How to use perpendicularoffset for PolygonSymbolizer in GeoServer?

Question

I want to fill the polygon in GeoServer with 2 parallel lines pattern. Example: 1 continuous and 1 dash line. For example like this image:

I can fill the polygon in GeoServer with shape://slash. And combine 2 block , I can create a pattern with 2 lines. But I couldn't offset the second line to make them parallel (tried with perpendicularoffset but always got errors).

<PolygonSymbolizer>
  <Fill>
   <GraphicFill>
     <Graphic>
       <Mark>
         <WellKnownName>shape://slash</WellKnownName>
         <Stroke>
           <CssParameter name="stroke">#e31a1c</CssParameter>
           <CssParameter name="stroke-width">2</CssParameter>
         </Stroke>
       </Mark>
       <Size>20</Size>
     </Graphic>
   </GraphicFill>
 </Fill>
</PolygonSymbolizer>

<PolygonSymbolizer>
  <Fill>
   <GraphicFill>
     <Graphic>
       <Mark>
         <WellKnownName>shape://slash</WellKnownName>
         <Stroke>
           <CssParameter name="stroke">#001cac</CssParameter>
           <CssParameter name="stroke-width">2</CssParameter>
           <CssParameter name="stroke-dasharray">5 2</CssParameter>
         </Stroke>

        <!-- Not sure how to insert Offset correctly -->
         <PerpendicularOffset>5</PerpendicularOffset>

       </Mark>
       <Size>20</Size>
     </Graphic>
   </GraphicFill>
 </Fill>
</PolygonSymbolizer>

The sample use perpendicularoffset seem only work with stroke (boundary of polygons).

So is there anyway I can define a sld file for that purpose?

I can fill with .svg file to meet the requirement but the disadvantage is the difficult to change color of line. In both ArcGIS & QGIS, I can easily define the pattern like that, so I don't understand why it seems not possible to do in GeoServer.

Answer 1

There is no way to offset a fill in GeoServer (why? because no one sponsored that functionality yet, but you can do something about it, either by contributing to the rendering engine in GeoTools, or sponsoring a commercial support provider to implement the functionality)

However, you can also change the colors in a SVG if you want: https://docs.geotools.org/latest/userguide/library/render/svg.html#parameter-extension