Metadata download: Do not auto trim downloaded covers

Trimming can sometimes have undesirable effects.

src/calibre/ebooks/metadata/sources/base.py

@@ -208,6 +208,8 @@ class Source(Plugin):
     #: If True this source can return multiple covers for a given query
     can_get_multiple_covers = False
 
+    #: If set to True covers downloaded by this plugin are automatically trimmed.
+    auto_trim_covers = False
 
     def __init__(self, *args, **kwargs):
         Plugin.__init__(self, *args, **kwargs)
@@ -446,11 +448,8 @@ class Source(Plugin):
         except Exception:
             self.log.exception('Failed to download cover from: %r'%url)
 
-
     # }}}
-
     # Metadata API {{{
-
     def get_book_url(self, identifiers):
         '''
         Return a 3-tuple or None. The 3-tuple is of the form:

src/calibre/ebooks/metadata/sources/covers.py

@@ -61,6 +61,7 @@ def process_result(log, result):
     try:
         im = Image()
         im.load(data)
+        if getattr(plugin, 'auto_trim_covers', False):
             im.trim(10)
         width, height = im.size
         fmt = im.format