Added documentation for ImageMorph module

docs/reference/ImageMorph.rst

@@ -4,10 +4,139 @@
 :py:mod:`~PIL.ImageMorph` module
 ================================
 
-The :py:mod:`~PIL.ImageMorph` module provides morphology operations on images.
+The :py:mod:`~PIL.ImageMorph` module provides morphological operations for
+binary and grayscale images. Morphology is a family of image-processing
+techniques based on the shape and structure of regions in an image. Basic
+uses are dilation, erosion, edge detection, and hit or miss pattern
+matching.
 
-.. automodule:: PIL.ImageMorph
+``ImageMorph`` works by applying a lookup table (LUT) to a binary representation
+of the input image. Patterns used for these operations are defined using small
+ASCII masks, which are converted into LUTs through :class:`LutBuilder`. The
+resulting LUTs can then be applied to an image using :class:`MorphOp`.
+
+This module is useful for tasks such as noise cleanup, detecting specific
+pixel shapes, extracting boundaries, thinning, or locating features defined by
+small structuring elements.
+
+Supported image modes
+---------------------
+
+Morphological operations in Pillow operate on images in mode ``"L"`` (8-bit
+grayscale). A nonzero pixel is treated as "on", and a zero-valued pixel as
+"off". To apply morphology to a binary image, ensure that the image is first
+converted to mode ``"L"``::
+
+    im = im.convert("L")
+
+Defining structuring element patterns
+-------------------------------------
+
+A structuring pattern is defined using a small ASCII mask consisting of the
+characters:
+
+* ``1`` — pixel must be "on"
+* ``0`` — pixel must be "off"
+* ``.`` or ``X`` — "don’t care" value (ignored during matching)
+
+For example, this mask detects a 2×2 corner shape::
+
+    pattern = [
+        "10",
+        "11",
+    ]
+
+Multiple patterns can be combined into a single LUT. Patterns must all be the
+same size, and Pillow builds a lookup table from them using
+:class:`LutBuilder`.
+
+Using :class:`LutBuilder`
+-------------------------
+
+The :class:`LutBuilder` class constructs a LUT that defines how a morphological
+operation should behave. A LUT maps every possible 3×3 neighborhood around a
+pixel to an output pixel value (either "on" or "off").
+
+Basic uses like dilation and erosion can be achieved by specifying preset operation
+names (``"corner"``, ``"dilation4"``, ``"dilation8"``, ``"erosion4"``, ``"erosion8"``,
+``"edge"``), or you may define custom patterns.
+
+For example, creating a LUT for a 2×2 corner detector::
+
+    from PIL import ImageMorph
+
+    patterns = [
+        "10",
+        "11",
+    ]
+
+    lb = ImageMorph.LutBuilder(op_name="corner")
+    lb.add_patterns(patterns)
+    lut = lb.build_lut()
+
+You can inspect, save, or reuse the LUT with :meth:`LutBuilder.get_lut`,
+:meth:`MorphOp.load_lut`, or :meth:`MorphOp.save_lut`.
+
+Applying morphology with :class:`MorphOp`
+-----------------------------------------
+
+Once a LUT is created, the :class:`MorphOp` class applies it to an image. The
+:meth:`MorphOp.apply` method performs the morphological operation and returns
+a tuple ``(count, out_image)`` where:
+
+* ``count`` is the number of pixels that changed, and
+* ``out_image`` is the resulting processed image.
+
+Example: applying a simple dilation operation::
+
+    from PIL import Image, ImageMorph
+
+    with Image.open("input.png") as im:
+        im = im.convert("L")
+
+    # Built-in 8-connected dilation
+    op = ImageMorph.MorphOp(op_name="dilation8")
+
+    count, out = op.apply(im)
+    out.save("dilated.png")
+
+You could also use the method :meth:`MorphOp.match` to check where a pattern
+matches without modifying the image, and :meth:`MorphOp.get_on_pixels` to
+get the coordinates of "on" pixels after pattern matching.
+
+Example: pattern matching without modifying the image::
+
+    op = ImageMorph.MorphOp(op_name="edge")
+    result = op.match(im)
+
+    # result is a list of (x, y) coordinates
+    print("Edge pixels found:", len(result))
+
+Saving and loading LUTs
+-----------------------
+
+LUTs created by :class:`LutBuilder` can be serialized and reused later. This
+is helpful when repeatedly applying the same pattern in a batch-processing
+workflow.
+
+Example::
+
+    lb = ImageMorph.LutBuilder(op_name="custom")
+    lb.add_patterns(patterns)
+    lb.build_lut()
+    lb.save_lut("custom.lut")
+
+    # Later...
+    op = ImageMorph.MorphOp()
+    op.load_lut("custom.lut")
+    count, out = op.apply(im)
+
+.. autoclass:: LutBuilder
+    :members:
+    :undoc-members:
+    :show-inheritance:
+
+.. autoclass:: MorphOp
     :members:
     :undoc-members:
     :show-inheritance:
-    :noindex: