Add compressor option to rechunking

Enables using the prefered compressor when writing the new chunks.

pytools/HedwigZarrImage.py

@@ -67,13 +67,17 @@ def shape(self) -> Tuple[int]:
         """
         return self._ome_ngff_multiscale_get_array(0).shape
 
-    def rechunk(self, chunk_size: int) -> None:
+    def rechunk(self, chunk_size: int, compressor=None) -> None:
         """
         Change the chunk size of each ZARR array inplace in the pyramid.
 
         The chunk_size is applied to all spacial dimension, and other dimension (CT) are the full size.
 
         The ImageZarrImage need write access to the ZARR.
+
+        :param chunk_size: The size as an integer to resize the chunk sizes.
+        :param compressor: The output arrays will be written with the provided compressor, if None then the compressor
+         of the input arrays will be used.
         """
 
         logger.info(f'Processing group: "{self.zarr_group.name}"...')
@@ -96,13 +100,15 @@ def rechunk(self, chunk_size: int) -> None:
                 logger.info("Chunks already requested size")
                 continue
 
+            if compressor is None:
+                compressor = arr.compressor
             # copy array to a temp zarr array on file
             zarr.copy(
                 arr,
                 self.zarr_group,
                 name=arr_name + ".temp",
                 chunks=chunks,
-                compressor=arr.compressor,
+                compressor=arr.compressor if compressor is None else compressor,
                 dimension_separator=arr._dimension_separator,
                 filters=arr.filters,
                 overwrite=False,

pytools/zarr_rechunk.py

@@ -3,6 +3,7 @@
 from pathlib import Path
 from pytools import __version__
 from pytools.HedwigZarrImages import HedwigZarrImages
+from numcodecs import Blosc
 
 
 @click.command()
@@ -17,14 +18,22 @@
     type=click.IntRange(min=1),
     help="The size of zarr chunks stored in spatial dimensions.",
 )
+@click.option(
+    "--recompress",
+    is_flag=True,
+    show_default=True,
+    default=False,
+    help="Use the preferred compressor when recompressing.",
+)
 @click.version_option(__version__)
-def main(input_zarr, log_level, chunk_size):
+def main(input_zarr, log_level, chunk_size, recompress):
     logging.basicConfig(format="%(levelname)s: %(message)s", level=logging.getLevelName(log_level))
 
+    compressor = Blosc(cname="zstd", clevel=5, shuffle=Blosc.SHUFFLE)
     z = HedwigZarrImages(input_zarr, read_only=False)
 
     for k in z.get_series_keys():
-        z[k].rechunk(chunk_size)
+        z[k].rechunk(chunk_size, compressor=compressor if recompress else None)
 
 
 if __name__ == "__main__":