Allow 1 mode images in MorphOp get_on_pixels()

Author: radarhere

Tests/test_imagemorph.py

@@ -188,9 +188,10 @@ def test_corner() -> None:
     assert len(coords) == 4
     assert tuple(coords) == ((2, 2), (4, 2), (2, 4), (4, 4))
 
-    coords = mop.get_on_pixels(Aout)
-    assert len(coords) == 4
-    assert tuple(coords) == ((2, 2), (4, 2), (2, 4), (4, 4))
+    for image in (Aout, Aout.convert("1")):
+        coords = mop.get_on_pixels(image)
+        assert len(coords) == 4
+        assert tuple(coords) == ((2, 2), (4, 2), (2, 4), (4, 4))
 
 
 def test_mirroring() -> None:

src/PIL/ImageMorph.py

@@ -232,13 +232,15 @@ def match(self, image: Image.Image) -> list[tuple[int, int]]:
         return _imagingmorph.match(bytes(self.lut), image.getim())
 
     def get_on_pixels(self, image: Image.Image) -> list[tuple[int, int]]:
-        """Get a list of all turned on pixels in a binary image
+        """Get a list of all turned on pixels in a 1 or L mode image.
 
         Returns a list of tuples of (x,y) coordinates
         of all matching pixels. See :ref:`coordinate-system`."""
 
-        if image.mode != "L":
-            msg = "Image mode must be L"
+        if image.mode == "1":
+            image = image.convert("L")
+        elif image.mode != "L":
+            msg = "Image mode must be 1 or L"
             raise ValueError(msg)
         return _imagingmorph.get_on_pixels(image.getim())