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# Pleroma: A lightweight social networking server
# Copyright © 2017-2021 Pleroma Authors <https://pleroma.social/>
# SPDX-License-Identifier: AGPL-3.0-only
defmodule Pleroma.Upload.Filter.Exiftool.ReadDescription do
@moduledoc """
Gets a valid description from the related EXIF tags and provides them in the response if no description is provided yet.
It will first check ImageDescription, when that doesn't probide a valid description, it will check iptc:Caption-Abstract.
A valid description means the fields are filled in and not too long (see `:instance, :description_limit`).
"""
@behaviour Pleroma.Upload.Filter
@spec filter(Pleroma.Upload.t()) :: {:ok, any()} | {:error, String.t()}
def filter(%Pleroma.Upload{description: description})
when is_binary(description),
do: {:ok, :noop}
def filter(%Pleroma.Upload{tempfile: file} = upload),
do: {:ok, :filtered, upload |> Map.put(:description, read_description_from_exif_data(file))}
def filter(_, _), do: {:ok, :noop}
defp read_description_from_exif_data(file) do
nil
|> read_when_empty(file, "-ImageDescription")
|> read_when_empty(file, "-iptc:Caption-Abstract")
end
defp read_when_empty(current_description, _, _) when is_binary(current_description),
do: current_description
defp read_when_empty(_, file, tag) do
try do
{tag_content, 0} =
System.cmd("exiftool", ["-b", "-s3", tag, file], stderr_to_stdout: true, parallelism: true)
tag_content = String.trim(tag_content)
if tag_content != "" and
String.length(tag_content) <=
Pleroma.Config.get([:instance, :description_limit]),
do: tag_content,
else: nil
rescue
_ in ErlangError -> nil
end
end
end
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