Default policy

The default policy is defined in the interface IImageMiniaturizer, implemented by the Miniaturizer component. Let’s have a quick overview:

>>> from dolmen.thumbnailer import IImageMiniaturizer

>>> print IImageMiniaturizer['scales'].default
{'large': (700, 700), 'mini': (250, 250), 'small': (128, 128), 'preview': (400, 400), 'thumb': (150, 150)}

>>> print IImageMiniaturizer['factory'].default
<class 'dolmen.file.file.NamedFile'>

Storage and adapter

Out-of-the-box, dolmen.thumbnailer provides a IImageMiniaturizer implementation as an adapter. While it uses the default scales and factory, it queries a dolmen.storage.IDelegatedStorage component for the storage. This storage is a dolmen.storage.AnnotationStorage named ‘thumbnail’, in order to write the store the thumbnails in the object annotations.

This means, we need a IAttributeAnnotatable object:

>>> miniaturizer = IImageMiniaturizer(mycontext)
Traceback (most recent call last):
...
TypeError: ('Could not adapt', <BasicContent object at ...>, <InterfaceClass dolmen.thumbnailer.interfaces.IImageMiniaturizer>)

>>> from zope.annotation import IAttributeAnnotatable
>>> from zope.interface import alsoProvides

>>> alsoProvides(mycontext, IAttributeAnnotatable)
>>> miniaturizer = IImageMiniaturizer(mycontext)
>>> miniaturizer
<dolmen.thumbnailer.components.Miniaturizer object at ...>

Now we obtain a Miniaturizer object. We can verify its conformity with the interface that describes it:

>>> from zope.interface import verify
>>> verify.verifyObject(IImageMiniaturizer, miniaturizer)
True

>>> miniaturizer.storage
<dolmen.thumbnailer.components.ThumbnailStorage object at ...>

>>> from dolmen.storage import IDelegatedStorage
>>> IDelegatedStorage.providedBy(miniaturizer.storage)
True

Generation

The Miniaturizer assumes that your data is stored on a field of the object. The methods provided by the component will use the fieldname to trigger their action.

Let’s add an image attribute to our content object:

>>> from dolmen.file import file
>>> mycontext.image = file.NamedFile(data=data)
>>> mycontext.image
<dolmen.file.file.NamedFile object at ...>

Our image is persisted on our object, in an attribute called ‘image’. Let’s trigger the thumbnails generation:

>>> miniaturizer.generate(fieldname="image")
True

The return value is a boolean representing the success of the generation. Let’s have a look at our storage, after the generation:

>>> list(miniaturizer.storage.keys())
['image.large', 'image.mini', 'image.preview', 'image.small', 'image.thumb']

Some errors are handled for you:

>>> miniaturizer.generate(fieldname="nonexisting")
False

>>> miniaturizer.generate(fieldname="__class__")
Traceback (most recent call last):
...
IOError: cannot identify image file

Retrieval

The thumbnails can be retrieved easily, using the scale name and the field name:

>>> scale = miniaturizer.retrieve('mini', fieldname="image")
>>> scale
<dolmen.file.file.NamedFile object at ...>

As we can see, the thumbnails data is wrapped in a dolmen.file.file.NamedFile object, which is the factory defined in your default policy:

>>> isinstance(scale, IImageMiniaturizer['factory'].default)
True

The Miniaturizer can fetch a thumbnail using a “fieldname.scalename” key:

>>> print miniaturizer['image.mini']
<dolmen.file.file.NamedFile object at ...>

>>> print miniaturizer.get('image.small')
<dolmen.file.file.NamedFile object at ...>

>>> print miniaturizer.get('image.nonexistance')
None
>>> print miniaturizer.get('image.nonexistance', 'nothing !')
nothing !

As usual, some error situations are handled for you:

>>> print miniaturizer.retrieve('manfred', fieldname="image")
None
>>> print miniaturizer.retrieve('manfred', fieldname="not there")
None

Deletion

The deletion action will use the fieldname to delete all the thumbnails generated for the given field:

>>> miniaturizer.delete(fieldname="image")
>>> list(miniaturizer.storage.keys())
[]

0.3 (2010-02-27)

• Cleaned dependencies. We no longer have zope.app dependencies.

• We now use dolmen.file.file.File as base files for the thumbnails.

0.2.3 (2010-02-19)

• Corrected the PIL version to 1.1.7

0.2.2 (2010-02-19)

• Updated dependency : PILwoTK to PIL.

0.2.1 (2009-10-25)

• Updated to the latest version of dolmen.field.

0.2 (2009-10-23)

• Now thumbnails can be named, if the factory implements dolmen.file.INamedFile.

• Corrected a bug where the specified mimeType was not a valid one.

0.1 (2009-10-21)

• Initial release