Tutorial 2 – ‘Hello,world!’ using XML configuration

Overview

Make sure you have mapnik installed and you’ve successfully run through GettingStarted Tutorial 1.

• 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. Therefore, an XML configuration is used by the Open Street Map project to do intense filtering of PostGIS data by attribute.

Two examples will be shown:

1) An XML configuration that exactly matches the map output from the pure python example in The Getting Started Tutorial 1.

• This is intended to help new users see the common usage of Mapnik style and rule parameters.
• Note: These samples are intentionally sparse and do not take full advantage of Mapnik capabilities.
  • See the rundemo.py script in the downloads for more advanced usage of python bindings.
  • See the OSM XML example in the tests folder for more advanced usage of XML.

2) An XML configuration that uses a world borders dataset with population attributes to create a chloropleth map by population size. This is intended to introduce the uses of rule filters and labeling in XML

Note: the code for example 1, along with the code from GettingStarted Tutorial 1 can be downloaded in a zip bundle from a link below. These downloads contain relative paths to a data folder where you should place the world_borders.shp.

Etape 1

Hello World XML

First you will still need a python script that sets the basic map parameters and points to the XML config file:

#!/usr/bin/env python
import mapnik mapfile = 'world_styles.xml'
map_output = 'hello_world_using_xml_config.png'
m = mapnik.Map(600, 300)
mapnik.load_map(m, mapfile)
bbox = mapnik.Envelope(mapnik.Coord(-180.0, -90.0), mapnik.Coord(180.0, 90.0))
m.zoom_to_box(bbox)
mapnik.render_to_file(m, map_output)

• Copy this code and save to a file called world_map.py

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

Note: you will need to specify the path to the same Mapping Hacks world borders shapefile using in Tutorial 1

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE Map>
<Map bgcolor="steelblue" srs="+proj=latlong +datum=WGS84">
  <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=latlong +datum=WGS84">
    <StyleName>My
      Style</StyleName>
    <Datasource>
      <Parameter name="type">shape</Parameter>
      <Parameter name="file">/path/to/your/world_borders</Parameter>
    </Datasource>
  </Layer>
</Map>

• Copy this XML and save to a file called world_styles.xml beside the world_map.py script

Now run that script with this command:

python world_map.py

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

Etape 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:

#!/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>

Attached files

hello_world.zip - Tutorial for Hello World Mapnik examples using pure python and XML config file.

world_population.png Map graphic output of Step 2 using XML configuration to display chloropleth map of world population.

world_population_minimized.png - Minimized version of the output of Step 2 for trac display.

world_borders.zip.