Added documentation for ImageMorph module

[johnnygitgud]

This pull request adds documentation for the ImageMorph module
For issue #713 ("Todo: Docs for ImageMorph").

The updated documentation has:

• Overview of morphological operations in Pillow
• Explanation of structuring element patterns and ASCII masks
• Usage examples for LutBuilder and MorphOp
• Examples demonstrating pattern matching and apply()
• Information about LUT loading, saving, and reuse
• Guidance on required image modes

[hugovk]

Thank you for filling this gap in the docs!

---

Please can you check the Sphinx warnings?

https://app.readthedocs.org/projects/pillow/builds/30336202/?utm_source=pillow&utm_content=notification#294395027--277

ImageMorph.rst:13: WARNING: py:class reference target not found: LutBuilder [ref.class]
ImageMorph.rst:13: WARNING: py:class reference target not found: MorphOp [ref.class]
ImageMorph.rst:54: WARNING: py:class reference target not found: LutBuilder [ref.class]
ImageMorph.rst:59: WARNING: py:class reference target not found: LutBuilder [ref.class]
ImageMorph.rst:62: WARNING: py:class reference target not found: LutBuilder [ref.class]
ImageMorph.rst:83: WARNING: py:meth reference target not found: LutBuilder.get_lut [ref.meth]
ImageMorph.rst:83: WARNING: py:meth reference target not found: LutBuilder.load_lut [ref.meth]
ImageMorph.rst:83: WARNING: py:meth reference target not found: LutBuilder.save_lut [ref.meth]
ImageMorph.rst:87: WARNING: py:class reference target not found: MorphOp [ref.class]
ImageMorph.rst:90: WARNING: py:class reference target not found: MorphOp [ref.class]
ImageMorph.rst:90: WARNING: py:meth reference target not found: MorphOp.apply [ref.meth]
ImageMorph.rst:109: WARNING: py:meth reference target not found: MorphOp.match [ref.meth]
ImageMorph.rst:109: WARNING: py:meth reference target not found: MorphOp.get_on_pixels [ref.meth]
ImageMorph.rst:125: WARNING: py:class reference target not found: LutBuilder [ref.class]
ImageMorph.rst:145: WARNING: py:mod reference target not found: _imagingmorph [ref.mod]
ImageMorph.rst:145: WARNING: py:class reference target not found: LutBuilder [ref.class]
ImageMorph.rst:145: WARNING: py:class reference target not found: MorphOp [ref.class]

[radarhere]

@johnnygitgud considering that our existing documentation says

. or X - Ignore

what made you think that - was the ignore value?

[radarhere]

This example doesn't work. It fails with

Traceback (most recent call last):
  File "demo.py", line 10, in <module>
    lut = lb.build_lut()
  File "PIL/ImageMorph.py", line 156, in build_lut
    raise Exception(msg)
Exception: Syntax error in pattern "10"

It is, for one thing, missing the 4/N/1/M operation. It feels like you haven't read

Pillow/src/PIL/ImageMorph.py

Lines 51 to 60 in 00e2198

	Operations:
	- 4 - 4 way rotation
	- N - Negate
	- 1 - Dummy op for no other operation (an op must always be given)
	- M - Mirroring
	Example::
	lb = LutBuilder(patterns = ["4:(... .1. 111)->1"])

If you haven't read the source code, that's kind of a red flag with a documentation suggestion.

Could you explain how you came up with this code?

[radarhere]

Looking at https://pillow--9302.org.readthedocs.build/en/9302/reference/ImageMorph.html, I feel like the initial description duplicates part of the LutBuilder class description. As I've pointed out in comments here, there have also been some surprising mistakes in this PR. I actually suspect this was generated using AI?

I've created #9349 as an alternative.

[radarhere]

#9349 has been merged instead.