Update BioWriter append functionality

src/bfio/backends.py

@@ -617,7 +617,15 @@ def _init_writer(self):
             f"Image:{Path(self.frontend._file_path).name}"
         )
 
-        if self.frontend.X * self.frontend.Y * self.frontend.bpp > 2**31:
+        if (
+            self.frontend.X
+            * self.frontend.Y
+            * self.frontend.Z
+            * self.frontend.C
+            * self.frontend.T
+            * self.frontend.bpp
+            > 2**31
+        ):
             big_tiff = True
         else:
             big_tiff = False
@@ -1405,8 +1413,9 @@ def _init_writer(self):
                   In the future, it may be reasonable to not enforce read-only
 
             """
-            if self.frontend._file_path.exists():
-                shutil.rmtree(self.frontend._file_path)
+            if self.frontend.append is False:
+                if self.frontend._file_path.exists():
+                    shutil.rmtree(self.frontend._file_path)
 
             shape = (
                 self.frontend.T,
@@ -1417,39 +1426,66 @@ def _init_writer(self):
             )
 
             compressor = Blosc(cname="zstd", clevel=1, shuffle=Blosc.SHUFFLE)
-
-            self._root = zarr.group(store=str(self.frontend._file_path.resolve()))
+            mode = "w"
+            if self.frontend.append is True:
+                mode = "a"
+            self._root = zarr.open_group(
+                store=str(self.frontend._file_path.resolve()), mode=mode
+            )
 
             # Create the metadata
             metadata_path = (
                 Path(self.frontend._file_path)
                 .joinpath("OME")
                 .joinpath("METADATA.ome.xml")
             )
-            metadata_path.parent.mkdir(parents=True, exist_ok=True)
-            with open(metadata_path, "w") as fw:
-                fw.write(str(self.frontend._metadata.to_xml()))
-
-            self._root.attrs["multiscales"] = [
-                {
-                    "version": "0.1",
-                    "name": self.frontend._file_path.name,
-                    "datasets": [{"path": "0"}],
-                    "metadata": {"method": "mean"},
-                }
-            ]
 
-            writer = self._root.zeros(
-                "0",
-                shape=shape,
-                chunks=(1, 1, 1, self.frontend._TILE_SIZE, self.frontend._TILE_SIZE),
-                dtype=self.frontend.dtype,
-                compressor=compressor,
-            )
+            if self.frontend.append is False or (
+                self.frontend.append is True and metadata_path.exists() is False
+            ):
+                metadata_path.parent.mkdir(parents=True, exist_ok=True)
+                with open(metadata_path, "w") as fw:
+                    fw.write(str(self.frontend._metadata.to_xml()))
+
+                self._root.attrs["multiscales"] = [
+                    {
+                        "version": "0.1",
+                        "name": self.frontend._file_path.name,
+                        "datasets": [{"path": "0"}],
+                        "metadata": {"method": "mean"},
+                    }
+                ]
+            if (
+                self.frontend.append is True
+                and len(sorted(self._root.array_keys())) > 0
+            ):
+                writer = self._root["0"]
+            else:
+                writer = self._root.zeros(
+                    "0",
+                    shape=shape,
+                    chunks=(
+                        1,
+                        1,
+                        1,
+                        self.frontend._TILE_SIZE,
+                        self.frontend._TILE_SIZE,
+                    ),
+                    dtype=self.frontend.dtype,
+                    compressor=compressor,
+                    dimension_separator="/",
+                )
 
             # This is recommended to do for cloud storage to increase read/write
             # speed, but it also increases write speed locally when threading.
-            zarr.consolidate_metadata(str(self.frontend._file_path.resolve()))
+            consolidated_metadata_file = Path(self.frontend._file_path).joinpath(
+                ".zmetadata"
+            )
+            if self.frontend.append is False or (
+                self.frontend.append is True
+                and consolidated_metadata_file.exists() is False
+            ):
+                zarr.consolidate_metadata(str(self.frontend._file_path.resolve()))
 
             self._writer = writer
 

src/bfio/bfio.py

@@ -52,6 +52,7 @@ class BioReader(BioBase):
         "_read_only",
         "_backend",
         "level",
+        "append",
     ]
 
     def __init__(
@@ -1070,6 +1071,11 @@ class if specified. *Defaults to None.*
                     setattr(self, k, v)
 
         self.set_backend(backend)
+        self.append = False
+        if kwargs and "append" in kwargs:
+            if kwargs["append"] is True:
+                self.append = True
+
         # Ensure backend is supported
         if self._backend_name == "python":
             self._backend = backends.PythonWriter(self)

tests/test_write.py

@@ -105,6 +105,68 @@ def test_write_java(self):
             assert np.array_equal(image[:], br[:])
 
 
+class TestPythonZarrWriter(unittest.TestCase):
+
+    def test_write_zarr_append_no_file(self):
+
+        with bfio.BioReader(str(TEST_DIR.joinpath("5025551.zarr"))) as br:
+
+            actual_shape = br.shape
+            actual_dtype = br.dtype
+            actual_image = br[:]
+            actual_mdata = br.metadata
+            print(br.shape)
+        with tempfile.TemporaryDirectory() as dir:
+
+            test_file_path = os.path.join(dir, "out/test.ome.zarr")
+
+            with bfio.BioWriter(
+                test_file_path, metadata=actual_mdata, backend="zarr", append=True
+            ) as bw:
+
+                expanded = np.expand_dims(actual_image, axis=-1)
+                bw[:, :, :, :, :] = expanded[:, :, :, :, :]
+
+            with bfio.BioReader(test_file_path) as br:
+
+                assert br.shape == actual_shape
+                assert br.dtype == actual_dtype
+
+                assert br[:].sum() == actual_image.sum()
+
+    def test_write_zarr_append_file_exist(self):
+
+        with bfio.BioReader(str(TEST_DIR.joinpath("5025551.zarr"))) as br:
+
+            actual_shape = br.shape
+            actual_dtype = br.dtype
+            actual_image = br[:]
+            actual_mdata = br.metadata
+        with tempfile.TemporaryDirectory() as dir:
+
+            test_file_path = os.path.join(dir, "out/test.ome.zarr")
+
+            with bfio.BioWriter(
+                test_file_path, metadata=actual_mdata, backend="zarr"
+            ) as bw:
+
+                expanded = np.expand_dims(actual_image, axis=-1)
+                bw[:, :, :, 0:13, :] = expanded[:, :, :, 0:13, :]
+
+            with bfio.BioWriter(
+                test_file_path, metadata=actual_mdata, backend="zarr", append=True
+            ) as bw:
+
+                expanded = np.expand_dims(actual_image, axis=-1)
+                bw[:, :, :, 13:, :] = expanded[:, :, :, 13:, :]
+            with bfio.BioReader(test_file_path) as br:
+
+                assert br.shape == actual_shape
+                assert br.dtype == actual_dtype
+
+                assert br[:].sum() == actual_image.sum()
+
+
 class TestOmeZarrWriter(unittest.TestCase):
 
     def test_write_zarr_tensorstore(self):