Add resizing filter to make sure pictures are not too big

Closes #810

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

config/config.exs

@@ -67,6 +67,7 @@ config :mobilizon, Mobilizon.Web.Upload,
   filters: [
     Mobilizon.Web.Upload.Filter.Dedupe,
     Mobilizon.Web.Upload.Filter.AnalyzeMetadata,
+    Mobilizon.Web.Upload.Filter.Resize,
     Mobilizon.Web.Upload.Filter.Optimize
   ],
   allow_list_mime_types: ["image/gif", "image/jpeg", "image/png", "image/webp"],

lib/web/upload/filter/resize.ex

@@ -0,0 +1,42 @@
+defmodule Mobilizon.Web.Upload.Filter.Resize do
+  @moduledoc """
+  Resize the pictures if they're bigger than maximum size.
+
+  This filter requires `Mobilizon.Web.Upload.Filter.AnalyzeMetadata` to be performed before.
+  """
+
+  @behaviour Mobilizon.Web.Upload.Filter
+
+  @maximum_width 1_920
+  @maximum_height 1_080
+
+  def filter(%Mobilizon.Web.Upload{
+        tempfile: file,
+        content_type: "image" <> _,
+        width: width,
+        height: height
+      }) do
+    file
+    |> Mogrify.open()
+    |> Mogrify.resize(string(limit_sizes({width, height})))
+    |> Mogrify.save(in_place: true)
+
+    {:ok, :filtered}
+  end
+
+  def filter(_), do: {:ok, :noop}
+
+  def limit_sizes({width, height}) when width > @maximum_width do
+    new_height = round(@maximum_width * height / width)
+    limit_sizes({@maximum_width, new_height})
+  end
+
+  def limit_sizes({width, height}) when height > @maximum_height do
+    new_width = round(@maximum_height * width / height)
+    limit_sizes({new_width, @maximum_height})
+  end
+
+  def limit_sizes({width, height}), do: {width, height}
+
+  defp string({width, height}), do: "#{width}x#{height}"
+end

lib/web/upload/upload.ex

@@ -60,9 +60,11 @@ defmodule Mobilizon.Web.Upload do
           tempfile: String.t(),
           content_type: String.t(),
           path: String.t(),
-          size: integer()
+          size: integer(),
+          width: integer(),
+          height: integer()
         }
-  defstruct [:id, :name, :tempfile, :content_type, :path, :size]
+  defstruct [:id, :name, :tempfile, :content_type, :path, :size, :width, :height]
 
   @spec store(source, options :: [option()]) :: {:ok, map()} | {:error, any()}
   def store(upload, opts \\ []) do

test/web/upload/filter/resize_test.exs

@@ -0,0 +1,20 @@
+defmodule Mobilizon.Web.Upload.Filter.ResizeTest do
+  use Mobilizon.DataCase, async: true
+  alias Mobilizon.Web.Upload.Filter.Resize
+
+  test "does not resize if dimensions are ok" do
+    assert {100, 150} == Resize.limit_sizes({100, 150})
+  end
+
+  test "does resize only width if needed" do
+    assert {1_920, 960} == Resize.limit_sizes({2_000, 1_000})
+  end
+
+  test "does resize only height if needed" do
+    assert {540, 1_080} == Resize.limit_sizes({1_000, 2_000})
+  end
+
+  test "does resize if dimentions are really big, and keeps ratio" do
+    assert {724, 1080} == Resize.limit_sizes({10_050, 15_000})
+  end
+end