GeoServer – Polygon Transparency Settings Using SLD Style File

colorgeoserverpolygonsldtransparency

I am trying to add transparency to a set of polygons (city bounds) within a .sld style file for OSM. Please see below:

As you can see the city bounds are overlapping Montana State University. My goal is to have no fill or transparent fill for the city bounds. In this image I have it set to #00FFFFFF and GeoServer is not liking it as you can see.

Here is the SLD chunk for the polygon:

<sld:Name>Boundary</sld:Name>
<sld:Title>Boundary</sld:Title> 
<sld:PolygonSymbolizer>
    <sld:Fill> 
        <sld:CssParameter name="fill">#00FFFFFF</sld:CssParameter>
    </sld:Fill>
    <sld:Stroke>
        <sld:CssParameter name="stroke">#6a7c87</sld:CssParameter> 
        <sld:CssParameter name="stroke-width">0.5</sld:CssParameter>
        <sld:CssParameter name="stroke-linejoin">round</sld:CssParameter>
    </sld:Stroke>

Best Answer

You will need to specify an opacity as a CssParameter

<sld:Fill> 
   <sld:CssParameter name="fill-opacity">0</sld:CssParameter>
</sld:Fill>

Related Solutions

[GIS] Setting transparency in an SLD file for a 4 channel GEOTIFF

I faced quite a similar problem and found here and here the following statements of people working for GeoSolutions:

"The colormap element can be used only on a single band to generate an RGB(A) raster where quantities can be mapped to colors."

"You cannot apply the ColorMap element when having 3 bands, you need only 1."

I found two ways to be able to add transparency using GDAL tools:

using gdalwarp as described in the link above: This adds a 4th band to the file containing a transparency mask.
- Set nodata masking values:
```
$ gdalwarp -of GTiff -srcnodata 0 -dstalpha inputfile.tif outputfile.tif
```
- After that, setting the default raster style for the Geoserver layer is enough to have a transparent background.
It is also mentioned that there are "extensions to SLD to support multiband color maps" or one could write custom WPS processes but I did not go further into that.
using gdal_translate as mentioned by @ian in the comments above: This sets 'no data' values to every band (I don't really understand whats going on there).
- Assign a specified nodata value to output bands:
```
$ gdal_translate -a_nodata 0 inputfile.tif outputfile.tif
```
- After that, you can set the InputTransparentColor in the Layer properties in your Geoserver Web Application to the desired value (here: 000000).
My OpenLayers preview could not deal with such a layer when the underlying GeoTIFF was of 16bit color depth (check with gdalinfo). One can reduce it to a manageable 8bits with $ gdal_translate -ot Byte inputfile.tif outputfile.tif.

[GIS] Geoserver SLD: Dynamic Variable Substitution

Instead of

<ogc:Literal>
   <ogc:PropertyName>city_name</ogc:PropertyName>-color
</ogc:Literal>

You need to use the function Concatenate

<ogc:Function name="Concatenate">
   <ogc:PropertyName>city_name</ogc:PropertyName>
   <ogc:Literal>-color</ogc:Literal>
</ogc:Function>

Best Answer

Related Solutions

[GIS] Setting transparency in an SLD file for a 4 channel GEOTIFF

[GIS] Geoserver SLD: Dynamic Variable Substitution

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