A little tool to render GeoJSON files as layers in an HTML output map file.

mapit.py

#!/usr/bin/env python

"""
A little tool to render GeoJSON files as layers in an HTML output map file.

The output map shows the region covered by the combined bounding box of all
GeoJSON input files. This was tested only with Python 3.5, but should also
work on Python >= 2.7.

The pygeoj package does calculate the bounding box correctly only for version
>= 0.2.5. Any existing bbox attributes inside a GeoJSON file are ignored.

No kind of styling is applied to the GeoJSON features here, yet.

Example:

    python mapit.py > map12.html
    python mapit.py 1.geojson 2.geojson > map12.html
"""

import os
import sys
import folium  # pip install folium
import pygeoj  # pip install pygeoj>=0.2.5


__author__  = "Dinu Gherman"
__date__    = "2017-07-07"
__license__ = "GPL3"
__version__ = "0.3"


def combine_bboxes(bboxes):
    """
    Return a combined bounding box from a list of individual ones.
    """
    λ0r, φ0r, λ1r, φ1r = bboxes[0]
    for bbox in bboxes[1:]:
        λ0, φ0, λ1, φ1 = bbox
        if λ0 < λ0r: λ0r = λ0
        if φ0 < φ0r: φ0r = φ0
        if λ1 > λ1r: λ1r = λ1
        if φ0 > φ1r: φ0r = φ1

    return (λ0r, φ0r, λ1r, φ1r)


def main(geo_paths):
    """
    Render one or more GeoJSON files as seperate layers in an HTML output map.
    """
    map = folium.Map(tiles="OpenStreetMap") # "Stamen Toner", ...

    for geo_path in geo_paths:
        name = os.path.basename(geo_path)
        folium.GeoJson(open(geo_path), name=name).add_to(map)

    boxes = [pygeoj.load(path).bbox for path in geo_paths]
    λ0, φ0, λ1, φ1 = combine_bboxes(boxes)
    map.fit_bounds([(φ0, λ0), (φ1, λ1)])
    folium.LayerControl().add_to(map)
    
    fp = os.fdopen(sys.stdout.fileno(), 'wb')
    map.save(fp)
    # map.save("output.html")


if __name__ == "__main__":
    main(sys.argv[1:])