[gdal-dev] Debugging mask copy issues when using Band interleaved COGs

[Even Rouault]

Owen,

Please create a ticket about that.

Even
Le 13/02/2025 à 04:40, Owen Glofcheski via gdal-dev a écrit :
> Hey all,
>
> I work with Kurt Schwehr, and we've been debugging failures where an 
> explicit mask isn't preserved through a CreateCopy operation to create 
> a COG through the GTiff driver at HEAD.
>
> This failure only started occurring after 
> https://github.com/OSGeo/gdal/commit/3bdc81a205bad8342688873e4ed5716f1208e8f5.
>
> After the CreateCopy, when we read back the mask, the mask is expanded 
> from the 1-bit mask to the 8-bit mask inside of gtiffoddbitsband.h. 
> However, the mask is not a 1-bit mask when I add logging here; 
> instead, it's the original 8-bit mask (with 255s and 0s). So when it 
> gets expanded to 8-bits, it's no longer the original mask:
> E.g., 255 0 255 255 becomes 255 255 ... 255 255 0 0 ... 0 0 255 255 ...
>
> So my guess is that somewhere along the line we either copy the mask 
> without turning it back into a bitmask, or we lose metadata tracking 
> that the mask is encoded a certain way.
>
> Does anything obvious jump out to folks here? The issue *does not* 
> occur when either COPY_SRC_OVERVIEWS="YES" is removed or INTERLEAVE is 
> set to PIXEL (it only fails on band interleaving).
>
> Here's a gist containing an example test that fails at head but 
> previously succeeded: 
> https://gist.github.com/orglofch/40cf4d9136978b0384141cc74d1039b6.
>
> Thanks,
> Owen
>
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