Encodes 3 strings into a colorful DataMatrix barcode

dmcolor.py

#!/usr/bin/env python3

# pip requirements:
# * Pillow 5.3.0
# * pylibdmtx 0.1.8

# license: BSD 0-clause

# This script encodes Data Matrix barcodes into each CMY color channel.

# No current software can decode this and is not a standard (as of yet).
# This is just a format I created for my own amusement.

import sys
from PIL import Image, ImageOps, ImageChops
from pylibdmtx.pylibdmtx import encode

if sys.argv[1] in ["-h", "--help"]:
	cmd = sys.argv[0]
	print("Uses:")
	print("%s (-h | --help)              - Display this message" % cmd)
	print("%s NAME STRING STRING STRING  - Encode 3 strings and name the file NAME" % cmd)
	sys.exit(0)

filename = sys.argv[1]
encdata = [encode(str.encode(val)) for val in sys.argv[2:5]]
imgs = [Image.frombytes("RGB", (img.width, img.height), img.pixels) for img in encdata]

# make sure matrix codes are the same size
if not (imgs[0].height == imgs[1].height == imgs[2].height):
	print("image sizes are not the same!")
	print("sizes are, in order given: %d %d %d" % (imgs[0].height, imgs[1].height, imgs[2].height))
	print("try changing or padding the messages to be the same size")
	sys.exit(1)

dims = (imgs[0].width, imgs[0].height)
final_img = Image.new("RGB", dims)

# original images start out black on white.
for (i, img) in enumerate(imgs):
	# turn them white on black
	img = ImageOps.invert(img)
	# replace white with the channel color
	img = img.getchannel(['R', 'G', 'B'][i])
	colors = [(255, 0, 0), (0, 255, 0), (0, 0, 255)]
	img = ImageOps.colorize(img, "black", colors[i])
	# and add to blank image
	final_img = ImageChops.add(final_img, img)

# invert it again
final_img = ImageOps.invert(final_img)
# we can't be clever by canceling out both inversions at once because
# overlapping CMY pixels added together saturate to white and erases the data.

# save, and we're done!
final_img.save(filename)