From 5e7ff45534c15f4b3c60dfde1c9d7644def2258d Mon Sep 17 00:00:00 2001
From: Tulir Asokan <tulir@maunium.net>
Date: Sun, 12 Feb 2023 14:39:07 +0200
Subject: [PATCH] Thumbnail webp images as webp to avoid losing transparency

---
 synapse/config/repository.py | 10 ++++++----
 synapse/media/thumbnailer.py |  2 +-
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/synapse/config/repository.py b/synapse/config/repository.py
index 4655882b4..05b4be638 100644
--- a/synapse/config/repository.py
+++ b/synapse/config/repository.py
@@ -54,10 +54,8 @@ THUMBNAIL_SIZE_YAML = """\
 THUMBNAIL_SUPPORTED_MEDIA_FORMAT_MAP = {
     "image/jpeg": "jpeg",
     "image/jpg": "jpeg",
-    "image/webp": "jpeg",
-    # Thumbnails can only be jpeg or png. We choose png thumbnails for gif
-    # because it can have transparency.
-    "image/gif": "png",
+    "image/webp": "webp",
+    "image/gif": "webp",
     "image/png": "png",
 }
 
@@ -109,6 +107,10 @@ def parse_thumbnail_requirements(
                 requirement.append(
                     ThumbnailRequirement(width, height, method, "image/png")
                 )
+            elif thumbnail_format == "webp":
+                requirement.append(
+                    ThumbnailRequirement(width, height, method, "image/webp")
+                )
             else:
                 raise Exception(
                     "Unknown thumbnail mapping from %s to %s. This is a Synapse problem, please report!"
diff --git a/synapse/media/thumbnailer.py b/synapse/media/thumbnailer.py
index 5538020be..a071dbf55 100644
--- a/synapse/media/thumbnailer.py
+++ b/synapse/media/thumbnailer.py
@@ -47,7 +47,7 @@ class ThumbnailError(Exception):
 
 
 class Thumbnailer:
-    FORMATS = {"image/jpeg": "JPEG", "image/png": "PNG"}
+    FORMATS = {"image/jpeg": "JPEG", "image/png": "PNG", "image/webp": "WEBP"}
 
     @staticmethod
     def set_limits(max_image_pixels: int) -> None: