Steganography (RMagick)

hide.rb

#! /usr/bin/env ruby

require 'rmagick'

if ARGV.length < 3
	puts "Usage: #{$0} input_file data output_file"
	abort("ERROR: Wrong arguments")
end

input = ARGV[0]
data = ARGV[1]
output = ARGV[2]

image = Magick::Image.read(input).first
data = IO.binread(data).unpack("B*")[0].split("").map(&:to_i)

col = image.columns
row = image.rows

if data.length > col * row
	abort("Data is too big for the image to contains.")
end

idx = 0
len = data.length
pixels = image.get_pixels(0, 0, col, row)

for pixel in pixels

	# clear lsb
	pixel.red &= ~1
	pixel.green &= ~1
	pixel.blue &= ~1

	if idx < data.length
		pixel.red |= data[idx]
		pixel.green |= data[idx]
		pixel.blue |= data[idx]
		idx += 1
	end

end

out = Magick::Image.new(col, row)

out.store_pixels(0, 0, col, row, pixels)

out.write(output)