SLD transformations

This section show how to GeoServer provides a number of filter functions that can actually manipulate geometries by transforming them into something different: this is what we call geometry transformations in SLD.

Extracting vertices

1. Using skills learned in the adding styles section, create a new style named mainrd_transform using the following SLD:

   <?xml version="1.0" encoding="ISO-8859-1"?>
   <StyledLayerDescriptor version="1.0.0"
     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"
     xsi:schemaLocation="http://www.opengis.net/sld http://schemas.opengis.net/sld/1.0.0/StyledLayerDescriptor.xsd">
     <NamedLayer>
       <Name>Roads and vertices</Name>
       <UserStyle>
         <FeatureTypeStyle>
           <Rule>
             <LineSymbolizer>
               <Stroke />
             </LineSymbolizer>
             <PointSymbolizer>
               <Geometry>
                 <ogc:Function name="vertices">
                   <ogc:PropertyName>the_geom</ogc:PropertyName>
                 </ogc:Function>
               </Geometry>
               <Graphic>
                 <Mark>
                   <WellKnownName>square</WellKnownName>
                   <Fill>
                     <CssParameter name="fill">#FF0000</CssParameter>
                   </Fill>
                 </Mark>
                 <Size>6</Size>
               </Graphic>
             </PointSymbolizer>
           </Rule>
         </FeatureTypeStyle>
       </UserStyle>
     </NamedLayer>
   </StyledLayerDescriptor>
   

   Note

   The vertices function returns a multi-point made with all the vertices of the original geometry

2. Using skills learned in the adding styles section, modify the styling of the Mainrd layer and add mainrd_transform as an alternate style (hint, select the mainrd_transform style in the first list below “available styles” and then use the right arrow to move it in the “selected styles”):

Adding the mainrd_transform style as a secondary style for Mainrd

1. Use the Preview link to display the Mainrd layer, then open the options box and choose the alternate style from the drop down:

   

   Extracting and showing the vertices out of a geometry

Line buffer

1. Using skills learned in the geoserver.addstyle section, create a new style mainrd_buffer using the following SLD

   <?xml version="1.0" encoding="ISO-8859-1"?>
   <StyledLayerDescriptor version="1.0.0"
   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"
   xsi:schemaLocation="http://www.opengis.net/sld http://schemas.opengis.net/sld/1.0.0/StyledLayerDescriptor.xsd">
         <NamedLayer>
           <Name>Roads and vertices</Name>
           <UserStyle>
                 <FeatureTypeStyle>
                   <Rule>
                         <PolygonSymbolizer>
                           <Geometry>
                                 <ogc:Function name="buffer">
                                   <ogc:PropertyName>the_geom</ogc:PropertyName>
                                   <ogc:Literal>200</ogc:Literal>
                                 </ogc:Function>
                           </Geometry>
                            <Fill>
                                 <CssParameter name="fill">#7F7F7F</CssParameter>
                                 <CssParameter name="fill-opacity">0.3</CssParameter>
                           </Fill>
                         </PolygonSymbolizer>
                         <LineSymbolizer>
                           <Stroke />
                         </LineSymbolizer>
                   </Rule>
                 </FeatureTypeStyle>
           </UserStyle>
         </NamedLayer>
   </StyledLayerDescriptor>
   

   Note

   The buffer function builds a polygon of all the points that are withing the specified distance from the original geometry.

2. As done previously, modify the styling of the Mainrd layer and add mainrd_buffer as an alternate style:

Adding the mainrd_buffer style as a secondary style for Mainrd

1. Use the Map Preview to preview the new style.

   

   Extracting start and end point of a line