FeinCMS Media Variations

Tools to extend the FeinCMS MediaFile with variations.

Idea

A MediaFile can have a variation. Simple example: an image has a thubnail. But there are other use cases for MediaFile variations: - An audiofile has a snipped, or low quality version, or version in other encoding - Same for a video. But a video can also have a preview image. - A PDF can also have a preview image

FeinCMS Media Variations is the basic framework to support this

Functionality

The feincms MediaFile is extended with a Variation Model. One MediaFile can have multiple variations. A variation is computed through a processor, which can be controlled through some options.

If a variation of a MediaFile is requested, there will be first a lookup, if this variation already exists. If not, the variation will be computed. If it already exists, the already computed variation will be given. Once a variation is created, it can be changed by the user. F.e. if we have a cropscale of an image, the crop is maybe bad (because it is computed). The user can now replace the cropscale with a nicer image. If the same variation is requested again, the user replaced image will be given.

To simplify the process, there are preselections. a preselection is a variation processor bundled with some options. F.e. if we need a 50px square of a user image several times, we can write a preselection named 'small_square', which calls the processor 'thumbnail' with the options {'height': 50, 'width': 50}

optionally, one can activate autocreation, to automatically create preselections if a MediaFile is created. by default, variations are created on the fly as they are requested.

Usage

• add :mod:`feincms_media_variations` to your :setting:`INSTALLED_APPS`

• run python manage.py syncdb because a new table will be created

• monkey-patch the MediaFile Class. best in models.py of the base app (to be organized):

  from feincms.module.medialibrary.models import MediaFile
  from feincms_media_variations.extensions import media_variation
  MediaFile.register_extension(media_variation)
  

• if you want to define some preselections, here is an example:

  from feincms_media_variations.models import MediaVariation
  MediaVariation.register_preselection(
      ('cropscale50x50', _('50px Square Thumbnail'), 'image-cropscale', {'height' : 50, 'width' : 50}),
      ('thumbnail150x99999', _('Max 150px wide image'), 'image-thumbnail', {'height' : 150, 'width' : 99999}),
  )
  

• if you want to activate autocreation, write something like this:

  from feinheit.media_variations.extensions import auto_creation
  MediaFile.register_extension(auto_creation)
  MediaFile.register_variation_auto_creation('cropscale50x50', 'thumbnail150x99999')
  

TODO

• refactor code: f.e. redundant code in processors.py
• multiple processors per MediaVariation
• processors should check, if they can handle a mediafile type (cropscaling audiofiles should throw some error)