Fix embed storage nifti

src/datasets/features/nifti.py

@@ -10,7 +10,7 @@
 from ..download.download_config import DownloadConfig
 from ..table import array_cast
 from ..utils.file_utils import is_local_path, xopen
-from ..utils.py_utils import string_to_dict
+from ..utils.py_utils import no_op_if_value_is_null, string_to_dict
 
 
 if TYPE_CHECKING:
@@ -125,9 +125,6 @@ def decode_example(self, value: dict, token_per_repo_id=None) -> "nib.nifti1.Nif
         Returns:
             `nibabel.Nifti1Image` objects
         """
-        if not self.decode:
-            raise NotImplementedError("Decoding is disabled for this feature. Please use Nifti(decode=True) instead.")
-
         if config.NIBABEL_AVAILABLE:
             import nibabel as nib
         else:
@@ -141,6 +138,9 @@ def decode_example(self, value: dict, token_per_repo_id=None) -> "nib.nifti1.Nif
             if path is None:
                 raise ValueError(f"A nifti should have one of 'path' or 'bytes' but both are None in {value}.")
             else:
+                # gzipped files have the structure: 'gzip://T1.nii::<local_path>'
+                if path.startswith("gzip://") and is_local_path(path.split("::")[-1]):
+                    path = path.split("::")[-1]
                 if is_local_path(path):
                     nifti = nib.load(path)
                 else:
@@ -150,11 +150,10 @@ def decode_example(self, value: dict, token_per_repo_id=None) -> "nib.nifti1.Nif
                         if source_url.startswith(config.HF_ENDPOINT)
                         else config.HUB_DATASETS_HFFS_URL
                     )
-                    try:
-                        repo_id = string_to_dict(source_url, pattern)["repo_id"]
-                        token = token_per_repo_id.get(repo_id)
-                    except ValueError:
-                        token = None
+                    source_url_fields = string_to_dict(source_url, pattern)
+                    token = (
+                        token_per_repo_id.get(source_url_fields["repo_id"]) if source_url_fields is not None else None
+                    )
                     download_config = DownloadConfig(token=token)
                     with xopen(path, "rb", download_config=download_config) as f:
                         nifti = nib.load(f)
@@ -172,6 +171,46 @@ def decode_example(self, value: dict, token_per_repo_id=None) -> "nib.nifti1.Nif
 
         return nifti
 
+    def embed_storage(self, storage: pa.StructArray, token_per_repo_id=None) -> pa.StructArray:
+        """Embed NifTI files into the Arrow array.
+
+        Args:
+            storage (`pa.StructArray`):
+                PyArrow array to embed.
+
+        Returns:
+            `pa.StructArray`: Array in the NifTI arrow storage type, that is
+                `pa.struct({"bytes": pa.binary(), "path": pa.string()})`.
+        """
+        if token_per_repo_id is None:
+            token_per_repo_id = {}
+
+        @no_op_if_value_is_null
+        def path_to_bytes(path):
+            source_url = path.split("::")[-1]
+            pattern = (
+                config.HUB_DATASETS_URL if source_url.startswith(config.HF_ENDPOINT) else config.HUB_DATASETS_HFFS_URL
+            )
+            source_url_fields = string_to_dict(source_url, pattern)
+            token = token_per_repo_id.get(source_url_fields["repo_id"]) if source_url_fields is not None else None
+            download_config = DownloadConfig(token=token)
+            with xopen(path, "rb", download_config=download_config) as f:
+                return f.read()
+
+        bytes_array = pa.array(
+            [
+                (path_to_bytes(x["path"]) if x["bytes"] is None else x["bytes"]) if x is not None else None
+                for x in storage.to_pylist()
+            ],
+            type=pa.binary(),
+        )
+        path_array = pa.array(
+            [os.path.basename(path) if path is not None else None for path in storage.field("path").to_pylist()],
+            type=pa.string(),
+        )
+        storage = pa.StructArray.from_arrays([bytes_array, path_array], ["bytes", "path"], mask=bytes_array.is_null())
+        return array_cast(storage, self.pa_type)
+
     def flatten(self) -> Union["FeatureType", Dict[str, "FeatureType"]]:
         """If in the decodable state, return the feature itself, otherwise flatten the feature into a dictionary."""
         from .features import Value

tests/features/test_nifti.py

@@ -2,9 +2,10 @@
 
 from pathlib import Path
 
+import pyarrow as pa
 import pytest
 
-from datasets import Dataset, Features, Nifti
+from datasets import Dataset, Features, Nifti, load_dataset
 from src.datasets.features.nifti import encode_nibabel_image
 
 from ..utils import require_nibabel
@@ -89,3 +90,41 @@ def test_encode_nibabel_image(shared_datadir):
     assert isinstance(encoded_example_bytes, dict)
     assert encoded_example_bytes["bytes"] is not None and encoded_example_bytes["path"] is None
     # this cannot be converted back from bytes (yet)
+
+
+@require_nibabel
+def test_embed_storage(shared_datadir):
+    from io import BytesIO
+
+    import nibabel as nib
+
+    nifti_path = str(shared_datadir / "test_nifti.nii")
+    img = nib.load(nifti_path)
+    nifti = Nifti()
+
+    bytes_array = pa.array([None], type=pa.binary())
+    path_array = pa.array([nifti_path], type=pa.string())
+    storage = pa.StructArray.from_arrays([bytes_array, path_array], ["bytes", "path"])
+
+    embedded_storage = nifti.embed_storage(storage)
+
+    embedded_bytes = embedded_storage[0]["bytes"].as_py()
+
+    bio = BytesIO(embedded_bytes)
+    fh = nib.FileHolder(fileobj=bio)
+    nifti_img = nib.Nifti1Image.from_file_map({"header": fh, "image": fh})
+
+    assert embedded_bytes is not None
+    assert nifti_img.header == img.header
+    assert (nifti_img.affine == img.affine).all()
+    assert (nifti_img.get_fdata() == img.get_fdata()).all()
+
+
+@require_nibabel
+def test_load_zipped_file_locally(shared_datadir):
+    import nibabel as nib
+
+    nifti_path = str(shared_datadir / "test_nifti.nii.gz")
+
+    ds = load_dataset("niftifolder", data_files=nifti_path)
+    assert isinstance(ds["train"][0]["nifti"], nib.nifti1.Nifti1Image)