def __init__(self, content):
""" With MapRenderer you can render an aktionskarten map in different
file formats like pdf, svg or png.
Internally it uses mapnik and cairo to archieve this. A valid style
has to be defined through `MAPNIK_OSM_XML`. Normally this a carto
derived `style.xml`. In this file your datasource is specified. This
can be for instance a postgres+postgis database with imported osm
data.
:param content: dict of map content
"""
# Mapnik uses mercator as internal projection. Our data is encoded in
# latlon. Therefor we need a transformer for coordindates from longlat
# to mercator
proj_merc = Projection('+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0\
+lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m \
+nadgrids=@null +no_defs +over')
proj_longlat = Projection('+proj=longlat +ellps=WGS84 +datum=WGS84 \
+no_defs')
transformer = ProjTransform(proj_longlat, proj_merc)
# our maps should be printable on a DIN A4 page with 150dpi
self._map = Map(1754, 1240)
bbox = transformer.forward(Box2d(*content['bbox']))
self._map.zoom_to_box(bbox)
self._map.buffer_size = 5
start = timer()
# add osm data (background)
load_map(self._map, current_app.config['MAPNIK_OSM_XML'])
mid = timer()
self._add_grid(content['grid'])
self._add_features(content['features'])
self._add_legend(content['name'], content['place'], content['datetime'],
content['attributes'])
end = timer()
print("Map.init - OSM: ", mid - start)
print("Map.init - Map: ", end - mid)
print("Map.init - Total: ", end - start)
# it to within the web mercator 'square world' if necessary.
#
# Example usage: latlon2merc.py -180 -90 180 90
import sys
from mapnik import Box2d, Coord, Projection, ProjTransform
latlon = Projection('+proj=latlong +datum=WGS84')
merc = Projection(
'+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs'
)
max_4326 = 85.0511287798066
max_3785 = 20037508.3427892
transform = ProjTransform(latlon, merc)
if len(sys.argv) == 3:
ll = transform.forward(Coord(float(sys.argv[1]), float(sys.argv[2])))
if (ll.y > max_3785):
print(' '.join([str(ll.x), str(max_3785)]))
elif (ll.y < -max_3785):
print(' '.join([str(ll.x), str(-max_3785)]))
else:
print(' '.join([str(ll.x), str(ll.y)]))
elif len(sys.argv) == 5:
minx, miny, maxx, maxy = (float(sys.argv[1]), float(sys.argv[2]),
float(sys.argv[3]), float(sys.argv[4]))
if (miny < -max_4326):
def transform(self, from_prj, to_prj):
trans = ProjTransform(from_prj, to_prj)
return trans.forward(self)
# note: requires mapnik SVN r822 or greater.
# Example of reprojecting the extent for the netherlands in epsg:28992 to google mercator and then back to the original netherlands extent.
import sys
try:
from mapnik import ProjTransform, Projection, Envelope
except ImportError, E:
sys.exit('Requires Mapnik SVN r822 or greater:\n%s' % E)
# http://spatialreference.org/ref/epsg/28992/
# http://mapnik.dbsgeo.com/days/2009-01-25
amersfoort_extent = Envelope(13599.999985, 306799.999985, 277999.999985,
619299.999985)
amersfoort_proj = Projection('+init=epsg:28992')
merc_proj = Projection(
'+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs'
)
transform = ProjTransform(amersfoort_proj, merc_proj)
merc_extent = transform.forward(amersfoort_extent)
if transform.backward(merc_extent).__repr__() == amersfoort_extent.__repr__():
print 'Transformation successful!'
print 'Original Dutch Extent: %s' % amersfoort_extent
print 'Merc Extent: %s' % merc_extent
else:
print 'Reprojection failure...'
