# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1444174705 -7200
# Node ID 28240372e1d85b18de295248bcc6543d24531091
# Parent  96453447feab2a6fb521b95845d1a6e34c68a77f
Reduced the propagated error by half.

diff -r 96453447feab -r 28240372e1d8 optimiser.py
--- a/optimiser.py	Wed Oct 07 01:21:07 2015 +0200
+++ b/optimiser.py	Wed Oct 07 01:38:25 2015 +0200
@@ -252,7 +252,7 @@
 
                     # Spread the error across adjacent pixels.
 
-                    error = tuple(map(lambda i: (i[0] - i[1]) / 2.0, zip(rgb, value)))
+                    error = tuple(map(lambda i: (i[0] - i[1]) / 4.0, zip(rgb, value)))
                     for xn in range(x, min(x + 2, width)):
                         rgbn = im.getpixel((xn, y+1))
                         rgbn = tuple(map(lambda i: clip(i[0] + i[1]), zip(rgbn, error)))