https://en.wikipedia.org/wiki/Visual_cryptography

visual_cryptography.py

# USAGE: python visual_cryptography.py file_to_encrypt.png

# $ pip install Pillow
from PIL import Image, ImageDraw
import os, sys

from random import SystemRandom
random = SystemRandom()

# If you want to use the more powerful PyCrypto ($ pip install pycrypto) then uncomment the next line and comment out the previous two lines
#from Crypto.Random import random

if len(sys.argv)!=2:
	sys.exit("This takes one argument; the image to be encrypted.")

infile = str(sys.argv[1])

if not os.path.isfile(infile):
	sys.exit("The file '{infile}' does not exist.".format(infile = infile))

img = Image.open(infile)

f, e = os.path.splitext(infile)
out_filename_A = f+"_A.png"
out_filename_B = f+"_B.png"

img = img.convert('1')

width = img.size[0]*2
height = img.size[1]*2
out_image_A = Image.new('1', (width, height))
out_image_B = Image.new('1', (width, height))
draw_A = ImageDraw.Draw(out_image_A)
draw_B = ImageDraw.Draw(out_image_B)

patterns=((1,1,0,0), (1,0,1,0), (1,0,0,1), (0,1,1,0), (0,1,0,1), (0,0,1,1))

for x in range(0, int(width/2)):
	for y in range(0, int(height/2)):
		pixel=img.getpixel((x,y))
		pat=random.choice(patterns)

		draw_A.point((x*2, y*2), pat[0])
		draw_A.point((x*2+1, y*2), pat[1])
		draw_A.point((x*2, y*2+1), pat[2])
		draw_A.point((x*2+1, y*2+1), pat[3])
		if pixel==0:
			draw_B.point((x*2, y*2), 1-pat[0])
			draw_B.point((x*2+1, y*2), 1-pat[1])
			draw_B.point((x*2, y*2+1), 1-pat[2])
			draw_B.point((x*2+1, y*2+1), 1-pat[3])
		else:
			draw_B.point((x*2, y*2), pat[0])
			draw_B.point((x*2+1, y*2), pat[1])
			draw_B.point((x*2, y*2+1), pat[2])
			draw_B.point((x*2+1, y*2+1), pat[3])

out_image_A.save(out_filename_A, 'PNG')
out_image_B.save(out_filename_B, 'PNG')
sys.exit("Done.")

Example image: https://iili.io/2m0iDB4.png
Split part A: https://iili.io/2m0sqEQ.png
Split part B: https://iili.io/2m0sFQj.png
Both parts merged: https://iili.io/2m0sfCx.png