# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1443995736 -7200
# Node ID 4b9192e71fb852f0ada19a32fccb43bbfec76dad
# Parent  2e2722f377b05cbf3a7de07d86000f256036f1d2
Introduced a distance-based approach to obtain suitable alternative colours.

diff -r 2e2722f377b0 -r 4b9192e71fb8 optimiser.py
--- a/optimiser.py	Sun Oct 04 21:47:16 2015 +0200
+++ b/optimiser.py	Sun Oct 04 23:55:36 2015 +0200
@@ -1,6 +1,6 @@
 #!/usr/bin/env python
 
-from random import random, randrange
+from random import choice, random, randrange
 from os.path import splitext
 import EXIF
 import PIL.Image
@@ -20,8 +20,14 @@
 
 def nearest(rgb, values):
     l = [(distance(rgb, value), value) for value in values]
-    l.sort()
-    return l[0][1]
+    total = sum([d for d, value in l])
+    l = [(d / total, value) for d, value in l]
+    l.sort(reverse=True)
+    lc = [(d, value) for d, value in l if common(rgb, value)]
+    return get_from_distribution(rgb, lc or l)
+
+def common(rgb1, rgb2):
+    return sum(map(lambda x: x[0] * x[1], zip(rgb1, rgb2))) != 0
 
 def restore(srgb):
     return tuple(map(lambda x: int(x * 255.0), srgb))
@@ -72,15 +78,18 @@
     l.sort(reverse=True)
     return l
 
-def get_value(rgb):
+def get_from_distribution(rgb, dist):
     choose = random()
     threshold = 0
-    for f, c in pattern(rgb):
+    for f, c in dist:
         threshold += f
         if choose < threshold:
             return c
     return c
 
+def get_value(rgb):
+    return get_from_distribution(rgb, pattern(rgb))
+
 def sign(x):
     return x >= 0 and 1 or -1
 
@@ -212,7 +221,7 @@
 
             value = get_value(rgb)
             if value in least:
-                value = nearest(value, most)
+                value = nearest(rgb, most)
 
             im.putpixel((x, y), value)