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

[Andreas Neumann]

done: https://trac.osgeo.org/qgis/ticket/1898

Andreas

On Wed, August 26, 2009 3:30 pm, Marco Hugentobler wrote:
> 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
>


-- 
Andreas Neumann
http://www.carto.net/neumann/
http://www.svgopen.org/