[GIS] Can’t set transparent raster alpha channel in GeoExplorer!

geoserver

I am trying to get transparent parts of an 3-channel raster with NoData pixel values in GeoServer.

As suggested in here, I created alpha channel with pixels that have No Data Value (0) as a mask using GDAL
`gdalwarp -srcnodata 0 -dstalpha input.tif output.tif`
As a result I got 4-channel (RGB+alpha) where the pixels that previously were 0 now have 0 values in all four channels and those, that were > 0, in alpha channel have value 255. Also No Data Value is set to 0.

When I upload raster to GeoServer (v2.5.2) using QGIS plugin OpenGeo Explorer, instead of transparent pixels I get black pixels. What could be the problem? I have also tried without setting No Data Value without results.

—————EDIT—————-
Geoserver version: 2.5.2
Raster style:

   <?xml version="1.0" encoding="UTF-8"?>
   <sld:StyledLayerDescriptor xmlns="http://www.opengis.net/sld" xmlns:sld="http://www.opengis.net/sld" xmlns:ogc="http://www.opengis.net/ogc" xmlns:gml="http://www.opengis.net/gml" version="1.0.0">
     <sld:NamedLayer>
<sld:Name>RGB raster</sld:Name>
<sld:UserStyle>
  <sld:Name>RGB raster</sld:Name>
  <sld:FeatureTypeStyle>
    <sld:Name>name</sld:Name>
    <sld:Rule>
      <sld:Name>Single symbol</sld:Name>
      <sld:RasterSymbolizer>
        <sld:ChannelSelection>
          <sld:RedChannel>
            <sld:SourceChannelName>1</sld:SourceChannelName>
          </sld:RedChannel>
          <sld:GreenChannel>
            <sld:SourceChannelName>2</sld:SourceChannelName>
          </sld:GreenChannel>
          <sld:BlueChannel>
            <sld:SourceChannelName>3</sld:SourceChannelName>
          </sld:BlueChannel>
        </sld:ChannelSelection>
      </sld:RasterSymbolizer>
    </sld:Rule>
  </sld:FeatureTypeStyle>
</sld:UserStyle>

Here is the request:
request=GetMap&layers=jaun:ORO2&styles=&bbox=515813.19564,305943.471,516026.19564,306105.471&width=512&height=389&srs=EPSG:3059&format=application/openlayers&transparent=true

Best Answer

Ciao, the style you are using is stripping out the alpha band. Use the standard/default raster.sld style.

Simone.

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