OSM

Add this line to your application's Gemfile:

gem 'osm-rb'

And then execute:

$ bundle

Or install it yourself as:

$ gem install osm-rb

OSM-rb exposes two distincts APIs.

The calculator helps you with everything regarding projections, tile names and bounds.

You can use the calculator to calculate and set the required zoom level to fit your bounds

path = [
  OpenStruct.new(lat: 46.95127, lng: 7.43878),
  OpenStruct.new(lat: 46.92771, lng: 7.44610),
  OpenStruct.new(lat: 46.94764, lng: 7.37527)
]
padding = OpenStruct.new(x: 50, y: 40)
target_size = OpenStruct.new(x: 800, y: 600)

zoom_level = OSM::Calculator.get_zoom_level(path, padding, target_size)
zoom_level # => 13

Once you know the required zoom level, you can create a calculator. You always need to pass it a zoom level, target padding and the target map size

calculator = Calculator.new(padding, target_size)

Calculate required tiles to fit the map as specified

tiles = calculator.tiles(path)
tiles[0].x # => 136485
tiles[0].y # => 92249

Calculate the number of tiles required

dimensions = calculator.tile_dimensions(path)
dimensions.x # => 12
dimensions.y # => 8

The exporter allows you to donwload and store tile images. It is also able to automatically stitch them together.

To create an exporter, you have to pass it an array of tile server url templates and a zoom level

urls = [
  'https://a.tile.opentopomap.org/{z}/{x}/{y}.png',
  'https://b.tile.opentopomap.org/{z}/{x}/{y}.png',
  'https://c.tile.opentopomap.org/{z}/{x}/{y}.png'
]
zoom_level = 13
exporter = OSM::Exporter.new(urls, zoom_level)

Download the specified tiles

tiles = [
  OpenStruct.new(lat: 46.95127, lng: 7.43878),
  OpenStruct.new(lat: 46.92771, lng: 7.44610),
  OpenStruct.new(lat: 46.94764, lng: 7.37527)
]
images = exporter.download_tiles_as_blob(tiles)
# images is an array of the binary data of the tiles

You can use any of the compatible caches for Typhoeus and follow their instructions.

To use a Redis cache

require 'redis'
redis = Redis.new(...)
Typhoeus::Config.cache = Typhoeus::Cache::Redis.new(redis)

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/code-fabrik/osm-rb. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

The gem is available as open source under the terms of the MIT License.

Everyone interacting in the OSM project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.