mapnik/tests/visual_tests/styles/marker-with-background-image-and-hsla-transform.xml

<Map srs="+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs" background-image="../../data/images/checker.jpg">

    <Style name="ellipse"
      direct-image-filters="scale-hsla(0,1,0,1,0,1,0,.5)"
      image-filters="scale-hsla(.1,.9,.5,1,.5,1,.2,1)"
      >
        <Rule>
            <MarkersSymbolizer
              width="240"
              height="240"
              fill="steelblue"
              fill-opacity=".7"
              stroke="yellow"
              stroke-width="16"
              stroke-opacity=".3"
            />
            <MarkersSymbolizer
              width="100"
              opacity=".5"
              fill="darkorange"
              comp-op="multiply"
              transform="skewX(50)"
              allow-overlap="true"
            />
            <MarkersSymbolizer
              width="100"
              opacity=".5"
              fill="darkred"
              comp-op="color-burn"
              transform="skewX(-50)"
              allow-overlap="true"
            />
        </Rule>
    </Style>

    <Layer name="layer" srs="+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs">
        <StyleName>ellipse</StyleName>
        <Datasource>
            <Parameter name="type">csv</Parameter>
            <Parameter name="inline">
x,y
2.5,2.5
            </Parameter>
        </Datasource>
    </Layer>

    <!-- points to frame data view -->

    <Style name="frame">
        <Rule>
            <PointSymbolizer />
        </Rule>
    </Style>

    <Layer name="frame" srs="+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs">
        <StyleName>frame</StyleName>
        <Datasource>
            <Parameter name="type">csv</Parameter>
            <Parameter name="inline">
x,y
0,0
5,0
0,5
5,5
            </Parameter>
        </Datasource>
    </Layer>
    
</Map>