Pillow/docs/releasenotes/8.3.0.rst

8.3.0
-----

Security
========

:cve:`2021-34552`: Fix buffer overflow
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

PIL since 1.1.4 and Pillow since 1.0 allowed parameters passed into a convert
function to trigger buffer overflow in ``Convert.c``.

Parsing XML
^^^^^^^^^^^

Pillow previously parsed XMP data using Python's ``xml`` module. However, this module
is not secure.

- :py:meth:`~PIL.Image.Image.getexif` has used ``xml`` to potentially retrieve
  orientation data since Pillow 7.2.0. It has been refactored to use ``re`` instead.
- ``getxmp()`` was added to :py:class:`~PIL.JpegImagePlugin.JpegImageFile` in Pillow
  8.2.0. It will now use ``defusedxml`` instead. If the dependency is not present, an
  empty dictionary will be returned and a warning raised.

Deprecations
============

JpegImagePlugin.convert_dict_qtables
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

JPEG ``quantization`` is now automatically converted, but still returned as a
dictionary. The ``convert_dict_qtables`` method no longer
performs any operations on the data given to it, has been deprecated and will be
removed in Pillow 10.0.0 (2023-07-01).

API Changes
===========

Changed WebP default "method" value when saving
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Previously, it was 0, for the best speed. The default has now been changed to 4, to
match WebP's default, for higher quality with still some speed optimisation.

Default resampling filter for special image modes
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Pillow 7.0 changed the default resampling filter to ``Image.BICUBIC``. However, as this
is not supported yet for images with a custom number of bits, the default filter for
those modes has been reverted to ``Image.NEAREST``.

ImageMorph incorrect mode errors
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

For ``apply()``, ``match()`` and ``get_on_pixels()``, if the image mode is not L, an
:py:exc:`Exception` was thrown. This has now been changed to a :py:exc:`ValueError`.

getxmp()
^^^^^^^^

`XMP data <https://en.wikipedia.org/wiki/Extensible_Metadata_Platform>`_ can now be
returned for PNG and TIFF images, through ``getxmp()`` for each format.

The returned dictionary will start from the base of the XML, meaning that the top level
should contain an "xmpmeta" key. JPEG's ``getxmp()`` method has also been updated to
this structure.

TIFF getexif()
^^^^^^^^^^^^^^

TIFF :py:attr:`~PIL.TiffImagePlugin.TiffImageFile.tag_v2` data can now be accessed
through :py:meth:`~PIL.Image.Image.getexif`. This also provides access to the GPS and
EXIF IFDs, through ``im.getexif().get_ifd(0x8825)`` and
``im.getexif().get_ifd(0x8769)`` respectively.

API Additions
=============

ImageOps.contain
^^^^^^^^^^^^^^^^

Returns a resized version of the image, set to the maximum width and height within
``size``, while maintaining the original aspect ratio.

To compare it to other ImageOps methods:

- :py:meth:`~PIL.ImageOps.fit` expands an image until is fills ``size``, cropping the
  parts of the image that do not fit.
- :py:meth:`~PIL.ImageOps.pad` expands an image to fill ``size``, without cropping, but
  instead filling the extra space with ``color``.
- :py:meth:`~PIL.ImageOps.contain` is similar to :py:meth:`~PIL.ImageOps.pad`, but it
  does not fill the extra space. Instead, the original aspect ratio is maintained. So
  unlike the other two methods, it is not guaranteed to return an image of ``size``.

ICO saving: bitmap_format argument
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

By default, Pillow saves ICO files in the PNG format. They can now also be saved in BMP
format, through the new ``bitmap_format`` argument::

    im.save("out.ico", bitmap_format="bmp")

Other Changes
=============

Added DDS BC5 reading and uncompressed saving
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Support has been added to read the BC5 format of DDS images, whether UNORM, SNORM or
TYPELESS.

Support has also been added to write the uncompressed format of DDS images.