[udig-devel] strange problems with png8 image format

Andrea Aime aaime at opengeo.org
Tue May 18 23:55:27 PDT 2010

Frank Gasdorf ha scritto:
> Well, I just created new pictures with the missing parameter 
> *transparency=true* and the returned pictures of these requests are 
> different. The "ugly" labels using the image format png8 are generated 
> from geoserver. My fault :(

Labels use antialising heavily, when we do color reduction to 256 colors
that will suffer inevitably, especially with transparent output.
There is nothing easy that can be done for that unfortunately,
we'd need a color reduction algorithm that supports alpha in the
palette, something that an open source project, pngnq, does, but
it's not trivial at all to port over.

I'd estimate it would take 3-5 days of work for a developer
that knows _very_ well its way in the raster data manipulation
algorithms and will probably result in a 2-10 times slowdown
compared to the current color reduction algorithm


Andrea Aime
OpenGeo - http://opengeo.org
Expert service straight from the developers.

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