r2flickr is a Ruby implementation of the Flickr API.
It is a fork of rflickr, which is no longer maintained.
The Flickr API reference is on:
https://www.flickr.com/services/api/
You first need to get an API key as explained here:
https://www.flickr.com/services/api/misc.api_keys.html
You'll need to authorize your application's API key for each account
which you want to access. The authentication process is described on:
https://www.flickr.com/services/api/auth.spec.html
Here is a sample you can use to get started:
  flickr = Flickr.new(token_cache_file, MY_APPLICATION_KEY, MY_SHARED_SECRET)
  unless flickr.auth.token
    flickr.auth.getFrob
    url = @flickr.auth.login_link
    puts "You must visit #{url} to authorize this application. Press enter " \
      "when you have done so. This is the only time you will have to do this."
    gets
    flickr.auth.getToken
    flickr.auth.cache_token
  end
  <... do flickr stuff now ...>
The general idea is that once you cache the token, the user will not
have to reauthorize your application unless the file where the token
is cached (the first argument to the new method on Flickr) is deleted.
When you create a new Flickr and pass in a file path to the cached
token, the API will attempt to load the token from the file. If found
and loaded, the Flickr instance's auth.token is present. If the token
could not be found in the file specified, then the instance's
auth.token will be nil, and you will have to have the user authorize
the application before it can be used.
For convenience, you can set your API_KEY and SHARED_SECRET in the
installed version of flickr/base.rb rather than including it in every
application.
https://github.com/markoa/r2flickr/tree/master
Developers:
Trevor Schroeder (rflickr author)
Marko Anastasov
Dustin Sallings