Fix webp header unpacking

panel/pane/image.py

@@ -522,22 +522,12 @@ class WebP(ImageBase):
 
     @classmethod
     def _imgshape(cls, data):
-        import struct
-        b = BytesIO(data)
-        b.read(12)  # Skip RIFF header
-        chunk_header = b.read(4)
-        if chunk_header == b'VP8 ':  # Lossy WebP
-            b.read(3)  # Skip VP8 header
-            w, h = struct.unpack("<HH", b.read(4))  # Width and height are little-endian
-        elif chunk_header == b'VP8L':  # Lossless WebP
-            b.read(1)  # Skip VP8L header
-            bits = struct.unpack("<I", b.read(4))[0]  # Read width and height bits
-            w = (bits & 0x3FFF) + 1  # Width is stored in the 14 least significant bits
-            h = ((bits >> 14) & 0x3FFF) + 1  # Height is stored in the next 14 bits
-        elif chunk_header == b'VP8X':  # Extended WebP
-            b.read(4)  # Skip VP8X header
-            w = struct.unpack("<I", b.read(3))[0] + 1  # Width is stored in the next 3 bytes
-            h = struct.unpack("<I", b.read(3))[0] + 1  # Height is stored in the next 3 bytes
-        else:
-            raise ValueError("Invalid WebP file")
+        with BytesIO(data) as b:
+            b.read(12)  # Skip RIFF header
+            chunk_header = b.read(8)
+            if chunk_header[:3] != b'VP8':
+                raise ValueError("Invalid WebP file")
+            b.read(4)
+            w = int.from_bytes(b.read(3), 'little') + 1
+            h = int.from_bytes(b.read(3), 'little') + 1
         return int(w), int(h)

panel/tests/pane/test_image.py

@@ -70,8 +70,8 @@ def test_svg_pane(document, comm):
           b'ACEQMRAD8AA0qs5HvTHQcJdsChioXSbOr/2Q==',
     ico = b'AAABAAEAAgEAAAEAIAA0AAAAFgAAACgAAAACAAAAAgAAAAEAIAAAAAAACAAAAHQ' + \
           b'SAAB0EgAAAAAAAAAAAAD//////////wAAAAA=',
-    webp= b'UklGRi4AAABXRUJQVlA4ICIAAACQAQCdASoCAAEAAgA0JZwAAudZuFQA/vXf1fmh' + \
-          b'/Al4AAAA'
+    webp= b'UklGRkIAAABXRUJQVlA4WAoAAAAQAAAAAQAAAAAAQUxQSAMAAAAAAAAAVlA4IBg' + \
+          b'AAAAwAQCdASoCAAEAAUAmJaQAA3AA/v02aAA='
           )