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Introduce scan_size for overlapping scans #248

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19 changes: 19 additions & 0 deletions pyresample/gradient/__init__.py
Original file line number Diff line number Diff line change
Expand Up @@ -178,15 +178,34 @@ def reshape_to_stacked_3d(array):
return np.stack(layers, axis=-1)


def _fix_overlapping_gradient(arr, scan_size=0):
arr[::scan_size] = arr[1::scan_size]
arr[scan_size - 1::scan_size] = arr[scan_size - 2::scan_size]
return arr


def parallel_gradient_search(data, src_x, src_y, dst_x, dst_y, **kwargs):
"""Run gradient search in parallel in input area coordinates."""
if data.ndim not in [2, 3]:
raise NotImplementedError('Gradient search resampling only supports 2D or 3D arrays.')
if data.ndim == 2:
data = data[np.newaxis, :, :]
# TODO: Make sure the data is uniformly chunked.
scan_size = kwargs.get('scan_size', 0)
src_gradient_xl, src_gradient_xp = np.gradient(src_x, axis=[0, 1])
src_gradient_yl, src_gradient_yp = np.gradient(src_y, axis=[0, 1])
if scan_size > 0:
new_chunks = (scan_size, src_gradient_xl.shape[1])
old_chunks = src_gradient_xl.chunks
src_gradient_xl = src_gradient_xl.rechunk(new_chunks)
src_gradient_yl = src_gradient_yl.rechunk(new_chunks)
src_gradient_xl = da.map_blocks(_fix_overlapping_gradient, src_gradient_xl,
dtype=src_gradient_xl.dtype, can_size=scan_size)
src_gradient_yl = da.map_blocks(_fix_overlapping_gradient, src_gradient_yl,
dtype=src_gradient_yl.dtype, scan_size=scan_size)
src_gradient_xl = src_gradient_xl.rechunk(old_chunks)
src_gradient_yl = src_gradient_yl.rechunk(old_chunks)

arrays = reshape_arrays_in_stacked_chunks((src_x, src_y,
src_gradient_xl, src_gradient_xp, src_gradient_yl, src_gradient_yp),
src_x.chunks)
Expand Down