Pillow/docs/releasenotes/4.3.0.rst

4.3.0
-----

Get One Channel From Image
==========================

New method :py:meth:`PIL.Image.Image.getchannel` is added.
It returns single channel by index or name. For example,
``image.getchannel("A")`` will return alpha channel as separate image.
``getchannel`` should work up to 6 times faster than ``image.split()[0]``
in previous Pillow versions.


Box Blur
========

New filter :py:class:`PIL.ImageFilter.BoxBlur` is added.


Partial Resampling
==================

Added new argument ``box`` for :py:meth:`PIL.Image.Image.resize`. This
argument defines a source rectangle from within the source image to be
resized.  This is very similar to the ``image.crop(box).resize(size)``
sequence except that ``box`` can be specified with subpixel accuracy.


Loading 16-bit TIFF Images
==========================

Pillow now can read 16-bit multichannel TIFF files including files
with alpha transparency. The image data is truncated to 8-bit
precision.


Performance
===========

This release contains several performance improvements:

* Many memory bandwidth-bounded operations such as crop, image allocation,
  conversion, split into bands and merging from bands are up to 2x faster.
* Upscaling of multichannel images (such as RGB) is accelerated by 5-10%
* JPEG loading is accelerated up to 15% and JPEG saving up to 20% when
  using a recent version of libjpeg-turbo.


TIFF Metadata Changes
=====================

* TIFF tags with unknown type/quantity now default to being bare
  values if they are 1 element, where previously they would be a
  single element tuple. This is only with the new api, not the legacy
  api. This normalizes the handling of fields, so that the metadata
  with inferred or image specified counts are handled the same as
  metadata with count specified in the TIFF spec. 
* The ``PhotoshopInfo``, ``XMP``, and ``JPEGTables`` tags now have a
  defined type (bytes) and a count of 1.
* The ``ImageJMetaDataByteCounts`` tag now has an arbitrary number of
  items, as there can be multiple items, one for UTF-8, and one for
  UTF-16.


Core Image API Changes
======================

These are internal functions that should not have been used by user
code, but they were accessible from the python layer.

Debugging code within ``Image.core.grabclipboard`` was removed. It had been
marked as ``will be removed in future versions`` since PIL. When enabled, it
identified the format of the clipboard data.

The ``PIL.Image.core.copy`` and ``PIL.Image.Image.im.copy2`` methods
have been removed.