I've had a poke through the raster legend code, and it is much more similar
to the feature version than I expected, down to using the same
getApplicableRules function call that I was planning on overloading. That
gives me some hope that we can use the same call for both raster and
feature, but I think that would take it down the rabbit hole of different
reader behavior you mention. Is that similar to what you had in mind?
I'll have a look at the DuplicatingStyleVisitor and see what we can make
of it as well, thanks for the pointer.
--
Mark
On 12 May 2013 18:22, Andrea Aime <andrea.a...@geo-solutions.it> wrote:
> On Fri, May 10, 2013 at 1:46 AM, Mark Leslie <mark.les...@lisasoft.com>wrote:
>
>> Here is a Draft GSIP for review. We are proposing to add two optional
>> parameters to the GetLegendGraphics handler to allow the specification of a
>> bounding box and associated srs. These would then be used to determine
>> what symbology will actually be used when rendering a those bounds and
>> produce a legend graphic only with what will be displayed on the map.
>>
>>
>> http://geoserver.org/display/GEOS/GSIP+95+-+GetLegendGraphics+BBOX+and+SRS+parameter
>>
>>
>> We are hoping to validate our approach before we quote our customer to
>> make sure we're going down the right path, so any feedback would be greatly
>> appreciated.
>>
>
> The proposal sounds reasonable.
>
> Excluding rasters completely seems imho a bit too much, a simple
> implementation that checks the BBOX against the
> raster original envelope is just a bit more than a one liner and gets you
> 90% of the functionality (a full fledged implementation
> would have to read a scaled down version in that area and see if the
> returned coverage is empty, but it would also fall
> prey of different behaviors in the readers, some might return a null
> value, others might return a value filled with nodata).
> Anyways, your choice, not a blocker, just wanted to point out it might not
> be hard at all.
>
> The case of excluding attribute generated by attribute reference is
> probably not worth mentioning: the getLegendGraphics
> code is not able to generate a legend in that case, at least if the case
> is having the attribute in the external graphics url.
> If instead we are talking about attribute based filters, I guess combining
> them with the bbox will do the trick, no?
>
> As for categorize/interpolate/recode, the current code is not able to
> generate a legend anyways.
>
> About the two stage alternative approach that would depend on GSIP 81:
> Carlo (cc'ed) abandoned the GSIP
> at the community level because of lack of feedback, but he actually
> implemented it in a fork of GeoServer
> that he's maintaining for a customer and it's in use, don't know if it can
> be revived or not.
>
> Ah, one thing performance wise: styles with multiple FeatureTypeStyle tend
> to contains the same rule
> filters in the different FTS (think of a road style that needs to depict a
> highway with cased lines), there
> is potential for optimization if the results are somehow cached during the
> transformation.
> A DuplicatingStyleVisitor subclass should do the trick, and it could
> contain, now or in the future, the filter
> evaluation caching logic. Just thinking out loud, by no means a
> requirement.
>
> Cheers
> Andrea
>
> --
> ==
> GeoServer training in Milan, 6th & 7th June 2013! Visit
> http://geoserver.geo-solutions.it for more information.
> ==
>
> Ing. Andrea Aime
> @geowolf
> Technical Lead
>
> GeoSolutions S.A.S.
> Via Poggio alle Viti 1187
> 55054 Massarosa (LU)
> Italy
> phone: +39 0584 962313
> fax: +39 0584 1660272
> mob: +39 339 8844549
>
> http://www.geo-solutions.it
> http://twitter.com/geosolutions_it
>
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--
Mark Leslie
Geospatial Software Architect
LISAsoft
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