[Qgis-developer] Adding blending modes for labels, to have 'transparenting' labels?

[Richard Duivenvoorde]

On 01-10-16 11:57, Nyall Dawson wrote:

>> OR is the usecase a custom blending mode (we are wondering then how the
>> dutch cadastre and the swiss topo are doing this... because it is NOT
>> part of esri apparently too....).
> 
> It's not a blending mode - it's a technique called "variable depth
> buffers" or "smart halos".
> 
> - ArcGIS offers it, but requires precreation of a raster layer (see
> https://blogs.esri.com/esri/arcgis/2011/11/28/variable-depth-masking-contour-label-example/).
> - It can be done in Mapnik - see http://mapnik.org/news/smart-halos
> 
> Hugo has been looking into this for QGIS - see
> https://github.com/qgis/QGIS-Enhancement-Proposals/issues/63

Yep, that is exactly where we are talking about (looking at the
pictures)....

Though the Mapnik example is different: these have buffer/halo's on
every color.

I think the subtle difference is, is that it is NOT a clipping of the
whole 'buffer' because as you see in the examples: other colors then the
color of the label text are NOT clipped. To me this looks like some
special kind of blending using the text color over the background...

Mmm, I was hoping it was one of the QPainter tricks we were missing... :-(

Thanks for looking into this...

Regards,

Richard