from PIL import Image
import sys
infile1 = Image.open(sys.argv[1])
infile2 = Image.open(sys.argv[2])
infile3 = Image.open(sys.argv[3])
infile4 = Image.open(sys.argv[4])
outfile1 = Image.new('1', infile1.size)
outfile2 = Image.new('1', infile1.size)
outfile3 = Image.new('1', infile1.size)
for x in range(infile1.size[0]):
for y in range(infile1.size[1]):
outfile1.putpixel((x, y), max(infile1.getpixel((x, y)), infile2.getpixel((x, y))))
outfile2.putpixel((x, y), max(infile3.getpixel((x, y)), infile4.getpixel((x, y))))
outfile3.putpixel((x, y), max(outfile1.getpixel((x, y)), outfile2.getpixel((x, y))))
outfile1.save('result.png')
infile1, infile2, infile3 and infile4 are png images that are given as input. These .png files are the output of a visual cryptography scheme where one input image is split into 4 different images (shares). you can find it here: http://www.datagenetics.com/blog/november32013/index.html
While splitting the original image into 4 shares
for x in range(0, image.size[0]):
for y in range(0, image.size[1]):
sourcepixel = image.getpixel((x, y))
print sourcepixel
assert sourcepixel in (0, 255)
coinflip = random.random()
#coinflip = 0.6
print coinflip
if sourcepixel == 0: #if it's black
if coinflip < .5:
print "black pixel with less than 0.5"
#arrangement 1
#black, white, white top row [(0,0),(1,0),(2,)]
share1.putpixel((x * 2, y * 2), 0)
share1.putpixel((x * 2 + 1, y * 2 ), 255)
share1.putpixel((x * 2 + 2, y * 2 ), 255)
#black,black,black mid row
share1.putpixel((x * 2, y * 2 + 1), 0)
share1.putpixel((x * 2 + 1, y * 2 + 1), 0)
share1.putpixel((x * 2 + 2, y * 2 + 1), 0)
#white, black, white bottom row
share1.putpixel((x * 2, y * 2 + 2), 255)
share1.putpixel((x * 2 + 1, y * 2 + 2), 0 )
share1.putpixel((x * 2 + 2, y * 2 + 2), 255)
#arrangement 2
#white,black,white
share2.putpixel((x * 2, y * 2), 255)
share2.putpixel((x * 2 + 1, y * 2 ), 0)
share2.putpixel((x * 2 + 2, y * 2 ), 255)
#black,black,white
share2.putpixel((x * 2, y * 2 + 1), 0)
share2.putpixel((x * 2 + 1, y * 2 + 1), 0)
share2.putpixel((x * 2 + 2, y * 2 + 1), 255)
#black,black,white
share2.putpixel((x * 2, y * 2 + 2), 0)
share2.putpixel((x * 2 + 1, y * 2 + 2), 0 )
share2.putpixel((x * 2 + 2, y * 2 + 2), 255)
else:
#arrangement 3
#white,black,white
share3.putpixel((x * 2, y * 2), 255)
share3.putpixel((x * 2 + 1, y * 2 ), 0)
share3.putpixel((x * 2 + 2, y * 2 ), 255)
#black,black,black
share3.putpixel((x * 2, y * 2 + 1), 0)
share3.putpixel((x * 2 + 1, y * 2 + 1), 0)
share3.putpixel((x * 2 + 2, y * 2 + 1), 0)
#white,white,black
share3.putpixel((x * 2, y * 2 + 2), 255)
share3.putpixel((x * 2 + 1, y * 2 + 2), 255)
share3.putpixel((x * 2 + 2, y * 2 + 2), 0)
#arrangement 4
#white,black,black
share4.putpixel((x * 2, y * 2), 255)
share4.putpixel((x * 2 + 1, y * 2 ), 0)
share4.putpixel((x * 2 + 2, y * 2 ), 0)
#white,black,black
share4.putpixel((x * 2, y * 2 + 1), 255)
share4.putpixel((x * 2 + 1, y * 2 + 1), 0)
share4.putpixel((x * 2 + 2, y * 2 + 1), 0)
#white,black,white
share4.putpixel((x * 2, y * 2 + 2), 255)
share4.putpixel((x * 2 + 1, y * 2 + 2), 0)
share4.putpixel((x * 2 + 2, y * 2 + 2), 255)
elif sourcepixel == 255: # if it's white
if coinflip < .5:
print "white pixel with less than 0.5"
#arrangement 1
#white, white, white top row [(0,0),(1,0),(2,)]
share1.putpixel((x * 2, y * 2), 255)
share1.putpixel((x * 2 + 1, y * 2 ), 255)
share1.putpixel((x * 2 + 2, y * 2 ), 255)
#black,black,black mid row
share1.putpixel((x * 2, y * 2 + 1), 0)
share1.putpixel((x * 2 + 1, y * 2 + 1), 0)
share1.putpixel((x * 2 + 2, y * 2 + 1), 0)
#black, black, white bottom row
share1.putpixel((x * 2, y * 2 + 2), 0)
share1.putpixel((x * 2 + 1, y * 2 + 2), 0 )
share1.putpixel((x * 2 + 2, y * 2 + 2), 255)
#arrangement 2
#white,black,white
share2.putpixel((x * 2, y * 2), 255)
share2.putpixel((x * 2 + 1, y * 2 ), 255)
share2.putpixel((x * 2 + 2, y * 2 ), 0)
#black,black,white
share2.putpixel((x * 2, y * 2 + 1), 0)
share2.putpixel((x * 2 + 1, y * 2 + 1), 0)
share2.putpixel((x * 2 + 2, y * 2 + 1), 255)
#black,white,black
share2.putpixel((x * 2, y * 2 + 2), 0)
share2.putpixel((x * 2 + 1, y * 2 + 2), 255 )
share2.putpixel((x * 2 + 2, y * 2 + 2), 0)
else:
#arrangement 3
#white,black,white
share3.putpixel((x * 2, y * 2), 255)
share3.putpixel((x * 2 + 1, y * 2 ), 0)
share3.putpixel((x * 2 + 2, y * 2 ), 255)
#black,black,white
share3.putpixel((x * 2, y * 2 + 1), 0)
share3.putpixel((x * 2 + 1, y * 2 + 1), 0)
share3.putpixel((x * 2 + 2, y * 2 + 1), 255)
#white,black,black
share3.putpixel((x * 2, y * 2 + 2), 255)
share3.putpixel((x * 2 + 1, y * 2 + 2), 0)
share3.putpixel((x * 2 + 2, y * 2 + 2), 0)
#arrangement 4
#white,black,black
share4.putpixel((x * 2, y * 2), 255)
share4.putpixel((x * 2 + 1, y * 2 ), 0)
share4.putpixel((x * 2 + 2, y * 2 ), 0)
#black,black,black
share4.putpixel((x * 2, y * 2 + 1), 0)
share4.putpixel((x * 2 + 1, y * 2 + 1), 0)
share4.putpixel((x * 2 + 2, y * 2 + 1), 0)
#white,white,white
share4.putpixel((x * 2, y * 2 + 2), 255)
share4.putpixel((x * 2 + 1, y * 2 + 2), 255)
share4.putpixel((x * 2 + 2, y * 2 + 2), 255)
share1.save('share1.png')
share2.save('share2.png')
share3.save('share3.png')
share4.save('share4.png')
I created a simple testfile.png in paintbrush, a white background with some black shapes on it. The shares are divided, often leaving more information on 2 shares than the others.
On combining these shares however, the result file doesn't look anything like the original image. Any suggestions on how to test if the shares are made fine, and if they are then how would i combine them (over lay them so that the original image is returned) ?
