Now using contribute_to_class.

By creating the Descriptor using contribute_to_class (instead of in
ImageModelBase's __init__), we take the first step towards eliminating the need
to extend ImageModel at all.

imagekit/models.py

@@ -8,7 +8,7 @@ from django.db.models.signals import post_delete
 from django.utils.html import conditional_escape as escape
 from django.utils.translation import ugettext_lazy as _
 
-from imagekit.specs import ImageSpec, Descriptor
+from imagekit.specs import ImageSpec
 from imagekit.lib import *
 from imagekit.options import Options
 from imagekit.utils import img_to_fobj
@@ -46,7 +46,6 @@ class ImageModelBase(ModelBase):
         
         for k, v in attrs.items():
             if isinstance(v, ImageSpec):
-                setattr(self, k, Descriptor(v, k))
                 specs.append(v)
             elif not default_image_field and isinstance(v, models.ImageField):
                 default_image_field = k

imagekit/specs.py

@@ -41,6 +41,9 @@ class ImageSpec(object):
         img.format = fmt
         return img, fmt
 
+    def contribute_to_class(self, cls, name):
+        setattr(cls, name, Descriptor(self, name))
+
 
 class Accessor(object):
     def __init__(self, obj, spec, property_name):