3 files changed, 68 insertions, 7 deletions
diff --git a/lib/pleroma/application_requirements.ex b/lib/pleroma/application_requirements.ex
index 06d388694..ea1ee71c0 100644
--- a/lib/pleroma/application_requirements.ex
+++ b/lib/pleroma/application_requirements.ex
@@ -165,6 +165,7 @@ defmodule Pleroma.ApplicationRequirements do
   defp check_system_commands!(:ok) do
     filter_commands_statuses = [
       check_filter(Pleroma.Upload.Filter.Exiftool, "exiftool"),
+      check_filter(Pleroma.Upload.Filter.ExiftoolReadData, "exiftool"),
       check_filter(Pleroma.Upload.Filter.Mogrify, "mogrify"),
       check_filter(Pleroma.Upload.Filter.Mogrifun, "mogrify"),
       check_filter(Pleroma.Upload.Filter.AnalyzeMetadata, "mogrify"),
diff --git a/lib/pleroma/upload.ex b/lib/pleroma/upload.ex
index 242813dcd..db2909276 100644
--- a/lib/pleroma/upload.ex
+++ b/lib/pleroma/upload.ex
@@ -60,12 +60,23 @@ defmodule Pleroma.Upload do
           width: integer(),
           height: integer(),
           blurhash: String.t(),
+          description: String.t(),
           path: String.t()
         }
-  defstruct [:id, :name, :tempfile, :content_type, :width, :height, :blurhash, :path]
-
-  defp get_description(opts, upload) do
-    case {opts[:description], Pleroma.Config.get([Pleroma.Upload, :default_description])} do
+  defstruct [
+    :id,
+    :name,
+    :tempfile,
+    :content_type,
+    :width,
+    :height,
+    :blurhash,
+    :description,
+    :path
+  ]
+
+  defp get_description(upload) do
+    case {upload.description, Pleroma.Config.get([Pleroma.Upload, :default_description])} do
       {description, _} when is_binary(description) -> description
       {_, :filename} -> upload.name
       {_, str} when is_binary(str) -> str
@@ -81,7 +92,7 @@ defmodule Pleroma.Upload do
     with {:ok, upload} <- prepare_upload(upload, opts),
          upload = %__MODULE__{upload | path: upload.path || "#{upload.id}/#{upload.name}"},
          {:ok, upload} <- Pleroma.Upload.Filter.filter(opts.filters, upload),
-         description = get_description(opts, upload),
+         description = get_description(upload),
          {_, true} <-
            {:description_limit,
             String.length(description) <= Pleroma.Config.get([:instance, :description_limit])},
@@ -152,7 +163,8 @@ defmodule Pleroma.Upload do
          id: UUID.generate(),
          name: file.filename,
          tempfile: file.path,
-         content_type: file.content_type
+         content_type: file.content_type,
+         description: opts.description
        }}
     end
   end
@@ -172,7 +184,8 @@ defmodule Pleroma.Upload do
          id: UUID.generate(),
          name: hash <> "." <> ext,
          tempfile: tmp_path,
-         content_type: content_type
+         content_type: content_type,
+         description: opts.description
        }}
     end
   end
diff --git a/lib/pleroma/upload/filter/exiftool_read_data.ex b/lib/pleroma/upload/filter/exiftool_read_data.ex
new file mode 100644
index 000000000..c8bedfbf8
--- /dev/null
+++ b/lib/pleroma/upload/filter/exiftool_read_data.ex
@@ -0,0 +1,47 @@
+# 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.ExiftoolReadData do
+  @moduledoc """
+  Gets the 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's too long or empty, it will check iptc:Caption-Abstract.
+  When the description is too long (see `:instance, :description_limit`), an empty string is returned.
+  """
+  @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)
+
+      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