# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1444598606 -7200
# Node ID 4a75d044c6447b4e2ffa34589498f08f098e9d20
# Parent  344be4db9c1f289f8c52fbd244369e769a4756dc
Added support for choosing the colour combination with the least error.
Added interpretation of "-" as the input filename to suppress processing and
output generation, thus providing a more concise way of verifying an image.

diff -r 344be4db9c1f -r 4a75d044c644 optimiser.py
--- a/optimiser.py	Sun Oct 11 20:10:50 2015 +0200
+++ b/optimiser.py	Sun Oct 11 23:23:26 2015 +0200
@@ -118,11 +118,18 @@
 -D - Darken the input image (optional float, 1.0 if unspecified)
 -B - Brighten the input image (optional float, 1.0 if unspecified)
 
--r - Rotate the input image clockwise
+-l - Use colours producing the least error
+     (slower but useful for fewer than 4 colours)
+
+-r - Rotate the input image clockwise explicitly
+     (EXIF information is used otherwise)
 -p - Generate a separate preview image
 -h - Make the preview image with half horizontal resolution (MODE 2)
 -v - Verify the output image (loaded if -n is given)
 -n - Generate no output image
+
+An input filename of - implies the -n option, and is useful for verifying
+previously generated images.
 """ % split(sys.argv[0])[1]
         sys.exit(1)
 
@@ -149,11 +156,12 @@
 
     # General output options.
 
+    least_error = "-l" in options
     rotate = "-r" in options
     preview = "-p" in options
     half_resolution_preview = "-h" in options
     verify = "-v" in options
-    no_normal_output = "-n" in options
+    no_normal_output = "-n" in options or input_filename == "-"
     make_image = not no_normal_output
 
     # Load the input image if requested.
@@ -184,7 +192,7 @@
     # Generate an output image if requested.
 
     if make_image:
-        convert_image(im, number_of_colours)
+        convert_image(im, number_of_colours, least_error)
         im.save(output_filename)
 
     # Verify the output image (which may be loaded) if requested.
diff -r 344be4db9c1f -r 4a75d044c644 optimiserlib.py
--- a/optimiserlib.py	Sun Oct 11 20:10:50 2015 +0200
+++ b/optimiserlib.py	Sun Oct 11 23:23:26 2015 +0200
@@ -22,6 +22,7 @@
 
 from random import random, randrange
 import itertools
+import math
 
 corners = [
     (0, 0, 0), (255, 0, 0), (0, 255, 0), (255, 255, 0),
@@ -36,6 +37,9 @@
 def clip(v):
     return int(within(v, 0, 255))
 
+def distance(rgb1, rgb2):
+    return math.sqrt(pow(abs(rgb1[0] - rgb2[0]), 2) + pow(abs(rgb1[1] - rgb2[1]), 2) + pow(abs(rgb1[2] - rgb2[2]), 2))
+
 def restore(srgb):
     r, g, b = srgb
     return int(r * 255.0), int(g * 255.0), int(b * 255.0)
@@ -257,7 +261,7 @@
                 x += 1
             y += 1
 
-def convert_image(im, colours):
+def convert_image(im, colours, least_error=False):
 
     "Convert image 'im' to an appropriate output representation."
 
@@ -271,19 +275,22 @@
 
         for l in get_combinations(c, colours):
             most = [value for f, value in l]
-            missing = 0
+            error = 0
 
             x = 0
             while x < width:
                 rgb = im.getpixel((x, y))
-                value = get_value(rgb, most, True)
-                if value is None:
-                    missing += 1
+                value = get_value(rgb, most)
+                if least_error:
+                    error += distance(value, rgb)
+                elif value is None:
+                    error += 1
                 x += 1
 
-            if not missing:
+            if not least_error and not error:
                 break # use this combination
-            suggestions.append((missing, l))
+
+            suggestions.append((error, l))
 
         # Find the most accurate suggestion.