AnalyzeMetadata: Don't crash on grayscale image blurhash

lib/pleroma/upload/filter/analyze_metadata.ex

@@ -90,9 +90,13 @@ defmodule Pleroma.Upload.Filter.AnalyzeMetadata do
       {:ok, rgb} =
         if Image.has_alpha?(resized_image) do
           # remove alpha channel
-          resized_image
-          |> Operation.extract_band!(0, n: 3)
-          |> Image.write_to_binary()
+          case Operation.extract_band(resized_image, 0, n: 3) do
+            {:ok, data} ->
+              Image.write_to_binary(data)
+
+            _ ->
+              Image.write_to_binary(resized_image)
+          end
         else
           Image.write_to_binary(resized_image)
         end

test/pleroma/upload/filter/analyze_metadata_test.exs

@@ -34,6 +34,20 @@ defmodule Pleroma.Upload.Filter.AnalyzeMetadataTest do
     assert meta.blurhash == "eXJi-E:SwCEm5rCmn$+YWYn+15K#5A$xxCi{SiV]s*W:Efa#s.jE-T"
   end
 
+  test "it gets dimensions for grayscale images" do
+    upload = %Pleroma.Upload{
+      name: "break_analyze.png",
+      content_type: "image/png",
+      path: Path.absname("test/fixtures/break_analyze.png"),
+      tempfile: Path.absname("test/fixtures/break_analyze.png")
+    }
+
+    {:ok, :filtered, meta} = AnalyzeMetadata.filter(upload)
+
+    assert %{width: 1410, height: 2048} = meta
+    assert is_nil(meta.blurhash)
+  end
+
   test "adds the dimensions for videos" do
     upload = %Pleroma.Upload{
       name: "coolvideo.mp4",