[mapguide-users] transparency and gdal again

[Frank Warmerdam]

robert fritz wrote:
> Hello,
> 
> I have looked up the mailing list archive but I did not find a sufficient
> answer to these questions:
> 
> 1) I have 2 colored black-white raster images (Geotiff, Group 4 Fax
> Encoding) and tried to set the background color to "transparent" or
> "backgroundcolor of the map window" in MapGuide Studio, but the images are
> still shown not transparent. Do I something wrong or does the GDAL driver
> not support transparency up to now? (GDAL works very fine in Mapserver -
> transparency and performance).

Robert,

How do you do this?  I don't see anything obvious about transparency in
the generic data connection dialog, or the layer dialog.  Certainly I am
not aware of any way that such information would be translated back to the
actual raster provider.

> 2) There is no functionality (in Studio) to set transparency for a color in
> multi-color images (as in Mapserver)? Do I have to create transparency using
> PhotoShop or something else?

The fdo gdal based raster provider can communicate a nodata value up to
MapGuide, though I don't know if this is utilized for anything.  Also the
data provider can return alpha transparency if requested.  So you could
preprocess your data into an RGBA image on disk and set the alpha appropriately
to get transparency through to MapGuide.

Hopefully the mapguide folks will have a comment on how this is supposed to
work.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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and watch the world go round - Rush    | President OSGeo, http://osgeo.org