create image variant with permanent redact fields for submitter

config/initializers/active_storage.rb

@@ -4,6 +4,7 @@ ActiveSupport.on_load(:active_storage_attachment) do
   attribute :uuid, :string, default: -> { SecureRandom.uuid }
 
   has_many_attached :preview_images
+  has_many_attached :preview_secured_images
 end
 
 ActiveStorage::LogSubscriber.detach_from(:active_storage) if Rails.env.production?

lib/templates/process_document.rb

@@ -5,6 +5,7 @@ module Templates
     DPI = 200
     FORMAT = '.jpg'
     ATTACHMENT_NAME = 'preview_images'
+    SECURED_ATTACHMENT_NAME = 'preview_secured_images'
 
     PDF_CONTENT_TYPE = 'application/pdf'
     Q = 35
@@ -60,5 +61,37 @@ module Templates
         )
       end
     end
+
+    def generate_pdf_secured_preview_images(template, attachment, data)
+      ActiveStorage::Attachment.where(name: SECURED_ATTACHMENT_NAME, record: attachment).destroy_all
+      number_of_pages = PDF::Reader.new(StringIO.new(data)).pages.size - 1
+      (0..number_of_pages).each do |page_number|
+        pdf = Vips::Image.new_from_buffer(data, '', dpi: DPI, page: page_number)
+        pdf = pdf.resize(MAX_WIDTH / pdf.width.to_f)
+        redacted_boxes = template.fields.select { |field| field['type'] == 'redact' && field['areas'][0]['page'] == page_number }
+        if !redacted_boxes.empty?
+          redacted_boxes.each do |box|
+            x = (box['areas'][0]['x'] * pdf.width).to_i
+            y = (box['areas'][0]['y'] * pdf.height).to_i
+            w = (box['areas'][0]['w'] * pdf.width).to_i
+            h = (box['areas'][0]['h'] * pdf.height).to_i
+            black_rect = Vips::Image.black(w, h)
+            pdf = pdf.insert(black_rect, x, y)
+          end
+        end
+        
+        io = StringIO.new(pdf.write_to_buffer(FORMAT, Q: Q))
+  
+        ActiveStorage::Attachment.create!(
+          blob: ActiveStorage::Blob.create_and_upload!(
+            io: io, filename: "#{page_number}#{FORMAT}",
+            metadata: { analyzed: true, identified: true, width: pdf.width, height: pdf.height }
+          ),
+          name: SECURED_ATTACHMENT_NAME,
+          record: attachment
+        )
+      end
+    end
+
   end
 end