===========
pillowcases

Library that makes it possible to work in a concise, algebraic way with Python Imaging Library image objects.

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Installation and Usage

This library is available as a package on PyPI <https://pypi.org/project/pillowcases>__:

.. code-block:: bash

python -m pip install pillowcases

The library can be imported in the usual way:

.. code-block:: python

import pillowcases

Examples
^^^^^^^^

To use this library, the PIL.Image module from the pillow <https://pillow.readthedocs.io/en/stable>__ library must be imported. If the pillowcases module is imported afterwards, the PIL.Image module's PIL.Image.Image class is redefined to refer to the pillowcases.Image class (which is itself derived from the PIL.Image.Image class):

.. code-block:: python

>>> import PIL.Image
>>> import pillowcases
>>> i = PIL.Image.frombytes('RGBA', (2, 2), bytes([0]*16))
>>> isinstance(i, pillowcases.Image)
True

.. |set| replace:: set
.. _set: https://docs.python.org/3/library/stdtypes.html#set

.. |dict| replace:: dict
.. _dict: https://docs.python.org/3/library/stdtypes.html#dict

Because instances of pillowcases.Image are hashable <https://docs.python.org/3/glossary.html#term-hashable>__, they can be added as elements to |set|_ objects and can be used as keys in |dict|_ objects:

.. code-block:: python

>>> j = PIL.Image.frombytes('RGBA', (2, 2), bytes([0]*16))
>>> k = PIL.Image.frombytes('RGBA', (2, 2), bytes([255]*16))
>>> len({i, j, k})
2
>>> d = {j: 1, k: 2}
>>> d[k]
2

Compare the above to the default behavior of the PIL.Image.Image class, demonstrated below:

.. code-block:: python

>>> from importlib import reload
>>> PIL.Image = reload(PIL.Image)
>>> i = PIL.Image.frombytes('RGBA', (2, 2), bytes([0]*16))
>>> j = PIL.Image.frombytes('RGBA', (2, 2), bytes([0]*16))
>>> j = PIL.Image.frombytes('RGBA', (2, 2), bytes([255]*16))
>>> len({i, j, k})
Traceback (most recent call last):
    ...
TypeError: unhashable type: 'Image'

Development

All installation and development dependencies are fully specified in pyproject.toml. The project.optional-dependencies object is used to specify optional requirements <https://peps.python.org/pep-0621>__ for various development tasks. This makes it possible to specify additional options (such as docs, lint, and so on) when performing installation using pip <https://pypi.org/project/pip>__:

.. code-block:: bash

python -m pip install .[docs,lint]

Documentation
^^^^^^^^^^^^^
The documentation can be generated automatically from the source files using Sphinx <https://www.sphinx-doc.org>__:

.. code-block:: bash

python -m pip install .[docs]
cd docs
sphinx-apidoc -f -E --templatedir=_templates -o _source .. && make html

Testing and Conventions
^^^^^^^^^^^^^^^^^^^^^^^
All unit tests are executed and their coverage is measured when using pytest <https://docs.pytest.org>__ (see the pyproject.toml file for configuration details):

.. code-block:: bash

python -m pip install .[test]
python -m pytest

Alternatively, all unit tests are included in the module itself and can be executed using doctest <https://docs.python.org/3/library/doctest.html>__:

.. code-block:: bash

python src/pillowcases/pillowcases.py -v

Style conventions are enforced using Pylint <https://pylint.readthedocs.io>__:

.. code-block:: bash

python -m pip install .[lint]
python -m pylint src/pillowcases

Contributions
^^^^^^^^^^^^^
In order to contribute to the source code, open an issue or submit a pull request on the GitHub page <https://github.com/lapets/pillowcases>__ for this library.

Versioning
^^^^^^^^^^
The version number format for this library and the changes to the library associated with version number increments conform with Semantic Versioning 2.0.0 <https://semver.org/#semantic-versioning-200>__.

Publishing
^^^^^^^^^^
This library can be published as a package on PyPI <https://pypi.org/project/pillowcases>__ by a package maintainer. First, install the dependencies required for packaging and publishing:

.. code-block:: bash

python -m pip install .[publish]

Ensure that the correct version number appears in pyproject.toml, and that any links in this README document to the Read the Docs documentation of this package (or its dependencies) have appropriate version numbers. Also ensure that the Read the Docs project for this library has an automation rule <https://docs.readthedocs.io/en/stable/automation-rules.html>__ that activates and sets as the default all tagged versions. Create and push a tag for this version (replacing ?.?.? with the version number):

.. code-block:: bash

git tag ?.?.?
git push origin ?.?.?

Remove any old build/distribution files. Then, package the source into a distribution archive:

.. code-block:: bash

rm -rf build dist src/*.egg-info
python -m build --sdist --wheel .

Finally, upload the package distribution archive to PyPI <https://pypi.org>__:

.. code-block:: bash

python -m twine upload dist/*