clojure-polyline

Decoding and encoding of the google polyline algorithm as described at https://developers.google.com/maps/documentation/utilities/polylinealgorithm

Usage

(require '[com.michaelgaare.clojure-polyline :as polyline])

;; Decode a polyline string:
(polyline/decode "_p~iF~ps|U_ulLnnqC_mqNvxq`@")
;; => [[38.5 -120.2] [40.7 -120.95] [43.252 -126.453]]

;; Encode a collection of coordinates:
(polyline/encode [[38.5 -120.2] [40.7 -120.95] [43.252 -126.453]])
;; => "_p~iF~ps|U_ulLnnqC_mqNvxq`@"

encode expects a collection of vectors of the format [latitude longitude], and returns the polyline encoded string.

decode returns a vector of [latitude longitude] vectors for a given polyline encoded string.

You can add additional transforms to the encoder and decoder transducer stacks, which are bound to encoder and decoder vars respectively. For instance, to decode a polyline string as [longitude latitude] pairs as some systems expect, you can do:

(into [] (comp polyline/decoder (map polyline/lonlat)) your-polystring)`

Changelog

• Release 0.4.1 on 2018-11-07

  • Support for ClojureScript
  • 5 decimal place encode and decode (aligning with the google algorithm)

• Release 0.4.0 on 2018-10-01

  • BREAKING CHANGE: the decode API now matches the encode API: encode was always [[lat lon]] => String, now decode is String => [[lat lon]].
  • The decode codepath was completely rewritten as transducers, about 4x performance improvement.
  • Removed the old transform utility functions that worked in terms of maps with :latitude and :longitude keys
  • Exposed access to the encoding and decoding transducer stacks as the encoder and decoder vars respectively
  • Replaced the old compact-coords function - my least favorite code remaining in the project - with a compress transducer

• Release 0.3.0 on 2018-09-24

  • Minimum Clojure version is now 1.7 (because transducers)
  • The encode codepath completely rewritten to scrub out some of the wacky stuff I did 6 years ago. As a result it's 19x faster.

Contributors

• Alex Scott (AXRS)

License

Copyright © 2018 Michael Gaare

Distributed under the Eclipse Public License, the same as Clojure.