Hi Andrea,
As far as I know ArcGIS has maplex a rather sophisticated label engine that
provides many features regarding placement of labels and clutter handling.
There are quite some years however that I have to work with it and I do not
remember many details. Regarding QGIS I am not aware of its labelling
features.
Your suggestion about providing all possible quadrant positions (I suppose
you mean every 45 degrees) has some validity in order to cover all cases
however I do not know if in practice it is so useful. Why for example would
it be needed to strictly position a label diagonal when a conflict is
detected? My initial suggestion for this extra option stems from my
personal experience recenlty working in some cadastral applications. There
it often happened to have point (or polygon) features in different layers
that have some relation and have a very minor displacement in position (or
centroid position). In that case during printing it was a requirement to
have these labels somewhat align so that it was evident that they were
related, and follow a common rule of displaying it compared to the actual
feature marker (i.e. always above or below it).
That is why I suggested this improvement and proposed displacement modes
related only to the vertical axis. Displacement related to horizontal axis
now in my opinion is less useful for points and polygons and poses some
challenges since it may introduces some undesired results (i.e. the label
may be printed quite far away from the feature it refers to or we may have
cases that labels are put in a straight line, one next to the other,
without proper spacing). Of course if you think it is needed in order to be
more generic we can check it.
My humble opinion however is that if some spacial rules/modes regarding
displacement of labels is needed (in addition to the standard
'displacement' vendor option) then vertical modes would be the one used
99% of all cases.
2017-12-11 18:18 GMT+02:00 Andrea Aime <[email protected]>:
> Hi Nikolaos,
> the values seem a bit rigid to me... what about giving all the quadrant
> positions
> a name, and then allow the user to provide a comma separated list of
> positions
> that they want the engine to try instead?
>
> Did you check what desktop applications like ArcGIS or QGIS do? Would be
> interested not to steer too far away from that as both systems have
> converters
> from their styling language to GeoTools own SLD (without getting crazy
> with
> extra work, of course!)
>
> Cheers
> Andrea
>
>
> On Thu, Dec 7, 2017 at 8:36 AM, Nikolaos Pringouris <[email protected]>
> wrote:
>
>> Hi,
>> Currently the label conflict resolution for a feature is affected mainly
>> by the vendor option maxDisplacement which tries to compute a a suitable
>> not overlapping position moving in a counterclockwise cycle with 45 degrees
>> steps until success or the max displacement radius is reached. It would be
>> good to have finer control over the way displacement takes place since many
>> times we want labels to be i.e. vertical aligned compared to a feature
>> position.
>> Based on that I have created https://osgeo-org.atlassian.ne
>> t/browse/GEOT-5882 which propose an extra vendor option
>> (displacementMode) that can be used to enhance displacement capabilities
>> (mainly for point and polygon features.
>> Below a jpeg is given illustrating an example of the existing behavior
>> and the new one proposed
>>
>> [image: Ενσωματωμένη εικόνα 3]
>>
>>
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>>
>
>
> --
>
> Regards,
>
> Andrea Aime
>
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