[gdal-dev] Setting the noData flag in a GeoTIFF

[Jonathan Moules]

Hi Even,
That worked great.
It figures that I'd tried about 6 different permutations, including a few
without "-hidenodata"; but none of them was the right one it seems.

It's no problem recreating the tifs as they're small test tifs that takes a
few seconds to process.

Many thanks!
Jonathan

On 3 December 2013 16:02, Even Rouault <even.rouault at mines-paris.org> wrote:

> Selon Jonathan Moules <jonathanmoules at warwickshire.gov.uk>:
>
> > Hi List,
> >   I have a question about setting a value as "noData" in GeoTIFFs.
> >
> > I'm creating a Geotiff with this two stage process (mosaicing a lot of
> > tiles together):
> >
> > gdalbuildvrt -hidenodata -srcnodata 255 -vrtnodata 255 -input_file_list
> > >> tiff_list.txt 255.vrt
> > >
> > >
> > >> gdal_translate -of GTiff -co TILED=YES -co BIGTIFF=YES -co
> COMPRESS=JPEG
> > >>  -co JPEG_QUALITY=80 -co BLOCKXSIZE=512 -co BLOCKYSIZE=512 -co
> > >> PHOTOMETRIC=YCBCR 255.vrt 255mask.tif
> > >
> > >
> > The resultant image is fine, but when I access it, both via ArcGIS and
> QGIS
> > it says that there is no noData value set.
>
> Yes, and gdalinfo on 255mask.tif would report the same too. The reason is
> the
> "-hidenodata" flag in the gdalbuildvrt. Remove it and it should work as
> expected.
>
> You don't need to rebuild your 255mask.tif. Just try :
>
> python gdal_edit.py -a_nodata 255 255mask.tif (cf
> http://www.gdal.org/gdal_edit.html)
>
> >
> > I've tried reading into it and came across this -
> > http://www.gdal.org/frmt_gtiff.html - but it requires a deeper level of
> the
> > GeoTIFF library than I have to make much sense of it.
> >
> > I did see "GDAL_TIFF_INTERNAL_MASK" and tried to set it to true (using
> -co
> > and --config), but GDAL just complained about it not being a valid
> > configuration option.
>
> Masks are more unusual and difficult to master.
>
> >
> > Can GeoTiffs have a noData value in them that applications will see and
> > honour? If so, can I set it in GDAL?
> > It's not critically important, more nice-to-have and also trying to
> > understand the format better
> >
> > Thanks,
> > Jonathan
> >
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>

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