Inherit classes with abstractmethod from ABC

src/PIL/BlpImagePlugin.py

@@ -291,7 +291,7 @@ class BlpImageFile(ImageFile.ImageFile):
         self.tile = [ImageFile._Tile(decoder, (0, 0) + self.size, offset, args)]
 
 
-class _BLPBaseDecoder(ImageFile.PyDecoder):
+class _BLPBaseDecoder(abc.ABC, ImageFile.PyDecoder):
     _pulls_fd = True
 
     def decode(self, buffer: bytes | Image.SupportsArrayInterface) -> tuple[int, int]:

src/PIL/Image.py

@@ -2966,7 +2966,7 @@ class Image:
 # Abstract handlers.
 
 
-class ImagePointHandler:
+class ImagePointHandler(abc.ABC):
     """
     Used as a mixin by point transforms
     (for use with :py:meth:`~PIL.Image.Image.point`)
@@ -2977,7 +2977,7 @@ class ImagePointHandler:
         pass
 
 
-class ImageTransformHandler:
+class ImageTransformHandler(abc.ABC):
     """
     Used as a mixin by geometry transforms
     (for use with :py:meth:`~PIL.Image.Image.transform`)

src/PIL/ImageFile.py

@@ -438,7 +438,7 @@ class ImageFile(Image.Image):
         return self.tell() != frame
 
 
-class StubHandler:
+class StubHandler(abc.ABC):
     def open(self, im: StubImageFile) -> None:
         pass
 

src/PIL/ImageFilter.py

@@ -27,7 +27,7 @@ if TYPE_CHECKING:
     from ._typing import NumpyArray
 
 
-class Filter:
+class Filter(abc.ABC):
     @abc.abstractmethod
     def filter(self, image: _imaging.ImagingCore) -> _imaging.ImagingCore:
         pass

src/PIL/ImageShow.py

@@ -192,7 +192,7 @@ if sys.platform == "darwin":
     register(MacViewer)
 
 
-class UnixViewer(Viewer):
+class UnixViewer(abc.ABC, Viewer):
     format = "PNG"
     options = {"compress_level": 1, "save_all": True}