book_image.ex

defmodule Project.BookImage do
  use Arc.Definition
  use Arc.Ecto.Definition

  # To add a thumbnail version:
  @versions [:original, :small, :thumb]

  @extension_whitelist ~w(.jpg .jpeg .gif .png)

  def validate({file, _}) do
    file_extension = file.file_name |> Path.extname |> String.downcase
    Enum.member?(@extension_whitelist, file_extension)
  end

  def transform(:small, _) do
    {:convert, "-strip -thumbnail 200x200 -format jpg"}
  end

  def transform(:thumb, _) do
    {:convert, "-strip -thumbnail 75x75 -format jpg"}
  end

  # Override the persisted filenames:
  def filename(version, _) do
    version
  end

  # Override the storage directory:
  def storage_dir(version, {_, scope}) do
    "uploads/books/#{scope.uuid}/"
  end

  # Provide a default URL if there hasn't been a file uploaded
  def default_url(:small, _) do
    "http://placehold.it/200x200"
  end

  def default_url(:thumb, _) do
    "http://placehold.it/75x75"
  end

  def default_url(_version, _) do
    "http://placehold.it/200x250"
  end
end