[gdal-dev] Extracting Subsampled Mask Band from VRT Returning 1st Band Rather Than Mask Band

[Even Rouault]

On mercredi 15 mai 2019 11:17:57 CET Patrick Young wrote:
> Hi all,
> 
> I'm experiencing some strange behavior when extracting a mask band using
> gdal_translate from a VRT vs the source GTiff at a reduced resolution.  I
> have a 3 band, 8 bit JPEG compressed (YCbCR) RGB geotiff with an internal
> no data mask and with internal overviews.  Making a VRT of this and running
> 
> gdal_translate -b mask in.vrt mask.tif
> 
> 
> Returns the expected no data mask.
> 
> However, if I add in "-outsize 10% 0", I instead get the first band back as
> the mask tif rather than the mask band.  Any -outsize setting has the same
> effect.
> 
> Repeating this with the source geotiff rather than the vrt works as
> expected.

For the record, the above issue has been fixed per
https://github.com/OSGeo/gdal/pull/2018

> Interestingly, running
> 
> gdalinfo -oo OVERVIEW_LEVEL=1 in.vrt
> 
> reports no mask flags set at all (they are reported without the -oo
> option), but running on the original geotiff rather than the vrt does
> report the mask flags.
> 

And this point about -oo OVERVIEW_LEVEL is addressed per
https://github.com/OSGeo/gdal/pull/2021

Even

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