I everyone
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.
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.
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?
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.
Suggestions how the SLD could look like:
For the Mark implementation if the wellknown names are not fixed :
<sld:PointSymbolizer>
<sld:Geometry>
<!-- The Simple Feature will then hold the string eg. "ambulance" or
"SHAPMF---------" -->
<sld:PropertyName>WellKnownIconAttribute</sld:PropertyName>
</sld:Geometry>
<sld:Graphic>
<sld:Mark>
<!-- This will tell us we are working with WellKnownName Icons for the point
-->
<sld:WellKnownName>WellKnownIcon</sld:WellKnownName>
</sld:Mark>
<sld:Opacity>
<ogc:Literal>1</ogc:Literal>
</sld:Opacity>
<sld:Size>
<ogc:Literal>14</ogc:Literal>
</sld:Size>
<sld:Rotation>
<ogc:Literal>0.0</ogc:Literal>
</sld:Rotation>
</sld:Graphic>
</sld:PointSymbolizer>
for the ExternalGraphic implenetation:
<sld:PointSymbolizer>
<sld:Geometry>
<sld:PropertyName>WellKnownIconAttribute</sld:PropertyName>
</sld:Geometry>
<sld:Graphic>
<sld:ExternalGraphic>
<!-- Something must go here for indicating a WellknowNameIcon -->
<sld:OnlineResource/>
</sld:ExternalGraphic>
<Mark/>
<sld:Opacity>
<ogc:Literal>1</ogc:Literal>
</sld:Opacity>
<sld:Size>
<ogc:Literal>14</ogc:Literal>
</sld:Size>
<sld:Rotation>
<ogc:Literal>0.0</ogc:Literal>
</sld:Rotation>
</sld:Graphic>
</sld:PointSymbolizer>
Any input will be appreciated
Thanks
Theuns Heydenrych
--
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