[Qgis-developer] No data value in raster transparency list

[Marco Hugentobler]

Hi Radim

I don't have a strong opinion about wether to show nodata value in 
transparency list in the GUI or not. After all, the renderer sees only 
the transparency list and does not care which of them is the nodata 
value (except for the decision if the renderer is using transparency or 
not).

If you think it is a big useability plus to hide that from the user, 
that's ok for me.

>we have to add support for it in GUI (set color)
>and renderers. Currently there is no such support.

There is. If you e.g. have -9999 as nodata value and configure 
singleband pseudocolor renderer to render this as red, you can do it in 
the dialog.

>There are other standard ways to highlight nodata:
>- set background color
>- set nodata pixels to a different value (r.null) and assign a color to it

Yes, but it is less convenient. But nodata analysis does not happen to 
often for me, so I could live with a workaround.

Regards,
Marco

Am 23.08.2012 13:59, schrieb Radim Blazek:
> On Thu, Aug 23, 2012 at 8:15 AM, Marco Hugentobler
> <marco.hugentobler at sourcepole.ch> wrote:
>> Hi Radim
>>
>> Nodata should be rendered transparent in most cases. But it could also be
>> possible you want to render it differently. E.g. the interpolation plugin
>> writes nodata value in case it encounters numerical problems. Then it is
>> useful to have the nodata values coloured to see where problems happened.
> There are other standard ways to highlight nodata:
> - set background color
> - set nodata pixels to a different value (r.null) and assign a color to it
>
> If you and other users insist that it should be possible to render
> nodata with a color, we have to add support for it in GUI (set color)
> and renderers. Currently there is no such support.
>
> Radim
>
>> Maybe there are other use cases as well.
>>
>> Regards,
>> Marco
>>
>> Am 22.08.2012 17:49, schrieb Radim Blazek:
>>> Hi,
>>> does anybody know why raster no data value is automatically added to
>>> transparency list in properties dialog? It makes no sense IMO. No data
>>> values are always rendered as transparent, no need to define them also
>>> in transparent list.
>>>
>>> Radim
>>> _______________________________________________
>>> Qgis-developer mailing list
>>> Qgis-developer at lists.osgeo.org
>>> http://lists.osgeo.org/mailman/listinfo/qgis-developer
>>
>>
>> --
>> Dr. Marco Hugentobler
>> Sourcepole -  Linux & Open Source Solutions
>> Weberstrasse 5, CH-8004 Zürich, Switzerland
>> marco.hugentobler at sourcepole.ch http://www.sourcepole.ch
>> Technical Advisor QGIS Project Steering Committee
>>
>>
>> _______________________________________________
>> Qgis-developer mailing list
>> Qgis-developer at lists.osgeo.org
>> http://lists.osgeo.org/mailman/listinfo/qgis-developer


-- 
Dr. Marco Hugentobler
Sourcepole -  Linux & Open Source Solutions
Weberstrasse 5, CH-8004 Zürich, Switzerland
marco.hugentobler at sourcepole.ch http://www.sourcepole.ch
Technical Advisor QGIS Project Steering Committee