fix: lower Chinese full stop to bitmap cell baseline

tools/fix_full_stop.py

@@ -0,0 +1,45 @@
+"""Patch only U+3002 pixels in an existing CJK atlas; preserve its TGA bytes."""
+import argparse
+import json
+from pathlib import Path
+from build_cjk import lower_full_stop, tga_to_image, tga_geometry
+
+
+def patch_atlas(raw, metadata):
+    image, desc = tga_to_image(raw)
+    cell = metadata['cell']
+    if list(image.size) != metadata['atlas']:
+        raise ValueError('atlas geometry mismatch')
+    entry = metadata['cells'][str(int.from_bytes('。'.encode('gb2312'), 'big'))]
+    if entry['uni'] != '。':
+        raise ValueError('full-stop cell mismatch')
+    x, y = entry['x'], entry['y']
+    tile = image.crop((x, y, x + cell, y + cell))
+    fixed = lower_full_stop(tile)
+    idlen, _, w, h, _, _ = tga_geometry(raw)
+    result = bytearray(raw)
+    for j in range(cell):
+        row = y + j if desc & 0x20 else h - 1 - y - j
+        for i in range(cell):
+            offset = 18 + idlen + (row * w + x + i) * 4
+            r, g, b, a = fixed.getpixel((i, j))
+            result[offset:offset + 4] = bytes((b, g, r, a))
+    return bytes(result)
+
+
+def main():
+    p = argparse.ArgumentParser(description=__doc__)
+    p.add_argument('--source', type=Path, required=True)
+    p.add_argument('--cells', type=Path, required=True)
+    p.add_argument('--out', type=Path, required=True)
+    args = p.parse_args()
+    if args.source.resolve() == args.out.resolve():
+        p.error('output must differ from source')
+    result = patch_atlas(args.source.read_bytes(), json.loads(args.cells.read_text(encoding='utf-8')))
+    args.out.parent.mkdir(parents=True, exist_ok=True)
+    args.out.write_bytes(result)
+    print('Full stop anchored at cell bottom; other atlas bytes preserved.')
+
+
+if __name__ == '__main__':
+    main()