diff --git a/oml/item/icons.py b/oml/item/icons.py
index d4228bc..a1f021f 100644
--- a/oml/item/icons.py
+++ b/oml/item/icons.py
@@ -82,6 +82,15 @@ class Icons(dict):
         c.close()
         conn.close()
 
+    def clear(self, prefix):
+        sql = 'DELETE FROM icon WHERE id LIKE ?'
+        conn = self.connect()
+        c = conn.cursor()
+        c.execute(sql, (prefix + '%', ))
+        conn.commit()
+        c.close()
+        conn.close()
+
 icons = Icons(icons_db_path)
 
 @run_async
@@ -122,9 +131,7 @@ def get_icon(id, type_, size, callback):
     callback(data)
 
 def clear_default_cover_cache():
-    for resolution in (64, 128, 256, 512, 1024):
-        key = '%s:%s:%s' % ('default', 'cover', resolution)
-        del icons[key]
+    icons.clear('default:cover:')
 
 @run_async
 def get_icon_app(id, type_, size, callback):
diff --git a/oml/item/models.py b/oml/item/models.py
index f82ee77..1ea5e61 100644
--- a/oml/item/models.py
+++ b/oml/item/models.py
@@ -21,7 +21,7 @@ from .icons import icons
 from .person import get_sort_name, Person
 from queryparser import Parser
 from settings import config
-from utils import remove_empty_folders
+from utils import remove_empty_folders, get_ratio
 from websocket import trigger_event
 import db
 import media
@@ -310,13 +310,7 @@ class Item(db.Model):
         if path:
             return getattr(media, self.info['extension']).cover(path)
 
-    def update_icons(self):
-        def get_ratio(data):
-            try:
-                img = Image.open(BytesIO(data))
-                return img.size[0]/img.size[1]
-            except:
-                return 1
+    def update_cover(self):
         key = 'cover:%s'%self.id
         cover = None
         if 'cover' in self.meta and self.meta['cover']:
@@ -330,25 +324,35 @@ class Item(db.Model):
                 self.info['coverRatio'] = get_ratio(cover)
         else:
             del icons[key]
+        if not cover:
+            if 'previewRatio' in self.info:
+                self.info['coverRatio'] = self.info['previewRatio']
+            elif 'coverRatio' in self.info:
+                del self.info['coverRatio']
+        icons.clear('cover:%s:'%self.id)
+
+    def update_preview(self):
         key = 'preview:%s'%self.id
         preview = self.extract_preview()
         if preview:
             icons[key] = preview
             self.info['previewRatio'] = get_ratio(preview)
-            if not cover:
+            if not 'coverRatio' in self.info:
                 self.info['coverRatio'] = self.info['previewRatio']
         else:
             del icons[key]
             if 'previewRatio' in self.info:
                 del self.info['previewRatio']
-            if not cover and 'coverRatio' in self.info:
-                del self.info['coverRatio']
-        if cover and not preview:
-            self.info['previewRatio'] = self.info['coverRatio']
-        for key in ('cover', 'preview'):
-            key = '%s:%s' % (key, self.id)
-            for resolution in (128, 256, 512):
-                del icons['%s:%s' % (key, resolution)]
+        if not preview:
+            if 'coverRatio' in self.info:
+                self.info['previewRatio'] = self.info['coverRatio']
+            elif 'previewRatio' in self.info:
+                del self.info['previewRatio']
+        icons.clear('preview:%s:'%self.id)
+
+    def update_icons(self):
+        self.update_cover()
+        self.update_preview()
 
     def load_metadata(self):
         '''
diff --git a/oml/nodes.py b/oml/nodes.py
index c9768af..98c1cf2 100644
--- a/oml/nodes.py
+++ b/oml/nodes.py
@@ -384,8 +384,7 @@ class Node(Thread):
                 content = fileobj.read()
                 key = 'preview:' + item.id
                 icons[key] = content
-                for resolution in (128, 256, 512):
-                    del icons['preview:%s' % resolution]
+                icons.clear('preview:%s:'%item.id)
                 return True
             except:
                 logger.debug('preview download failed %s', url, exc_info=1)
diff --git a/oml/utils.py b/oml/utils.py
index f669146..bdb8ad2 100644
--- a/oml/utils.py
+++ b/oml/utils.py
@@ -391,3 +391,10 @@ def _to_json(python_object):
             return '%d-%02d-%02dT%02d:%02d%02dZ' % tuple(list(tt)[:6])
         return python_object.strftime('%Y-%m-%dT%H:%M:%SZ')
     raise TypeError(u'%s %s is not JSON serializable' % (repr(python_object), type(python_object)))
+
+def get_ratio(data):
+    try:
+        img = Image.open(BytesIO(data))
+        return img.size[0]/img.size[1]
+    except:
+        return 1