v4: a still is scaled from its first frame alone, a second image in its file made the copy flash — an avatar came out as a WebP of two frames looping at 40 ms each, the picture then a blank. A still's file may hold more than one image, a phone's JPEG carrying a gain map or a depth map after the photo, and ffmpeg reads each as a frame: only the JPEG and PNG copies were held to one, the WebP keeping them all as it does a GIF's. scalableImage (lib/upload.ts) now says whether the image is an animation, which a GIF alone is, and scaleImage (lib/ffmpeg.ts) writes one frame of anything else, in every format; the image proxy scales through the same call. The copies already made stay, a copy being current while it has its upload's date: uploads/scaled is to be deleted once on an instance that ran the previous version, everything in it being made again on first request.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

api/test/lib/upload.test.ts

@@ -94,17 +94,27 @@ Deno.test("scalableImage: an animated WebP and what isn't an image are served as
   assertEquals(scalableImage(webp(0x02)), null);
   // A reader without WebP gets a PNG of what may be transparent, a JPEG of
   // the rest.
-  assertEquals(scalableImage(webp(0x10)), { orientation: 1, compat: "png" });
+  const still = { orientation: 1, animated: false };
+  assertEquals(scalableImage(webp(0x10)), { ...still, compat: "png" });
   assertEquals(
     scalableImage(new TextEncoder().encode("RIFF\0\0\0\0WEBPVP8 ")),
-    { orientation: 1, compat: "png" },
+    { ...still, compat: "png" },
   );
-  assertEquals(scalableImage(PNG), { orientation: 1, compat: "png" });
-  assertEquals(scalableImage(jpegWithOrientation(1, true))?.compat, "jpg");
-  assertEquals(scalableImage(new TextEncoder().encode("BM-a-bitmap")), {
-    orientation: 1,
+  assertEquals(scalableImage(PNG), { ...still, compat: "png" });
+  assertEquals(scalableImage(jpegWithOrientation(1, true)), {
+    ...still,
     compat: "jpg",
   });
+  assertEquals(scalableImage(new TextEncoder().encode("BM-a-bitmap")), {
+    ...still,
+    compat: "jpg",
+  });
+  // Only a GIF's frames are an animation to keep.
+  assertEquals(scalableImage(new TextEncoder().encode("GIF89a")), {
+    orientation: 1,
+    animated: true,
+    compat: "png",
+  });
   assertEquals(scalableImage(new TextEncoder().encode("<svg/>")), null);
   assertEquals(scalableImage(new Uint8Array()), null);
 });

api/test/routes/avatars.test.ts

@@ -38,6 +38,24 @@ test("avatars: upload, serve, and 404 when there is none", async () => {
   );
 });
 
+test("avatars: a still holding a second image is scaled to its first alone", async () => {
+  if (!await hasFfmpeg()) return;
+  const user = await createUser();
+  // As a phone's photo carries a gain map after it, which ffmpeg reads as a
+  // second frame.
+  const photo = await makeImage(600, 400, "red");
+  const extra = await makeImage(150, 100, "white");
+  const both = new Uint8Array(photo.length + extra.length);
+  both.set(photo);
+  both.set(extra, photo.length);
+  await put("/api/me/avatar", { auth: user.auth, form: formWithFile(both) });
+
+  const small = await get(`/api/users/${user.id}/avatar?w=128`);
+  assertEquals(small.headers.get("content-type"), "image/webp");
+  assertEquals(webpWidth(small.bytes), 128);
+  assertFalse(new TextDecoder().decode(small.bytes).includes("ANMF"));
+});
+
 test("avatars: `?w=` answers a scaled copy, made again from a new avatar", async () => {
   if (!await hasFfmpeg()) return;
   const user = await createUser();