If I wanted to achieve such a thing in Java, I would try something along the
lines of:
int hash = feature.getFeatureId().hashCode();
String colorCode = String.format("#%06x", hash & 0xFFFFFF);
I believe there is a format function exposed in GeoServer's SLD
implementation - but I am not sure about a good SLD substitute for
.hashCode. If you have to, it's not hard for a Java developer to add a
filter function.
If you can modify your data, it might make sense to just add a column of
random values to it and reference those from the SLD - that would allow you
a bit more control if you find that the colors need tweaking (two similar
colors in adjacent polygons, etc.)
--
David Winslow
OpenGeo - http://opengeo.org/
2011/8/28 Håvard Wahl Kongsgård <[email protected]>
> Hi, I have a layer with multiple bordering polygons which needs to be
> visually separated.
>
> One possibility is to create a massive SLD template, defining random
> colors for specific polygons.
>
> However, I noticed this post
>
> http://osgeo-org.1803224.n2.nabble.com/Random-function-in-SLD-td6125434.html
>
> The problem with that approach is that polygons change colors when
> zooming, and when map tiles are enabled, polygons crossing different
> tiles have multiple colors. With SLD templates is there another way to
> do this?
>
>
> <?xml version="1.0" encoding="ISO-8859-1"?>
> <StyledLayerDescriptor version="1.0.0"
> xsi:schemaLocation="http://www.opengis.net/sld StyledLayerDescriptor.xsd"
> xmlns="http://www.opengis.net/sld";
> xmlns:ogc="http://www.opengis.net/ogc";
> xmlns:xlink="http://www.w3.org/1999/xlink";
> xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";>
> <!-- a Named Layer is the basic building block of an SLD document -->
> <NamedLayer>
> <Name>default_polygon</Name>
> <UserStyle>
> <!-- Styles can have names, titles and abstracts -->
> <Title>Default Polygon</Title>
> <Abstract>A sample style that draws a polygon</Abstract>
> <!-- FeatureTypeStyles describe how to render different features -->
> <!-- A FeatureTypeStyle for rendering polygons -->
> <FeatureTypeStyle>
> <Rule>
> <Name>rule1</Name>
> <PolygonSymbolizer>
> <Fill>
> <CssParameter name="fill">
> <ogc:Function name="numberFormat">
> <ogc:Literal>'#'000000</ogc:Literal>
> <ogc:Mul>
> <ogc:Function name="random"></ogc:Function>
> <ogc:Literal>1000000</ogc:Literal>
> </ogc:Mul>
> </ogc:Function>
> </CssParameter>
> <CssParameter name="fill-opacity">0.7</CssParameter>
> </Fill>
> <Stroke>
> <CssParameter name="stroke">#000000</CssParameter>
> <CssParameter name="stroke-width">1</CssParameter>
> </Stroke>
> </PolygonSymbolizer>
> </Rule>
> </FeatureTypeStyle>
> </UserStyle>
> </NamedLayer>
> </StyledLayerDescriptor>
>
> --
> Håvard Wahl Kongsgård
>
>
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