How to serve image assets from an Engine in a Rails app - ruby-on-rails

Question

I'm having trouble getting image assets in my engine to render inside the host app.
My host app is capable of grabbing css and javascript from then engine thanks to code like this in the view/layout/application.html.erb file:
<%= stylesheet_link_tag 'my_engine/application', :media => 'all' %>
<%= javascript_include_tag 'my_engine/application' %>
However, I don't know of a similar method for including the images from my engine. Any ideas on how I can get the engine's image files to render in the host app?
Edit:
In my engine's engine.rb file, I've added the images directory to the app's directory like this:
initializer :assets do |config|
Rails.application.config.assets.paths << root.join("app", "assets", "images", "my_engine", "some_subdirectory")
end
and the view has an image tag that looks like this:
<%= image_tag "/my_engine/some_subdirectory/picture.png" %>
but my server logs, I see this:
Started GET "/assets/some_subdirectory/picture.png" for 127.0.0.1 at 2014-04-06 20:11:38 -0500
Served asset /some_subdirectory/picture.png - 404 Not Found (3ms)
ActionController::RoutingError (No route matches [GET] "/assets/some_subdirectory/picture.png"):

Answer 1

You don't need to do this at all because Rails does it for you:
initializer :assets do |config|
Rails.application.config.assets.paths << root.join("app", "assets", "images", "my_engine", "some_subdirectory")
end
Instead, you can reference the images exactly the same way as you would as if they were in the application:
<%= image_tag "your_image.jpg" %>
I'm assuming here that your_image.jpg is at /app/assets/images/your_image.jpg within your engine. If it's in a subdirectory, then:
<%= image_tag "subdirectory/your_image.jpg" %>
There's no need to include the name of your engine in the path unless the file is at some place like app/assets/images/your_engine/your_image.jpg, in which case:
<%= image_tag "your_engine/your_image.jpg" %>
Would be the correct way to do this.
The Engines Guide contains more useful information about engines too.