10 Raster

Matthieu Bonnefoy edited this page 2016-04-20 14:19:59 +12:00

Table of Contents

• Installation
• Parameters
• Styling
• Usage
• Python
• C++

This plugin supports reading tiff and geotiff files.

Tiled or Stripped tiff files are required and when rasters are small < 200-300 MB this driver is faster that the GDAL plugin.

If files are larger it is recommended to build GDAL overviews (with gdaladdo command) and instead read with the GDAL plugin.

Note: overviews support is available only in Mapnik >= 0.7.0

A drawback(or advantage!) of this plugin is that it requires manually setting the file bounds.

• hint: create a GDAL datasource from your tiff in python, call the envelope() method to get the bounds, and use those.

For other plugins see: PluginArchitecture

Installation

To check if the raster plugin built and was installed correctly you can do:

>>> from mapnik import DatasourceCache as c
>>> 'raster' in c.plugin_names()
True

Parameters

parameter	value	description	default
file	string	geotiff file path
base	string	optional base path where to search for the tiff raster file
lox	double	lower x corner of the image in map coordinates
loy	double	lower y corner of the image in map coordinates
hix	double	upper x corner of the image in map coordinates
hiy	double	upper y corner of the image in map coordinates
extent	string	extent of the image in map coordinates, comma or space separated (at least or should be passed)
format	string	image format to use, currently only tiff is supported	tiff

Styling

To style a layer use the RasterSymbolizer

Usage

Python

<!-- NOTE: must be in the same SRS as your map-->
<Layer name="Raster">
    <StyleName>raster</StyleName>
    <Datasource>
        <Parameter name="type">raster</Parameter>
        <Parameter name="file">/path/to/my/raster/file.tiff</Parameter>
        <Parameter name="lox">min_x</Parameter>
        <Parameter name="loy">min_y</Parameter>
        <Parameter name="hix">max_x</Parameter>
        <Parameter name="hiy">max_y</Parameter>
    </Datasource>
</Layer>

from mapnik import Raster, Layer
raster = Raster(base='/home/mapnik/data',file='/path/to/my/raster/file.tiff',lox=minx,loy=min_y,hix=max_x,hiy=max_y)
lyr = Layer('Tiff Layer')
lyr.datasource = raster

C++

Plugin datasource initialization example code can be found on PluginArchitecture.

A Raster datasource may be created as follows:

{
    parameters p;
    p["type"]="raster";
    p["file"]="/path/to/my/raster/file.tiff";
    p["lox"]=min_x;
    p["loy"]=min_y;
    p["hix"]=max_x;
    p["hiy"]=max_y;

    set_datasource(datasource_cache::instance()->create(p));

    layer lyr("Raster");
    lyr.add_style("raster");
    m.add_layer(lyr);
}