[gdal-dev] Why COG does not support predictor=3?

[Rahkonen Jukka (MML)]

Hi,

The cloud optimized GeoTIFF generator has a creation option PREDICTOR=YES that is Boolean. Tiffinfo reveals that it means that predictor=2 is used "Predictor: horizontal differencing 2 (0x2)". However, for floating point images predictor=3 could give much better compression. In a quick test with regular GeoTIFFs the difference between predictor=2 and predictor=3 was 218 kB vs. 148 kB. The difference when using no predictor at all vs. predictor=2 was much less, only 227 kB vs. 218 kB.  Is there some special reason for dropping the predictor=3 support from COG?

-Jukka Rahkonen-


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