[#2497] Image preview proxy: implemented ffmpeg-based resizing, removed eimp & mogrify-based resizing.

3 files changed, 71 insertions, 66 deletions

diff --git a/lib/pleroma/helpers/media_helper.ex b/lib/pleroma/helpers/media_helper.ex
new file mode 100644
index 000000000..6d1f8ab22
--- /dev/null
+++ b/lib/pleroma/helpers/media_helper.ex
@@ -0,0 +1,62 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Helpers.MediaHelper do
+  @moduledoc """
+  Handles common media-related operations.
+  """
+
+  @ffmpeg_opts [{:sync, true}, {:stdout, true}]
+
+  def ffmpeg_resize_remote(uri, max_width, max_height) do
+    cmd = ~s"""
+    curl -L "#{uri}" |
+    ffmpeg -i pipe:0 -vf \
+      "scale='min(#{max_width},iw)':min'(#{max_height},ih)':force_original_aspect_ratio=decrease" \
+      -f image2 pipe:1 | \
+    cat
+    """
+
+    with {:ok, [stdout: stdout_list]} <- Exexec.run(cmd, @ffmpeg_opts) do
+      {:ok, Enum.join(stdout_list)}
+    end
+  end
+
+  @doc "Returns a temporary path for an URI"
+  def temporary_path_for(uri) do
+    name = Path.basename(uri)
+    random = rand_uniform(999_999)
+    Path.join(System.tmp_dir(), "#{random}-#{name}")
+  end
+
+  @doc "Stores binary content fetched from specified URL as a temporary file."
+  @spec store_as_temporary_file(String.t(), binary()) :: {:ok, String.t()} | {:error, atom()}
+  def store_as_temporary_file(url, body) do
+    path = temporary_path_for(url)
+    with :ok <- File.write(path, body), do: {:ok, path}
+  end
+
+  @doc "Modifies image file at specified path by resizing to specified limit dimensions."
+  @spec mogrify_resize_to_limit(String.t(), String.t()) :: :ok | any()
+  def mogrify_resize_to_limit(path, resize_dimensions) do
+    with %Mogrify.Image{} <-
+           path
+           |> Mogrify.open()
+           |> Mogrify.resize_to_limit(resize_dimensions)
+           |> Mogrify.save(in_place: true) do
+      :ok
+    end
+  end
+
+  defp rand_uniform(high) do
+    Code.ensure_loaded(:rand)
+
+    if function_exported?(:rand, :uniform, 1) do
+      :rand.uniform(high)
+    else
+      # Erlang/OTP < 19
+      apply(:crypto, :rand_uniform, [1, high])
+    end
+  end
+end
diff --git a/lib/pleroma/helpers/mogrify_helper.ex b/lib/pleroma/helpers/mogrify_helper.ex
deleted file mode 100644
index 67edb35c3..000000000
--- a/lib/pleroma/helpers/mogrify_helper.ex
+++ /dev/null
@@ -1,25 +0,0 @@
-# Pleroma: A lightweight social networking server
-# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
-# SPDX-License-Identifier: AGPL-3.0-only
-
-defmodule Pleroma.Helpers.MogrifyHelper do
-  @moduledoc """
-  Handles common Mogrify operations.
-  """
-
-  @spec store_as_temporary_file(String.t(), binary()) :: {:ok, String.t()} | {:error, atom()}
-  @doc "Stores binary content fetched from specified URL as a temporary file."
-  def store_as_temporary_file(url, body) do
-    path = Mogrify.temporary_path_for(%{path: url})
-    with :ok <- File.write(path, body), do: {:ok, path}
-  end
-
-  @spec store_as_temporary_file(String.t(), String.t()) :: Mogrify.Image.t() | any()
-  @doc "Modifies file at specified path by resizing to specified limit dimensions."
-  def in_place_resize_to_limit(path, resize_dimensions) do
-    path
-    |> Mogrify.open()
-    |> Mogrify.resize_to_limit(resize_dimensions)
-    |> Mogrify.save(in_place: true)
-  end
-end
diff --git a/lib/pleroma/web/media_proxy/media_proxy_controller.ex b/lib/pleroma/web/media_proxy/media_proxy_controller.ex
index 8d8d073e9..fb4b80379 100644
--- a/lib/pleroma/web/media_proxy/media_proxy_controller.ex
+++ b/lib/pleroma/web/media_proxy/media_proxy_controller.ex
@@ -6,7 +6,7 @@ defmodule Pleroma.Web.MediaProxy.MediaProxyController do
   use Pleroma.Web, :controller
 
   alias Pleroma.Config
-  alias Pleroma.Helpers.MogrifyHelper
+  alias Pleroma.Helpers.MediaHelper
   alias Pleroma.ReverseProxy
   alias Pleroma.Web.MediaProxy
 
@@ -82,51 +82,19 @@ defmodule Pleroma.Web.MediaProxy.MediaProxyController do
     {thumbnail_max_width, thumbnail_max_height}
   end
 
-  defp thumbnail_binary(url, body, params) do
-    {thumbnail_max_width, thumbnail_max_height} = thumbnail_max_dimensions(params)
-
-    with true <- Config.get([:media_preview_proxy, :enable_eimp]),
-         {:ok, [type: image_type, width: source_width, height: source_height]} <-
-           :eimp.identify(body),
-         scale_factor <-
-           Enum.max([source_width / thumbnail_max_width, source_height / thumbnail_max_height]),
-         {:ok, thumbnail_binary} =
-           :eimp.convert(body, image_type, [
-             {:scale, {round(source_width / scale_factor), round(source_height / scale_factor)}}
-           ]) do
-      {:ok, thumbnail_binary}
-    else
-      _ ->
-        mogrify_dimensions = "#{thumbnail_max_width}x#{thumbnail_max_height}"
-
-        with {:ok, path} <- MogrifyHelper.store_as_temporary_file(url, body),
-             %Mogrify.Image{} <-
-               MogrifyHelper.in_place_resize_to_limit(path, mogrify_dimensions),
-             {:ok, thumbnail_binary} <- File.read(path),
-             _ <- File.rm(path) do
-          {:ok, thumbnail_binary}
-        else
-          _ -> :error
-        end
-    end
-  end
-
   defp handle_preview("image/" <> _ = content_type, %{params: params} = conn, url) do
-    with {:ok, %{status: status, body: image_contents}} when status in 200..299 <-
-           url
-           |> MediaProxy.url()
-           |> Tesla.get(opts: [adapter: [timeout: preview_timeout()]]),
-         {:ok, thumbnail_binary} <- thumbnail_binary(url, image_contents, params) do
+    with {thumbnail_max_width, thumbnail_max_height} <- thumbnail_max_dimensions(params),
+         media_proxy_url <- MediaProxy.url(url),
+         {:ok, thumbnail_binary} <-
+           MediaHelper.ffmpeg_resize_remote(
+             media_proxy_url,
+             thumbnail_max_width,
+             thumbnail_max_height
+           ) do
       conn
       |> put_resp_header("content-type", content_type)
       |> send_resp(200, thumbnail_binary)
     else
-      {_, %{status: _}} ->
-        send_resp(conn, :failed_dependency, "Can't fetch the image.")
-
-      {:error, :recv_response_timeout} ->
-        send_resp(conn, :failed_dependency, "Downstream timeout.")
-
       _ ->
         send_resp(conn, :failed_dependency, "Can't handle image preview.")
     end