Setting transparency for no data in raster in geoserver

Question

I have a raster published in my geoserver with default raster style as below

<NamedLayer>
<Name>default_raster</Name>
<UserStyle>
<!-- Styles can have names, titles and abstracts -->
  <Title>Default Raster</Title>
  <Abstract>A sample style that draws a raster, good for displaying imagery</Abstract>
  <!-- FeatureTypeStyles describe how to render different features -->
  <!-- A FeatureTypeStyle for rendering rasters -->
  <FeatureTypeStyle>
    <Rule>
      <Name>rule1</Name>
      <Title>Opaque Raster</Title>
      <Abstract>A raster with 100% opacity</Abstract>
      <RasterSymbolizer>
        <Opacity>1.0</Opacity>
      </RasterSymbolizer>
    </Rule>
  </FeatureTypeStyle>
</UserStyle>

And my imagery looks like

Which has black color set for no data. I want to make the no data to transparent. How that can be done?

Answer 1

I'm not sure if this question is still relevant to anyone, but I found a solution using YSLD. Check out the documentation on the raster symbolizer and note the "intervals" color ramp. You can simply set the interval containing the no-data value to transparent. For example, if your no-data value is something north of 36000:

title: Discrete Ramp'
feature-styles:
- name: raster
  rules:
  - name: raster
  - symbolizers:
    - raster:
        opacity: 1.0
        color-map:
          type: intervals
          entries:
          - ['#000000',0, 36000,'']

The format here is [<color>,<transparency>,<cell value>,<symbol>]. You can, of course, add more entries to symbolize other ranges of values. I hope this helps, even though it's a few years too late. :)

Answer 2

I don't think it can be done with SLD. Publish your imagery as a image mosaic and change the "input transparent color" to black instead.