mogrify.ex

defmodule Mogrify do
  use Mogrify.Compat

  alias Mogrify.Compat
  alias Mogrify.Image
  alias Mogrify.Option

  @doc """
  Opens image source.
  """
  def open(path) do
    path = Path.expand(path)
    unless File.regular?(path), do: raise(File.Error)

    %Image{path: path, ext: Path.extname(path)}
  end

  @doc """
  Saves modified image.

  ## Options

  * `:path` - The output path of the image. Defaults to a temporary file.
  * `:in_place` - Overwrite the original image, ignoring `:path` option. Default `false`.
  """
  def save(image, opts \\ []) do
    cmd_opts = [stderr_to_stdout: true]

    if opts[:in_place] do
      final_output_path = if image.dirty[:path], do: image.dirty[:path], else: image.path

      args = arguments_for_saving_in_place(image)
      {_, 0} = cmd_mogrify(args, cmd_opts)

      image_after_command(image, final_output_path)
    else
      cmd_output_path = output_path_for(image, opts)
      final_output_path = Keyword.get(opts, :path, cmd_output_path)
      create_folder_if_doesnt_exist!(cmd_output_path)
      create_folder_if_doesnt_exist!(final_output_path)

      args = arguments_for_saving(image, cmd_output_path)
      {_, 0} = cmd_convert(args, cmd_opts)

      # final output path may differ if temporary path was used for image format
      if cmd_output_path != final_output_path do
        # copy then rm, because File.rename/2 may fail across filesystem boundary
        File.copy!(cmd_output_path, final_output_path)
        File.rm!(cmd_output_path)
      end

      image_after_command(image, final_output_path)
    end
  end

  @doc """
  Creates or saves image.

  Uses the `convert` command, which accepts both existing images, or image
  operators. If you have an existing image, prefer save/2.

  ## Options

  * `:path` - The output path of the image. Defaults to a temporary file.
  * `:in_place` - Overwrite the original image, ignoring `:path` option. Default `false`.
  * `:buffer` - Pass `true` to write to Collectable in Image.buffer instead of file.
  * `:into` - Used with `:buffer` to specify a Collectable. Defaults to `""`. See `System.cmd/3`.
  """
  def create(image, opts \\ []) do
    if opts[:buffer] do
      cmd_opts = [stderr_to_stdout: false]
      cmd_opts = if opts[:into], do: cmd_opts ++ [into: opts[:into]], else: cmd_opts
      {image_collectable, 0} = cmd_convert(arguments(image), cmd_opts)
      image_after_buffer_command(image, image_collectable)
    else
      cmd_opts = [stderr_to_stdout: true]
      output_path = output_path_for(image, opts)
      create_folder_if_doesnt_exist!(output_path)

      {_, 0} = cmd_convert(arguments_for_creating(image, output_path), cmd_opts)
      image_after_command(image, output_path)
    end
  end

  @doc """
  Returns the histogram of the image

  Runs ImageMagick's `histogram:info:-` command.

  Results are returned as a list of maps where each map includes keys red,
  blue, green, hex and count.

  ## Examples

      iex> open("test/fixtures/rbgw.png") |> histogram
      [
        %{"alpha" => 255, "blue" => 255, "count" => 400, "green" => 0, "hex" => "#0000ff", "red" => 0},
        %{"alpha" => 255, "blue" => 0, "count" => 225, "green" => 255, "hex" => "#00ff00", "red" => 0},
        %{"alpha" => 255, "blue" => 0, "count" => 525, "green" => 0, "hex" => "#ff0000", "red" => 255},
        %{"alpha" => 255, "blue" => 255, "count" => 1350, "green" => 255, "hex" => "#ffffff", "red" => 255}
      ]

  """
  def histogram(image) do
    img = image |> custom("format", "%c")
    args = arguments(img) ++ [image.path, "histogram:info:-"]

    res = cmd_convert(args, stderr_to_stdout: false)

    res
    |> elem(0)
    |> process_histogram_output
  end

  defp image_after_command(image, output_path) do
    format = Map.get(image.dirty, :format, image.format)

    %{
      clear_operations(image)
      | path: output_path,
        ext: Path.extname(output_path),
        format: format
    }
  end

  defp image_after_buffer_command(image, image_collectable) do
    %{
      clear_operations(image)
      | buffer: image_collectable
    }
  end

  defp clear_operations(image) do
    %{image | operations: [], dirty: %{}}
  end

  defp cleanse_histogram(hist) do
    hist
    |> Enum.into(%{}, &clean_histogram_entry/1)
  end

  defp clean_histogram_entry({"hex", v}), do: {"hex", v}
  defp clean_histogram_entry({"alpha", ""}), do: {"alpha", 255}
  defp clean_histogram_entry({k, ""}), do: {k, 0}
  defp clean_histogram_entry({k, v}), do: {k, v |> Float.parse() |> elem(0) |> Float.round(0) |> trunc}

  def extract_histogram_data(entry) do
    ~r/^\s+(?<count>\d+):\s+\((?<red>[\d(?:\.\d+)?)\s]+),(?<green>[\d(?:\.\d+)?)\s]+),(?<blue>[\d(?:\.\d+)?)\s]+)(,(?<alpha>[\d(?:\.\d+)?)\s]+))?\)\s+(?<hex>\#[abcdef\d]{6,8})\s+/i
    |> Regex.named_captures(entry)
    |> Enum.map(fn {k, v} -> {k, v |> Compat.string_trim()} end)
    |> cleanse_histogram
  end

  defp process_histogram_output(histogram_output) do
    histogram_output
    |> String.split("\n")
    |> Enum.reject(fn s -> s |> String.length() == 0 end)
    |> Enum.map(&extract_histogram_data/1)
  end

  defp output_path_for(image, save_opts) do
    cond do
      save_opts[:in_place] -> image.path
      image.dirty[:path] -> temporary_path_for(image)  # temp file to ensure image format applied
      save_opts[:path] -> save_opts[:path]
      true -> temporary_path_for(image)
    end
  end

  # used with `convert`
  defp arguments_for_saving(image, path) do
    [image.path] ++ arguments(image) ++ [path]
  end

  # used with `mogrify`
  defp arguments_for_saving_in_place(image) do
    arguments(image) ++ [image.path]
  end

  defp arguments_for_creating(image, path) do
    basename = if image.path, do: Path.basename(image.path), else: Path.basename(path)
    base_arguments = [Path.join(Path.dirname(path), basename)]
    arguments(image) ++ base_arguments
  end

  defp arguments(image) do
    Enum.flat_map(image.operations, &normalize_arguments/1)
  end

  defp normalize_arguments({:image_operator, params}), do: String.split(params)
  defp normalize_arguments({"annotate", params}),
    do: ["-annotate"] ++ String.split(params, " ", parts: 2)
  defp normalize_arguments({"morphology", params}), do: ["-morphology"] ++ String.split(params)
  defp normalize_arguments({"histogram:" <> option, nil}), do: ["histogram:#{option}"]
  defp normalize_arguments({"pango", params}), do: ["pango:#{params}"]
  defp normalize_arguments({"stdout", params}), do: ["#{params}"]
  defp normalize_arguments({"plasma", params}), do: ["plasma:#{params}"]
  defp normalize_arguments({"canvas", params}), do: ["canvas:#{params}"]
  defp normalize_arguments({"+" <> option, nil}), do: ["+#{option}"]
  defp normalize_arguments({"-" <> option, nil}), do: ["-#{option}"]
  defp normalize_arguments({option, nil}), do: ["-#{option}"]
  defp normalize_arguments({"+" <> option, params}), do: ["+#{option}", to_string(params)]
  defp normalize_arguments({"-" <> option, params}), do: ["-#{option}", to_string(params)]
  defp normalize_arguments({:limit, params}), do: ["-limit"] ++ String.split(params)
  defp normalize_arguments({option, params}), do: ["-#{option}", to_string(params)]

  @doc """
  Makes a copy of original image.
  """
  def copy(image) do
    temp = temporary_path_for(image)
    File.cp!(image.path, temp)
    Map.put(image, :path, temp)
  end

  def temporary_path_for(%{dirty: %{path: dirty_path}} = _image) do
    do_temporary_path_for(dirty_path)
  end

  def temporary_path_for(%{path: path} = _image) do
    do_temporary_path_for(path)
  end

  defp do_temporary_path_for(path) do
    name = if path, do: Path.basename(path), else: Compat.rand_uniform(999_999)
    random = Compat.rand_uniform(999_999)
    Path.join(System.tmp_dir(), "#{random}-#{name}")
  end

  @doc """
  Provides detailed information about the image.

  This corresponds to the `mogrify -verbose` output which is similar to `identify`.
  It does NOT correspond to `identify -verbose` which prints out much more information.
  """
  def verbose(image) do
    Map.merge(image, identify(image.path))
  end

  @doc """
  Provides "identify" information about an image.
  """
  def identify(file_path) do
    args = [file_path]
    {output, 0} = cmd_identify(args, stderr_to_stdout: false)

    output
    |> image_information_string_to_map()
    |> put_frame_count(output)
  end

  @doc """
  Provides "identify" information about an image with raw access attribute.
  Example: identify(file_path, format: "'%[orientation]'")
  """
  def identify(file_path, format: option) do
    args = ["-format"] ++ [option] ++ [file_path]
    {output, 0} = cmd_identify(args, stderr_to_stdout: false)
    output |> String.replace("'", "")
  end

  defp image_information_string_to_map(image_information_string) do
    ~r/\b(?<animated>\[0])? (?<format>\S+) (?<width>\d+)x(?<height>\d+)/
    |> Regex.named_captures(image_information_string)
    |> Enum.map(&normalize_verbose_term/1)
    |> Enum.into(%{})
  end

  defp normalize_verbose_term({"animated", "[0]"}), do: {:animated, true}
  defp normalize_verbose_term({"animated", ""}), do: {:animated, false}

  defp normalize_verbose_term({key, value}) when key in ["width", "height"] do
    {String.to_atom(key), String.to_integer(value)}
  end

  defp normalize_verbose_term({key, value}), do: {String.to_atom(key), String.downcase(value)}

  defp put_frame_count(%{animated: false} = map, _),
    do: Map.put(map, :frame_count, 1)
  defp put_frame_count(map, text) do
    # skip the [0] lines which may be duplicated
    matches = Regex.scan(~r/\b\[[1-9][0-9]*] \S+ \d+x\d+/, text)
    # add 1 for the skipped [0] frame
    frame_count = length(matches) + 1
    Map.put(map, :frame_count, frame_count)
  end

  @doc """
  Converts the image to the image format you specify.
  """
  def format(image, format) do
    downcase_format = String.downcase(format)
    ext = ".#{downcase_format}"
    rootname = Path.rootname(image.path, image.ext)

    %{
      image
      | operations: image.operations ++ [format: format],
        dirty: %{path: "#{rootname}#{ext}", format: downcase_format, ext: ext}
               |> Enum.into(image.dirty)
    }
  end

  @doc """
  Resizes the image with provided geometry.
  """
  def resize(image, params) do
    %{image | operations: image.operations ++ [resize: params]}
  end

  @doc """
  Changes quality of the image to desired quality.
  """
  def quality(image, params) do
    %{image | operations: image.operations ++ [quality: params]}
  end

  @doc """
  Sets a pixel cache resource limit.
  """
  def limit(image, type, value) do
    image
    |> limit("#{type} #{value}")
  end

  @doc """
  Sets a pixel cache resource limit, in the form of a space-separated string (e.g. `"memory 30mb"`).
  """
  def limit(image, params) do
    %{image | operations: image.operations ++ [limit: params]}
  end

  @doc """
  Extends the image to the specified dimensions.
  """
  def extent(image, params) do
    %{image | operations: image.operations ++ [extent: params]}
  end

  @doc """
  Sets the gravity of the image.
  """
  def gravity(image, params) do
    %{image | operations: image.operations ++ [gravity: params]}
  end

  @doc """
  Resize the image to fit within the specified dimensions while retaining
  the original aspect ratio.

  Will only resize the image if it is larger than the specified dimensions. The
  resulting image may be shorter or narrower than specified in the smaller
  dimension but will not be larger than the specified values.
  """
  def resize_to_limit(image, params) do
    resize(image, "#{params}>")
  end

  @doc """
  Resize the image to fit within the specified dimensions while retaining
  the aspect ratio of the original image.

  If necessary, crop the image in the larger dimension.
  """
  def resize_to_fill(image, params) do
    [_, width, height] = Regex.run(~r/(\d+)x(\d+)/, params)
    image = Mogrify.verbose(image)
    {width, _} = Float.parse(width)
    {height, _} = Float.parse(height)
    cols = image.width
    rows = image.height

    if width != cols || height != rows do
      # .to_f
      scale_x = width / cols
      # .to_f
      scale_y = height / rows
      larger_scale = max(scale_x, scale_y)
      cols = (larger_scale * (cols + 0.5)) |> Float.round()
      rows = (larger_scale * (rows + 0.5)) |> Float.round()
      image = resize(image, if(scale_x >= scale_y, do: "#{cols}", else: "x#{rows}"))

      if width != cols || height != rows do
        extent(image, params)
      else
        image
      end
    else
      image
    end
  end

  def auto_orient(image) do
    %{image | operations: image.operations ++ ["auto-orient": nil]}
  end

  def canvas(image, color) do
    image_operator(image, "xc:#{color}")
  end

  def add_option(image, option) do
    validate_option!(option)
    custom(image, option.name, option.argument)
  end

  def custom(image, action, options \\ nil) do
    %{image | operations: image.operations ++ [{action, options}]}
  end

  def image_operator(image, operator) do
    %{image | operations: image.operations ++ [{:image_operator, operator}]}
  end

  defp valid_option?(%Option{require_arg: true, argument: nil}), do: false
  defp valid_option?(_), do: true

  defp validate_option!(%Option{name: name} = option) do
    if valid_option?(option) do
      option
    else
      [prefix, leading] = extract_prefix_and_leading(name)
      option_name = name |> String.replace_leading(leading, "") |> String.replace("-", "_")

      raise ArgumentError,
        message:
          "the option #{option_name} need arguments. Be sure to pass arguments to option_#{prefix}#{
            option_name
          }(arg)"
    end
  end

  defp extract_prefix_and_leading(name) do
    if String.contains?(name, "+") do
      ["plus_", "+"]
    else
      ["", "-"]
    end
  end

  defp cmd_magick(tool, args, opts) do
    {command, additional_args} = command_options(tool)
    System.cmd(command, additional_args ++ args, opts)
  rescue
    e in [ErlangError] ->
      if e.original == :enoent do
        raise "missing prerequisite: '#{tool}'"
      else
        reraise e, __STACKTRACE__
      end
  end

  defp cmd_mogrify(args, opts), do: cmd_magick(:mogrify, args, opts)

  defp cmd_identify(args, opts), do: cmd_magick(:identify, args, opts)

  @doc false
  def cmd_convert(args, opts), do: cmd_magick(:convert, args, opts)

  defp create_folder_if_doesnt_exist!(path) do
    path |> Path.dirname() |> File.mkdir_p!()
  end

  defp command_options(command) do
    config = Application.get_env(:mogrify, :"#{command}_command", [])
    path = Keyword.get(config, :path)
    args = Keyword.get(config, :args, [])
    if path do
      {path, args}
    else
      default_command(command)
    end
  end

  defp default_command(command) do
    case :os.type() do
      {:win32, _} -> {"magick", ["#{command}"]}
      _ -> {"#{command}", []}
    end
  end
end