From 9927e414d18cd27079bf827d8bf6e4eefdaa2e48 Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Sun, 13 Nov 2011 19:50:06 -0500
Subject: Slight improvement by using shift and clean up the dir structure.

---
 unshred.py | 33 ++++++++++++++++++++-------------
 1 file changed, 20 insertions(+), 13 deletions(-)

(limited to 'unshred.py')

diff --git a/unshred.py b/unshred.py
index ea20810..98b5fc5 100755
--- a/unshred.py
+++ b/unshred.py
@@ -17,11 +17,14 @@ image = Image.open(argv[1])
 data = image.getdata()
 
 def pixel(x, y):
-	pixel = data[y * image.size[0] + x]
-	return pixel
+	return data[y * image.size[0] + x]
 def pixel_distance(a, b):
-	opacity_a = a[3] / 255
-	opacity_b = b[3] / 255
+	try:
+		opacity_a = a[3] / 255
+		opacity_b = b[3] / 255
+	except:
+		opacity_a = 1
+		opacity_b = 1
 	a_r, a_g, a_b = (a[0] * opacity_a, a[1] * opacity_a, a[2] * opacity_a)
 	b_r, b_g, b_b = (b[0] * opacity_b, b[1] * opacity_b, b[2] * opacity_b)
 	return sqrt((a_r - b_r) ** 2 + (a_g - b_g) ** 2 + (a_b - b_b) ** 2)
@@ -31,9 +34,9 @@ for col in xrange(0, image.size[0] - 1):
 	for row in xrange(0, image.size[1]):
 		columns[col] += pixel_distance(pixel(col, row), pixel(col + 1, row))
 shred_width = -1
-for factor in xrange(2, image.size[0]):
+for factor in xrange(2, image.size[0] / 2):
 	if image.size[0] % factor != 0:	# Poor man's factorization! R.I.P. Sieve. Sorry instagram.
-		continue		# I'm also ignoring your guidelines about divisibility by 2.
+		continue
 	last_col = 0
 	success = True
 	for col in xrange(0, image.size[0], factor):
@@ -55,13 +58,17 @@ if shred_width == -1:
 	exit(-2)
 
 columns = image.size[0] / shred_width
-print "The image has %d columns." % columns
+print "%s image has %d columns." % (argv[1], columns)
 
 def match_score(left, right):
-	total = 0
+	straight = 0
 	for i in xrange(0, image.size[1]):
-		total += pixel_distance(pixel((left + 1) * shred_width - 1, i), pixel(right * shred_width, i))
-	return total
+		straight += pixel_distance(pixel((left + 1) * shred_width - 1, i), pixel(right * shred_width, i))
+	shifted = 0
+	offset = image.size[1] / 35
+	for i in xrange(offset, image.size[1] - offset):
+		shifted += pixel_distance(pixel((left + 1) * shred_width - 1, i + offset), pixel(right * shred_width, i - offset))
+	return straight / shifted
 
 column_matches = {}
 for i in xrange(0, columns):
@@ -90,10 +97,10 @@ for key, value in column_matches.iteritems():
 			break
 # Otherwise, if it amazingly wraps around, let's just remove the weakest link.
 if last == -1:
-	min_score = image.size[1] * 442 # = sqrt(3) * 255
+	max_score = 0
 	for key, value in column_matches.iteritems():
-		if value[1] < min_score:
-			min_score = value[1]
+		if value[1] > max_score:
+			max_score = value[1]
 			last = value[0]
 del column_matches[last]
 
-- 
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