how to cleanly remove plone.app.imaging scaled blobs in a blobstorage ZEO server?

Part of this question is already solved with another stackoverflow question but it seems that it doesn't clean up everything.

The steps are:

create a document with an image field
see that the blobstorage has one file
open a view with a scaled version of that image
see that the blobstorage now has two files, the image and the scaled image
do, as suggested on the other question, a zeopack with 0 days
see that there is still one blob on blobstorage, the scaled image

So the question is: how can one remove also this scaled images from blobstorage?

I tried running zeopack twice without success, the scaled blob is still around.

UPDATE: as vangheem pointed out, that does not happen for Archetypes Image content types. Still, this question remains valid, as for a Dexterity-based content types that have an image field.

The scales are only removed if you remove the document, which is not my use-case, I just want to remove the image (image credits have expired and the image can not be shown anymore).

Solution

Found it!

To remove the scales you actually have to remove the plone.scale annotation:

# assume 'document' is a Dexterity-based content type that has a NamedBlobImage field 
from zope.annotation.interfaces import IAnnotations
annotations = IAnnotations(document)
if 'plone.scale' in annotations:
    del annotations['plone.scale']
if getattr(document, 'image', None) is not None and document.image is not None:
    del document.image
    document.reindexObject()