Cache cover art thumbnails in SQLite database

src/gpodder/gtkui/model.py

@@ -441,6 +441,7 @@ class PodcastChannelProxy(object):
         self.auth_password = None
         self.pause_subscription = False
         self.sync_to_mp3_player = False
+        self.cover_thumb = None
         self.auto_archive_episodes = False
 
     def get_statistics(self):
@@ -452,6 +453,9 @@ class PodcastChannelProxy(object):
         return Model.sort_episodes_by_pubdate((e for c in self.channels
                 for e in c.get_all_episodes()), True)
 
+    def save(self):
+        pass
+
 
 class PodcastListModel(gtk.ListStore):
     C_URL, C_TITLE, C_DESCRIPTION, C_PILL, C_CHANNEL, \
@@ -598,12 +602,38 @@ class PodcastListModel(gtk.ListStore):
 
         return pixbuf
 
+    def _get_cached_thumb(self, channel):
+        if channel.cover_thumb is None:
+            return None
+
+        try:
+            loader = gtk.gdk.PixbufLoader('png')
+            loader.write(channel.cover_thumb)
+            loader.close()
+            return loader.get_pixbuf()
+        except Exception, e:
+            logger.warn('Could not load cached cover art for %s', channel.url, exc_info=True)
+            channel.cover_thumb = None
+            channel.save()
+            return None
+
+    def _save_cached_thumb(self, channel, pixbuf):
+        bufs = []
+        pixbuf.save_to_callback(lambda buf, data: data.append(buf), 'png', {}, bufs)
+        channel.cover_thumb = buffer(''.join(bufs))
+        channel.save()
+
     def _get_cover_image(self, channel, add_overlay=False):
         if self._cover_downloader is None:
             return None
 
-        pixbuf = self._cover_downloader.get_cover(channel, avoid_downloading=True)
-        pixbuf_overlay = self._resize_pixbuf(channel.url, pixbuf)
+        pixbuf_overlay = self._get_cached_thumb(channel)
+
+        if pixbuf_overlay is None:
+            pixbuf = self._cover_downloader.get_cover(channel, avoid_downloading=True)
+            pixbuf_overlay = self._resize_pixbuf(channel.url, pixbuf)
+            self._save_cached_thumb(channel, pixbuf_overlay)
+
         if add_overlay and channel.pause_subscription:
             pixbuf_overlay = self._overlay_pixbuf(pixbuf_overlay, self.ICON_DISABLED)
             pixbuf_overlay.saturate_and_pixelate(pixbuf_overlay, 0.0, False)
@@ -800,6 +830,8 @@ class PodcastListModel(gtk.ListStore):
 
         # Resize and add the new cover image
         pixbuf = self._resize_pixbuf(channel.url, pixbuf)
+        self._save_cached_thumb(channel, pixbuf)
+
         if channel.pause_subscription:
             pixbuf = self._overlay_pixbuf(pixbuf, self.ICON_DISABLED)
             pixbuf.saturate_and_pixelate(pixbuf, 0.0, False)

src/gpodder/model.py

@@ -681,6 +681,7 @@ class PodcastChannel(PodcastModelObject):
         self.download_folder = None
         self.pause_subscription = False
         self.sync_to_mp3_player = True
+        self.cover_thumb = None
 
         self.section = _('Other')
         self._common_prefix = None

src/gpodder/schema.py

@@ -66,9 +66,10 @@ PodcastColumns = (
     'payment_url',
     'download_strategy',
     'sync_to_mp3_player',
+    'cover_thumb',
 )
 
-CURRENT_VERSION = 5
+CURRENT_VERSION = 6
 
 
 # SQL commands to upgrade old database versions to new ones
@@ -96,7 +97,12 @@ UPGRADE_SQL = [
         # Version 5: Per-podcast MP3 player device synchronization option
         (4, 5, """
         ALTER TABLE podcast ADD COLUMN sync_to_mp3_player INTEGER NOT NULL DEFAULT 1
-        """)
+        """),
+
+        # Version 6: Add thumbnail for cover art
+        (5, 6, """
+        ALTER TABLE podcast ADD COLUMN cover_thumb BLOB NULL DEFAULT NULL
+        """),
 ]
 
 def initialize_database(db):
@@ -119,7 +125,8 @@ def initialize_database(db):
         section TEXT NOT NULL DEFAULT '',
         payment_url TEXT NULL DEFAULT NULL,
         download_strategy INTEGER NOT NULL DEFAULT 0,
-        sync_to_mp3_player INTEGER NOT NULL DEFAULT 1
+        sync_to_mp3_player INTEGER NOT NULL DEFAULT 1,
+        cover_thumb BLOB NULL DEFAULT NULL
     )
     """)