orMSB.rb

alpha = IO.binread("alpha_bitplane.bin")
red = IO.binread("red_bitplane.bin")
green = IO.binread("green_bitplane.bin")
blue = IO.binread("blue_bitplane.bin")

alphared = alpha.bytes.zip(red.bytes).map { |x,y| (x|y).chr}.join
alpharedgreen = alphared.bytes.zip(green.bytes).map { |x,y| (x|y).chr}.join
alpharedgreenblue = alpharedgreen.bytes.zip(blue.bytes).map { |x,y| (x|y).chr}.join

out = ""
alpharedgreenblue.each_byte { |n| out << ((n+0) %256).chr }

IO.binwrite("combined.bin",out)