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# frozen_string_literal: true
module GoogleDistanceMatrix
class PolylineEncoder
# Calculates deltas between lat_lng values, internal helper class for PolylineEncoder.
#
# According to the Google's polyline encoding spec:
# "Additionally, to conserve space, points only include the offset
# from the previous point (except of course for the first point)"
#
# @see GoogleDistanceMatrix::PolylineEncoder
class Delta
def initialize(precision = 1e5)
@precision = precision
end
# Takes a set of lat/lng pairs and calculates delta
#
# Returns a flatten array where each lat/lng delta pair is put in order.
def deltas_rounded(array_of_lat_lng_pairs)
rounded = round_to_precision array_of_lat_lng_pairs
calculate_deltas rounded
end
private
def round_to_precision(array_of_lat_lng_pairs)
array_of_lat_lng_pairs.map do |(lat, lng)|
[
(lat * @precision).round,
(lng * @precision).round
]
end
end
def calculate_deltas(rounded)
deltas = []
delta_lat = 0
delta_lng = 0
rounded.each do |(lat, lng)|
deltas << lat - delta_lat
deltas << lng - delta_lng
delta_lat = lat
delta_lng = lng
end
deltas
end
end
end
end
Version data entries
11 entries across 11 versions & 1 rubygems