[gdal-dev] NODATA values in diferents bands in a DataSet

[Even Rouault]

Abel,


there is a subtelty:

a) If bands may have invalid pixels at different locations on different 
bands, and that those bands have a different nodata value, then using 
GDALRasterBand::SetNoDataValue() is the way to go.

b) If a given pixel is invalid only if its value on all bands matches 
the nodata value on each band, then NODATA_VALUES should be set instead


Example with 2 bands:

- Band 1, NoData=1,  pixel_1=1, pixel_2=1

- Band 2, NoData=2,  pixel_1=2, pixel_2=0


In interpretation a), then pixel_1 and pixel_2 are invalid for Band 1, 
and pixel_1 is invalid for Band 2

In interpretation b), then only pixel_1 is invalid (for both bands)




Le 21/05/2025 à 08:46, Abel Pau via gdal-dev a écrit :
> Hello,
> I am implementing a driver that allows different NODATA values for 
> each band in a dataset.
> >From what I understand in the documentation, I should use the 
> |NODATA_VALUES| metadata item to document these values. However, I 
> don't see a clear way to indicate that a specific band has *no 
> NODATA* value within the tuple.
> On the other hand, the documentation also suggests that 
> |NODATA_VALUES| is *not widely honoured*, which is not very encouraging.
> Therefore, would you consider it good practice to separate bands with 
> different NODATA values into separate *sub*datasets instead?
> Thank you very much for the clarification.
>
> *Abel Pau Garcia 
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