Looks like there is a bug in this line:
https://github.com/davidkuhta/avatarex/blob/ecaa02a90558c8dfd6432100b408b32a00f79e83/lib/avatarex/Kitty.ex#L10
it should be:

:avatarex |> :code.priv_dir() |> Path.join(~w[sets kitty])

Same patch should be applied to the birdy …

Unfortunately current macro code does not allow it and I was in need to use it like:

defmodule Kitty do                               
  use AvatarexSet,
    dir: "deps/avatarex/priv/sets/kitty",
    keys: [:body, :eye, :fur, :mouth, :accessory]
end

which cannot be used in prod environment static paths are not guaranteed to work in all environments and therefore you should support: :code.priv_dir/1.

Similarly the macro does not allows to use a sigil for keys i.e.:

defmodule Kitty do                                                  
  use AvatarexSet,                                                  
    dir: "deps/avatarex/priv/sets/kitty",                                 
    keys: ~w[body eye fur mouth accessory]a
end
** (Protocol.UndefinedError) protocol Enumerable not implemented for {:sigil_w, [delimiter: "[", line: 5], [{:<<>>, [line: 5], ["body eye fur mouth accessory"]}, 'a']} of type Tuple. This protocol is implemented for the following type(s): Date.Range, File.Stream, Function, GenEvent.Stream, HashDict, HashSet, IO.Stream, List, Map, MapSet, Range, Stream
    (elixir 1.14.4) lib/enum.ex:1: Enumerable.impl_for!/1
    (elixir 1.14.4) lib/enum.ex:166: Enumerable.reduce/3
    (elixir 1.14.4) lib/enum.ex:4307: Enum.reduce/3
    (avatarex 0.1.0) expanding macro: AvatarexSet.__using__/1

The other problem is priv/renders. Once again there should be a :code.priv_dir/1 call. To support priv directory for current project you should use otp_app and pass this option to said function. Your documentation does not mentions to create such a directory which would not work in app generated using mix new task. I would recommend to create it automatically using File.mkdir_p with combination to :code.priv_dir/1 call mentioned above.

Also why do you use AvatarexSet instead of Avatarex.Set? It’s like reserving 2 namespaces for just one package and therefore it’s not seen as a good practice.

Updated with all your suggestions.

Already better, but you have still a lot to learn. I reserved some time, deeply investigated your code and created an example pull request with project rewrite proposal to show what code you would be able to write in future.

https://github.com/davidkuhta/avatarex/pull/1

If you do not understand something feel free to ask questions in this thread.

Have a nice day!