Pillow/docs/releasenotes/3.1.0.rst

3.1.0
=====

ImageDraw arc, chord and pieslice can now use floats
----------------------------------------------------

There is no longer a need to ensure that the start and end arguments for `arc`,
`chord` and `pieslice` are integers.

Note that these numbers are not simply rounded internally, but are actually
utilised in the drawing process.

Consistent multiline text spacing
---------------------------------

When using the ``ImageDraw`` multiline methods, the spacing between
lines was inconsistent, based on the combination on ascenders and
descenders.

This has now been fixed, so that lines are offset by their baselines,
not the absolute height of each line.

There is also now a default spacing of 4px between lines.

Exif, Jpeg and Tiff Metadata
----------------------------

There were major changes in the TIFF ImageFileDirectory support in
Pillow 3.0 that led to a number of regressions. Some of them have been
fixed in Pillow 3.1, and some of them have been extended to have
different behavior.

TiffImagePlugin.IFDRational
+++++++++++++++++++++++++++

Pillow 3.0 changed rational metadata to use a float. In Pillow 3.1,
this has changed to allow the expression of 0/0 as a valid piece of
rational metadata to reflect usage in the wild.

Rational metadata is now encapsulated in an ``IFDRational``
instance. This class extends the Rational class to allow a denominator
of 0. It compares as a float or a number, but does allow access to the
raw numerator and denominator values through attributes.

When used in a ``ImageFileDirectory_v1``, a 2 item tuple is returned
of the numerator and denominator, as was done previously.

This class should be used when adding a rational value to an
ImageFileDirectory for saving to image metadata. 

JpegImagePlugin._getexif
++++++++++++++++++++++++

In Pillow 3.0, the dictionary returned from the private, experimental,
but generally widely used ``_getexif`` function changed to reflect the
ImageFileDirectory_v2 format, without a fallback to the previous format. 

In Pillow 3.1, ``_getexif`` now returns a dictionary compatible with
Pillow 2.9 and earlier, built with
``ImageFileDirectory_v1`` instances. Additionally, any
single item tuples have been unwrapped and return a bare element.

The format returned by Pillow 3.0 has been abandoned. A more fully
featured interface for EXIF is anticipated in a future release.

Out of Spec Metadata
++++++++++++++++++++

In Pillow 3.0 and 3.1, images that contain metadata that is internally
consistent but not in agreement with the TIFF spec may cause an
exception when reading the metadata.  This can happen when a tag that
is specified to have a single value is stored with an array of values. 

It is anticipated that this behavior will change in future releases.