[Tilesathome] or/p now with proximity filter

[Frederik Ramm]

Hi,

    I have added a proximity filter to or/p that uses the same syntax as 
the original Osmarender.

The logic is a bit different however: or/p simply processes all objects, 
draws those whose "box" is not yet occupied (and marks the box as 
occupied), and ignores the others. This gives good results but the 
choice of labels is different than with Osmarender/XSLT, and probably 
even different if the data changes slightly.

Could someone with a better understanding of Osmarender/XSLT (bobkare? 
80n?) tell me whether the way it is done XSLT (somehow it seems to 
search for "pairs" of nearby objects and then discard one?) circumvents 
this problem and leads to more stable results?

My implementation supports an extra parameter called "proximityClass". 
If multiple selection rules share the same value for this optional 
parameter, they use the same "box space", i.e. objects selected by the 
first rule will still be known as "used" by the second rule.

(There's a slight caveat here, in that any object selected by a 
proximity rule is assumed to have "used" its space, even if the object 
should be deselected by a nested selection rule; and also proximity 
filters won't work properly with <else> branches.)

I was thinking that if we added to this a numerical comparison operator 
for tag values, then we could achieve a rendering of largest cities 
first, like so:

<select k="place" v="city">
    <select k="population" v=">1000000" horizontalProximity="0.6" 
verticalProximity="0.4" proximityClass="caption">
       ... render ...
    </select>
    <select k="population" v=">200000" horizontalProximity="0.6" 
verticalProximity="0.4" proximityClass="caption">
       ... render ...
    </select>
    <select k="population" v="*" horizontalProximity="0.6" 
verticalProximity="0.4" proximityClass="caption">
       ... render ...
    </select>
</select>

But that numerical comparison operator doesn't exist yet, I don't know 
if this would be a good way to do it. Another possibility would be to 
introduce sorted selection results, like so:

<select k="place" v="city" descending_sort="population" 
horizontalProximity="0.6" verticalProximity="0.4">
       ... render ...
</select>

Bye
Frederik

-- 
Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00'09" E008°23'33"