mapnik/tests/visual_tests/styles/style-level-compositing-tiled-1,1.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="purple">
    <Parameters>
        <Parameter name="sizes">512,512</Parameter>
        <Parameter name="bbox">0,-20037508.342,20037508.342,0</Parameter>
    </Parameters>
    <Style name="style" direct-image-filters="agg-stack-blur(5,5)" image-filters-inflate="true">
        <Rule>
            <PolygonSymbolizer fill="yellow" fill-opacity=".6"/>
        </Rule>
    </Style>
    <Layer name="world" 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>style</StyleName>
        <Datasource>
            <Parameter name="file">../../data/shp/world_merc</Parameter>
            <Parameter name="type">shape</Parameter>
        </Datasource>
    </Layer>

    <Style name="mask" image-filters="agg-stack-blur(5,5)" opacity=".8" comp-op="dst-in">
        <Rule>
            <PolygonSymbolizer />
        </Rule>
    </Style>
    <Layer name="mask" 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>mask</StyleName>
        <Datasource>
            <Parameter name="inline">
            wkt,name
            "Polygon((-10000000 -5000000, -10000000 10000000, -5000000 10000000, -5000000 -5000000, -10000000 -5000000))","bounds"
            </Parameter>
            <Parameter name="type">csv</Parameter>
        </Datasource>
    </Layer>
</Map>