A tool for renaming files.

Emoji image files we get from upstream sometimes use the 'canonical'
sequences from the unicode data, which can contain emoji variation
selectors in the sequence.  For our image data we wish to ignore
variation selectors.  This tool renames files in a directory to the
corresponding sequence without emoji variation selectors, so that
other tooling doesn't need to account for them.

strip_vs_from_filenames.py

@@ -0,0 +1,87 @@
+#!/usr/bin/env python
+#
+# Copyright 2017 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import argparse
+import glob
+import os
+from os import path
+import sys
+
+"""Rename image files based on codepoints to remove the emoji variation
+selector from the name.  For our emoji image data, this codepoint is not
+relevant."""
+
+EMOJI_VS = 0xfe0f
+
+
+def str_to_seq(seq_str):
+  return tuple([int(s, 16) for s in seq_str.split('_')])
+
+
+def seq_to_str(seq):
+  return '_'.join('%04x' % cp for cp in seq)
+
+
+def strip_vs(seq):
+  return tuple([cp for cp in seq if cp != EMOJI_VS])
+
+
+def strip_vs_from_filenames(imagedir, prefix, ext, dry_run=False):
+  prefix_len = len(prefix)
+  suffix_len = len(ext) + 1
+  names = [path.basename(f)
+           for f in glob.glob(
+               path.join(imagedir, '%s*.%s' % (prefix, ext)))]
+  renames = {}
+  for name in names:
+    seq = str_to_seq(name[prefix_len:-suffix_len])
+    if seq and EMOJI_VS in seq:
+      newname = '%s%s.%s' % (prefix, seq_to_str(strip_vs(seq)), ext)
+      if newname in names:
+        print >> sys.stderr, '%s non-vs name %s already exists.' % (
+            name, newname)
+        return
+      renames[name] = newname
+
+  for k, v in renames.iteritems():
+    if dry_run:
+      print '%s -> %s' % (k, v)
+    else:
+      os.rename(path.join(imagedir, k), path.join(imagedir, v))
+  print 'renamed %d files in %s' % (len(renames), imagedir)
+
+
+def main():
+  parser = argparse.ArgumentParser()
+  parser.add_argument(
+      '-d', '--imagedir', help='directory containing images to rename',
+      metavar='dir', required=True)
+  parser.add_argument(
+      '-e', '--ext', help='image filename extension (default png)',
+      choices=['ai', 'png', 'svg'], default='png')
+  parser.add_argument(
+      '-p', '--prefix', help='image filename prefix (default emoji_u)',
+      default='emoji_u', metavar='pfx')
+  parser.add_argument(
+      '-n', '--dry_run', help='compute renames and list only',
+      action='store_true')
+
+  args = parser.parse_args()
+  strip_vs_from_filenames(args.imagedir, args.prefix, args.ext, args.dry_run)
+
+
+if __name__ == '__main__':
+  main()