Graphic symbology in GeoServer¶

Standard symbols¶

The SLD specification mandates the support of the following symbols:

Shape symbols¶

The shape symbols set adds extra symbols that are not part of the basic set. Their names are prefixed by shape://

The weather symbols are prefixed by the extshape:// protocol in the SLD:

Name	Description	Produces
extshape://triangle	cold front
extshape://emicircle	warm front
extshape://triangleemicircle	stationary front

You can use extshape:// for a few additional built-in shapes:

More complex symbols like Wind Barbs can be created with the windbarbs:// prefix. There are some examples:

Custom WKT Shapes¶

Custom shapes can be defined using your own Geometry. Geometry is defined using the same well-known-text format used for CQL_FILTER.

<LineSymbolizer>
  <Stroke>
    <GraphicStroke>
      <Graphic>
        <Mark>
          <WellKnownName>wkt://MULTILINESTRING((-0.25 -0.25, -0.125 -0.25), (0.125 -0.25, 0.25 -0.25), (-0.25 0.25, -0.125 0.25), (0.125 0.25, 0.25 0.25))</WellKnownName>
          <Fill>
            <CssParameter name="fill">#0000ff</CssParameter>
          </Fill>
          <Stroke>
            <CssParameter name="stroke">#0000ff</CssParameter>
            <CssParameter name="stroke-width">1</CssParameter>
          </Stroke>
        </Mark>
        <Size>6</Size>
      </Graphic>
    </GraphicStroke>
  </Stroke>
</LineSymbolizer>

Which produces double dashed line:

You can also make use of curves when defining WKT:

<LineSymbolizer>
  <Stroke>
    <GraphicStroke>
      <Graphic>
        <Mark>
          <WellKnownName>wkt://COMPOUNDCURVE((0 0, 0.25 0), CIRCULARSTRING(0.25 0, 0.5 0.5, 0.75 0), (0.75 0, 1 0))</WellKnownName>
          <Fill>
            <CssParameter name="fill">#0000ff</CssParameter>
          </Fill>
          <Stroke>
            <CssParameter name="stroke">#0000ff</CssParameter>
            <CssParameter name="stroke-width">1</CssParameter>
          </Stroke>
        </Mark>
        <Size>10</Size>
      </Graphic>
    </GraphicStroke>
  </Stroke>
</LineSymbolizer>

Producing an “emi circle” line:

Bulk WKT Shapes¶

It is possible to create a symbol set of your own custom marks using a property file.

Here is an example.properties:

zig=LINESTRING(0.0 0.25, 0.25 0.25, 0.5 0.75, 0.75 0.25, 1.00 0.25)
block=POLYGON((0 0, 1 0, 1 1, 0 1, 0 0))

To reference the above property file in your SLD, prefixed like this (note the protocol changed to “wktlib://”):

<WellKnownName>wktlib://example.properties#zig</WellKnownName>

Bulk TTF marks¶

It is possible to create a mark using glyphs from any decorative or symbolic True Type Font, such as Wingdings, WebDings, or the many symbol fonts available on the internet. The syntax for specifying this is:

ttf://<fontname>#<hexcode>

where fontname is the full name of a TTF font available to GeoServer, and hexcode is the hexadecimal code of the symbol. To get the hex code of a symbol, use the “Char Map” utility available in most operating systems (Windows and Linux Gnome both have one).

For example, to use the “shield” symbol contained in the WebDings font, the Gnome charmap reports the symbol hex code as shown:

Selecting a symbol hex code in the Gnome char map

The SLD to use the shield glyph as a symbol is:

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 <PointSymbolizer>
     <Graphic>
       <Mark>
         <WellKnownName>ttf://Webdings#0x0064</WellKnownName>
         <Fill>
           <CssParameter name="fill">#AAAAAA</CssParameter>
         </Fill>
         <Stroke/>
       </Mark>
     <Size>16</Size>
   </Graphic>
 </PointSymbolizer>

This results in the following map display:

Shield symbols rendered on the map

Extending the Mark subsytem using Java¶

The Mark subsystem is user-extensible. To do this using Java code, implement the MarkFactory interface and declare the implementation in the META-INF/services/org.geotools.renderer.style.MarkFactory file.

For further information see the Javadoc of the GeoTools MarkFactory, along with the following example code:

• The factory SPI registration file
• The TTFMarkFactory implementation
• The ShapeMarkFactory implementation

Symbol Positioning¶

Graphic symbols are rendered so that the center of the graphic extent lies on the placement point (or points, in the case of repeated or tiled graphics). If it is desired to have a graphic offset from a point (such as a symbol which acts as a pointer) it is necessary to offset the visible portion of the graphic within the overall extent. For images this can be accomplished by extending the image with transparent pixels. For SVG graphics this can be done by surrounding the shape with an invisible rectangle with the desired relative position.