Add a Paperclip.register_processor configuration.

lib/paperclip.rb

@@ -92,19 +92,24 @@ def interpolates key, &block
     # This method can log the command being run when
     # Paperclip.options[:log_command] is set to true (defaults to false). This
     # will only log if logging in general is set to true as well.
-    def run cmd, *params
+    def run(cmd, *params)
       if options[:image_magick_path]
         Paperclip.log("[DEPRECATION] :image_magick_path is deprecated and will be removed. Use :command_path instead")
       end
       Cocaine::CommandLine.path = options[:command_path] || options[:image_magick_path]
       Cocaine::CommandLine.new(cmd, *params).run
     end
 
-    def processor name #:nodoc:
-      name = name.to_s.camelize
-      load_processor(name) unless Paperclip.const_defined?(name)
-      processor = Paperclip.const_get(name)
-      processor
+    def processor(name) #:nodoc:
+      @known_processors ||= {}
+      if @known_processors[name.to_s]
+        @known_processors[name.to_s]
+      else
+        name = name.to_s.camelize
+        load_processor(name) unless Paperclip.const_defined?(name)
+        processor = Paperclip.const_get(name)
+        @known_processors[name.to_s] = processor
+      end
     end
 
     def load_processor(name)
@@ -113,6 +118,23 @@ def load_processor(name)
       end
     end
 
+    def clear_processors!
+      @known_processors.try(:clear)
+    end
+
+    # You can add your own processor via the Paperclip configuration. Normally
+    # Paperclip will load all processors from the
+    # Rails.root/lib/paperclip_processors directory, but here you can add any
+    # existing class using this mechanism.
+    #
+    #   Paperclip.configure do |c|
+    #     c.register_processor :watermarker, WatermarkingProcessor.new
+    #   end
+    def register_processor(name, processor)
+      @known_processors ||= {}
+      @known_processors[name.to_s] = processor
+    end
+
     def each_instance_with_attachment(klass, name)
       class_for(klass).all.each do |instance|
         yield(instance) if instance.send(:"#{name}?")

test/paperclip_test.rb

@@ -272,4 +272,26 @@ def self.should_validate validation, options, valid_file, invalid_file
     end
 
   end
+
+  context "configuring a custom processor" do
+    setup do
+      @freedom_processor = Class.new do
+        def make(file, options = {}, attachment = nil)
+          file
+        end
+      end.new
+
+      Paperclip.configure do |config|
+        config.register_processor(:freedom, @freedom_processor)
+      end
+    end
+
+    should "be able to find the custom processor" do
+      assert_equal @freedom_processor, Paperclip.processor(:freedom)
+    end
+
+    teardown do
+      Paperclip.clear_processors!
+    end
+  end
 end