Decoding itanimulli's images: discussion at https://hackaday.io/project/8762-itanimulli-code-crackers/log/29279-border-graphical-analysis/discussion-43675

itanimulli_extract_bits_avg.py

import gd
import argparse
from sys import stdout

parser = argparse.ArgumentParser(
        description='Extract bits from the average colour of each tile',
        formatter_class=argparse.RawTextHelpFormatter)
parser.add_argument('--image', help='Image file to parse')
parser.add_argument('--invert', help='Invert the bits',
        action='store_const', default=False, const=True)
parser.add_argument('--binary', help='Write binary',
        action='store_const', default=False, const=True)
parser.add_argument('--bits', help='Number of bits per grouping',
                                type=int, default=8)
parser.add_argument('--output', help='Output file')
parser.add_argument('--tile-w', type=int, default=12,
                                help='Width of FEZ tile')
parser.add_argument('--tile-h', type=int, default=12,
                                help='Height of FEZ tile')
parser.add_argument('--offset-x', type=int, default=1,
                                help='X co-ordinate of first tile')
parser.add_argument('--offset-y', type=int, default=1,
                                help='Y co-ordinate of first tile')
parser.add_argument('--direction', default='rd',
        help='''Order of traversal, one of:
            - rd ("right then down": Start top-left, scan to bottom-right,
                  horizontally)
            - ld ("left then down": Start top-right, scan to bottom-left,
                  horizontally)
            - ru ("right then up": Start bottom-left, scan to top-right,
                  horizontally)
            - lu ("left then up": Start bottom-right, scan to top-left,
                  horizontally)
            - dr ("down then right": Start top-left, scan to bottom-right,
                  vertically)
            - dl ("down then left": Start top-right, scan to bottom-left,
                  vertically)
            - ur ("up then right": Start bottom-left, scan to top-right,
                  vertically)
            - ul ("up then left": Start bottom-right, scan to top-left,
                  vertically)''')
args = parser.parse_args()

img = gd.image(args.image)
if args.output is not None:
    out = file(args.output,'w')
else:
    out = stdout

# Compute number of tiles
(p_width, p_height) = img.size()
width = (p_width - args.offset_x) // args.tile_w
height = (p_height - args.offset_y) // args.tile_h
tile_pos = lambda x, y : (((x*args.tile_w) + args.offset_x), \
                            ((y*args.tile_h) + args.offset_y))

# Compute the number of pixels in a tile
tile_num = args.tile_w * args.tile_h

# Bit threshold
threshold = tile_num // 2

# Enumerate a list of co-ordinates to read.
if args.direction[0] in ('d','u'):
    v_dir = args.direction[0]
    h_dir = args.direction[1]
    hv_dir = 'v'
elif args.direction[0] in ('l','r'):
    h_dir = args.direction[0]
    v_dir = args.direction[1]
    hv_dir = 'h'
else:
    raise ValueError('Invalid direction %r' % args.direction)
x_posn = range(0, width)
y_posn = range(0, height)
if h_dir == 'l':
    x_posn.reverse()
if v_dir == 'u':
    y_posn.reverse()

if hv_dir == 'v':
    coordinates = [tile_pos(x,y) for x in x_posn for y in y_posn]
else:
    coordinates = [tile_pos(x,y) for y in y_posn for x in x_posn]

# Inversion logic
if args.invert:
    read_bit = lambda p : not bool(p)
else:
    read_bit = lambda p : bool(p)

# Average bit of tile
def avg_bit(c):
    (tx, ty) = c
    colour = 0
    for py in range(ty, ty + args.tile_h):
        for px in range(tx, tx + args.tile_w):
            if read_bit(img.getPixel((px,py))):
                colour += 1
    return colour > threshold

# Traverse the image, collect bits.
bits = args.bits
byte = 0
for c in coordinates:
    bit = avg_bit(c)
    if args.binary:
        byte <<= 1
        if bit:
            byte |= 1
    else:
        if bit:
            out.write('1')
        else:
            out.write('0')
    bits -= 1
    if bits <= 0:
        bits = args.bits
        if args.binary:
            out.write(chr(byte))
            byte = 0
        else:
            out.write('\n')

if bits != args.bits:
    if args.binary:
        out.write(chr(byte))
    else:
        out.write('\n')