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I have a polygon layer published in GeoServer through PostgreSQL (PostGIS) and I am trying to build a legend to use with GetLegendGraphich. The layer is requested as WMS layer in client with Leaflet on an Angular project.

My goal is to build a legend with properties 'fill' and 'fill-opacity' coming from the database (and not hard-coded in the style).

The layer is composed of following data:

  • id (Integer)
  • id_class (Integer)
  • fill_color (String). It is a hexadecimal color code.
  • fill_opacity (BigDecimal)
  • geom (MultiPolygon)

The primary key is {id, id_class}. 'id' is used as a filter:

SELECT id, id_class, fill_color, fill_opacity, geom
FROM table
WHERE id = %id%

So far, I am using fields 'fill_color' and 'fill_opacity' to set the symbology in the layer's SLD style (but without any legend). Like this:

  <NamedLayer>
    <Name>layer_name</Name>
    <UserStyle>
      <Title>layer_title</Title>
      <FeatureTypeStyle>
        
        <Rule>
          <Name>rule_name</Name>
          <Title>rule_title</Title>
          <PolygonSymbolizer>
             <Fill>
               <CssParameter name="fill-opacity">
                    <ogc:PropertyName>fill_opacity</ogc:PropertyName>
               </CssParameter>
               <CssParameter name="fill">
                   <ogc:PropertyName>fill_color</ogc:PropertyName>
               </CssParameter>
             </Fill>
             <Stroke>
                <CssParameter name="stroke">#000000</CssParameter>
                <CssParameter name="stroke-width">0.2</CssParameter>
             </Stroke>
          </PolygonSymbolizer>
        </Rule>

      </FeatureTypeStyle>
    </UserStyle>
  </NamedLayer>

My goal is to build a legend like this one:

My goal is to build a legend like this one:

enter image description here

which I have built using the following SLD style:

  <NamedLayer>
    <Name>layer_name</Name>
    <UserStyle>
      <Title>legend</Title>
      <FeatureTypeStyle>
        
        <Rule>
          <RasterSymbolizer>
            <ChannelSelection>
              <GrayChannel>
                <SourceChannelName>1</SourceChannelName>
              </GrayChannel>
            </ChannelSelection>
            <ColorMap type="values">
              <ColorMapEntry label=" [a - b]" quantity="1" color="#32ce80"/>
              <ColorMapEntry label=" (b - c]" quantity="2" color="#e3e926"/>
              <ColorMapEntry label=" (c - d]" quantity="3" color="#e8ad15"/>
              <ColorMapEntry label=" (d - e]" quantity="4" color="#ec0037"/>
              <ColorMapEntry label=" > e" quantity="5" color="#a0009d"/>
            </ColorMap>
          </RasterSymbolizer>
        </Rule>

      </FeatureTypeStyle>
    </UserStyle>
  </NamedLayer>

So, I could use the first one (which uses PolygonSymbolizer properly) for symbology and the latter for producing a legend image (which would be a hack).

However, I would like to have one style: color + opacity coming from data fields (not hard-coded), and the legend.

I tried to separate each 'id_class' into a different rule, but could not make it work. The fill colors are not used in the legend:

enter image description here

  <NamedLayer>
    <Name>layer_name</Name>
    <UserStyle>
      <Title>layer_title</Title>
      <FeatureTypeStyle>
        
        <Rule>
          <Name>class_1</Name>
          <Title>[a - b]</Title>          
          <ogc:Filter>              
              <ogc:PropertyIsEqualTo>
                  <ogc:PropertyName>id_class</ogc:PropertyName>
                  <ogc:Literal>1</ogc:Literal>                
               </ogc:PropertyIsEqualTo>                                
          </ogc:Filter>          
          <PolygonSymbolizer>
             <Fill>
               <CssParameter name="fill-opacity">
                    <ogc:PropertyName>fill_opacity</ogc:PropertyName>
               </CssParameter>
               <CssParameter name="fill">
                   <ogc:PropertyName>fill_color</ogc:PropertyName>
               </CssParameter>
             </Fill>
             <Stroke>
                <CssParameter name="stroke">#000000</CssParameter>
                <CssParameter name="stroke-width">0.2</CssParameter>
             </Stroke>
          </PolygonSymbolizer>
        </Rule>
        
        <Rule>
          <Name>class_2</Name>
          <Title>(b - c]</Title>          
          <ogc:Filter>              
              <ogc:PropertyIsEqualTo>
                  <ogc:PropertyName>id_class</ogc:PropertyName>
                  <ogc:Literal>2</ogc:Literal>                
               </ogc:PropertyIsEqualTo>                                
          </ogc:Filter>          
          <PolygonSymbolizer>
             <Fill>
               <CssParameter name="fill-opacity">
                    <ogc:PropertyName>fill_opacity</ogc:PropertyName>
               </CssParameter>
               <CssParameter name="fill">
                   <ogc:PropertyName>fill_color</ogc:PropertyName>
               </CssParameter>
             </Fill>
             <Stroke>
                <CssParameter name="stroke">#000000</CssParameter>
                <CssParameter name="stroke-width">0.2</CssParameter>
             </Stroke>
          </PolygonSymbolizer>
        </Rule>
       
        <Rule>
          <Name>class_3</Name>
          <Title>(c - d]</Title>          
          <ogc:Filter>              
              <ogc:PropertyIsEqualTo>
                  <ogc:PropertyName>id_class</ogc:PropertyName>
                  <ogc:Literal>3</ogc:Literal>                
               </ogc:PropertyIsEqualTo>                                
          </ogc:Filter>          
          <PolygonSymbolizer>
             <Fill>
               <CssParameter name="fill-opacity">
                    <ogc:PropertyName>fill_opacity</ogc:PropertyName>
               </CssParameter>
               <CssParameter name="fill">
                   <ogc:PropertyName>fill_color</ogc:PropertyName>
               </CssParameter>
             </Fill>
             <Stroke>
                <CssParameter name="stroke">#000000</CssParameter>
                <CssParameter name="stroke-width">0.2</CssParameter>
             </Stroke>
          </PolygonSymbolizer>
        </Rule>
        
        <Rule>
          <Name>class_4</Name>
          <Title>(d - e]</Title>          
          <ogc:Filter>              
              <ogc:PropertyIsEqualTo>
                  <ogc:PropertyName>id_class</ogc:PropertyName>
                  <ogc:Literal>4</ogc:Literal>                
               </ogc:PropertyIsEqualTo>                                
          </ogc:Filter>          
          <PolygonSymbolizer>
             <Fill>
               <CssParameter name="fill-opacity">
                    <ogc:PropertyName>fill_opacity</ogc:PropertyName>
               </CssParameter>
               <CssParameter name="fill">
                   <ogc:PropertyName>fill_color</ogc:PropertyName>
               </CssParameter>
             </Fill>
             <Stroke>
                <CssParameter name="stroke">#000000</CssParameter>
                <CssParameter name="stroke-width">0.2</CssParameter>
             </Stroke>
          </PolygonSymbolizer>
        </Rule>        

        <Rule>
          <Name>class_5</Name>
          <Title>> e</Title>          
          <ogc:Filter>              
              <ogc:PropertyIsEqualTo>
                  <ogc:PropertyName>id_class</ogc:PropertyName>
                  <ogc:Literal>5</ogc:Literal>                
               </ogc:PropertyIsEqualTo>                                
          </ogc:Filter>          
          <PolygonSymbolizer>
             <Fill>
               <CssParameter name="fill-opacity">
                    <ogc:PropertyName>fill_opacity</ogc:PropertyName>
               </CssParameter>
               <CssParameter name="fill">
                   <ogc:PropertyName>fill_color</ogc:PropertyName>
               </CssParameter>
             </Fill>
             <Stroke>
                <CssParameter name="stroke">#000000</CssParameter>
                <CssParameter name="stroke-width">0.2</CssParameter>
             </Stroke>
          </PolygonSymbolizer>
        </Rule>        
      
      </FeatureTypeStyle>
    </UserStyle>
  </NamedLayer>

https://my_server/geoserver/wms?REQUEST=GetLegendGraphic&VERSION=1.0.0&FORMAT=image/png&LAYER=my_layer

Is there a way or I must use hard-coded fill color values?

Improve this question
4
  • You can create a PNG of the required legend graphic and add that to the layer.
    – Ian Turton ♦
    Mar 8 at 13:39
  • Tks Ian. The whole point is to change the hex color code directly in the database and have symbology and legend altered. Would your suggestion work like that?
    – Andre Silva
    Mar 8 at 13:46
  • Then GeoServer would need to read the entire table for each legend display
    – Ian Turton ♦
    Mar 8 at 18:57
  • For each id (used in the filter) there are up to five features (rows) (one for each 'id_class'). Would that be a problem?
    – Andre Silva
    Mar 8 at 19:12

1 Answer 1

Reset to default
0

You can prepare a style with sections that are meant just legend production, and section just for rendering (or for both). See here:

https://docs.geoserver.org/stable/en/user/styling/sld/extensions/rendering-selection.html#rendering-selection

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2
  • Sorry, I completely missed your answer at the time. I got the following error: line : cvc-complex-type.2.4.d: Invalid content was found starting with element 'VendorOption'. No child element is expected at this point.. Used the vendor option after </Stroke> and before </PolygonSymbolizer> in the first SLD example of my question. Also, I got it how I could use this in the map part, but I did not understand how I could build the legend getting the colors from my layer field. Could you expand your answer to include an example? Thanks.
    – Andre Silva
    May 9 at 15:56
  • 1
    Don't stop at the validation results (it's a formal check only) and try to actually save and use the style.
    – Andrea Aime
    May 10 at 7:02

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