module ChunkyPNG::Canvas::Adam7Interlacing

def adam7_pass_size(pass, original_width, original_height)
  m_o = adam7_multiplier_offset(pass)
  [ ((original_width  - m_o[:x_offset] ) / m_o[:x_multiplier].to_f).ceil,
    ((original_height - m_o[:y_offset] ) / m_o[:y_multiplier].to_f).ceil]
end