diff --git a/danmaku2ass.py b/danmaku2ass.py
index 078de37..eaec8b3 100755
--- a/danmaku2ass.py
+++ b/danmaku2ass.py
@@ -2,7 +2,6 @@
 
 import argparse
 import calendar
-import colorsys
 import gettext
 import io
 import json
@@ -461,11 +460,6 @@ def ConvertType2(row, height, bottomReserved):
     return height-bottomReserved-row
 
 
-def NeedWhiteBorder(rgb):
-    h, l, s = colorsys.rgb_to_hls(((rgb >> 16) & 0xff)/255.0, ((rgb >> 8) & 0xff)/255.0, (rgb & 0xff)/255.0)
-    return (1/12 < h < 7/12 and l < 1/3) or l < 5/12
-
-
 def ConvertToFile(filename_or_file, *args, **kwargs):
     if isinstance(filename_or_file, str):
         return open(filename_or_file, *args, **kwargs)