Fix resample interpolation coordinate mapping (#1202)#1204
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brendancol merged 1 commit intomasterfrom Apr 15, 2026
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The interpolation path used scipy.ndimage.zoom's edge-aligned formula which maps output pixel o to input pixel o*(N_in-1)/(N_out-1). This pinned the first output pixel to the first input pixel and the last to the last, creating a systematic half-pixel spatial shift vs. the block-centered output coordinate metadata. Switch all four backend paths (numpy, cupy, dask+numpy, dask+cupy) to use map_coordinates with the block-centered formula: input_pixel = (out_pixel + 0.5) * (N_in / N_out) - 0.5 This brings the interpolation path into alignment with both the aggregation path and the output coordinate labels.
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Summary
resample()usedscipy.ndimage.zoom's edge-aligned coordinate formula, which doesn'tmatch the block-centered output coordinates produced by
_new_coords.This caused a systematic half-pixel spatial shift at the raster edges.
scipy.ndimage.zoomwithmap_coordinatesusing theblock-centered formula
(o + 0.5) * (N_in / N_out) - 0.5across allfour backend paths (numpy, cupy, dask+numpy, dask+cupy).
the output coordinate labels.
Closes #1202
Test plan