[Qgis-user] NoData in RGB Imagery

[Johannes Kröger (WhereGroup)]

Hey Richard,

do you have different NODATA pixels between the three bands (R, G, B) or 
is it the same? If there are no differences then you can use an 
additional channel as mask. I would suggest you store your imagery in 
GeoTIFF with an "internal mask". Even posted a nice example of this in 
https://lists.osgeo.org/pipermail/gdal-dev/2014-August/039907.html
If your format supports RGBA (e.g. PNG), then that would be another way 
to achieve this but a nice GeoTIFF should be the best solution.


Cheers, Hannes

Am 13.01.22 um 18:35 schrieb Richard McDonnell:
>
> Hi all,
>
> I have a general GIS query and am hoping I can get some insight from 
> the community.
>
> It relates to how we deal with pixels with no data in RGB Imagery. It 
> seems to be typical to produce RGB imagery as 8bit with pixel values 
> between 0 and 255, with either 0 or 255 being used as the NoDATA 
> value. To me this is problematic, as there can be valid pixels within 
> your image with 0 or 255. To me the solution is to use 16bit Imagery 
> and to assign the NoDATA value to any value outside of the 0 – 255 range.
>
> I know in DEM’s its usual to use -9999 as your NoDATA value but my 
> question is, Is there a standardised way to deal with NoDATA in RGB?
>
> I welcome any comments and suggestions.
>
> Regards & Thanks in advance,
>
>
> Richard.
>
>
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