faster

app/lib/snail_mail/preview.rb

@@ -1,9 +1,11 @@
 require "open3"
 require "rmagick"
+require "parallel"
 
 module SnailMail
   module Preview
     OUTPUT_DIR = Rails.root.join("app", "frontend", "images", "template_previews")
+    PREVIEW_DPI = 150
 
     class FakeAddress < OpenStruct
       def us_format
@@ -34,6 +36,17 @@ module SnailMail
     def self.generate_previews
       OUTPUT_DIR.mkpath
 
+      templates = SnailMail::Components::Registry.available_templates
+      Rails.logger.info("Generating #{templates.size} template previews in parallel...")
+
+      Parallel.each(templates, in_threads: Parallel.processor_count, progress: "Generating previews") do |name|
+        generate_single_preview(name)
+      end
+
+      Rails.logger.info("Finished generating #{templates.size} template previews")
+    end
+
+    def self.generate_single_preview(name)
       return_address = OpenStruct.new(
         name: "Hack Club",
         line_1: "15 Falls Rd",
@@ -53,50 +66,76 @@ module SnailMail
 
       usps_mailer_id = OpenStruct.new(mid: "111111")
 
-      SnailMail::Components::Registry.available_templates.each do |name|
-        template = SnailMail::Components::Registry.get_component_class(name)
-        sender, recipient = names.sample(2)
+      template = SnailMail::Components::Registry.get_component_class(name)
+      sender, recipient = names.sample(2)
 
-        mock_letter = OpenStruct.new(
-          address: FakeAddress.new(
-            line_1: "8605 Santa Monica Blvd",
-            line_2: "Apt. 86294",
-            city: "West Hollywood",
-            state: "CA",
-            postal_code: "90069",
-            country: "US",
-            name_line: sender,
-          ),
-          return_address:,
-          return_address_name_line: recipient,
-          postage_type: "stamps",
-          postage: 0.73,
-          usps_mailer_id:,
-          imb_serial_number: "1337",
-          metadata: {},
-          rubber_stamps: "here's where rubber stamps go!",
-          public_id: "ltr!PR3V13W",
-        )
+      mock_letter = OpenStruct.new(
+        address: FakeAddress.new(
+          line_1: "8605 Santa Monica Blvd",
+          line_2: "Apt. 86294",
+          city: "West Hollywood",
+          state: "CA",
+          postal_code: "90069",
+          country: "US",
+          name_line: sender,
+        ),
+        return_address:,
+        return_address_name_line: recipient,
+        postage_type: "stamps",
+        postage: 0.73,
+        usps_mailer_id:,
+        imb_serial_number: "1337",
+        metadata: {},
+        rubber_stamps: "here's where rubber stamps go!",
+        public_id: "ltr!PR3V13W",
+      )
 
-        Rails.logger.info("generating preview for #{name}...")
-        pdf = SnailMail::PhlexService.generate_label(mock_letter, template: name)
+      Rails.logger.info("generating preview for #{name}...")
+      pdf = SnailMail::PhlexService.generate_label(mock_letter, template: name)
+      pdf_data = pdf.render
 
-        png_path = OUTPUT_DIR.join("#{template.name.split("::").last.underscore}.png")
+      png_path = OUTPUT_DIR.join("#{template.name.split("::").last.underscore}.png")
 
-        begin
-          image = Magick::Image.from_blob(pdf.render) do |i|
-            i.density = 300
-          end.first
+      convert_pdf_to_png(pdf_data, png_path)
+    end
 
-          image.alpha(Magick::RemoveAlphaChannel)
-          image.background_color = "white"
-          image.pixel_interpolation_method = Magick::IntegerInterpolatePixel
-          image.write(png_path)
-        rescue => e
-          Rails.logger.error("Failed to convert PDF to PNG: #{e.message}")
-          raise e
+    def self.convert_pdf_to_png(pdf_data, png_path)
+      if pdftoppm_available?
+        convert_with_pdftoppm(pdf_data, png_path)
+      else
+        convert_with_rmagick(pdf_data, png_path)
+      end
+    end
+
+    def self.pdftoppm_available?
+      @pdftoppm_available ||= system("which pdftoppm > /dev/null 2>&1")
+    end
+
+    def self.convert_with_pdftoppm(pdf_data, png_path)
+      base_path = png_path.to_s.sub(/\.png$/, "")
+
+      Open3.popen3("pdftoppm", "-png", "-r", PREVIEW_DPI.to_s, "-singlefile", "-", base_path) do |stdin, stdout, stderr, wait_thr|
+        stdin.binmode
+        stdin.write(pdf_data)
+        stdin.close
+
+        unless wait_thr.value.success?
+          raise "pdftoppm failed: #{stderr.read}"
         end
       end
     end
+
+    def self.convert_with_rmagick(pdf_data, png_path)
+      image = Magick::Image.from_blob(pdf_data) do |i|
+        i.density = PREVIEW_DPI
+      end.first
+
+      image.alpha(Magick::RemoveAlphaChannel)
+      image.background_color = "white"
+      image.write(png_path)
+    rescue => e
+      Rails.logger.error("Failed to convert PDF to PNG: #{e.message}")
+      raise e
+    end
   end
 end