convert trac code chunks to github style
Dane Springmeyer
parent
6c8fd72419
commit
007716312b
1 changed files with 96 additions and 84 deletions
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@ -14,18 +14,20 @@ The simple check is to start python interpreter from a command line by typing py
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and then just type:
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#!python
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>>> import mapnik
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```python
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>>> import mapnik
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```
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and if you don't see any complaints, you're on the right track. If you do, you have to check your installation again.
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* Note: If you have built mapnik in debug mode you should see the available datasources listed, including:
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#!python
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>>> import mapnik
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registered datasource : gdal
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registered datasource : postgis
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registered datasource : raster
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registered datasource : shape
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```python
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>>> import mapnik
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registered datasource : gdal
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registered datasource : postgis
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registered datasource : raster
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registered datasource : shape
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```
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## Step 2
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@ -34,73 +36,79 @@ The code below can be pasted into your python interpreter. Ideally paste line by
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Import the mapnik python toolkit and setup the basic map parameters
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#!python
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import mapnik
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```
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import mapnik
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# Instantiate a map object with given width, height and spatial reference system
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m = mapnik.Map(600,300,"+proj=latlong +datum=WGS84")
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# Set background colour to 'steelblue'.
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# You can use 'named' colours, #rrggbb, #rgb or rgb(r%,g%,b%) format
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m.background = mapnik.Color('steelblue')
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# Instantiate a map object with given width, height and spatial reference system
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m = mapnik.Map(600,300,"+proj=latlong +datum=WGS84")
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# Set background colour to 'steelblue'.
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# You can use 'named' colours, #rrggbb, #rgb or rgb(r%,g%,b%) format
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m.background = mapnik.Color('steelblue')
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```
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* Note, Mapnik accepts any projection that Proj.4 handles. See http://spatialreference.org for the proj4 strings for various projections. For example http://spatialreference.org/ref/epsg/4326/mapnikpython/ will give you the exact parameters for EPSG 4326.
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Create the Styles and Rules for the map symbology
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#!python
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# Now lets create a style and add it to the Map.
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s = mapnik.Style()
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# A Style can have one or more rules. A rule consists of a filter, min/max scale
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# demoninators and 1..N Symbolizers. If you don't specify filter and scale denominators
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# you get default values :
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# Filter = 'ALL' filter (meaning symbolizer(s) will be applied to all features)
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# MinScaleDenominator = 0
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# MaxScaleDenominator = INF
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# Lets keep things simple and use default value, but to create a map we
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# we still must provide at least one Symbolizer. Here we want to fill countries polygons with
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# greyish colour and draw outlines with a bit darker stroke.
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```python
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# Now lets create a style and add it to the Map.
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s = mapnik.Style()
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# A Style can have one or more rules. A rule consists of a filter, min/max scale
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# demoninators and 1..N Symbolizers. If you don't specify filter and scale denominators
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# you get default values :
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# Filter = 'ALL' filter (meaning symbolizer(s) will be applied to all features)
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# MinScaleDenominator = 0
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# MaxScaleDenominator = INF
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# Lets keep things simple and use default value, but to create a map we
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# we still must provide at least one Symbolizer. Here we want to fill countries polygons with
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# greyish colour and draw outlines with a bit darker stroke.
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r=mapnik.Rule()
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r.symbols.append(mapnik.PolygonSymbolizer(mapnik.Color('#f2eff9')))
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r.symbols.append(mapnik.LineSymbolizer(mapnik.Color('rgb(50%,50%,50%)'),0.1))
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s.rules.append(r)
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r=mapnik.Rule()
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r.symbols.append(mapnik.PolygonSymbolizer(mapnik.Color('#f2eff9')))
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r.symbols.append(mapnik.LineSymbolizer(mapnik.Color('rgb(50%,50%,50%)'),0.1))
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s.rules.append(r)
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```
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Connect the style information to your map and your data
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#!python
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# Here we have to add our style to the Map, giving it a name.
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m.append_style('My Style',s)
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```python
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# Here we have to add our style to the Map, giving it a name.
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m.append_style('My Style',s)
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# Here we instantiate our data layer, first by giving it a name and srs (proj4 projections string), and then by giving it a datasource.
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lyr = mapnik.Layer('world',"+proj=latlong +datum=WGS84")
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# Then provide the full filesystem path to a shapefile in WGS84 or EPSG 4326 projection without the .shp extension
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# A sample shapefile can be downloaded from http://mapnik-utils.googlecode.com/svn/data/world_borders.zip
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lyr.datasource = mapnik.Shapefile(file='/Users/path/to/your/data/world_borders')
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lyr.styles.append('My Style')
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# Here we instantiate our data layer, first by giving it a name and srs (proj4 projections string), and then by giving it a datasource.
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lyr = mapnik.Layer('world',"+proj=latlong +datum=WGS84")
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# Then provide the full filesystem path to a shapefile in WGS84 or EPSG 4326 projection without the .shp extension
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# A sample shapefile can be downloaded from http://mapnik-utils.googlecode.com/svn/data/world_borders.zip
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lyr.datasource = mapnik.Shapefile(file='/Users/path/to/your/data/world_borders')
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lyr.styles.append('My Style')
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```
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Finally add the layers to the map and zoom to the full extent of the data layer
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#!python
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```python
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m.layers.append(lyr)
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m.zoom_to_box(lyr.envelope())
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```
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Finish up by making the world map image
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#!python
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# Write the data to a png image called world.png in the base directory of your user
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mapnik.render_to_file(m,'world.png', 'png')
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```python
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# Write the data to a png image called world.png in the base directory of your user
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mapnik.render_to_file(m,'world.png', 'png')
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# Exit the python interpreter
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exit()
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# Exit the python interpreter
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exit()
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```
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Then back in your normal shell type:
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#!sh
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# On a mac
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open world.png
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# On windows
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start world.png
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``sh
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# On a mac
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open world.png
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# On windows
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start world.png
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```
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Or navigate to your base directory and open world.png and the result should look like this:
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[[BR]]
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@ -113,30 +121,32 @@ The next logical step is to run the same code as a python script from your shell
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This can be done by adding a line at the top of the script like:
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#!python
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#!/usr/bin/env python
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```sh
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#!/usr/bin/env python
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```
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Copy this entire text below and save as a file called world.py.
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```python
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#!/usr/bin/env python
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#!python
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#!/usr/bin/env python
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import mapnik
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m = mapnik.Map(600,300,"+proj=latlong +datum=WGS84")
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m.background = mapnik.Color('steelblue')
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s = mapnik.Style()
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r=mapnik.Rule()
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r.symbols.append(mapnik.PolygonSymbolizer(mapnik.Color('#f2eff9')))
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r.symbols.append(mapnik.LineSymbolizer(mapnik.Color('rgb(50%,50%,50%)'),0.1))
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s.rules.append(r)
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m.append_style('My Style',s)
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lyr = mapnik.Layer('world',"+proj=latlong +datum=WGS84")
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lyr.datasource = mapnik.Shapefile(file='/Users/path/to/your/data/world_borders')
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lyr.styles.append('My Style')
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m.layers.append(lyr)
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m.zoom_to_box(lyr.envelope())
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mapnik.render_to_file(m,'world.png', 'png')
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```
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import mapnik
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m = mapnik.Map(600,300,"+proj=latlong +datum=WGS84")
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m.background = mapnik.Color('steelblue')
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s = mapnik.Style()
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r=mapnik.Rule()
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r.symbols.append(mapnik.PolygonSymbolizer(mapnik.Color('#f2eff9')))
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r.symbols.append(mapnik.LineSymbolizer(mapnik.Color('rgb(50%,50%,50%)'),0.1))
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s.rules.append(r)
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m.append_style('My Style',s)
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lyr = mapnik.Layer('world',"+proj=latlong +datum=WGS84")
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lyr.datasource = mapnik.Shapefile(file='/Users/path/to/your/data/world_borders')
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lyr.styles.append('My Style')
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m.layers.append(lyr)
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m.zoom_to_box(lyr.envelope())
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mapnik.render_to_file(m,'world.png', 'png')
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* Don't forget to change the path to your world_borders shapefile.
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* Note: Mapnik accepts both the absolute path to your data as well as the relative path
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* Note: Same goes for the path to where you want to save your file
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@ -144,20 +154,22 @@ Copy this entire text below and save as a file called world.py.
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Next make the script executable. On Mac or Linux you would do this with the command:
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#!sh
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```sh
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chmod +x world.py
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```
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Finally run the script with the command:
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#!sh
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# You must be in the same directory as you saved the script
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./world.py
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# Add a second optional command to open the resulting file with one keystroke
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# On a mac
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./world.py; open world.png
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# On windows
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start world.py && start world.png
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```sh
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# You must be in the same directory as you saved the script
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./world.py
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# Add a second optional command to open the resulting file with one keystroke
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# On a mac
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./world.py; open world.png
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# On windows
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start world.py && start world.png
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```
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* Run this way the script will continually write over and open the world.png map.
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* Now you can easily open the script in a separate text editor and try changing the dimensions, colors, or datasource (remember to use the correct projection).
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