Hi, I would like to share with the list the following piece of code,
Together with gdal2tiles it allows generating a geojson layers from an
html client-side image map, for browsing with openlayers.
Usage:
gdal2tiles.py test.png test/
map2geojson.py 220.0 520.0 1.0 < test.map > test/polygon.json
add in openlayers.html
+ gml = new OpenLayers.Layer.GML("GeoJSON", "polygon.json", {format:
OpenLayers.Format.GeoJSON});
+ map.addLayer(gml);
+ selectFeature = new OpenLayers.Control.SelectFeature(gml, {hover:
true});
+ map.addControl(selectFeature);
+ selectFeature.activate();
You can see the result here:
http://ligamen.org/work/test/openlayers.html
Let me know if it is worth including in gdal2tiles, or if it needs more
love ?
Thanks.
--
Johan Euphrosine <pro...@aminche.com>
#!/usr/bin/env python
###############################################################################
#
# Purpose: Convert html client-side image map into geojson metadata.
# Author: Johan Euphrosine <pro...@aminche.com>
#
###############################################################################
# Copyright (c) 2009, Johan Euphrosine <pro...@aminche.com>
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Library General Public
# License as published by the Free Software Foundation; either
# version 2 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Library General Public License for more details.
#
# You should have received a copy of the GNU Library General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301 USA
###############################################################################
import sys
import os
from lxml import objectify
import simplejson as json
import unittest
def map2geojson(areas, size, scale):
w, h = size
def to_features(areas):
for area in areas:
values = [int(c) for c in area.get("coords").split(",")]
coords = zip([x*scale for x in values[::2]], [h-(y*scale) for y in values[1::2]])
yield {"type": "Feature",
"geometry": {"type": "Polygon",
"coordinates": [coords]},
"properties": { "name": area.get("title") }}
root = objectify.fromstring('<map2geojson>%s</map2geojson>' % areas)
return json.dumps({"type": "FeatureCollection",
"features": list(to_features(root.area))})
class Map2GeoJsonTestCase(unittest.TestCase):
def test(self):
map = """<area shape="polygon" title="a" coords="142,200,136,206,124,209,124,209,133,201,142,200" />
<area shape="polygon" title="b" coords="142,200,133,199,123,192,123,192,135,194,142,200" />"""
size = (220.0, 520.0)
scaled = (3000.0, 7090.0)
scale = scaled[0]/size[0]
geojson = json.loads(map2geojson(map, scaled, scale))
features = geojson["features"]
self.assertEquals("a", features[0]["properties"]["name"])
self.assertEquals([[[1936.3636363636365, 4362.7272727272721], [1854.5454545454545, 4280.909090909091], [1690.909090909091, 4240.0], [1690.909090909091, 4240.0], [1813.6363636363637, 4349.090909090909], [1936.3636363636365, 4362.7272727272721]]], features[0]["geometry"]["coordinates"])
self.assertEquals("b", features[1]["properties"]["name"])
self.assertEquals([[[1936.3636363636365, 4362.7272727272721], [1813.6363636363637, 4376.363636363636], [1677.2727272727273, 4471.818181818182], [1677.2727272727273, 4471.818181818182], [1840.909090909091, 4444.545454545454], [1936.3636363636365, 4362.7272727272721]]], features[1]["geometry"]["coordinates"])
if __name__ == '__main__':
if len(sys.argv) == 1:
unittest.main()
else:
print map2geojson(sys.stdin.read(), (float(sys.argv[1]), float(sys.argv[2])), float(sys.argv[3]))
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