Saving images
=============
In Willow there are separate save operations for each image format:
- :meth:`~Image.save_as_jpeg`
- :meth:`~Image.save_as_png`
- :meth:`~Image.save_as_gif`
- :meth:`~Image.save_as_webp`
All three take one positional argument, the file-like object to write the image
data to.
For example, to save an image as a PNG file:
.. code-block:: python
with open('out.png', 'wb') as f:
i.save_as_png(f)
Changing the quality setting
---------------------------------
:meth:`~Image.save_as_jpeg` and :meth:`~Image.save_as_webp` takes a ``quality``
keyword argument, which is a number between 1 and 100. It defaults to 85
for :meth:`~Image.save_as_jpeg` and 80 for :meth:`~Image.save_as_webp`.
Decreasing this number will decrease the output file size at the cost
of losing image quality.
For example, to save an image with low quality:
.. code-block:: python
with open('low_quality.jpg', 'wb') as f:
i.save_as_jpeg(f, quality=40)
Progressive JPEGs
-----------------
By default, JPEG's are saved in the same format as their source file but you
can force Willow to always save a "progressive" JPEG file by setting the
``progressive`` keyword argument to ``True``:
.. code-block:: python
with open('progressive.jpg', 'wb') as f:
i.save_as_jpeg(f, progressive=True)
Lossless WebP
-----------------
You can encode the image to WebP without any loss by setting the
``lossless`` keyword argument to ``True``:
.. code-block:: python
with open('lossless.webp', 'wb') as f:
i.save_as_webp(f, lossless=True)
Image optimisation
------------------
:meth:`~Image.save_as_jpeg` and :meth:`~Image.save_as_png` both take an
``optimize`` keyword that when set to true, will output an optimized image.
.. code-block:: python
with open('optimized.jpg', 'wb') as f:
i.save_as_jpeg(f, optimize=True)
This feature is currently only supported in the Pillow backend, if you use Wand
this argument will be ignored.
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