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Re: [udig-devel] Arrowhead Symbolizers
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Right now SLD renders a point symbolizer half way along the line I think.
Andrea and I are just talking about how to do this; what we need to do
is "preprocess" the geometry prior to letting a point symbolizer draw
it. We are thinking of allowing the point symbolizer to define a
geometry expression (rather than just a geometry); however there are
some problems with this approach (since it makes figuring out what
bounding box to request difficult) unless the function can be
"inverted" or something. The alternative is to strictly define the
available geometry preprocess options (first point; last point;
buffer; etc...). I would like to do better then this in order to
allow linear referencing system style drawing (draw the line from 20%
to 80% in this color).
Cheers,
Jody
On Tue, Apr 7, 2009 at 7:51 PM, Wellmann, Harald
<harald.wellmann@xxxxxxxxxx> wrote:
> How to style line features with an arrowhead at either end? Preferably
> using SLD, other methods are welcome if SLD does not support that.
>
> I found this thread on the subject:
> http://www.nabble.com/Directional-Symbology-td12231197.html
>
> ...but it does fully answer the question.
>
> Given a line feature type with a LineSymbolizer, if I define an
> additional PointSymbolizer for that type, where do the point symbols get
> placed? At the first vertex, the last, somewhere in the middle of the
> line?
>
> Do I have to create an additional point feature just to position the
> arrow icon on a line feature?
>
> And of course it is not enough to place an arrowhead icon at the
> endpoint of a line, you want the arrowhead to be correctly oriented.
>
> I'm thinking of something like
>
> <sld:LineSymbolizer>
> <sld:Stroke>
> <sld:CssParameter name="arrow-direction">
> <ogc:Literal>backward</ogc:Literal>
> </sld:CssParameter>
> <sld:CssParameter name="arrow-head">
> <ogc:Literal>double</ogc:Literal>
> </sld:CssParameter>
> </sld:Stroke>
> </sld:LineSymbolizer>
>
>
> where
>
> arrow-direction = none|forward|backward|bothways
>
> arrow-head = simple|double|filled|...
>
> and maybe you want an additional tag for placing the arrows either at
> the endpoint of the line or in the middle.
>
>
> Regards,
>
> Harald
>
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