330 lines
8.3 KiB
Python
330 lines
8.3 KiB
Python
from cStringIO import StringIO
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from PIL import Image, ImageDraw
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from math import ceil, sqrt
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ALTCONST = sqrt(3) / 2.0
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ISIZE = 784.0
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IMARGIN = 22.0
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def empty_hex(size):
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c = 0
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points = []
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for i in range(2, size * 2 + 2, 2):
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points.append([0] * i)
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middle = []
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for i in range(size * 2 - 1):
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row = [0] * (size * 2)
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middle.append(row)
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epoints = list(row[:] for row in points[::-1])
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return points + middle + epoints
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def intify(points):
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return map(lambda c: (int(c[0]), int(c[1])), points)
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def draw_triangle(im, points, cell, size):
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draw = ImageDraw.Draw(im)
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# draw.polygon(points, outline=(0, 0, 0))
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if cell:
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draw.polygon(intify(points), fill=(0, 0, 0))
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return im
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def getsection(i, size):
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return 0 if i <= size - 1 else (1 if i < 3 * size - 1 else 2)
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def getspace(size):
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return max(0, sum(len(filter(lambda a: a == 0, b)) for b in empty_hex(size)) - 2)
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def generate_image(string, debug=False):
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size = 0
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binstring = bin(int(string.encode("hex"), 16)).strip("0b")
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while size < 2 or getspace(size + 1) < len(binstring):
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size += 1
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n = getspace(size)
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# print size, len(binstring)
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if debug: print "SIZE", size, " n =", n
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im = Image.new("RGB", (int(ISIZE), int(ISIZE)), "white")
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pattern = empty_hex(size)
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# print len(binstring)
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# print sum(len(i) for i in pattern)
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pattern[0][len(string) % 2] = 1
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curr = (1, 1 + len(string) % 2, 3 - len(string) % 2)
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# 0 1
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# 3 2
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for c in range(n): # range(len(binstring)):
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i, j, d = curr
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row = pattern[i]
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if c < len(binstring):
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b = int(binstring[c])
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pattern[i][j] = b
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if c % 2 == 0:
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pattern[i][j] ^= 1
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section = getsection(i, size)
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leftfacing = [j % 2 == 0, j % 2 != (i - size) % 2, j % 2 == 0][section]
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if debug: print "c =", c, ", i =", i, ", j =", j, ", d =", d, ", s =", section, ", l =", leftfacing
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if section == 0:
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if getsection(i + 1, size) == 0:
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if leftfacing:
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if d == 0:
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if j == 0:
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curr = i + 1, j, (d + 2) % 4
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else:
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curr = i - 1, j - 1, d
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elif d == 1 or d == 2:
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curr = i, j + 1, d
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elif d == 3:
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curr = i + 1, j + 1, d
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else:
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if d == 0:
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curr = i, j - 1, d
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elif d == 1:
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if j == len(row) - 1:
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curr = i + 1, j + 2, (d + 2) % 4
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else:
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curr = i - 1, j - 1, d
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elif d == 2:
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curr = i + 1, j + 1, d
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elif d == 3:
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curr = i, j - 1, d
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elif getsection(i + 1, size) == 1:
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if leftfacing:
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if d == 0:
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if j == 0:
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curr = i + 1, j, (d + 2) % 4
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else:
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curr = i - 1, j - 1, d
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elif d == 1 or d == 2:
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curr = i, j + 1, d
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elif d == 3:
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curr = i + 1, j, d
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else:
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if d == 0:
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curr = i, j - 1, d
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elif d == 1:
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if j == len(row) - 1:
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curr = i + 1, j, (d + 2) % 4
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else:
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curr = i - 1, j - 1, d
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elif d == 2:
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curr = i + 1, j, d
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elif d == 3:
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curr = i, j - 1, d
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elif section == 1:
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if getsection(i - 1, size) == 0:
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if leftfacing:
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if j == len(row) - 1:
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if d == 1:
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curr = i + 2, j, (d + 2) % 4
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elif d == 2:
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curr = i + 2, j, (d + 2) % 4
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elif d == 3:
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curr = i + 1, j, d
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else:
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if d == 0:
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curr = i - 1, j, d
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elif d == 1 or d == 2:
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curr = i, j + 1, d
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elif d == 3:
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curr = i + 1, j, d
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else:
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if j == 0:
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if d == 0:
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curr = i + 2, j, (d + 2) % 4
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elif d == 2:
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curr = i + 1, j, d
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elif d == 3:
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curr = i + 2, j, (d + 2) % 4
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else:
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if d == 0 or d == 3:
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curr = i, j - 1, d
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elif d == 1:
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curr = i - 1, j, d
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elif d == 2:
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curr = i + 1, j, d
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elif getsection(i - 1, size) == 1:
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if getsection(i + 1, size) == 1:
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if leftfacing:
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if j == len(row) - 1:
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if d == 0:
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curr = i - 1, j, d
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elif d == 1:
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curr = i + 2, j, (d + 2) % 4
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elif d == 2:
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curr = i + 2, j, (d + 2) % 4
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elif d == 3:
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curr = i + 1, j, d
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else:
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if d == 0:
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curr = i - 1, j, d
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elif d == 1 or d == 2:
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curr = i, j + 1, d
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elif d == 3:
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curr = i + 1, j, d
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else:
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if j == 0:
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if d == 0:
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curr = i + 2, j, (d + 2) % 4
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elif d == 1:
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curr = i - 1, j, d
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elif d == 2:
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curr = i + 1, j, d
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elif d == 3:
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curr = i + 2, j, (d + 2) % 4
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else:
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if d == 0 or d == 3:
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curr = i, j - 1, d
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elif d == 1:
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curr = i - 1, j, d
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elif d == 2:
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curr = i + 1, j, d
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elif getsection(i + 1, size) == 2:
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if leftfacing:
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if j == len(row) - 1:
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if d == 0:
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curr = i - 1, j, d
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elif d == 2:
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curr = i + 1, j, (d + 2) % 4
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else:
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if d == 0:
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curr = i - 1, j, d
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elif d == 1:
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curr = i, j + 1, d
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elif d == 2:
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curr = i, j + 1, d
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elif d == 3:
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curr = i + 1, j, d
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else:
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if d == 0:
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curr = i, j - 1, d
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elif d == 1:
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curr = i - 1, j, d
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elif d == 2:
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curr = i + 1, j, d
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elif d == 3:
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if j == 0:
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curr = i + 1, j, (d + 2) % 4
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else:
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curr = i, j - 1, d
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elif section == 2:
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if getsection(i - 1, size) == 1:
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if leftfacing:
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if d == 0:
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curr = i - 1, j, d
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elif d == 1:
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curr = i, j + 1, d
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elif d == 2:
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curr = i, j + 1, d
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elif d == 3:
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if j == 0:
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curr = i + 1, j, (d + 2) % 4
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else:
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curr = i + 1, j - 1, d
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else:
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if d == 0 or d == 3:
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curr = i, j - 1, d
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elif d == 1:
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curr = i - 1, j, d
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elif d == 2:
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if j == len(row) - 1:
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curr = i + 1, j - 2, (d + 2) % 4
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else:
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curr = i + 1, j - 1, d
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elif getsection(i - 1, size) == 2:
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if leftfacing:
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if d == 0:
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curr = i - 1, j + 1, d
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elif d == 1 or d == 2:
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curr = i, j + 1, d
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elif d == 3:
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if j == 0:
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curr = i + 1, j, (d + 2) % 4
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else:
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curr = i + 1, j - 1, d
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else:
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if j == len(row) - 1:
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if d == 0:
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curr = i, j - 1, d
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elif d == 1:
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curr = i - 1, j + 1, d
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elif d == 2:
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curr = i + 1, j - 2, (d + 2) % 4
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else:
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if d == 0 or d == 3:
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curr = i, j - 1, d
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elif d == 1:
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curr = i - 1, j + 1, d
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elif d == 2:
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curr = i + 1, j - 1, d
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# for i in range(len(pattern)):
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# for j in range(len(pattern[i])):
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# section = 0 if i <= size - 1 else (1 if i < 3 * size - 1 else 2)
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# leftfacing = [j % 2 == 0, j % 2 != (i - size) % 2, j % 2 == 0][section]
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# if not leftfacing:
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# print j,
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# print
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sidelen = (ISIZE - IMARGIN * 2) / (2.0 * size)
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altitude = sidelen * ALTCONST
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# print sidelen, altitude
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for i in range(len(pattern)):
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section = getsection(i, size)
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row = pattern[i]
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rowleft = (ISIZE / 2) - (altitude * len(row) / 2)
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if section % 2 == 0:
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evenrow = i % 2 == 0
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for j in range(len(row)):
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cell = row[j]
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top = ceil(i / 2.0) * sidelen - (0.5 * sidelen if not evenrow else 0) + IMARGIN
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bottom = top + sidelen
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if j % 2 == 0:
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points = [
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(rowleft + altitude * j, top + sidelen / 2),
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(rowleft + altitude * (j + 1), top), (rowleft + altitude * (j + 1), bottom)
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]
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else:
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points = [
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(rowleft + altitude * (j + 1), top + sidelen / 2),
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(rowleft + altitude * j, top), (rowleft + altitude * j, bottom)
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]
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draw_triangle(im, points, cell, size)
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else:
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evenrow = (i - size) % 2 == 1
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for j in range(len(row)):
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cell = row[j]
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top = ceil(i / 2.0) * sidelen - (0.5 * sidelen if i % 2 == 1 else 0) + IMARGIN
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bottom = top + sidelen
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if j % 2 == (i - size) % 2:
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points = [
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(rowleft + altitude * (j + 1), top + sidelen / 2),
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(rowleft + altitude * j, top), (rowleft + altitude * j, bottom)
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]
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else:
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points = [
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(rowleft + altitude * j, top + sidelen / 2),
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(rowleft + altitude * (j + 1), top), (rowleft + altitude * (j + 1), bottom)
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]
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draw_triangle(im, points, cell, size)
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return im
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FLAG = "are_triangles_more_secure_than_squares?_%s}"
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def get_salt(random):
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salt = "".join([random.choice("0123456789abcdef") for i in range(8)])
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return salt
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def generate_flag(random):
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salt = get_salt(random)
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im = generate_image("easyctf{%s}" % (FLAG % salt))
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flag = StringIO()
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im.save(flag, format="PNG")
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return flag
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def generate(random):
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return dict(files={
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"flag.png": generate_flag
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})
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def grade(random, key):
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salt = get_salt(random)
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if key.find(FLAG % salt) >= 0:
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return True, "Correct!"
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return False, "Nope."
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