fix: lower Chinese full stop to bitmap cell baseline

tools/build_cjk.py

@@ -157,6 +157,16 @@ def pick_font(size):
     raise SystemExit("no CJK ttf found")
 
 
+def lower_full_stop(tile):
+    """Anchor the Chinese full stop at the bottom of its full-width cell."""
+    bbox = tile.getchannel('A').getbbox()
+    if bbox is None:
+        return tile.copy()
+    result = Image.new('RGBA', tile.size, (0, 0, 0, 0))
+    result.paste(tile.crop(bbox), (bbox[0], tile.height - (bbox[3] - bbox[1])))
+    return result
+
+
 def main():
     ap = argparse.ArgumentParser()
     ap.add_argument("--game", default=DEFAULT_GAME)
@@ -211,6 +221,8 @@ def main():
         x = col * cell
         y = args.cjk_y0 + row * cell
         d.text((x, y + args.draw_dy), uni, font=font, fill=(255, 255, 255, 255))
+        if uni == '\u3002':
+            atlas.paste(lower_full_stop(atlas.crop((x, y, x + cell, y + cell))), (x, y))
         cells[code] = {"x": x, "y": y, "uni": uni}
         # sanity: ink must fit the cell
         bb = atlas.crop((x, y, x + cell, y + cell)).getbbox()