simplify points in geojson file using opencv implementation of Douglas–Peucker : https://en.wikipedia.org/wiki/Ramer%E2%80%93Douglas%E2%80%93Peucker_algorithm

simplify.py

import cv2, numpy as np, json, sys


def simplify(data):
    d = np.array(data).astype(np.float32)
    if d.size > 3:
        simple = cv2.approxPolyDP(d, thresh, False).tolist()
        data = [[round(n, 6), round(p, 6)] for n,p in np.reshape(simple, [-1, 2]).tolist()]
    else:
        print "not reducing {}".format(d)
    print "reduced {} to {}".format(len(d), len(data))
    return data

if __name__ == '__main__':
    thresh = float(sys.argv[1])
    with open(sys.argv[2]) as f:
        data = json.load(f)
    for feature in data['features']:
        geo = feature['geometry']
        if geo['type'] in ['LineString', 'Polygon']:
            geo['coordinates'] = simplify(geo['coordinates'])
        elif geo['type'] in ['MultiLineString', 'MultiPolygon']:
            for indx, line in enumerate(geo['coordinates']):
                geo['coordinates'][indx] = simplify(line)
        elif geo['type'] == 'GeometryCollection':
            print "Reducing Geometry inside GeometryCollection is not supported"
        else:
            print "Unknown geometry: {}".format(geo['type'])
    with open(sys.argv[3], 'w') as output_file:
        output_file.write(json.dumps(data))