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springmeyer edited this page Jan 9, 2012 · 16 revisions

Tutorial 2 -- 'Hello,world!' using an XML stylesheet

Overview

Make sure you have mapnik installed and you've successfully run through Getting Started Python Tutorial.

  • This page will guide you through using the Mapnik python bindings along with a separate XML file for your map styles.

  • This is a useful approach to manage your map styles/rules separately from your python code, and can be advantageous for very complex formatting.

Two examples will be shown:

  1. An XML stylesheet that exactly matches the map output from the pure python example in Getting Started Python Tutorial.

  2. An XML stylesheet that uses a world borders dataset with population attributes to create a chloropleth map (aka thematic) by population size.

Step 1

Hello World XML

First you will need a python script that sets the basic map parameters and points to the XML stylesheet

#!/usr/bin/env python
import mapnik
stylesheet = 'world_style.xml'
image = 'world_style.png'
m = mapnik.Map(600, 300)
mapnik.load_map(m, stylesheet)
m.zoom_all() 
mapnik.render_to_file(m, image)
  • Copy the above code and save to a file called world_map.py

Next you will need to create the world_style.xml file referenced in the world_map.py script.

<Map bgcolor="steelblue" srs="+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs">

  <Style name="My Style">
    <Rule>
      <PolygonSymbolizer>
        <CssParameter name="fill">#f2eff9</CssParameter>
      </PolygonSymbolizer>
      <LineSymbolizer>
        <CssParameter name="stroke">rgb(50%,50%,50%)</CssParameter>
        <CssParameter name="stroke-width">0.1</CssParameter>
      </LineSymbolizer>
    </Rule>
  </Style>

  <Layer name="world" srs="+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs">
    <StyleName>My Style</StyleName>
    <Datasource>
      <Parameter name="type">shape</Parameter>
      <Parameter name="file">world_borders.shp</Parameter>
    </Datasource>
  </Layer>

</Map>
  • Copy this XML and save to a file called world_style.xml beside the world_map.py script.

Now run that script:

python world_map.py
  • It should output a png graphic in the same folder that matches the Getting Started Tutorial.

Step 2

World Population XML

Attached below and included as code samples, here is a sample python script that accesses a 'population.xml map configuration.

Note: you will need to download the modified world borders shapefile.

  • Note: this file is originally from Thematic Mapping Blog. The version attached here is the simpler shapefile provided there with some modification made to avoid problems that occur when displaying the map in projections such as 900913/3785 (this tutorial does not use this projection so you can use the original shapefiles as well). See ticket 308 for details.

This script should result in a graphic like this:

/images/world_population_minimized.png

    #!/usr/bin/env python
    
    import mapnik
    mapfile = "population.xml"
    m = mapnik.Map(1400, 600)
    mapnik.load_map(m, mapfile)
    bbox = mapnik.Envelope(mapnik.Coord(-180.0, -75.0), mapnik.Coord(180.0, 90.0))
    m.zoom_to_box(bbox) 
    mapnik.render_to_file(m, 'world_population.png', 'png')

And here is the xml file:

    <?xml version="1.0" encoding="utf-8"?>
    <!DOCTYPE Map>
    <!-- Sample Mapnik XML template by Dane Springmeyer -->
    <Map bgcolor="white" srs="+proj=latlong +datum=WGS84">
      
      <Style name="population">
    
         <Rule>
          <!-- Built from Seven Class sequential YIGnBu from www.colorbrewer.org -->
          <!-- Quantile breaks originally from QGIS layer classification -->
          <Filter>[POP2005] = 0 </Filter>
          <PolygonSymbolizer>
            <CssParameter name="fill">#ffffcc</CssParameter>
          </PolygonSymbolizer>
          <!-- Outlines for Antarctica look good -->
          <LineSymbolizer>
            <CssParameter name="stroke">black</CssParameter>
            <CssParameter name="stroke-width">.1</CssParameter>
          </LineSymbolizer>
         </Rule>
         
         <Rule>
          <Filter>[POP2005] &gt; 0 and [POP2005] &lt; 15000</Filter>
          <PolygonSymbolizer>
            <CssParameter name="fill">#c7e9b4</CssParameter>
          </PolygonSymbolizer>
          <!-- Outlines for Antarctica look good -->
          <LineSymbolizer>
            <CssParameter name="stroke">black</CssParameter>
            <CssParameter name="stroke-width">.1</CssParameter>
          </LineSymbolizer>
         </Rule>
         
         <Rule>
          <Filter>[POP2005] &gt;= 15000 and [POP2005] &lt; 255000</Filter>
          <PolygonSymbolizer>
            <CssParameter name="fill">#7fcdbb</CssParameter>
          </PolygonSymbolizer>
         </Rule>
         
         <Rule>
          <Filter>[POP2005] &gt;= 255000 and [POP2005] &lt; 1300000</Filter>
          <PolygonSymbolizer>
            <CssParameter name="fill">#1d91c0</CssParameter>
          </PolygonSymbolizer>
         </Rule>
         
         <Rule>
          <Filter>[POP2005] &gt;= 1300000 and [POP2005] &lt; 4320000</Filter>
          <PolygonSymbolizer>
            <CssParameter name="fill">#41b6c3</CssParameter>
          </PolygonSymbolizer>
         </Rule>
              
         <Rule>
          <Filter>[POP2005] &gt;= 4320000 and [POP2005] &lt; 9450000</Filter>
          <PolygonSymbolizer>
            <CssParameter name="fill">#225ea8</CssParameter>
          </PolygonSymbolizer>
         </Rule>
              
         <Rule>
          <Filter>[POP2005] &gt;= 9450000 and [POP2005] &lt; 25650000</Filter>
          <PolygonSymbolizer>
            <CssParameter name="fill">#225ea8</CssParameter>
          </PolygonSymbolizer>
         </Rule>
              
         <Rule>
          <Filter>[POP2005] &gt;= 25650000 and [POP2005] &lt; 1134000000</Filter>
          <PolygonSymbolizer>
            <CssParameter name="fill">#122F7F</CssParameter>
          </PolygonSymbolizer>
         </Rule>
              
         <Rule>
          <ElseFilter/> <!-- This will catch all other values - in this case just India and China -->
          <!-- A dark red polygon fill and black outline is used here to highlight these two countries -->
          <PolygonSymbolizer>
            <CssParameter name="fill">darkred</CssParameter>
          </PolygonSymbolizer>
          <LineSymbolizer>
            <CssParameter name="stroke">black</CssParameter>
            <CssParameter name="stroke-width">.7</CssParameter>
          </LineSymbolizer>
         </Rule>
        
       </Style>
        
       <Style name="countries_label">
         <Rule>
          <!--  Only label those countries with over 9 Million People -->
          <!--  Note: Halo and Fill are reversed to try to make them subtle -->
          <Filter>[POP2005] &gt;= 4320000 and [POP2005] &lt; 9450000</Filter>
          <TextSymbolizer name="NAME" face_name="DejaVu Sans Bold" size="7" fill="black" halo_fill= "#DFDBE3" halo_radius="1" wrap_width="20" spacing="5" allow_overlap="false" avoid_edges="false" min_distance="10"/>
         </Rule>
              
         <Rule>
          <!--  Only label those countries with over 9 Million People -->
          <!--  Note: Halo and Fill are reversed to try to make them subtle -->
          <Filter>[POP2005] &gt;= 9450000 and [POP2005] &lt; 25650000</Filter>
          <TextSymbolizer name="NAME" face_name="DejaVu Sans Book" size="9" fill="black" halo_fill= "#DFDBE3" halo_radius="1" wrap_width="20" spacing="5" allow_overlap="false" avoid_edges="false" min_distance="10"/>
         </Rule>
         
         <Rule>
          <!--  Those with over 25 Million get larger labels -->
          <Filter>[POP2005] &gt;= 25650000 and [POP2005] &lt; 1134000000</Filter>
          <TextSymbolizer name="NAME" face_name="DejaVu Sans Book" size="12" fill="white" halo_fill= "#2E2F39" halo_radius="1" wrap_width="20" spacing="5" allow_overlap="false" avoid_edges="true" min_distance="10"/>
         </Rule>
              
         <Rule>
          <!--  Those with over 25 Million get larger labels -->
          <!--  Note: allow_overlap is true here to allow India to sneak through -->
          <Filter>[POP2005] &gt;= 1134000000</Filter>
          <TextSymbolizer name="NAME" face_name="DejaVu Sans Book" size="15" fill="white" halo_fill= "black" halo_radius="1" wrap_width="20" spacing="5" allow_overlap="true" avoid_edges="true" min_distance="10"/>
         </Rule>
      </Style>
      
      <Layer name="countries" srs="+proj=latlong +datum=WGS84" status="on">
        <!-- Style order determines layering hierarchy -->
        <!-- Labels go on top so they are listed second -->
        <StyleName>population</StyleName>
        <StyleName>countries_label</StyleName>
        <Datasource>
          <Parameter name="type">shape</Parameter>
         <!-- FIXME -->
         <!-- Note:  'TM_WORLD_BORDERS_SIMPL-0.3' is the name of the shapefile (without the .shp file extension) -->
          <Parameter name="file">/PATH/TO/THE/TM_WORLD_BORDERS_SIMPL-0.3</Parameter>
        </Datasource>
      </Layer>
    
    </Map>
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