require 'net/http'

uri = URI('http://images-dev.collections.yale.edu/iiif/2/ypm:85f1f218-30c1-48a4-8546-17d681f59c35.tif/full/20,/0/default.jpg')
api_key = ENV['YPM_SECRET']

req = Net::HTTP::Get.new(uri)
req['Authorization'] = "Bearer #{api_key}"

res = Net::HTTP.start(uri.hostname, uri.port,
                      use_ssl: uri.scheme == 'https') do |http|
  http.request(req)
end

open('out.jpg', 'w') do |f|
  f.write(res.read_body)
end

https://media.collections.yale.edu/tiff/{unit}/{uuid}.tif