================ Image Processors

Easy thumbnails generates thumbnail images by passing the source image through a series of image processors. Each processor may alter the image, often dependent on the options it receives.

This makes the system very flexible, as the processors an image passes through can be defined in :attr:~easy_thumbnails.conf.Settings.THUMBNAIL_PROCESSORS and even overridden by an individual :class:easy_thumbnails.files.Thumbnailer (via the :attr:~easy_thumbnails.files.Thumbnailer.thumbnail_processors attribute).

Built-in processors

Following is a list of the built-in processors, along with the thumbnail options which they use.

.. automodule:: easy_thumbnails.processors :members:

Custom processors

You can replace or leave out any default processor as suits your needs. Following is an explanation of how to create and activate a custom processor.

When defining the :attr:~easy_thumbnails.conf.Settings.THUMBNAIL_PROCESSORS setting, remember that this is the order through which the processors are run. The image received by a processor is the output of the previous processor.

Create the processor

First create a processor like this::

def whizzbang_processor(image, bang=False, **kwargs):
	"""
	Whizz bang the source image.

	"""
    if bang:
        image = whizz(image)
    return image

The first argument for a processor is the source image.

All other arguments are keyword arguments which relate to the list of options received by the thumbnail generator (including size and quality). Ensure you list all arguments which could be used (giving them a default value of False), as the processors arguments are introspected to generate a list of valid options.

You must also use **kwargs at the end of your argument list because all options used to generate the thumbnail are passed to processors, not just the ones defined.

Whether a processor actually modifies the image or not, they must always return an image.

Use the processor

Next, add the processor to :attr:~easy_thumbnails.conf.Settings.THUMBNAIL_PROCESSORS in your settings module::

from easy_thumbnails.conf import Settings as easy_thumbnails_defaults

THUMBNAIL_PROCESSORS = easy_thumbnails_defaults.THUMBNAIL_PROCESSORS + (
    'wb_project.thumbnail_processors.whizzbang_processor',
)