ttf_glitch.rb

# ruby ttf_glitch.rb target.ttf > glitched.ttf

def main
  filename = ARGV.shift
  open(filename, 'rb') do |f|
    content = f.read

    offset = glyph_offset(content)
    length = glyph_length(content)

    head = content[0, offset]
    glyphs = content[offset, length]
    other = content[offset + length .. -1]

    glyphs.gsub!(/\w/, '0')

    print head + glyphs + other
  end
end

def glyph_offset(data)
  data[data.index('glyf') + 8, 4].unpack("N")[0]
end

def glyph_length(data)
  data[data.index('glyf') + 12, 4].unpack("N")[0]
end

main