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Added docs for JPEG qtables and subsampling

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wiredfool 2014-06-20 01:39:42 -07:00
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docs/handbook/image-file-formats.rst
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@ -147,6 +147,29 @@ The :py:meth:`~PIL.Image.Image.save` method supports the following options:
If present, indicates that this image should be stored as a progressive
JPEG file.
**subsampling**
If present, sets the subsampling for the encoder.
* ``keep``: Only valid for JPEG files, will retain the original image setting.
* ``4:4:4``, ``4:2:2``, ``4:1:1``: Specific sampling values
* ``-1``: equivalent to ``keep``
* ``0``: equivalent to ``4:4:4``
* ``1``: equivalent to ``4:2:2``
* ``2``: equivalent to ``4:1:1``
**qtables**
If present, sets the qtables for the encoder. This is listed as an
advanced option for wizards in the JPEG documentation. Use with
caution. ``qtables`` can be one of several types of values:
* a string, naming a preset, e.g. ``keep``, ``web_low``, or ``web_high``
* a list, tuple, or dictionary (with integer keys =
range(len(keys))) of lists of 64 integers. There must be
between 2 and 4 tables.
.. versionadded:: 2.5.0
.. note::
To enable JPEG support, you need to build and install the IJG JPEG library