Allow 1 mode images in MorphOp (#9348)

Author: hugovk

Tests/images/morph_a.png

@@ -15,13 +15,10 @@ def string_to_img(image_string: str) -> Image.Image:
     rows = [s for s in image_string.replace(" ", "").split("\n") if len(s)]
     height = len(rows)
     width = len(rows[0])
-    im = Image.new("L", (width, height))
-    for i in range(width):
-        for j in range(height):
-            c = rows[j][i]
-            v = c in "X1"
-            im.putpixel((i, j), v)
-
+    im = Image.new("1", (width, height))
+    for x in range(width):
+        for y in range(height):
+            im.putpixel((x, y), rows[y][x] in "X1")
     return im
 
 
@@ -42,10 +39,10 @@ def img_to_string(im: Image.Image) -> str:
     """Turn a (small) binary image into a string representation"""
     chars = ".1"
     result = []
-    for r in range(im.height):
+    for y in range(im.height):
         line = ""
-        for c in range(im.width):
-            value = im.getpixel((c, r))
+        for x in range(im.width):
+            value = im.getpixel((x, y))
             assert not isinstance(value, tuple)
             assert value is not None
             line += chars[value > 0]
@@ -165,10 +162,12 @@ def test_edge() -> None:
     )
 
 
-def test_corner() -> None:
+@pytest.mark.parametrize("mode", ("1", "L"))
+def test_corner(mode: str) -> None:
     # Create a corner detector pattern
     mop = ImageMorph.MorphOp(patterns=["1:(... ... ...)->0", "4:(00. 01. ...)->1"])
-    count, Aout = mop.apply(A)
+    image = A.convert(mode) if mode == "L" else A
+    count, Aout = mop.apply(image)
     assert count == 5
     assert_img_equal_img_string(
         Aout,
@@ -184,7 +183,7 @@ def test_corner() -> None:
     )
 
     # Test the coordinate counting with the same operator
-    coords = mop.match(A)
+    coords = mop.match(image)
     assert len(coords) == 4
     assert tuple(coords) == ((2, 2), (4, 2), (2, 4), (4, 4))
 
@@ -232,14 +231,14 @@ def test_negate() -> None:
 
 
 def test_incorrect_mode() -> None:
-    im = hopper("RGB")
+    im = hopper()
     mop = ImageMorph.MorphOp(op_name="erosion8")
 
-    with pytest.raises(ValueError, match="Image mode must be L"):
+    with pytest.raises(ValueError, match="Image mode must be 1 or L"):
         mop.apply(im)
-    with pytest.raises(ValueError, match="Image mode must be L"):
+    with pytest.raises(ValueError, match="Image mode must be 1 or L"):
         mop.match(im)
-    with pytest.raises(ValueError, match="Image mode must be L"):
+    with pytest.raises(ValueError, match="Image mode must be 1 or L"):
         mop.get_on_pixels(im)
 
 

Tests/test_imagemorph.py

@@ -5,7 +5,7 @@
 ================================
 
 The :py:mod:`~PIL.ImageMorph` module allows `morphology`_ operators ("MorphOp") to be
-applied to L mode images::
+applied to 1 or L mode images::
 
   from PIL import Image, ImageMorph
   img = Image.open("Tests/images/hopper.bw")

docs/reference/ImageMorph.rst

@@ -233,14 +233,15 @@ def apply(self, image: Image.Image) -> tuple[int, Image.Image]:
         Returns a tuple of the number of changed pixels and the
         morphed image.
 
+        :param image: A 1-mode or L-mode image.
         :exception Exception: If the current operator is None.
-        :exception ValueError: If the image is not L mode."""
+        :exception ValueError: If the image is not 1 or L mode."""
         if self.lut is None:
             msg = "No operator loaded"
             raise Exception(msg)
 
-        if image.mode != "L":
-            msg = "Image mode must be L"
+        if image.mode not in ("1", "L"):
+            msg = "Image mode must be 1 or L"
             raise ValueError(msg)
         outimage = Image.new(image.mode, image.size)
         count = _imagingmorph.apply(bytes(self.lut), image.getim(), outimage.getim())
@@ -253,29 +254,29 @@ def match(self, image: Image.Image) -> list[tuple[int, int]]:
         Returns a list of tuples of (x,y) coordinates of all matching pixels. See
         :ref:`coordinate-system`.
 
-        :param image: An L-mode image.
+        :param image: A 1-mode or L-mode image.
         :exception Exception: If the current operator is None.
-        :exception ValueError: If the image is not L mode."""
+        :exception ValueError: If the image is not 1 or L mode."""
         if self.lut is None:
             msg = "No operator loaded"
             raise Exception(msg)
 
-        if image.mode != "L":
-            msg = "Image mode must be L"
+        if image.mode not in ("1", "L"):
+            msg = "Image mode must be 1 or L"
             raise ValueError(msg)
         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 grayscale 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 non-empty pixels. See
         :ref:`coordinate-system`.
 
-        :param image: An L-mode image.
-        :exception ValueError: If the image is not L mode."""
+        :param image: A 1-mode or L-mode image.
+        :exception ValueError: If the image is not 1 or L mode."""
 
-        if image.mode != "L":
-            msg = "Image mode must be L"
+        if image.mode not in ("1", "L"):
+            msg = "Image mode must be 1 or L"
             raise ValueError(msg)
         return _imagingmorph.get_on_pixels(image.getim())