # Check if hdr and img refer to same file; this can happen with odd
         # analyze images but most often this is because it's a single nifti

nibabel/cifti2/cifti2.py

@@ -19,14 +19,18 @@
 import re
 from collections.abc import MutableSequence, MutableMapping, Iterable
 from collections import OrderedDict
+from warnings import warn
+
+import numpy as np
+
 from .. import xmlutils as xml
 from ..filebasedimages import FileBasedHeader, SerializableImage
 from ..dataobj_images import DataobjImage
 from ..nifti1 import Nifti1Extensions
 from ..nifti2 import Nifti2Image, Nifti2Header
 from ..arrayproxy import reshape_dataobj
 from ..caret import CaretMetaData
-from warnings import warn
+from ..volumeutils import make_dt_codes
 
 
 def _float_01(val):
@@ -41,6 +45,22 @@ class Cifti2HeaderError(Exception):
     """
 
 
+_dtdefs = (  # code, label, dtype definition, niistring
+    (2, 'uint8', np.uint8, "NIFTI_TYPE_UINT8"),
+    (4, 'int16', np.int16, "NIFTI_TYPE_INT16"),
+    (8, 'int32', np.int32, "NIFTI_TYPE_INT32"),
+    (16, 'float32', np.float32, "NIFTI_TYPE_FLOAT32"),
+    (64, 'float64', np.float64, "NIFTI_TYPE_FLOAT64"),
+    (256, 'int8', np.int8, "NIFTI_TYPE_INT8"),
+    (512, 'uint16', np.uint16, "NIFTI_TYPE_UINT16"),
+    (768, 'uint32', np.uint32, "NIFTI_TYPE_UINT32"),
+    (1024, 'int64', np.int64, "NIFTI_TYPE_INT64"),
+    (1280, 'uint64', np.uint64, "NIFTI_TYPE_UINT64"),
+)
+
+# Make full code alias bank, including dtype column
+data_type_codes = make_dt_codes(_dtdefs)
+
 CIFTI_MAP_TYPES = ('CIFTI_INDEX_TYPE_BRAIN_MODELS',
                    'CIFTI_INDEX_TYPE_PARCELS',
                    'CIFTI_INDEX_TYPE_SERIES',
@@ -103,6 +123,10 @@ def _underscore(string):
     return re.sub(r'([a-z0-9])([A-Z])', r'\1_\2', string).lower()
 
 
+class LimitedNifti2Header(Nifti2Header):
+    _data_type_codes = data_type_codes
+
+
 class Cifti2MetaData(CaretMetaData):
     """ A list of name-value pairs
 
@@ -1363,7 +1387,8 @@ def __init__(self,
                  header=None,
                  nifti_header=None,
                  extra=None,
-                 file_map=None):
+                 file_map=None,
+                 dtype=None):
         """ Initialize image
 
         The image is a combination of (dataobj, header), with optional metadata
@@ -1392,12 +1417,13 @@ def __init__(self,
             header = Cifti2Header.from_axes(header)
         super(Cifti2Image, self).__init__(dataobj, header=header,
                                           extra=extra, file_map=file_map)
-        self._nifti_header = Nifti2Header.from_header(nifti_header)
+        self._nifti_header = LimitedNifti2Header.from_header(nifti_header)
 
         # if NIfTI header not specified, get data type from input array
-        if nifti_header is None:
-            if hasattr(dataobj, 'dtype'):
-                self._nifti_header.set_data_dtype(dataobj.dtype)
+        if dtype is not None:
+            self.set_data_dtype(dtype)
+        elif nifti_header is None and hasattr(dataobj, 'dtype'):
+            self.set_data_dtype(dataobj.dtype)
         self.update_headers()
 
         if self._dataobj.shape != self.header.matrix.get_data_shape():

nibabel/cifti2/tests/test_cifti2.py

@@ -12,7 +12,7 @@
 import pytest
 
 from nibabel.tests.test_dataobj_images import TestDataobjAPI as _TDA
-from nibabel.tests.test_image_api import SerializeMixin
+from nibabel.tests.test_image_api import SerializeMixin, DtypeOverrideMixin
 
 
 def compare_xml_leaf(str1, str2):
@@ -415,7 +415,7 @@ def test_underscoring():
         assert ci.cifti2._underscore(camel) == underscored
 
 
-class TestCifti2ImageAPI(_TDA, SerializeMixin):
+class TestCifti2ImageAPI(_TDA, SerializeMixin, DtypeOverrideMixin):
     """ Basic validation for Cifti2Image instances
     """
     # A callable returning an image from ``image_maker(data, header)``
@@ -426,6 +426,8 @@ class TestCifti2ImageAPI(_TDA, SerializeMixin):
     ni_header_maker = Nifti2Header
     example_shapes = ((2,), (2, 3), (2, 3, 4))
     standard_extension = '.nii'
+    storable_dtypes = (np.int8, np.uint8, np.int16, np.uint16, np.int32, np.uint32,
+                       np.int64, np.uint64, np.float32, np.float64)
 
     def make_imaker(self, arr, header=None, ni_header=None):
         for idx, sz in enumerate(arr.shape):

nibabel/tests/test_image_api.py

@@ -55,6 +55,8 @@
 from .test_parrec import EXAMPLE_IMAGES as PARREC_EXAMPLE_IMAGES
 from .test_brikhead import EXAMPLE_IMAGES as AFNI_EXAMPLE_IMAGES
 
+from nibabel.arraywriters import WriterError
+
 
 def maybe_deprecated(meth_name):
     return pytest.deprecated_call() if meth_name == 'get_data' else nullcontext()
@@ -181,7 +183,7 @@ def validate_get_data_deprecated(self, imaker, params):
         assert_array_equal(np.asanyarray(img.dataobj), data)
 
 
-class GetSetDtypeMixin(object):
+class GetSetDtypeMixin:
     """ Adds dtype tests
 
     Add this one if your image has ``get_data_dtype`` and ``set_data_dtype``.
@@ -666,6 +668,46 @@ def prox_imaker():
             yield make_prox_imaker(arr.copy(), aff, hdr), params
 
 
+class DtypeOverrideMixin(GetSetDtypeMixin):
+    """ Test images that can accept ``dtype`` arguments to ``__init__`` and
+    ``to_file_map``
+    """
+
+    def validate_init_dtype_override(self, imaker, params):
+        img = imaker()
+        klass = img.__class__
+        for dtype in self.storable_dtypes:
+            if hasattr(img, 'affine'):
+                new_img = klass(img.dataobj, img.affine, header=img.header, dtype=dtype)
+            else:  # XXX This is for CIFTI-2, these validators might need refactoring
+                new_img = klass(img.dataobj, header=img.header, dtype=dtype)
+            assert new_img.get_data_dtype() == dtype
+
+            if self.has_scaling and self.can_save:
+                with np.errstate(invalid='ignore'):
+                    rt_img = bytesio_round_trip(new_img)
+                assert rt_img.get_data_dtype() == dtype
+
+    def validate_to_file_dtype_override(self, imaker, params):
+        if not self.can_save:
+            raise unittest.SkipTest
+        img = imaker()
+        orig_dtype = img.get_data_dtype()
+        fname = 'image' + self.standard_extension
+        with InTemporaryDirectory():
+            for dtype in self.storable_dtypes:
+                try:
+                    img.to_filename(fname, dtype=dtype)
+                except WriterError:
+                    # It's possible to try to save to a dtype that requires
+                    # scaling, and images without scale factors will fail.
+                    # We're not testing that here.
+                    continue
+                rt_img = img.__class__.from_filename(fname)
+                assert rt_img.get_data_dtype() == dtype
+                assert img.get_data_dtype() == orig_dtype
+
+
 class ImageHeaderAPI(MakeImageAPI):
     """ When ``self.image_maker`` is an image class, make header from class
     """
@@ -674,7 +716,12 @@ def header_maker(self):
         return self.image_maker.header_class()
 
 
-class TestAnalyzeAPI(ImageHeaderAPI):
+class TestSpatialImageAPI(ImageHeaderAPI):
+    klass = image_maker = SpatialImage
+    can_save = False
+
+
+class TestAnalyzeAPI(TestSpatialImageAPI, DtypeOverrideMixin):
     """ General image validation API instantiated for Analyze images
     """
     klass = image_maker = AnalyzeImage
@@ -685,11 +732,6 @@ class TestAnalyzeAPI(ImageHeaderAPI):
     storable_dtypes = (np.uint8, np.int16, np.int32, np.float32, np.float64)
 
 
-class TestSpatialImageAPI(TestAnalyzeAPI):
-    klass = image_maker = SpatialImage
-    can_save = False
-
-
 class TestSpm99AnalyzeAPI(TestAnalyzeAPI):
     # SPM-type analyze need scipy for mat file IO
     klass = image_maker = Spm99AnalyzeImage