Add IKOption.storage to explicitly set cached thumbnail storage.

Original image storage is still the default, and the original image
is always read from its own storage.

imagekit/models.py

@@ -93,6 +93,10 @@ class ImageModel(models.Model):
     @property
     def _imgfield(self):
         return getattr(self, self._ik.image_field)
+    
+    @property
+    def _storage(self):
+        return getattr(self._ik, 'storage', self._imgfield.storage)
 
     def _clear_cache(self):
         for spec in self._ik.specs:

imagekit/options.py

@@ -16,8 +16,9 @@ class Options(object):
     cache_filename_format = "%(filename)s_%(specname)s.%(extension)s"
     admin_thumbnail_spec = 'admin_thumbnail'
     spec_module = 'imagekit.defaults'
+    #storage = defaults to image_field.storage
     
     def __init__(self, opts):        
         for key, value in opts.__dict__.iteritems():
             setattr(self, key, value)
-            self.specs = []
+            self.specs = []

imagekit/specs.py

@@ -63,13 +63,13 @@ class Accessor(object):
         self._img, self._fmt = self.spec.process(Image.open(fp), self._obj)
         # save the new image to the cache
         content = ContentFile(self._get_imgfile().read())
-        self._obj._imgfield.storage.save(self.name, content)
+        self._obj._storage.save(self.name, content)
         
     def _delete(self):
-        self._obj._imgfield.storage.delete(self.name)
+        self._obj._storage.delete(self.name)
 
     def _exists(self):
-        return self._obj._imgfield.storage.exists(self.name)
+        return self._obj._storage.exists(self.name)
 
     @property
     def name(self):
@@ -98,12 +98,12 @@ class Accessor(object):
                 current_count = getattr(self._obj, fieldname)
                 setattr(self._obj, fieldname, current_count + 1)
                 self._obj.save(clear_cache=False)
-        return self._obj._imgfield.storage.url(self.name)
+        return self._obj._storage.url(self.name)
         
     @property
     def file(self):
         self._create()
-        return self._obj._imgfield.storage.open(self.name)
+        return self._obj._storage.open(self.name)
         
     @property
     def image(self):