Hi all,
I'm writing this mail to explore the possibility of extending
our current SLD support for symbolizer geometry.
With the current SLD 1.0 (and even with SE 1.1) we're stuck
with just telling the symbolizer which geometry attribute to
use, as the <sld:geometry> element is hard coded to be a
PropertyName.
This is lame, things would be much more flexible if that
was an Expression instead.
Coupled with filter functions that we already have today
and a handful of new ones we could get:
- on the fly geometry generation, such as buffering
points and lines to draw buffer areas on the fly
- on the fly slice and dice, such as drawing only a portion
of a line with a certain color, or making sure the
geometry is sliced against the bouding box before
rendering it into a vector format (I'm thinking PDF,
using the Graphics object provided by iText)
- drop shadow effect, which could be achieved by just
offsetting the geometry and drawing it with a darker
color
- draw a line vertexes (typical selection style) by
turning the line into a multipoint on the fly
Add the ability to define you own geometry manipulation
functions and the possibilities are endless.
Unfortunately there is a significant drawback: everything
in the current api is stuck to geometryName <=> String.
Soo... how could we add such support without breaking things
too much? One thing that comes to mind is to have a new
element, <GeometryEx> that is declared as an Expression.
This could be added to the existing symbolizer
classes/interfaces without much breakage, and extending
the parser to handle that as well.
The xml would look like:
<PointSymbolizer>
<GeometryEx>
<Function name="extractVertex">
<ogc:PropertyName>myLineStringGeom</ogc:PropertyName>
</Function>
</GeometryEx>
...
</PointSymbolizer>
What do you think?
Cheers
Andrea
--
Andrea Aime
OpenGeo - http://opengeo.org
Expert service straight from the developers.
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