Apply TIFF Orientation tag (274) on read#1521
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brendancol wants to merge 1 commit intoxarray-contrib:mainfrom
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Apply TIFF Orientation tag (274) on read#1521brendancol wants to merge 1 commit intoxarray-contrib:mainfrom
brendancol wants to merge 1 commit intoxarray-contrib:mainfrom
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The reader was ignoring tag 274 and returning the file's stored pixel order regardless of which corner the data was meant to start from. Files written with orientation 2-8 came back as silently flipped or rotated arrays. Parse the tag in `IFD.orientation` (default 1 = top-left, no transform) and apply the TIFF 6.0 spec table after decode in `_apply_orientation`. Orientations 5-8 swap rows and columns, so the GeoTransform's pixel_width and pixel_height swap too -- coords end up with the right size on each axis after the remap. A windowed read on a non-default orientation has ambiguous semantics (does the window refer to file pixels or display pixels?), so the combination raises ValueError rather than silently picking one. Tests cover all eight orientations against a manually-computed expected output, the dim-swap for 5-8, default-tag behaviour, and the window combination raising. tifffile's `imread` does not itself apply the tag, so the comparison target is computed from the source array; that's the only reliable way to verify the spec without depending on a second oriented decoder.
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Closes #1503.
The reader was ignoring tag 274. Files written with orientation 2-8 came back as silently flipped or rotated arrays. Pixel values were correct, geometry was wrong.
What changed
_header.py: parse tag 274 asIFD.orientation(default 1)._reader.py:_apply_orientationremaps the decoded array per the TIFF 6.0 table. For orientations 5-8 the row and column axes swap, so the GeoTransform'spixel_widthandpixel_heightswap too, keeping y/x coord shapes consistent with the displayed array._reader.py: a windowed read with non-default orientation raises ValueError. The semantics of "window in file pixels vs. display pixels" are ambiguous and supporting it is its own design call.Tests
23 new tests in
tests/test_orientation.py:imreaddoes not itself apply the tag, so the comparison target is computed from the source array).window=+ non-default orientation raises ValueError;window=+ orientation 1 still works.Test plan
pytest xrspatial/geotiff/tests/test_orientation.py(23 passed)pytest xrspatial/geotiff/tests/(713 passed, 4 skipped, 3 pre-existing matplotlib palette failures unrelated)