Image processing
================

Images are processed by the `Python Imaging Library (Pillow)
<https://pillow.readthedocs.io/en/stable/index.html>`_ which supports a `wide
variety
<https://pillow.readthedocs.io/en/stable/handbook/image-file-formats.html>`_ of
image formats. Processed images are stored in the :ref:`overview-object-store`
using the `webp <https://developers.google.com/speed/webp>`_ format. Images are
resampled using a `Lanczos filter
<https://pillow.readthedocs.io/en/stable/handbook/concepts.html#PIL.Image.Resampling.LANCZOS>`_.

Scaling
-------

By default, images are scaled to fit within the bounds of ``4200x2000`` pixels
for display in the reader, and ``1680x800`` pixels for use as thumbnails. These
values are optimized for larger displays and may be :ref:`changed in the
configuration file <cfg-scale>` if you do not require such high resolutions.