ocr.rb

require 'base64'
require 'open-uri'
require 'net/http'
require 'net/https'
require 'json'

class OCR
  attr_reader :api_key, :image_url

  def self.scan(api_key:, image_url:)
    ocr = new(api_key: api_key, image_url: image_url)
    return ocr.text
  end

  def initialize(api_key:, image_url:)
    @api_key = api_key
    @image_url = image_url
  end

  def request
    begin
      http = Net::HTTP.new request_uri.host, request_uri.port
      http.use_ssl = true
      http.verify_mode = OpenSSL::SSL::VERIFY_PEER

      req = Net::HTTP::Post.new request_uri
      req.add_field 'Content-Type', 'application/json'
      req.body = JSON.dump request_body

      http.request(req)
    rescue StandardError => e
      puts "HTTP Request failed (#{e.message})"
    end
  end

  def text
    res = request

    if res && res.body
      json_body = JSON.parse res.body

      if json_body['responses'] && json_body['responses'].first
        response = json_body['responses'].first

        if response['textAnnotations'] && response['textAnnotations'].first
          annotation = response['textAnnotations'].first
          annotation['description']
        end
      end
    end
  end

  private

  def encoded_image
    @encoded_image ||= Base64.encode64 open(URI.parse(image_url)).read
  end

  def request_body
    {
      'requests' => [
        {
          'image' => { 'content' => encoded_image },
          'features' => [
            { 'type' => 'TEXT_DETECTION' }
          ]
        }
      ]
    }
  end

  def request_uri
    url = "https://vision.googleapis.com/v1/images:annotate?key=#{api_key}"
    URI(url)
  end
end

api_key = 'google_api_key'
demo_url = 'https://example.com/example.jpg'
text = OCR.scan(api_key: api_key, image_url: demo_url)
puts text