[gdal-dev] Re: several No data value

[ludovic]

Thanks Frank for these remarks.

I work on pds driver (in fact the subdriver ISIS2). I agree with you
that
"some folks would want to distinguish the various kinds of nodata
values".

And it's the reason i would like the default behaviour is "we have
various no data value"
but we can add a flag option for that we try to open a file we can
merge all no data value.

I had read the rfc15 and i will think about this

Best Regards

Ludovic


On 8 déc, 18:46, Frank Warmerdam <warmer... at pobox.com> wrote:
> I have lost track of what driver we are discussing.  It is certainly
> possible for a theory to remap various nodata values to a single one
> if that is perceived as appropriate for that driver.  However, in the
> situation you described it seems plausible that some folks would want
> to distinguish the various kinds of nodata values and that merging
> them is interfering with access to the original raster data in a way
> that might be detrimental.
>
> I hesitate to bring it up, but another option is to return a validity
> mask for the dataset derived by checking for the various nodata values.
> There is already automated support for generating validity masks from
> regular bands with single nodata values built into the core.  One
> downside to this approach (not counting complexity) is that relatively
> few applications honour the mask concept at this time.
>
>    http://trac.osgeo.org/gdal/wiki/rfc15_nodatabitmask
>
> Best regards,
> --
> ---------------------------------------+--------------------------------------
> I set the clouds in motion - turn up   | Frank Warmerdam, warmer... at pobox.com
> light and sound - activate the windows |http://pobox.com/~warmerdam
> and watch the world go round - Rush    | Geospatial Programmer for Rent
>
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