Adding JPG strategy from IIIF Print

This is an almost direct copy of IIIF Print's existing code

Related to:

- scientist-softserv/iiif_print#194
- samvera/bulkrax#760
- scientist-softserv/utk-hyku#343
- https://github.com/scientist-softserv/adventist-dl/issues/330

lib/space_stone/pdf_splitter/strategies.rb

@@ -9,3 +9,4 @@ module Strategies
 end
 
 require 'space_stone/pdf_splitter/strategies/base'
+require 'space_stone/pdf_splitter/strategies/jpg'

lib/space_stone/pdf_splitter/strategies/base.rb

@@ -22,6 +22,8 @@ class Base
         # What is the image quality we're using?
         class_attribute :quality, default: nil
 
+        class_attribute :gsdevice, instance_accessor: false
+
         ##
         # @param path [String] the path to the source PDF that we're processing.
         # @param baseid [String] used for creating a unique identifier
@@ -93,6 +95,8 @@ def gsconvert
         # rubocop:enable Metrics/MethodLength
 
         def gsdevice
+          return self.class.gsdevice if self.class.gsdevice
+
           raise NotImplementedError
         end
 

lib/space_stone/pdf_splitter/strategies/jpg.rb

@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+module SpaceStone
+  module PdfSplitter
+    module Strategies
+      # The purpose of this class is to split the PDF into constituent jpg files.
+      class Jpg < Strategies::Base
+        self.image_extension = 'jpg'
+        self.quality = '50'
+        self.gsdevice = 'jpeg'
+      end
+    end
+  end
+end

spec/space_stone/pdf_splitter/strategies/base_spec.rb

@@ -6,4 +6,15 @@
 
   # Becasue the described class is an abstract class, we want to verify its public interface.
   it { is_expected.to be_a(Enumerable) }
+
+  describe '.gsdevice' do
+    subject { described_class.gsdevice }
+    it { is_expected.to be_nil }
+  end
+
+  describe '#gsdevice' do
+    it "expects that you will have set .gsdevice in the subclass" do
+      expect { subject.send(:gsdevice) }.to raise_error(NotImplementedError)
+    end
+  end
 end

spec/space_stone/pdf_splitter/strategies/jpg_spec.rb

@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe SpaceStone::PdfSplitter::Strategies::Jpg do
+  let(:path) { __FILE__ }
+  let(:pdf_pages_summary) { double(SpaceStone::PdfSplitter::PdfPagesSummary) }
+  let(:splitter) { described_class.new(path, pdf_pages_summary: pdf_pages_summary) }
+
+  describe '.gsdevice' do
+    subject { described_class.gsdevice }
+    it { is_expected.to eq('jpeg') }
+  end
+
+  describe '#gsdevice' do
+    subject { splitter.send(:gsdevice) }
+    it { is_expected.to eq('jpeg') }
+  end
+
+  describe '#quality' do
+    subject { splitter.quality }
+    it { is_expected.to eq(described_class.quality) }
+  end
+
+  describe '#quality?' do
+    subject { splitter.quality? }
+    it { is_expected.to be_truthy }
+  end
+
+  describe '#image_extension' do
+    subject { splitter.image_extension }
+    it { is_expected.to eq('jpg') }
+  end
+end