theunsgis ha scritto:
> I everyone
Hi. Sorry for the late response.
> sorry for the long explanation , but i would like to give as much detail i
> can to get the
> right message across.
>
> I would like to implement a plug-in for Well known Icons.
> The challenge started when you investigated how to display Mil2525B icons on
> a geotools layer ,
> where the icon images is generated dynamically in code , so there are no
> images saved in any files.
>
> The geotools library does make provision for the display of points by either
> a mark or
> external graphics.
>
> By using a mark implementation , you can specify a well known name for a
> symbol to be displayed like
> “square”, “circle”, “triangle”, “star”, “cross”,and “x”.
> further more geotools also try to implement the library according to
> the OGC standard , and according to the standard these ("star" , "circle"
> etc.) are the allowed
> values , if i am wrong please set me right.
So far so good :)
> By using the ExternalGraphic implementation , you have to supply a URL to
> the graphic file
> saved somewhere and the format of the graphic file.
>
> Me and Jody Garnett had a few emails flowing about this issue.
> Jody also add a page to the geotools site about this issue
> http://docs.codehaus.org/display/GEOTOOLS/Custom+Symbols+for+MIL2525B+and+EmergencyResponse
>
> where he suggest a WellKnownNameIconFactory interface and a
> WellKnownNameIconFinder class for finding
> the correct icon for display. I totally agree with Jody's suggestions for
> the problem.
Yep, the suggestion seems tine to me to.
> The big challenge is to HOW TO KNOW that the representation of the point
> must be for a well known icon,
> e.g "ambulance", "police-car","SHAPMF---------" were the later is the
> mil2525 string representation
> for military fixed wing, and some of the icons can be generated dynamically
> in a class.
> In the above example of well known icon names , we have three deferent
> organizations who have
> well known icons in there own domains, like the Emergency Response domain
> ("ambulance") ,
> the Police Reaction Domain ("Police-car") and
> the Military domain (Mil2525 String for Military Fixed Wing).
> So each domain can provide a plug-in class for the interface
> WellKnownNameIconFactory mentioned
> on the web page
> http://docs.codehaus.org/display/GEOTOOLS/Custom+Symbols+for+MIL2525B+and+EmergencyResponse
>
>
> Now saying all that , is the well known names (“square”, “circle”,
> “triangle”, “star”, “cross”,and “x”) for the mark implementation fixed to
> the few names of the OGC?
I think we already went beyond the OGC limitations and I see no reason
to stick with them. We just have to warn people that by using well known
names other than the standard ones they will bind themselves to geotools
, that is, the same SLD won't be usable with other softwares.
> If its is not fixed then , the Well known name of the mark implementation
> could be used to indicate
> we are working with a WellknownName Icon , and the geometry property can
> hold the WellknownName
> icon string eg. "ambulance" or "police-car" or "SHAPMF---------".
>
> If the above is not feasible then we have to use the ExternalGraphic route,
> which i personally
> feel is the right thing , because we are working with a image representation
> of the point.
> However i can't figure out , without breaking the rules , how to show we are
> working
> with wellknownname Icon that will be generated dynamically , its not saved
> in a file.
Me neither, since the url should point to a network accessible address.
There have been thoughts about setting up a "symbol server" that people
could use for extra symbology, but this has never been pursued fully
because the SLD spec says the url is a static string, whilst most
of the time you'd like to pass over a dynamically generated url
containing some feature attributes (and Expression, instead of a Literal).
So in the end I think an extensible approach using a name made up of
authority and symbol, like militar:tank or font:wingdings!g is going
to serve us better than an eventual external symbol server.
To tell the truth, the well known name is an xs:string, so we would
not be allowed to use an expression there either, but at least
the xml is using an element for that SLD part, so it's easy to extend
it to use an expression, whilst the external graphics url is an
attribute, that leaves no place for putting an expression...
Cheers
Andrea
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