exmagick

# Copyright (c) 2015, Diego Souza
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# Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
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# 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
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# 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
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defmodule ExMagick do
  use ExMagick.Bang

  @docmodule """

  NIF bindings to GraphicsImage API. All functions returns an tuple in
  the form `{:ok, image}` or `{:error, reason}` and for each function
  there is the bang version of it.

  Following a couple of examples. The first one transforms a PNG image
  to JPEG. The second one queries a file about its type.

  iex> ExMagick.image!
  ...> |> ExMagick.image_load(Path.join(__DIR__, "../test/images/elixir.png"))
  ...> |> ExMagick.image_dump("/tmp/elixir.jpg")

  iex> ExMagick.image!
  ...> |> ExMagick.image_load(Path.join(__DIR__, "../test/images/elixir.png"))
  ...> |> ExMagick.attr(:magick) # == PNG
  """

  @on_load {:load, 0}
  def load do
    sofile = Path.join([:code.priv_dir(:exmagick), "lib", "libexmagick"])
    :erlang.load_nif(sofile, 0)
  end

  @doc """
  Change image attributes. Currently the following attributes are
  available:

  * adjoin [default: true]: unset to produce single image for each
  frame;
  """

  @defbang {:attr, 3}
  def attr(img, k, v) when is_atom(k) do
    case k do
      :adjoin when is_boolean(v) -> set_attr(img, k, v)
      _                          -> {:error, "unknown attr #{k}/#{v}"}
    end
  end

  @doc """
  Query image attribute. In addition to the attrs defined in `attr/3`
  the following is avaialble:

  * magick: Image encoding format (e.g. "GIF");
  """
  @defbang {:attr, 2}
  def attr(img, k), do: get_attr(img, k)

  @dock """
  Query image size. Returns a {width, height} tuple.
  """
  @defbang {:size, 1}
  def size(img) do
    with({:ok, width}  <- attr(img, :columns),
          {:ok, height} <- attr(img, :rows)) do
      {:ok, %{width: width, height: height}}
    end
  end

  @dock """
  Resizes an image.
  """
  @defbang {:size, 3}
  def size(_img, _width, _height), do: fail

  @dock """
  Generates a thumbnail for an image.
  """
  @defbang {:thumb, 3}
  def thumb(_img, _width, _height), do: fail

  @doc false
  @defbang {:image, 0}
  def image do
    IO.puts :stderr, "warning: image is deprecated in favor of init." <> Exception.format_stacktrace
    init
  end

  @doc """
  Creates a new image handle with default values. You may tune
  image params using the `attr` function.
  """
  @defbang {:init, 0}
  def init do
    IO.puts :stderr, "warning: image is deprecated in favor of init." <> Exception.format_stacktrace
    init
  end

  @doc """
  Loads an image from a file.
  """
  @defbang {:image_load, 2}
  def image_load(_img, _path), do: fail

  @doc """
  Saves an image to one or multiple files. If the attr `adjoin` is
  false multiple files will be created and the filename is expected to
  have a printf-formatting sytle (ex.: foo%0d.png).
  """
  @defbang {:image_dump, 2}
  def image_dump(_img, _path), do: fail

  defp set_attr(_img, _key, _val), do: fail
  defp get_attr(_img, _key), do: fail

  defp fail, do: {:error, "native function"}
end