Rails 4 images not loading on heroku

Question

I have spent the better part of the day trying to get images to load on my heroku app. Everything I try works locally, but not after being deployed to heroku.

I have png files saved in the images folder under my assets. I am referencing these images with syntax in my css such as;

#signin {
  background: url(<%= asset_path 'sf.png' %>);
  background-size: 100%;
}

In heroku when I inspect the background the assets/sf.png link is there but when you click it it shows a broken image, suggesting it did not load properly.

I've tried toggling config.serve_static_assets = false in the production.rb file between true and false and neither works.

I also have

group :production do
  gem 'pg'
  gem 'rails_12factor'
end

Precompile is always successful.

Rails 4. Any ideas on what else to try?

Answer 1

I needed to combine several solutions to make this work, here is what I did:

Gemfile

gem 'rails_12factor', group: :production

in my Heroku console

heroku labs:enable user-env-compile -a yourapp

production.rb

config.serve_static_assets = true
config.action_dispatch.x_sendfile_header = 'X-Accel-Redirect'
config.assets.compile = true

I didn't need to precompile the assets locally.