require 'libpng'


half = true if ARGV.delete '--half'

p = Png.read(ARGV.shift)
colmap = ARGV.shift || '01234567abcdefgh'

if half
	tog = true
	p.lines.delete_if { tog = !tog }
	p.lines.each { |l| l.replace l.unpack('C*').find_all { tog = !tog }.pack('C*') }
end

puts p.lines.map { |l| l = l.unpack('C*') unless l.kind_of?(::Array) ; l.map { |i| colmap[i] ? colmap[i, 1] : ' ' }.join }