/usr/share/pyshared/stepic.py is in python-stepic 0.3-5.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 | # stepic - Python image steganography
# Copyright (C) 2007 Lenny Domnitser
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
'''Python image steganography
Stepic hides arbitrary data inside PIL images.
Stepic uses the Python Image Library
(apt: python-imaging, web: <http://www.pythonware.com/products/pil/>).
'''
__author__ = 'Lenny Domnitser <http://domnit.org/>'
__version__ = '0.3'
import warnings
try:
import Image
except:
warnings.warn('Could not find PIL. Only encode_imdata and decode_imdata will work.',
ImportWarning, stacklevel=2)
__all__ = ('encode_imdata','encode_inplace', 'encode',
'decode_imdata', 'decode',
'Steganographer')
def _validate_image(image):
if image.mode not in ('RGB', 'RGBA', 'CMYK'):
raise ValueError('Unsupported pixel format: '
'image must be RGB, RGBA, or CMYK')
if image.format == 'JPEG':
raise ValueError('JPEG format incompatible with steganography')
def encode_imdata(imdata, data):
'''given a sequence of pixels, returns an iterator of pixels with
encoded data'''
datalen = len(data)
if datalen == 0:
raise ValueError('data is empty')
if datalen * 3 > len(imdata):
raise ValueError('data is too large for image')
imdata = iter(imdata)
for i in xrange(datalen):
pixels = [value & ~1 for value in
imdata.next()[:3] + imdata.next()[:3] + imdata.next()[:3]]
byte = ord(data[i])
for j in xrange(7, -1, -1):
pixels[j] |= byte & 1
byte >>= 1
if i == datalen - 1:
pixels[-1] |= 1
pixels = tuple(pixels)
yield pixels[0:3]
yield pixels[3:6]
yield pixels[6:9]
def encode_inplace(image, data):
'''hides data in an image'''
_validate_image(image)
w = image.size[0]
(x, y) = (0, 0)
for pixel in encode_imdata(image.getdata(), data):
image.putpixel((x, y), pixel)
if x == w - 1:
x = 0
y += 1
else:
x += 1
def encode(image, data):
'''generates an image with hidden data, starting with an existing
image and arbitrary data'''
image = image.copy()
encode_inplace(image, data)
return image
def decode_imdata(imdata):
'''Given a sequence of pixels, returns an iterator of characters
encoded in the image'''
imdata = iter(imdata)
while True:
pixels = list(imdata.next()[:3] + imdata.next()[:3] + imdata.next()[:3])
byte = 0
for c in xrange(7):
byte |= pixels[c] & 1
byte <<= 1
byte |= pixels[7] & 1
yield chr(byte)
if pixels[-1] & 1:
break
def decode(image):
'''extracts data from an image'''
_validate_image(image)
return ''.join(decode_imdata(image.getdata()))
class Steganographer:
'deprecated'
def __init__(self, image):
self.image = image
warnings.warn('Steganographer class is deprecated, and will be removed before 1.0',
DeprecationWarning, stacklevel=2)
def encode(self, data):
return encode(self.image, data)
def decode(self):
return decode(self.image)
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