Ever needed to refresh (regenerate, update) attachment_fu attachments on amazon-s3? Here you go!

attachment_fu.rake

def logger
  @logger_for_attachment_fu_rake_task ||= Logger.new STDOUT
end

def raise_with_logger(msg)
    logger.error msg
    raise msg
end

def obtain_class
  class_name = ENV['CLASS'] || ENV['class']
  raise_with_logger "Must specify CLASS" unless class_name
  class_name
end

def obtain_id
  ENV['ID'] || ENV['id']
end

# attachment_fu uses some methods on updated_data. So implement them!
def extend_file_data_with_required_methods(image)
  def image.original_filename
    URI.unescape(base_uri.path).split('/').last.scan(/([\w\.-]*\.(?:png|jpe?g|gif|bmp))/i).flatten.first
  end

  def image.filename; original_filename; end
end

# Upload old original image, and then resave it.
# Attachment_fu should handle the rest (thumbnails, resizing, and etc.)
def refresh_attachments_for(instance)
  logger.info "Refreshing #{instance.class.name} with id #{instance.id}..."
  def instance.save_attachment?; true; end
  image = open URI.parse(URI.escape instance.public_filename)
  extend_file_data_with_required_methods(image)
  logger.info "\tUploaded binary data for attachment. Size: #{"%.2fkb" % (image.size/1024.0)}."
  logger.info "\tURL: #{instance.public_filename}"
  logger.info "\tContent type: #{image.content_type}"
  logger.info "\tFilename: #{image.original_filename}"
  instance.uploaded_data = image
  instance.save!
  logger.info "\t#{instance.class.name} with id #{instance.id} refreshed successfully."
  rescue => e
  logger.error "!!! Failed to refresh: #{e}"
end

namespace :attachment_fu do
  desc "Refresh attachments for given class. Use: rake attachment_fu:refresh CLASS=CustomAvatar and if you would like to refresh specific object, pass an ID attr."
  task :refresh => :environment do
    require 'open-uri'

    klass = obtain_class.constantize
    raise_with_logger "Wrong class specified (should repond to :content_types message)."  unless klass.respond_to? :content_types

    if obtain_id.present?
      refresh_attachments_for klass.find(obtain_id)
    else
      klass.find_each :batch_size => 500, :conditions => {:parent_id => nil} do |instance|
        refresh_attachments_for(instance)
      end
    end
  end
end

Very nice! Saved me a ton of time! Thanks!