# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1444175486 -7200
# Node ID e017e76791a0602895f727aaa07f138a2af89b32
# Parent  075e5f1f12e316c69e5f2f4c83bcbbf5c3d10fbd
Reduced the propagated error by half.

diff -r 075e5f1f12e3 -r e017e76791a0 optimiser.py
--- a/optimiser.py	Wed Oct 07 00:49:40 2015 +0200
+++ b/optimiser.py	Wed Oct 07 01:51:26 2015 +0200
@@ -17,7 +17,7 @@
     return min(max(v, lower), upper)
 
 def clip(v):
-    return within(v, 0, 255)
+    return int(within(v, 0, 255))
 
 def distance(rgb1, rgb2):
     r1, g1, b1 = rgb1
@@ -250,7 +250,7 @@
 
                 if y < height - 1:
                     rgbn = im.getpixel((x, y+1))
-                    rgbn = tuple(map(lambda i: clip(i[0] + i[1] - i[2]), zip(rgbn, rgb, value)))
+                    rgbn = tuple(map(lambda i: clip(i[0] + (i[1] - i[2]) / 2.0), zip(rgbn, rgb, value)))
                     im.putpixel((x, y+1), rgbn)
 
         im.save(output_filename)