scheme: better light/dark theme detection

scheme/getlightness.py

@@ -0,0 +1,8 @@
+#!/bin/python3
+
+import sys
+from colorsys import rgb_to_hls
+
+if __name__ == "__main__":
+    for arg in sys.argv[1:]:
+        print(rgb_to_hls(*tuple(int(arg[i:i+2], 16) for i in (0, 2, 4)))[1])