[officialpm]

Fixes #10139

• Add greyscale TIFF support for ExtraSamples 0 (unspecified) and 1 (associated alpha), for both byte orders.
• ExtraSamples 0 opens as L using the new LX raw mode, which skips the unspecified sample rather than treating it as alpha. ExtraSamples 1 opens as La; value 2 remains LA.

Tested with a source build using libtiff 4.3.0: python -m pytest Tests/test_file_tiff.py -q (87 passed, 2 skipped). Also checked the reporter's four raw/LZW TIFFs and the modes for ExtraSamples 0, 1 and 2. Ruff is clean.

[officialpm]

A note on ExtraSamples 0 (unspecified): I mapped it to LA, so the extra sample is kept as the second band. Dropping it and opening as L would need a new C raw mode, which seemed too big for this fix. ExtraSamples 1 (associated alpha) opens as La, matching how the existing entries treat it.

Thanks to @street1983nk for the sample files in #10139. They are small (324 bytes LZW, about 6 kB raw), so if you'd like them as fixtures I'm happy to add them to Tests/images and test against them. Right now the test builds the TIFF in memory and patches the tag.

[radarhere]

which seemed too big for this fix

Sounds like it would be ok to me. I've created officialpm#1 with this change.

[officialpm]

Thanks @radarhere, merged your follow-up into the branch. I rebuilt with libtiff enabled and checked all four reporter files: ExtraSamples 0 opens as L, and ExtraSamples 1 remains La. ExtraSamples 2 still opens as LA. Tests/test_file_tiff.py passes (87 passed, 2 skipped).