---
title:    Setting up config.rb
blurb:    Review the key configuration values for making this extension work.
layout:   template-logo-medium
---

<%= md_links %>
<% content_for :seeAlso do %>
<ul>
  <li><a href="/">Welcome to <code>middlemac-extras</code></a></li>
  <li><a href="css_image_sizes.html">The <code>css_image_sizes</code> helper</a></li>
  <li><a href="image_tag.html">The <code>image_tag</code> helper</a></li>
  <li><a href="md_images.html">The <code>md_images</code> helper</a></li>
  <li><a href="md_links.html">The <code>md_links</code> helper</a></li>
  <li><a href="api_reference.html">API Reference</a></li>
  <li><a href="cli.html">Command line interface</a></li>
  <li><a href="license.html">The MIT License</a></li>
</ul>
<% end %>

# <%= current_page.data.title %>
<%= current_page.data.blurb %>

Some minimal configuration in your `config.rb` project file is required in order
for `middlemac-extras` to be useful.

## Conflicting resources

This extension uses Middleman's resource map to generate a lot of the
information that it provides. Be sure to activate other extensions that
might manipulate the resource map before activating middlemac-extras,
such as MiddlemanPageGroups (which changes the output names of some files).

Also our `image_tag` helper should inherit from other `image_tag` helpers,
so it's best to make sure they're activated first.


## Extension Setup

This extension has to be activated before it can be used. If you’re happy with
the default configuration values, activation can be as simple as:

~~~ ruby
activate: MiddlemacExtras
~~~

Otherwise the block format should be used to set the extension’s configuration
variables:

~~~ ruby
activate :MiddlemacExtras do |config|

  # If set to true, then the enhanced image_tag helper will be used
  # to include @2x srcset automatically, if the image asset exists.
  config.retina_srcset = true

  # If set to true then the `image_tag` helper will work for images even
  # if you don't specify an extension, but only if a file exists on disk
  # that has one of the extensions in :img_auto_extensions_order.
  config.img_auto_extensions = true

  # Set this to an array of extensions in the order of precedence for
  # using `image_tag` without file extensions.
  config.img_auto_extensions_order = %w(.svg .png .jpg .jpeg .gif .tiff .tif)

end
~~~


### Extension Options

The extension options are described in the code snippet, above.