Transparency: group versus layer transparency/opacity

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Transparency: group versus layer transparency/opacity

Andreas Neumann-4
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-helps-solve-many-problems/

Maybe something to discuss at the Vienna meeting?

Should I file a feature request?

Thanks,
Andreas


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

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Re: Transparency: group versus layer transparency/opacity

Hugentobler  Marco
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
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Re: Transparency: group versus layer transparency/opacity

Andreas Neumann-4
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/

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