The original handler implementation ported code from the old ImageModel's
save method, but ended up duplicating the efforts of the ImageSpecFile's
_create method.
In the old IK API, processors (like `Transpose`) were able to access
the file by inspecting the model instance (which carried an options
object that specified the attribute name of the ImageField from which
the file could be extracted). Since the new API allows for multiple
ImageFields (and because IKOptions have been removed), it became
necessary to provide more information. Initially, this was accomplished
by passing the spec to `process()`, however with the addition of
ProcessedImageField, it became clear the a cleaner solution was to pass
only the field file (ImageSpecFile or ProcessedImageFieldFile).
This keeps the ORM stuff (fields, etc.) out of the `ImageProcessor` API
but (because field files, not just regular files, are passed) the
average hacker can still have their processor make use of model
information by accessing the model through the file's `instance`
property.
You're no longer restricted to just one, special-case admin thumbnail. Make as
many as you want by adding AdminThumbnailView properties to your model and
including them in your admin class's `list_display` tuple. You can also provide
a custom template. Note that (because this change introduces templates to
imagekit), imagekit is now required in INSTALLED_APPS.
Ideally we could get this stuff out of the model, but we'll have to look into
whether that's possible without making things really complicated.
