Preprocess thumbnails after upload

Only works in Rails 7.1

Author: tvdeyen

app/models/alchemy/picture.rb

@@ -97,7 +97,11 @@ def self.preprocessor_class=(klass)
     end
 
     # Use ActiveStorage image processing
-    has_one_attached :image_file, service: :alchemy_cms
+    has_one_attached :image_file, service: :alchemy_cms do |attachable|
+      # Only works in Rails 7.1
+      preprocessor_class.new(attachable).call
+      Preprocessor.generate_thumbs!(attachable)
+    end
 
     validates_presence_of :image_file
     validate :image_file_type_allowed, :image_file_not_too_big,

app/models/alchemy/picture/preprocessor.rb

@@ -3,8 +3,8 @@
 module Alchemy
   class Picture < BaseRecord
     class Preprocessor
-      def initialize(image_file)
-        @image_file = image_file
+      def initialize(attachable)
+        @attachable = attachable
       end
 
       # Preprocess images after upload
@@ -15,14 +15,28 @@ def initialize(image_file)
       #
       def call
         max_image_size = Alchemy::Config.get(:preprocess_image_resize)
-        image_file.thumb!(max_image_size) if max_image_size.present?
-        # Auto orient the image so EXIF orientation data is taken into account
-        image_file.auto_orient!
+        if max_image_size.present?
+          self.class.process_thumb(attachable, size: max_image_size)
+        end
       end
 
-      private
+      attr_reader :attachable
 
-      attr_reader :image_file
+      class << self
+        def generate_thumbs!(attachable)
+          Alchemy::Picture::THUMBNAIL_SIZES.values.each do |size|
+            process_thumb(attachable, size: size, flatten: true)
+          end
+        end
+
+        private
+
+        def process_thumb(attachable, options = {})
+          attachable.variant :thumb,
+            **Alchemy::DragonflyToImageProcessing.call(options),
+            preprocessed: true
+        end
+      end
     end
   end
 end