mapnik/tests/visual_tests/styles/tiff-opaque-edge-gdal.xml

<Map srs="+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs" background-color="white">
  <Parameters>
    <Parameter name="sizes">256,256; 969,793</Parameter>
  </Parameters>

<Style name="test">
  <Rule>
    <RasterSymbolizer scaling="bilinear" />
  </Rule>
</Style>

<Layer name="test" srs="+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs">
    <StyleName>test</StyleName>
    <Datasource>
       <!-- https://github.com/mapnik/mapnik/issues/1508 -->
       <!-- note: this mis-reports it is premultiplied - it is not -->
        <Parameter name="file">../../data/raster/river_wgs.tiff</Parameter>
        <Parameter name="type">gdal</Parameter>
    </Datasource>
</Layer>

</Map>