mapnik/tests/visual_tests/styles/tiff-nodata-tolerance.xml

<Map srs="+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over" background-color="white">
  <Parameters>
    <Parameter name="sizes">512,512</Parameter>
  </Parameters>

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

<Layer name="test" srs="+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over">
    <StyleName>test</StyleName>
    <Datasource>
        <Parameter name="file">../data/Yosemite_L9.tif</Parameter>
        <Parameter name="type">gdal</Parameter>
        <Parameter name="nodata">255</Parameter>
        <Parameter name="nodata_tolerance">100</Parameter>
    </Datasource>
</Layer>

</Map>