# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1444145616 -7200
# Node ID 1036d8b98d851872a7c994c9b50e20621a36054f
# Parent  9a8c24425be97b0590dc60d95b90f88166ffae31
Propagated colour errors between rows to determine the best colours.
Added darkening and brightening operations.
Removed the randomising operation.

diff -r 9a8c24425be9 -r 1036d8b98d85 optimiser.py
--- a/optimiser.py	Tue Oct 06 14:31:54 2015 +0200
+++ b/optimiser.py	Tue Oct 06 17:33:36 2015 +0200
@@ -13,6 +13,12 @@
     (0, 0, 255), (255, 0, 255), (0, 255, 255), (255, 255, 255)
     ]
 
+def within(v, lower, upper):
+    return min(max(v, lower), upper)
+
+def clip(v):
+    return within(v, 0, 255)
+
 def distance(rgb1, rgb2):
     r1, g1, b1 = rgb1
     r2, g2, b2 = rgb2
@@ -104,12 +110,28 @@
 def saturate_value(x, exp):
     return int(127.5 + sign(x - 127.5) * 127.5 * pow(abs(x - 127.5) / 127.5, exp))
 
-def replace(value, values):
-    if value not in values:
-        for i, v in list(enumerate(values))[::-1]:
-            if v != value:
-                values[i] = value
-                return
+def amplify_rgb(rgb, exp):
+    return tuple([amplify_value(x, exp) for x in rgb])
+
+def amplify_value(x, exp):
+    return int(pow(x / 255.0, exp) * 255.0)
+
+def get_colours(im, width, y):
+    c = {}
+    for x in range(0, width):
+        rgb = im.getpixel((x, y))
+
+        # Sum the colour probabilities.
+
+        for f, value in combination(rgb):
+            if not c.has_key(value):
+                c[value] = f
+            else:
+                c[value] += f
+
+    c = [(n/width, value) for value, n in c.items()]
+    c.sort(reverse=True)
+    return c
 
 def test():
     size = 512
@@ -159,9 +181,10 @@
     rotate = "-r" in sys.argv[3:]
     saturate = sys.argv[3:].count("-s")
     desaturate = sys.argv[3:].count("-d")
+    darken = sys.argv[3:].count("-D")
+    brighten = sys.argv[3:].count("-B")
     preview = "-p" in sys.argv[3:]
     square = "-2" in sys.argv[3:] and square or (lambda x: x)
-    randomise = "-R" in sys.argv[3:]
 
     x = EXIF.process_file(open(input_filename))
     im = PIL.Image.open(input_filename).convert("RGB")
@@ -169,30 +192,18 @@
 
     width, height = im.size
 
-    colours = []
-
-    for y in range(0, height):
-        c = {}
-        for x in range(0, width):
-            rgb = im.getpixel((x, y))
-
-            # Saturate if requested.
+    if saturate or desaturate or darken or brighten:
+        for y in range(0, height):
+            for x in range(0, width):
+                if saturate or desaturate:
+                    rgb = im.getpixel((x, y))
+                    rgb = saturate_rgb(rgb, saturate and math.pow(0.5, saturate) or math.pow(2, desaturate))
+                    im.putpixel((x, y), rgb)
 
-            if saturate or desaturate:
-                rgb = saturate_rgb(rgb, saturate and math.pow(0.5, saturate) or math.pow(2, desaturate))
-                im.putpixel((x, y), rgb)
-
-            # Sum the colour probabilities.
-
-            for f, value in combination(rgb):
-                if not c.has_key(value):
-                    c[value] = f
-                else:
-                    c[value] += f
-
-        c = [(n/width, value) for value, n in c.items()]
-        c.sort(reverse=True)
-        colours.append(c)
+                if darken or brighten:
+                    rgb = im.getpixel((x, y))
+                    rgb = amplify_rgb(rgb, brighten and math.pow(0.5, brighten) or math.pow(2, darken))
+                    im.putpixel((x, y), rgb)
 
     if preview:
         imp = im.copy()
@@ -203,27 +214,21 @@
                 imp.putpixel((x, y), value)
         imp.save(preview_filename)
 
-    for y, c in enumerate(colours):
+    for y in range(0, height):
+        c = get_colours(im, width, y)
         most = [value for n, value in c[:4]]
         least = [value for n, value in c[4:]]
 
-        if least and randomise:
-            switched = []
-            for j in 1, 2:
-                i = randrange(0, 4)
-                n, value = c[i]
-                if n < 0.1:
-                    switched.append(c[i])
-                    del c[i]
-            c += switched
-            most = [value for n, value in c[:4]]
-            least = [value for n, value in c[4:]]
-
         for x in range(0, width):
             rgb = im.getpixel((x, y))
             value = get_value(rgb, most)
             im.putpixel((x, y), value)
 
+            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)))
+                im.putpixel((x, y+1), rgbn)
+
     im.save(output_filename)
 
 # vim: tabstop=4 expandtab shiftwidth=4