Add a new plugin: thumbnails

Generate thumbnails for albums, based on freedesktop specification. This
plugin is POSIX-only.

Require Python Imaging Library or Image Magick

beetsplug/thumbnails.py

@@ -0,0 +1,96 @@
+# -*- coding: utf-8 -*-
+# This file is part of beets.
+# Copyright 2015, Bruno Cauet
+#
+# Permission is hereby granted, free of charge, to any person obtaining
+# a copy of this software and associated documentation files (the
+# "Software"), to deal in the Software without restriction, including
+# without limitation the rights to use, copy, modify, merge, publish,
+# distribute, sublicense, and/or sell copies of the Software, and to
+# permit persons to whom the Software is furnished to do so, subject to
+# the following conditions:
+#
+# The above copyright notice and this permission notice shall be
+# included in all copies or substantial portions of the Software.
+
+"""Create freedesktop.org-compliant thumnails for album folders"""
+
+from __future__ import (division, absolute_import, print_function,
+                        unicode_literals)
+
+from hashlib import md5
+import os
+import shutil
+from pathlib import PurePosixPath
+
+from xdg import BaseDirectory
+
+from beets.plugins import BeetsPlugin
+from beets.ui import Subcommand, decargs
+from beets.util import syspath, displayable_path
+from beets.util.artresizer import ArtResizer
+
+
+class ThumbnailsPlugin(BeetsPlugin):
+    def __init__(self):
+        super(ThumbnailsPlugin, self).__init__()
+        if self._check_local_ok():
+            self.register_listener('album_imported', self.imported)
+
+    def commands(self):
+        thumbnails_command = Subcommand("thumbnails",
+                                        help="Create album thumbnails")
+        thumbnails_command.func = self.process_query
+        return [thumbnails_command]
+
+    def imported(self, lib, album):
+        self.process_album(album)
+
+    def process_query(self, lib, opts, args):
+        if self._check_local_ok():
+            for album in lib.albums(decargs(args)):
+                self.process_album(album)
+
+    def _check_local_ok(self):
+        if not ArtResizer.local:
+            self._log.warning("No local image resizing capabilities, "
+                              "cannot generate thumbnails")
+            return False
+        return True
+
+    def process_album(self, album):
+        """Produce a thumbnail for the album folder
+
+        The thumbnail is a PNG of resolution either 256x256 or lower than
+        128x128
+        """
+        if not album.artpath:
+            self._log.info(u'album {0} has no art', album)
+            return
+
+        # FIXME should create dirs if needed?
+
+        # FIXME should handle covers smaller than 256x256
+        # see http://standards.freedesktop.org/thumbnail-spec/latest/x122.html
+
+        target = os.path.join(BaseDirectory.xdg_cache_home,
+                              "thumbnails", "large",
+                              self.thumbnail_file_name(album.path))
+
+        resized = ArtResizer.shared.resize(256,
+                                           syspath(album.artpath),
+                                           syspath(target))
+
+        # FIXME should add tags
+        # see http://standards.freedesktop.org/thumbnail-spec/latest/x142.html
+
+        shutil.move(resized, target)
+        self._log.info(u'wrote thumbnail for {0}', album)
+        self._log.debug(u'thumbnail is at {0}', displayable_path(target))
+
+    @staticmethod
+    def thumbnail_file_name(path):
+        # http://standards.freedesktop.org/thumbnail-spec/latest/x227.html
+        uri = PurePosixPath(path).as_uri()
+        hash = md5(uri).hexdigest()
+        return "{0}.png".format(hash)

setup.py

@@ -106,6 +106,7 @@ setup(
         'mpdstats': ['python-mpd'],
         'web': ['flask', 'flask-cors'],
         'import': ['rarfile'],
+        'thumbnails': ['pathlib'],
     },
     # Non-Python/non-PyPI plugin dependencies:
     # replaygain: mp3gain || aacgain