Fixes #90

sticker/lib/util.py

@@ -28,9 +28,8 @@ open_utf8 = partial(open, encoding='UTF-8')
 
 def convert_image(data: bytes, max_w=256, max_h=256) -> (bytes, int, int):
     image: Image.Image = Image.open(BytesIO(data)).convert("RGBA")
-    new_file = BytesIO()
-    image.save(new_file, "png")
     w, h = image.size
+    
     if w > max_w or h > max_h:
         # Set the width and height to lower values so clients wouldn't show them as huge images
         if w > h:
@@ -39,6 +38,10 @@ def convert_image(data: bytes, max_w=256, max_h=256) -> (bytes, int, int):
         else:
             w = int(w / (h / max_h))
             h = max_h
+        image = image.resize((w, h), Image.LANCZOS)
+
+    new_file = BytesIO()
+    image.save(new_file, "png")
     return new_file.getvalue(), w, h
 
 
@@ -91,4 +94,4 @@ def add_thumbnails(stickers: List[matrix.StickerInfo], stickers_data: Dict[str,
         
         name = sticker["url"].split("/")[-1]
         thumbnail_path = thumbnails / name
-        thumbnail_path.write_bytes(image_data)
+        thumbnail_path.write_bytes(image_data)