Check for masthead image when generating MOBI periodicals

src/calibre/ebooks/mobi/writer.py

@@ -386,8 +386,16 @@ class MobiWriter(object):
     def _map_image_names(self):
         index = 1
         self._images = images = {}
+        mh_href = None
+
+        if 'masthead' in self._oeb.guide:
+            mh_href = self._oeb.guide['masthead'].href
+            images[mh_href] = 1
+            index += 1
+
         for item in self._oeb.manifest.values():
             if item.media_type in OEB_RASTER_IMAGES:
+                if item.href == mh_href: continue
                 images[item.href] = index
                 index += 1
 
@@ -1195,6 +1203,13 @@ class MobiWriter(object):
             self._oeb.logger.info('metadata missing timestamp needed for periodical')
             return False
 
+        # Periodicals also need a mastheadImage in the manifest
+        has_mastheadImage = 'masthead' in self._oeb.guide
+
+        if not has_mastheadImage :
+            self._oeb.logger.info('mastheadImage missing from manifest, aborting periodical indexing')
+            return False
+
         self._oeb.logger.info('TOC structure and pubdate verified')
         return True