class ChunkyPNG::Datastream

def from_io(io)
  verify_signature!(io)
  ds = self.new
  until io.eof?
    chunk = ChunkyPNG::Chunk.read(io)
    case chunk
      when ChunkyPNG::Chunk::Header;       ds.header_chunk = chunk
      when ChunkyPNG::Chunk::Palette;      ds.palette_chunk = chunk
      when ChunkyPNG::Chunk::Transparency; ds.transparency_chunk = chunk
      when ChunkyPNG::Chunk::ImageData;    ds.data_chunks << chunk
      when ChunkyPNG::Chunk::End;          ds.end_chunk = chunk
      else ds.other_chunks << chunk
    end
  end
  return ds
end