Add support for specifying OCR language in Tika

This change ensure that Tika can specify the language configuration
for its internal Tesseract OCR Parser.

Close #302

config/app.yml

@@ -29,4 +29,7 @@ libreoffice_path: <%= ENV['LIBREOFFICE_PATH'] %>
 tesseract_path: <%= ENV['TESSERACT_PATH'] %>
 tika_path: <%= ENV['TIKA_PATH'] %>
 wkhtmltopdf_path: <%= ENV['WKHTMLTOPDF_PATH'] %>
+
+# Other settings
+tika_config_directory: <%= ENV['TIKA_CONFIG_DIRECTORY'] %>
 wkhtmltopdf_params: '-d 100 --encoding UTF-8'

lib/colore.rb

@@ -9,3 +9,4 @@
 require_relative 'document'
 require_relative 'heathen'
 require_relative 'sidekiq_workers'
+require_relative 'tika_config'

lib/config.rb

@@ -41,6 +41,8 @@ class C_
  attr_accessor :tika_path
  # @return [String] Path to the wkhtmltopdf binary. Defaults to `"wkhtmltopdf"`
  attr_accessor :wkhtmltopdf_path
+ # @return [String] Relative path to the writable tika config directory. Defaults to `"../tmp/tika"`
+ attr_accessor :tika_config_directory
  # @return [String] Params for wkhtmltopdf
  attr_accessor :wkhtmltopdf_params
 
@@ -65,6 +67,8 @@ def self.config
  c.tesseract_path = yaml['tesseract_path'] || 'tesseract'
  c.tika_path = yaml['tika_path'] || 'tika'
  c.wkhtmltopdf_path = yaml['wkhtmltopdf_path'] || 'wkhtmltopdf'
+
+ c.tika_config_directory = yaml['tika_config_directory'] || '../tmp/tika'
  c.wkhtmltopdf_params = yaml['wkhtmltopdf_params'] || ''
 
  c

lib/heathen/processor_methods/libreoffice.rb

@@ -55,6 +55,7 @@ def libreoffice(format:)
  if to_suffix == 'txt'
  executioner.execute(
  Colore::C_.tika_path,
+ "--config=#{Colore::TikaConfig.path_for(job.language)}",
  '--text',
  job.content_file,
  binary: true

lib/heathen/processor_methods/pdftotext.rb

@@ -7,6 +7,7 @@ def pdftotext
 
  executioner.execute(
  Colore::C_.tika_path,
+ "--config=#{Colore::TikaConfig.path_for(job.language)}",
  '--text',
  job.content_file,
  binary: true

lib/tika_config.rb

@@ -0,0 +1,61 @@
+# frozen_string_literal: true
+
+require 'fileutils'
+require 'pathname'
+
+module Colore
+ # The Colore Tika is a module to help with Tika-related configuration files.
+ module TikaConfig
+ # The configuration template version
+ VERSION = 'v1'
+
+ # The default language to use when the language has not been found
+ DEFAULT_LANGUAGE = 'eng'
+
+ # Config template
+ TEMPLATE = <<~XML
+ <?xml version="1.0" encoding="UTF-8"?>
+ <properties>
+ <parsers>
+ <parser class="org.apache.tika.parser.DefaultParser"></parser>
+ <parser class="org.apache.tika.parser.ocr.TesseractOCRParser">
+ <params>
+ <param name="language" type="string">%<language_alpha3>s</param>
+ </params>
+ </parser>
+ </parsers>
+ </properties>
+ XML
+
+ class << self
+ private
+
+ def tika_config_path
+ Pathname.new File.expand_path(Colore::C_.tika_config_directory, __dir__)
+ end
+
+ def path_for!(language_alpha3)
+ file = tika_config_path.join('ocr', VERSION, "tika.#{language_alpha3}.xml")
+ return file if file.file?
+
+ FileUtils.mkdir_p(tika_config_path.join('ocr', VERSION))
+ File.write(file, format(TEMPLATE, language_alpha3: language_alpha3))
+ file
+ end
+ end
+
+ # Returns the file path of the Tika configuration for performing OCR
+ # detection in a specified language.
+ #
+ # @param [String] language The language code in either ISO 639-1 (two-letter) or ISO 639-2 (three-letter) format.
+ # Supported languages are those with corresponding Tika configuration files.
+ #
+ # @return [Pathname] The path to the Tika configuration file for the specified language or
+ # the configuration file for DEFAULT_LANGUAGE if the language is not found.
+ def self.path_for(language)
+ language_alpha3 = Colore::Utils.language_alpha3(language) || DEFAULT_LANGUAGE
+
+ path_for!(language_alpha3)
+ end
+ end
+end

spec/fixtures/heathen/quickfox.ar.txt

@@ -0,0 +1 @@
+الثعلب البني السريع مفتون بالكلاب الكسولة

spec/heathen/processor_methods/pdftotext_spec.rb

@@ -4,7 +4,8 @@
 
 RSpec.describe Heathen::Processor do
  let(:content) { fixture('heathen/quickfox.pdf').read }
- let(:job) { Heathen::Job.new 'foo', content, 'en' }
+ let(:job) { Heathen::Job.new 'foo', content, language }
+ let(:language) { 'en' }
  let(:processor) { described_class.new job: job, logger: spec_logger }
 
  after do
@@ -14,7 +15,19 @@
  describe '#pdftotext' do
  it 'converts PDF to TXT' do
  processor.pdftotext
+ expect(job.content).to eq 'The quick brown fox jumps lazily over the dog'
  expect(job.content.mime_type).to eq 'text/plain; charset=us-ascii'
  end
+
+ context 'with Arabic files' do
+ let(:content) { fixture('heathen/quickfox.ar.pdf').read }
+ let(:language) { 'ar' }
+
+ it 'extracts Arabic text from images' do
+ processor.pdftotext
+ expect(job.content).to eq fixture('heathen/quickfox.ar.txt').read.strip.force_encoding(Encoding::ASCII_8BIT)
+ expect(job.content.mime_type).to eq 'text/plain; charset=utf-8'
+ end
+ end
  end
 end

spec/lib/tika_config_spec.rb

@@ -0,0 +1,59 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require 'fileutils'
+require 'pathname'
+
+RSpec.describe Colore::TikaConfig do
+ let(:tika_config_directory) { '../tmp/tika-test' }
+ let(:tika_test_config_path) { Pathname.new(File.expand_path('../../tmp/tika-test', __dir__)) }
+
+ before do
+ allow(Colore::C_.config).to receive(:tika_config_directory).and_return tika_config_directory
+ FileUtils.mkdir_p tika_test_config_path
+ FileUtils.rm_rf tika_test_config_path
+ end
+
+ after do
+ FileUtils.rm_rf tika_test_config_path
+ end
+
+ describe '.path_for' do
+ subject(:path_for) { described_class.path_for(language) }
+
+ context 'when the language is found' do
+ let(:language) { 'fr' }
+
+ before do
+ allow(Colore::Utils).to receive(:language_alpha3).with('fr').and_return('fra')
+ end
+
+ it 'returns the correct configuration file path' do
+ expect(path_for).to eq tika_test_config_path.join('ocr', described_class::VERSION, 'tika.fra.xml')
+ end
+ end
+
+ context 'when the language is not found' do
+ let(:language) { 'unknown' }
+
+ it 'returns the default configuration file path' do
+ expect(path_for).to eq tika_test_config_path.join('ocr', described_class::VERSION, "tika.#{described_class::DEFAULT_LANGUAGE}.xml")
+ end
+ end
+
+ context 'when the configuration file is already present' do
+ let(:language) { 'en' }
+
+ before do
+ allow(File).to receive(:write)
+ .with(tika_test_config_path.join('ocr', described_class::VERSION, 'tika.eng.xml'), an_instance_of(String))
+ .and_call_original
+ end
+
+ it 'does not overwrite it' do
+ 2.times { described_class.path_for(language) }
+ expect(File).to have_received(:write).once
+ end
+ end
+ end
+end