[Qgis-developer] Transparency: group versus layer transparency/opacity

[Marco Hugentobler]

Hi Andreas

Yes, please fill a feature request.

Additionally, there could be a transparency on classification level where each 
QgsSymbol has its own transparency (OGC SLD style).

Regards,
Marco 

Am Mittwoch, 26. August 2009 09.21:33 schrieb Andreas Neumann:
> Hi QGIS developers,
>
> For QGIS 1.3 (or whatever the successor is called) I would like to discuss
> whether we can add group transparency in addition to the regular layer
> transparency.
>
> This is a concept available in SVG. The difference is that with group
> opacity/transparency, the layers in the group are rendered first
> individually (with or without opacity) and then the transparency is added
> on the intermediate rendering result of the group as a whole.
>
> The difference is clearly seen if you have layers in a group where
> polygons of different layers overlap. You don't want opacity on the
> individual layers (since this would change colors), but you want to be
> able to set the opacity on the parent group, for being able to have a
> background base map shine through.
>
> Here are two links on the topic:
> http://www.w3.org/TR/SVG/masking.html#ObjectAndGroupOpacityProperties
> and
> http://labs.trolltech.com/blogs/2009/04/23/layered-rendering-part-2-it-help
>s-solve-many-problems/
>
> Maybe something to discuss at the Vienna meeting?
>
> Should I file a feature request?
>
> Thanks,
> Andreas


-- 
Dr. Marco Hugentobler
Institute of Cartography
ETH Zurich
Technical Advisor QGIS Project Steering Committee