[gdal-dev] gdaladdo problems with compression

[Even Rouault]

Le lundi 14 septembre 2015 11:46:45, Stefan Ziegler a écrit :
> Hi
> 
> we are facing problems with the compression of the overviews we are adding
> with gdaladdo. The filesize does not differ whether we are using
> compression parameters or not. The filesize of the input raster is approx.
> 100 mb. The following both commands resulting in an identical filesize of
> approx. 140mb.
> 
> gdaladdo -r average  591252_12_5cm.tif 2 4 8 16 32
> 
> gdaladdo -r average --config COMPRESS_OVERVIEW JPEG --config
> PHOTOMETRIC_OVERVIEW YCBCR --config INTERLEAVE_OVERVIEW PIXEL
> 591252_12_5cm.tif 2 4 8 16 32

Stefan,

The config options are only used for external overviews (-ro flag). For internal 
overviews, the same compression scheme as the full resolution image is used. 
In theory they could also use a different compression scheme, but this isn't 
currently implemented.

Even

> 
> The input raster is tiled and compressed with deflate (and predictor=2)
> 
> I would expect that the latter one would be smaller. Did we misunderstand
> something? Or do we use the parameters the wrong way?
> 
> GDAL 1.11.2 and dev.
> 
> regards
> Stefan

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