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FixedScaleOffset flattens arrays, breaking further image codecs #852
Description
I've just noticed that FixedScaleOffset flattens arrays on encoding.
This is not stated in the documentation
This breaks further images encoding in the pipeline.
Minimal test to reproduce:
import numpy as np
from numcodecs import FixedScaleOffset
shape = (8, 4, 5)
x = (200.0 + np.arange(np.prod(shape), dtype=np.float32).reshape(shape) * 0.001)
fso = FixedScaleOffset(offset=200.0, scale=1000.0, dtype="<f4", astype="<u2")
# Expected (8, 4, 5)
# Actuel (160, )
print(fso.shape)
Activity
d-v-b commentedon Aug 3, 2026
that's an unfortunate bug! how are you using
FixedScaleOffset? If you are working with zarr v3 data, then there are alternatives that don't have this problem (thecast_valueandscale_offsetcodecs, which are defined here: https://github.com/zarr-developers/cast-value.py)raphaeljolivet commentedon Aug 3, 2026
Thanks, I didn't notice there were several scal/offset codec.
I am working with both zarr2 and zarr3 actually.
I will try wih this one.
I still think this should be fixed, or stated in the documentation.
Maybe an option like "keep_dimensions" would make the change backward compatible.
d-v-b commentedon Aug 3, 2026
This makes sense, i don't have time to add this but if you want to open a PR i can review it