PgRaster

This plugin supports reading raster datasets from PostGIS.

Installation

Make sure that running python scons/scons.py shows the following line

Checking for pg_config... yes

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

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

Parameters

parameter	value	description	default
host	string	name of the postgres host
port	integer	name of the postgres port
dbname	string	name of the database
user	string	username to use for connecting
password	string	user password to use for connecting
table	string	name of the table to fetch, this can be a sub-query; subquery has to use syntax of: '( ) as subquery'.
raster_field	string	name of the raster field, in case you have more than one in a single table.	Deduced from metadata tables if possible
raster_table	string	name of the table containing the returned raster; for determining SRIDs with subselects
srid	integer	srid of the table, if this is > 0 then fetching data will avoid an extra database query for knowing the srid of the table	0
extent	string	maxextent of the rasters	determined by querying the metadata for the table
extent_from_subquery	boolean	evaluate the extent of the subquery, this might be a performance issue	false
estimate_extent	boolean	estimate extent from statistics table if not specified	false
connect_timeout	integer	timeout is seconds for the connection to take place	4
persist_connection	boolean	choose whether to share the same connection for subsequent queries	true
row_limit	integer	max number of rows to return when querying data, 0 means no limit	0
cursor_size	integer	if this is > 0 then server cursor will be used, and will prefetch this number of features	0
initial_size	integer	initial size of the stateless connection pool	1
max_size	integer	max size of the stateless connection pool	10
prescale_rasters	boolean	whether to automatically scale input rasters	false
use_overviews	boolean	whether to use raster overviews when available	false
clip_rasters	boolean	whether to automatically clip input rasters	false
max_async_connection	integer	max number of PostGIS queries for rendering one map in asynchronous mode. Full doc here.	1
band	integer	request for a specific raster band index (1-based). 0 means to read all bands. Note that a band read from a single band raster gets interpreted as Grayscale if band=0 is specified while they retain their original value when explicitly referenced with the "band" parameter. This affects effectiveness of RasterColorizer	0

Styling

To style a layer from PgRaster use the RasterSymbolizer