Use mask as alpha when reprojecting a masked array #3156
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The tests of this PR are now only run for GDAL 3.8+ because the outputs are too variable.
| crs=src_crs, | ||
| copy=True) | ||
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| if hasattr(source, "mask"): |
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we have twice the if hasattr(source, "mask") test, could those block be merged together?
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@vincentsarago except that the first block needs to run before the input is reshaped and the second block needs to run after the input is reshaped. It's a bit gross, but I'm inclined to let it go for now.
vincentsarago
approved these changes
Aug 30, 2024
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Background:
reproject()can take an array and return an array. GDAL's warper requires input and output GDALDatasetH, so we construct them using the GDAL "MEM" driver, pointing at the memory location of two arrays.What this PR does is add alpha bands to those datasets when the inputs and outputs are masked arrays. For input, 3-D array masks are reduced to a 2-D array via
logical_or()(because GDAL needs a single alpha mask channel). For output, the alpha mask band is repeated over the number of image bands.I suspect the approach could be made more efficient. Copying is required in some cases because the "MEM" driver needs a precise memory layout.
Resolves #2575.