Mapnik demo of loading a single map and rendering each layer inside it. Originally forked example from https://gist.github.com/springmeyer/7459452

README.md

Mapnik example

This shows how to programmatically turn on and off layers on a Mapnik map from python.

Then the map is rendered twice to show how only active layers are displayed.

Depends

Mapnik >= 2.2 and the python bindings

Usage

git clone https://gist.github.com/8364280.git mapnik-layer-example
cd mapnik-layer-example
python render.py
# then look at the images: you should see how one shows points and one shows lines

line.png

map.xml

<Map
    background-color="#eee"
    srs="+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs">
 
    <Style name="point">
        <Rule>
            <MarkersSymbolizer />
        </Rule>
    </Style>
 
    <Layer name="point" srs="+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs">
        <StyleName>point</StyleName>
        <Datasource>
            <Parameter name="type">csv</Parameter>
            <Parameter name="inline">
id|name|wkt
1|null island|Point(0 0)
            </Parameter>
        </Datasource>
    </Layer>

    <Style name="line">
        <Rule>
            <LineSymbolizer />
        </Rule>
    </Style>
 
    <Layer name="line" srs="+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs">
        <StyleName>line</StyleName>
        <Datasource>
            <Parameter name="type">csv</Parameter>
            <Parameter name="inline">
wkt|name
LineString(-180.0 -85.0, 0 0, 180.0 0))|line
            </Parameter>
        </Datasource>
    </Layer>

</Map>

point.png

render.py

import mapnik
m = mapnik.Map(256,256)
mapnik.load_map(m,'map.xml')
m.zoom_all()
# turn off second layer
# and render just first
m.layers[1].status = False
im = mapnik.Image(m.width,m.height)
mapnik.render(m,im)
im.save('point.png')
# then flip active layers
m.layers[0].status = False
m.layers[1].status = True
im = mapnik.Image(m.width,m.height)
mapnik.render(m,im)
im.save('line.png')