def test_line_accumulating_error(self):
"""
Generate a line of 40 points. Each point's x coordinate, x[n] is at x[n - 1] + 1 + d, where
d is a floating point number that just rounds to 0 at 6 decimal places, i.e. 0.00000049.
Therefore a delta compression method that only computes x[n] - x[n - 1] and rounds to 6 d.p.
will get a constant delta of 1.000000. The result will be an accumulated error along the
line of 0.00000049 * 40 = 0.0000196 over the full length.
"""
feature = {
'type': 'MultiPolygon',
'coordinates': [[[]]],
}
points = 40
# X coordinates[0, 1.00000049, 2.00000098, 3.00000147, 4.00000196, ...,
# 37.00001813, 38.00001862, 39.00001911, 40.00001960, 0]
feature['coordinates'][0][0] = [[i * 1.00000049, 0]
for i in range(0, points + 1)]
feature['coordinates'][0][0].append([0, 0])
pbf = Encoder().encode(feature)
round_tripped = Decoder().decode(pbf)
def round_x(coord):
x, _ = coord
return round(x * 1000000) / 1000000.0
xs_orig = [round_x(coord) for coord in feature['coordinates'][0][0]]
xs_round_tripped = [
round_x(coord) for coord in round_tripped['coordinates'][0][0]
]
assert xs_round_tripped == xs_orig
def test_high_precision():
filename = os.path.join(os.path.dirname(__file__),
"fixtures/precision.json")
with open(filename) as f:
geojson = json.loads(f.read())
pbf = Encoder().encode(geojson)
geojson2 = Decoder().decode(pbf)
ring = geojson2['features'][0]['geometry']['coordinates'][0]
assert ring[0] == ring[4]
def test_circle_accumulating_error():
feature = {
'type': 'MultiPolygon',
'coordinates': [[[]]],
}
points = 16
feature['coordinates'][0][0] = [[
math.cos(math.pi * 2.0 * i / points),
math.sin(math.pi * 2.0 * i / points)
] for i in range(0, points + 1)]
pbf = Encoder().encode(feature)
round_tripped = Decoder().decode(pbf)
def round_coord(coord):
x, y = coord
return [round(x * 1000000), round(y * 1000000)]
ring_orig = [round_coord(coord) for coord in feature['coordinates'][0][0]]
ring_round_tripped = [
round_coord(coord) for coord in round_tripped['coordinates'][0][0]
]
assert ring_round_tripped == ring_orig
def test_coding(filename):
geojson = json.loads(open(filename).read())
pb = Encoder().encode(geojson)
geojson2 = Decoder().decode(pb)
assert geojson == geojson2
def test_high_precision(self):
pbf = Encoder().encode(self.precision_data)
geojson2 = Decoder().decode(pbf)
ring = geojson2['features'][0]['geometry']['coordinates'][0]
assert ring[0] == ring[4]