Crop emoji images to square before scaling.

When building the font, images are composited onto a slightly
rectangular canvas that's 4 pixels wider on the left and right.
The thumbnails though are required to be 72x72, i.e. square.
In order that they look the intended size we need to crop off
the margins that were added earlier.

generate_emoji_thumbnails.py

@@ -36,12 +36,19 @@ from nototools import unicode_data
 
 logger = logging.getLogger('emoji_thumbnails')
 
-def create_thumbnail(src_path, dst_path):
-  # uses imagemagik
-  # we need images exactly 72x72 in size, with transparent background
-  subprocess.check_call([
-      'convert', '-thumbnail', '72x72', '-gravity', 'center', '-background',
-      'none', '-extent', '72x72', src_path, 'PNG32:' + dst_path])
+def create_thumbnail(src_path, dst_path, crop):
+  # Uses imagemagik
+  # We need images exactly 72x72 in size, with transparent background.
+  # Remove 4-pixel LR margins from 136x128 source images if we crop.
+  if crop:
+    cmd = [
+        'convert', src_path, '-crop', '128x128+4+0!', '-thumbnail', '72x72',
+        'PNG32:' + dst_path]
+  else:
+    cmd = [
+        'convert', '-thumbnail', '72x72', '-gravity', 'center', '-background',
+        'none', '-extent', '72x72', src_path, 'PNG32:' + dst_path]
+  subprocess.check_call(cmd)
 
 
 def get_inv_aliases():
@@ -77,14 +84,16 @@ def sequence_to_filename(seq, prefix, suffix):
   return ''.join((prefix, unicode_data.seq_to_string(seq), suffix))
 
 
-def create_thumbnails_and_aliases(src_dir, dst_dir, dst_prefix):
+def create_thumbnails_and_aliases(src_dir, dst_dir, crop, dst_prefix):
   """Creates thumbnails in dst_dir based on sources in src.dir, using
   dst_prefix. Assumes the source prefix is 'emoji_u' and the common suffix
   is '.png'."""
 
+  src_dir = tool_utils.resolve_path(src_dir)
   if not path.isdir(src_dir):
     raise ValueError('"%s" is not a directory')
-  dst_dir = tool_utils.ensure_dir_exists(dst_dir)
+
+  dst_dir = tool_utils.ensure_dir_exists(tool_utils.resolve_path(dst_dir))
 
   src_prefix = 'emoji_u'
   suffix = '.png'
@@ -104,8 +113,9 @@ def create_thumbnails_and_aliases(src_dir, dst_dir, dst_prefix):
     dst_file = sequence_to_filename(seq, dst_prefix, suffix)
     dst_path = path.join(dst_dir, dst_file)
 
-    create_thumbnail(src_path, dst_path)
-    logger.info('wrote thumbnail: %s' % dst_file)
+    create_thumbnail(src_path, dst_path, crop)
+    logger.info('wrote thumbnail%s: %s' % (
+        ' with crop' if crop else '', dst_file))
 
     for alias_seq in inv_aliases.get(seq, ()):
       alias_file = sequence_to_filename(alias_seq, dst_prefix, suffix)
@@ -115,15 +125,22 @@ def create_thumbnails_and_aliases(src_dir, dst_dir, dst_prefix):
 
 
 def main():
+  SRC_DEFAULT = '[emoji]/build/compressed_pngs'
+  PREFIX_DEFAULT = 'android_'
+
   parser = argparse.ArgumentParser()
   parser.add_argument(
-      '-s', '--src_dir', help='source images', metavar='dir', required=True)
+      '-s', '--src_dir', help='source images (default \'%s\')' % SRC_DEFAULT,
+      default=SRC_DEFAULT, metavar='dir')
   parser.add_argument(
       '-d', '--dst_dir', help='destination directory', metavar='dir',
       required=True)
   parser.add_argument(
-      '-p', '--prefix', help='prefix for thumbnail', metavar='str',
-      default='android_')
+      '-p', '--prefix', help='prefix for thumbnail (default \'%s\')' %
+      PREFIX_DEFAULT, default=PREFIX_DEFAULT, metavar='str')
+  parser.add_argument(
+      '-c', '--crop', help='crop images (will automatically crop if '
+      'src dir is the default)', action='store_true')
   parser.add_argument(
       '-v', '--verbose', help='write log output', metavar='level',
       choices='warning info debug'.split(), const='info',
@@ -133,8 +150,9 @@ def main():
   if args.verbose is not None:
     logging.basicConfig(level=getattr(logging, args.verbose.upper()))
 
+  crop = args.crop or (args.src_dir == SRC_DEFAULT)
   create_thumbnails_and_aliases(
-      args.src_dir, args.dst_dir, args.prefix)
+      args.src_dir, args.dst_dir, crop, args.prefix)
 
 
 if __name__ == '__main__':