Small Module For Parsing and Encoding RGB Values

rgb.ex

defmodule RGB do
  import Enum, only: [map: 2, join: 1, filter: 2, chunk: 2, count: 1]

  def encode(rgb) when is_list rgb do
    hex = rgb |>
      map(&(integer_to_list &1, 16)) |>
      map(fn [x] -> [x, x]; x  -> x end) |>
      map(&String.from_char_list!/1) |>
      join
    "#" <> hex
  end

  def decode(rgb_string) when is_binary rgb_string do
    rgb_string |>
      rgb_hex |>
      String.split("") |>
      filter(&(&1 != "")) |>
      fn list -> chunk(list, div(count(list), 3)) end.() |>
      map(&join/1) |>
      map(&(binary_to_integer &1, 16))
  end

  defp rgb_hex("#" <> rest), do: rest
  defp rgb_hex("0x" <> rest), do: rest
  defp rgb_hex(full), do: full
end