Skip mask IFDs when resolving overview_level (#1504)#1518
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brendancol wants to merge 1 commit intoxarray-contrib:mainfrom
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Skip mask IFDs when resolving overview_level (#1504)#1518brendancol wants to merge 1 commit intoxarray-contrib:mainfrom
brendancol wants to merge 1 commit intoxarray-contrib:mainfrom
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open_geotiff(path, overview_level=N) was indexing the IFD list directly. When a TIFF puts a transparency-mask IFD (NewSubfileType bit 2) between the full-res IFD and the overviews, as some GDAL COGs do, overview_level=1 returned the 1-bit mask instead of the first overview. The reader now filters out IFDs whose NewSubfileType has bit 2 set before indexing, matching what GDAL and rasterio do. Out-of-range overview_level raises ValueError with the actual count of non-mask IFDs (and any masks) instead of silently clamping to the last IFD. - IFD.subfile_type and IFD.is_mask properties on parsed IFDs - select_overview_ifd helper in _header.py - routed the four overview_level call sites (CPU read, COG-over-HTTP, GPU read, _read_geo_info) through the helper
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Closes #1504.
open_geotiff(path, overview_level=N)was indexing the IFD list directly. When a TIFF puts a transparency-mask IFD (NewSubfileType bit 2) between the full-res IFD and the overviews, as some GDAL COGs do,overview_level=1returned the 1-bit mask instead of the first overview.The reader now filters out IFDs whose NewSubfileType has bit 2 set before indexing, matching what GDAL and rasterio do. An out-of-range
overview_levelraisesValueErrorwith the actual count of non-mask IFDs (and any mask IFDs present), instead of silently clamping to the last IFD.Changes:
IFD.subfile_typeandIFD.is_maskproperties on the parsed IFDselect_overview_ifdhelper in_header.pyoverview_levelcall sites (local CPU read, COG-over-HTTP, GPU read,_read_geo_info) through the helperTests in
xrspatial/geotiff/tests/test_overview_filter.pywrite a 3-IFD TIFF with a mask wedged between the full-res IFD and an overview, then check thatopen_geotiff(..., overview_level=1)returns the overview rather than the mask. The ValueError path and a normal 4-IFD COG (no masks) are covered too.