Hi Ivan, > > Since the SetNoDataValue and GetNodataValue is based on the limitation of > GeoTiff I would not expect DeleteNoDataValue to be any different. For > example, there is no way to set/get NoData for individuals bands, there is > no way to set/get an array of NoData values or NoData value ranges.
More than one nodata value is perhaps better modelled with a nodata mask. > For > drivers that support such thinks, the DeleteNoDataValue will probably > delete all NoData values from the dataset. Yes, it will for GeoTIFF. > > But that is something that can't be resolved by the RFC 58. I think. That's indeed an orthogonal issue. There's nothing in the absolute that would prevent from having a per-band nodata value in GeoTIFF. But currently the TIFF GDAL_NODATA tag is only documented to contain one value. Perhaps a new tag should be created for per-band nodata values. With the caveat that per-band nodata isn't always clearly defined: is it really per-band or is the unique combination (nodata1, nodata2, .... nodataN) the nodata value... ( the later is the semantics of the special NODATA_VALUES metadata item. See http://www.gdal.org/gdal_datamodel.html ) > > Very often, I find unsigned 8 bit images with absurd NoData value, like > -9999. That is probably a software specific flag value. The problem is > that in gdal_translate there is no option to prevent that NoData to be > passed from one format to another. So I am about to implement a value > range check on the CreateCopy to avoid that. > > Would that be feasible to accept the option "-a_nodata NO" on GDAL command > lines, to indicate that NoData should not pass from the input to the > output dataset? Perhaps you're looking for this ;-) ? <dt> <b>-a_nodata</b> <i>value</i>:</dt><dd> Assign a specified nodata value to output bands. Starting with GDAL 1.8.0, can be set to <i>none</i> to avoid setting a nodata value to the output file if one exists for the source file. Note that, if the input dataset has a nodata value, this does not cause pixel values that are equal to that nodata value to be changed to the value specified with this option.</dd> Even -- Spatialys - Geospatial professional services http://www.spatialys.com _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
