Simplified code for encoding byte messages into images

encode_message.dart

/// Steps for encoding the message
Uint16List expandedMsg = expandMsg(msg2bytes(msg));
Uint16List paddedMsg = padMsg(getEncoderCapacity(img), expandedMsg);

/// Helper function to convert string to bytes
Uint16List msg2bytes(String msg) {
  return Uint16List.fromList(msg.codeUnits);
}

/// Helper function to expand byte messages to bit messages
Uint16List expandMsg(Uint16List msg) {
  Uint16List expanded = Uint16List(msg.length * dataLength);
  for (int i = 0; i < msg.length; ++i) {
    int msgByte = msg[i];
    for (int j = 0; j < dataLength; ++j) {
      int lastBit = msgByte & 1;
      expanded[i * dataLength + (dataLength - j - 1)] = lastBit;
      msgByte = msgByte >> 1;
    }
  }
  return expanded;
}