In Rails 5.x apps it is not necessary to require 'rails_12factor' gem because its functions are now included be default:
https://github.com/heroku/rails_12factor#rails-5
Just tested and image (/app/assets/images/image.jpg) was loaded correctly with default settings in production configuration:
config.assets.compile = false
config.public_file_server.enabled = ENV['RAILS_SERVE_STATIC_FILES'].present?
if ENV["RAILS_LOG_TO_STDOUT"].present?
logger = ActiveSupport::Logger.new(STDOUT)
logger.formatter = config.log_formatter
config.logger = ActiveSupport::TaggedLogging.new(logger)
end
and without this options (in any config):
config.serve_static_assets = true
config.assets.digest = true
publicor inassets? How are the images included in the views, via its name or do you use the asset pipeline? Did you try to load the images directly by their URLs, did that work?