********
Settings
********

.. highlight:: python

``THUMBNAIL_DEBUG``
===================

- Default: ``False``

When set to ``True`` the ``ThumbnailNode.render`` method can raise errors.
Django recommends that tags never raise errors in the ``Node.render`` method
but since sorl-thumbnail is such a complex tag we will need to have more
debugging available.


``THUMBNAIL_BACKEND``
=====================

- Default: ``'sorl.thumbnail.base.ThumbnailBackend'``

This is the entry point for generating thumbnails, you probably want to keep the
default one but just in case you would like to generate thumbnails filenames
differently or need some special functionality you can override this and use
your own implementation.


``THUMBNAIL_KVSTORE``
=====================

- Default: ``'sorl.thumbnail.kvstores.cached_db_kvstore.KVStore'``

sorl-thumbnail needs a Key Value Store to :doc:`/operation`.
sorl-thumbnail ships with support for three Key Value Stores:

Cached DB
---------
``sorl.thumbnail.kvstores.cached_db_kvstore.KVStore``. This is the default and
preferred Key Value Store.

Features
^^^^^^^^
* Fast persistent storage
* First query uses database which is slow. Successive queries are cached and if
  you use memcached this is very fast.
* Easy to transfer data between environments since the data is in the default
  database.
* If you get the database and fast cache out of sync there could be problems.

Redis
-----
``sorl.thumbnail.kvstores.redis_kvstore.KVStore``. It requires you to install a
Redis server as well as a `redis python client
<https://github.com/andymccurdy/redis-py/>`_.

Features
^^^^^^^^
* Fast persistent storage
* More dependencies
* Requires a little extra work to transfer data between environments

Dbm
---
``sorl.thumbnail.kvstores.dbm_kvstore.KVStore``. A simple Key Value Store has no
dependencies outside the standard Python library and uses the DBM modules to
store the data.

Features
^^^^^^^^
* No external dependencies, besides the standard library
* No extra components required, e.g., database or cache
* Specially indicated for local development environments


``THUMBNAIL_KEY_DBCOLUMN``
==========================

- Default ``'key'``

Since MSSQL reserved the ``key`` name for db columns you can change this to
something else using this setting.


``THUMBNAIL_ENGINE``
====================

- Default: ``'sorl.thumbnail.engines.pil_engine.Engine'``

This is the processing class for sorl-thumbnail. It does all the resizing,
cropping or whatever processing you want to perform. sorl-thumbnail ships with
four engines:

PIL
---
``'sorl.thumbnail.engines.pil_engine.Engine'``. This is the default engine
because it is what most people have installed already. Features:

* Easy to install
* Produces good quality images but not the best
* It is fast
* Can not handle CMYK sources

Pgmagick
--------
``'sorl.thumbnail.engines.pgmagick_engine.Engine'``. Pgmagick uses `Graphics
<http://www.graphicsmagick.org/>`_. Fatures:

* Not easy to install unless on linux, very slow to compile
* Produces high quality images
* It is a tad slow?
* Can handle CMYK sources

ImageMagick / GraphicsMagick
----------------------------
``'sorl.thumbnail.engines.convert_engine.Engine'``. This engine uses the
ImageMagick ``convert`` or  GraphicsMagic ``gm convert`` command. Features:

* Easy to install
* Produces high quality images
* It is pretty fast
* Can handle CMYK sources
* It is a command line command, that is less than ideal,

Wand
----------------------------
``'sorl.thumbnail.engines.wand_engine.Engine'``. This engine uses `Wand
<https://docs.wand-py.org/>`_, a ctypes-based simple ImageMagick binding for Python. 
Features:

* Easy to install
* Produces high quality images
* Can handle CMYK sources
* Works on Python 2.6, 2.7, 3.2, 3.3, and PyPy

``THUMBNAIL_CONVERT``
=====================

- Default ``'convert'``

Path to convert command, use ``'gm convert'`` for GraphicsMagick.
Only applicable for the convert Engine.


``THUMBNAIL_IDENTIFY``
======================

- Default ``'identify'``

Path to identify command, use ``'gm identify'`` for GraphicsMagick.
Only applicable for the convert Engine.


``THUMBNAIL_STORAGE``
=====================

- Default: ``settings.DEFAULT_FILE_STORAGE``

The storage class to use for the generated thumbnails.


``THUMBNAIL_REDIS_URL``
=======================

The Redis database URL to connect as used by `redis-py <https://redis-py.readthedocs.io/en/latest/#redis.Redis.from_url>`_

When specified, other ``THUMBNAIL_REDIS_*`` connection settings will be ignored.


``THUMBNAIL_REDIS_DB``
======================

- Default: ``0``

The Redis database. Only applicable for the Redis Key Value Store


``THUMBNAIL_REDIS_PASSWORD``
============================

- Default: ``''``

The password for Redis server. Only applicable for the Redis Key Value Store


``THUMBNAIL_REDIS_HOST``
========================

- Default: ``'localhost'``

The host for Redis server. Only applicable for the Redis Key Value Store


``THUMBNAIL_REDIS_PORT``
========================

- Default: ``6379``

The port for Redis server. Only applicable for the Redis Key Value Store


``THUMBNAIL_REDIS_TIMEOUT``
===========================

- Default: ``3600 * 24 * 365 * 10``

Cache timeout for Redis Key Value Store in seconds. You should probably keep this 
at maximum or ``None``.


``THUMBNAIL_DBM_FILE``
======================

- Default: ``thumbnail_kvstore``

Filename of the DBM database. Depending on the DBM engine selected by your
Python installation, this will be used as a prefix because multiple files may be
created. This can be an absolute path.


``THUMBNAIL_DBM_MODE``
======================

- Default: ``0x644``

Permission bits to use when creating new DBM files


``THUMBNAIL_CACHE_TIMEOUT``
===========================

- Default: ``3600 * 24 * 365 * 10``

Cache timeout for Cached DB Key Value Store in seconds. You should probably keep this 
at maximum or ``None`` if your caching backend can handle that as infinite.
Only applicable for the Cached DB Key Value Store.


``THUMBNAIL_CACHE``
===================

- Default: ``'default'``

Cache configuration for Cached DB Key Value Store. Defaults to the ``'default'`` cache
but some applications might have multiple cache clusters.


``THUMBNAIL_KEY_PREFIX``
========================

- Default: ``'sorl-thumbnail'``

Key prefix used by the key value store.


``THUMBNAIL_PREFIX``
====================

- Default: ``'cache/'``

The generated thumbnails filename prefix.


``THUMBNAIL_FORMAT``
====================

- Default: ``'JPEG'``

Default image format, supported formats are: ``'JPEG'``, ``'PNG'``. This also implicitly
sets the filename extension. This can be overridden by individual options.

``THUMBNAIL_PRESERVE_FORMAT``
=============================

- Default: ``False``

If ``True``, the format of the input file will be preserved. If ``False``,
``THUMBNAIL_FORMAT`` will be used.


``THUMBNAIL_COLORSPACE``
========================

- Default: ``'RGB'``

Default thumbnail color space, engines are required to implement: ``'RGB'``,
``'GRAY'`` Setting this to None will keep the original color space. This can be
overridden by individual options.


``THUMBNAIL_UPSCALE``
=====================

- Default: ``True``

Should we upscale by default? ``True`` means we upscale images by default.
``False`` means we don't. This can be overridden by individual options.


``THUMBNAIL_QUALITY``
=====================

- Default: ``95``

Default thumbnail quality. A value between 0 and 100 is allowed. This can be
overridden by individual options.

``THUMBNAIL_PROGRESSIVE``
=========================

- Default: ``True``

Saves jpeg thumbnails as progressive jpegs. This can be overridden by individual
options.


``THUMBNAIL_ORIENTATION``
=========================

- Default: ``True``

Orientate the thumbnail with respect to source EXIF orientation tag


``THUMBNAIL_DUMMY``
===================

- Default: ``False``

This is a very powerful option which came from real world frustration. The use
case is when you want to do development on a deployed project that has image
references in its database. Instead of downloading all the image files from the
server hosting the deployed project and all its thumbnails we just set this
option to ``True``. This will generate placeholder images for all thumbnails
missing input source.


``THUMBNAIL_DUMMY_SOURCE``
==========================

- Default ``https://dummyimage.com/%(width)sx%(height)s``

This is the generated thumbnail whensource of the presented thumbnail. Width and
Height is passed to the string for formatting.  Other options are for example:

- ``https://via.placeholder.com/%(width)sx%(height)s
- ``http://placekitten.com/%(width)s/%(height)s`` 


``THUMBNAIL_DUMMY_RATIO``
=========================

- Default: ``1.5``

This value sets an image ratio to all thumbnails that are not defined by width
**and** height since we cannot determine from the file input (since we don't
have that).

``THUMBNAIL_ALTERNATIVE_RESOLUTIONS``
=====================================

- Default: ``[]``
- Example: ``[1.5, 2]``

This value enables creation of additional high-resolution ("Retina") thumbnails
for every thumbnail. Resolution multiplicators, e.g. value 2 means for every thumbnail
of regular size x\*y, additional thumbnail of 2x\*2y size is created.

``THUMBNAIL_FILTER_WIDTH``
==========================

- Default: ``500``

This value sets the width of thumbnails inserted when running filters one texts
that regex replaces references to images with thumbnails.

``THUMBNAIL_URL_TIMEOUT``
=========================

- Default: ``None``

This value sets the timeout value in seconds when retrieving a source image from a URL. 
If no timeout value is specified, it will wait indefinitely for a response.

``THUMBNAIL_REMOVE_URL_ARGS``
=============================

- Default: ``True``

This value sets if URL arguments will be removed from the source URL of the image we want to generate a thumbnail of. E.g. if our source image is at ``<domain>/picture?height=600&width=600`` a ``True`` value would instead attempt to generate a thumbnail from ``<domain>/picture``.
