Re: [udig-devel] transparency

[Graham Davis <gdavis@xxxxxxxxxxxxxxx>]

Thanks Simone and Adrian,

I will try converting my image to RGBA and making the background color 
transparent.  Cheers,

Graham.


Simone Giannecchini wrote:
> Ciao Graham,
> the resample operation uses the warp operation form JAI.
> The warp operation fills up gaps in the resulting raster with some
> values which can be controlled via the backgroundValues input
> parameters. The default value is 0.
> This means that as an instance if you warp an RGB image the gaps will
> be filled with balck (0,0,0).
> If you want to be able to have the gaps transparent the best thing is
> to change the color model of the input raster to RGBA so taht you'll
> the gaps automatically set to transparent black.
>
> If my memory serves me right, there is no way to set the
> backgroundValues via the Resameple operation since it does some
> automagic computation on categories to get them.
>
> Hope that helps,
> Simone.
> -------------------------------------------------------
> Ing. Simone Giannecchini
> GeoSolutions S.A.S.
> Owner - Software Engineer
> Via Carignoni 51
> 55041  Camaiore (LU)
> Italy
>
> phone: +39 0584983027
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>
> http://www.geo-solutions.it
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>
> -------------------------------------------------------
>
>
>
> On Fri, Jan 23, 2009 at 7:17 PM, Graham Davis <gdavis@xxxxxxxxxxxxxxx> wrote:
>   
> > Hi all,
> >
> > I have a question about applying a transparency to a layer or coverage.
> >  Basically I've developed a tool for geo-referencing an image onto a map and
> > warping it to match the map's CRS.  The process for warping the image is to
> > create a GridCoverage of the image from a derived CRS using a transform,
> > then use the Operations.resample() method to get the result as a warped
> > coverage.  The result is the image warped to fit the CRS of the map.  My
> > problem is that the edges of the result where it was rotated are black.
> >
> > I'm trying to figure out the best way to make these black areas transparent.
> >  Is there a setting that can achieve this when I do the actual resampling?
> >  Or do I need to apply some sort of style/setting on the resulting coverage
> > afterwards?  I don't know how to achieve either or if there is another,
> > better way.  Can someone point me in the right direction?  Thanks,
> >
> > --
> > Graham Davis
> > Refractions Research Inc.
> > gdavis@xxxxxxxxxxxxxxx
> >
> > _______________________________________________
> > User-friendly Desktop Internet GIS (uDig)
> > http://udig.refractions.net
> > http://lists.refractions.net/mailman/listinfo/udig-devel
> >
> >     


--
Graham Davis
Refractions Research Inc.
gdavis@xxxxxxxxxxxxxxx