Decoupled page transformation interface, added default transformation support

settings.py

@@ -182,6 +182,7 @@ LOGIN_EXEMPT_URLS = (
 # Saving
 #DOCUMENTS_CHECKSUM_FUNCTION = lambda x: hashlib.sha256(x).hexdigest())
 #DOCUMENTS_UUID_FUNCTION = lambda:unicode(uuid.uuid4())
+#DOCUMENTS_DEFAULT_TRANSFORMATIONS = []
 
 # Storage
 #DOCUMENTS_STORAGE_DIRECTORY_NAME = 'documents'
@@ -192,6 +193,8 @@ LOGIN_EXEMPT_URLS = (
 #DOCUMENTS_THUMBNAIL_SIZE = '50x50'
 #DOCUMENTS_DISPLAY_SIZE = '1200'
 #DOCUMENTS_MULTIPAGE_PREVIEW_SIZE = '160x120'
+#DOCUMENTS_AVAILABLE_TRANSFORMATIONS = {}
+#example: DOCUMENTS_DEFAULT_TRANSFORMATIONS = [{'name':'rotate', 'arguments':"{'degrees':270}"}]
 
 # Groups
 #DOCUMENTS_GROUP_MAX_RESULTS = 20