[Qgis-developer] Re: Raster providers

[G. Allegri]

> What about an approach where the out-of-bound values are assigned the last
> value only if reprojection is used (and if the layer does not have a null
> value)?

My two cents, from a user perspective.
We're facing this dilemma with Geotools, where reprojected color mapped
rasters (thorugh SLD) result with borders having the lower color from the
SLD rastersymbolizer. This is a big problem for many users, and we have to
reproject the raster before serving it.
It would be very important to be able to manage nodata values for
out-of-border pixels, to be able to manage transparency and avoid those ugly
borders...

giovanni

2011/1/18 Marco Hugentobler <marco.hugentobler at sourcepole.ch>

> > Agreed, int to double conversion could be optimal.
>
> oops, that should be 'Agreed, int to double conversion could be
> problematic'
>
> Am Dienstag, 18. Januar 2011, um 09.19:23 schrieb Marco Hugentobler:
> > > I thought that if data type of the source is integer the provider
> > > could represent them as floating point. Byte can be represented as
> > > integer. Bad solution however.
> >
> > Agreed, int to double conversion could be optimal.
> >
>
> >
> > This would be quite similar to your current approach, except that people
> > will have the appropriate raster appearance if they don't use reproj. And
> > if they do, they have an undesired border, but still the right colors in
> > the raster area.
> >
> > Regards,
> > Marco
> >
> > Am Montag, 17. Januar 2011, um 17.34:22 schrieb Radim Blazek:
> > > On Mon, Jan 17, 2011 at 10:06 AM, Marco Hugentobler
> > > <marco.hugentobler at sourcepole.ch> > Using NaN sounds like a good idea
> > > and Qt has platform independent support for
> > >
> > > > it (qIsNan & co.).
> > > > All other solutions I can think of seem to be more complicated (e.g.
> > > > force a transparency value only if raster is reprojected).
> > > >
> > > >>float + NaN for byte/int?
> > > >>
> > > > This is not clear to me. Could you explain your approach for
> byte/int?
> > >
> > > I thought that if data type of the source is integer the provider
> > > could represent them as floating point. Byte can be represented as
> > > integer. Bad solution however.
> > >
> > > Radim
>
>
> --
> Dr. Marco Hugentobler
> Sourcepole -  Linux & Open Source Solutions
> Churerstrasse 22, CH-8808 Pfäffikon SZ, Switzerland
> marco.hugentobler at sourcepole.ch http://www.sourcepole.ch
> Technical Advisor QGIS Project Steering Committee
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