AW: [udig-devel] Arrowhead Symbolizers

["Wellmann, Harald" <harald.wellmann@xxxxxxxxxx>]

Thanks for all your replies!  I followed the link to the Geoserver Blog posted by Sophia, trying the approach with arrows combined from dashed lines.

It's a bit hackish, but it does the job. Have a look here:

http://hwellmann.blogspot.com/2009/04/arrows-with-styled-layer-descriptor.html

Of course, I'm still interested in a more direct solution, in uDig or at SLD level, but for now, I'm quite happy with this approach.

Cheers,
Harald


> -----Ursprüngliche Nachricht-----
> Von: udig-devel-bounces@xxxxxxxxxxxxxxxxxxxxx 
> [mailto:udig-devel-bounces@xxxxxxxxxxxxxxxxxxxxx] Im Auftrag 
> von Jody Garnett
> Gesendet: Dienstag, 7. April 2009 15:32
> An: User-friendly Desktop Internet GIS; Andrea Aime
> Betreff: Re: [udig-devel] Arrowhead Symbolizers
> 
> 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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