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add more information on how qtables parameter works with quality

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Kylian Ronfleux--Corail 2025-04-14 08:31:43 +00:00
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docs/handbook/image-file-formats.rst
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@ -557,6 +557,8 @@ The :py:meth:`~PIL.Image.Image.save` method supports the following options:
hardly any gain in image quality. The value ``keep`` is only valid for JPEG hardly any gain in image quality. The value ``keep`` is only valid for JPEG
files and will retain the original image quality level, subsampling, and files and will retain the original image quality level, subsampling, and
qtables. qtables.
For more information on how qtables are modified based on the quality parameter,
see the qtables section.
**optimize** **optimize**
If present and true, indicates that the encoder should make an extra pass If present and true, indicates that the encoder should make an extra pass
@ -621,6 +623,11 @@ The :py:meth:`~PIL.Image.Image.save` method supports the following options:
* a list, tuple, or dictionary (with integer keys = * a list, tuple, or dictionary (with integer keys =
range(len(keys))) of lists of 64 integers. There must be range(len(keys))) of lists of 64 integers. There must be
between 2 and 4 tables. between 2 and 4 tables.
If a quality parameter is provided, the qtables will be adjusted accordingly.
By default, the qtables are based on a standard JPEG table with a quality of 50.
The qtable values will be reduced if the quality is higher than 50 and increased
if the quality is lower than 50.
.. versionadded:: 2.5.0 .. versionadded:: 2.5.0