extractChannelMSB.rb

image = ChunkyPNG::Image.from_file('source.png')

bytes = Array.new(0)
bytes = []
done = ""
image.to_alpha_channel_stream.split("").each { |byte| bytes << byte.to_s.unpack('B*')[0][0] }
(0..image.to_alpha_channel_stream.length/8).each {|n| bits = bytes.shift(8); done << bits.join.to_i(2);  }
File.open("alpha_bitplane.bin", 'wb') { |file| file.write(done) }

puts "Wrote #{done.length} bytes:  alpha_bitplane.bin"

bytes = []
done = ""
red = image.to_rgb_stream.unpack('axx'*(image.to_rgb_stream.length/3)).join
red.split("").each { |byte| bytes << byte.to_s.unpack('B*')[0][0] }
(0..image.to_rgb_stream.length/24).each {|n| bits = bytes.shift(8); done << bits.join.to_i(2);  }
File.open("red_bitplane.bin", 'wb') { |file| file.write(done) }

puts "Wrote #{done.length} bytes:  red_bitplane.bin"

bytes = []
done = ""
green = image.to_rgb_stream.unpack('xax'*(image.to_rgb_stream.length/3)).join
green.split("").each { |byte| bytes << byte.to_s.unpack('B*')[0][0] }
(0..image.to_rgb_stream.length/24).each {|n| bits = bytes.shift(8); done << bits.join.to_i(2);  }
File.open("green_bitplane.bin", 'wb') { |file| file.write(done) }

puts "Wrote #{done.length} bytes:  green_bitplane.bin"

bytes = []
done = ""
blue = image.to_rgb_stream.unpack('xxa'*(image.to_rgb_stream.length/3)).join
blue.split("").each { |byte| bytes << byte.to_s.unpack('B*')[0][0] }
(0..image.to_rgb_stream.length/24).each {|n| bits = bytes.shift(8); done << bits.join.to_i(2);  }
File.open("blue_bitplane.bin", 'wb') { |file| file.write(done) }

puts "Wrote #{done.length} bytes:  blue_bitplane.bin"