encodeMessageIntoImage function

Implementation

EncodeResponse encodeMessageIntoImage(EncodeRequest req) {
  Uint16List img = Uint16List.fromList(req.original.getBytes().toList());
  String msg = req.msg;
  String token = req.token;
  if (req.shouldEncrypt()) {
    crypto.Key key = crypto.Key.fromUtf8(padCryptionKey(token));
    crypto.IV iv = crypto.IV.fromLength(16);
    crypto.Encrypter encrypter = crypto.Encrypter(crypto.AES(key));
    crypto.Encrypted encrypted = encrypter.encrypt(msg, iv: iv);
    msg = encrypted.base64;
  }
  Uint16List encodedImg = img;
  if (getEncoderCapacity(img) < getMsgSize(msg)) {
    throw FlutterError('image_capacity_not_enough');
  }
  Uint16List expandedMsg = expandMsg(msg2bytes(msg));
  Uint16List paddedMsg = padMsg(getEncoderCapacity(img), expandedMsg);
  if (paddedMsg.length != getEncoderCapacity(img)) {
    throw FlutterError('msg_container_size_not_match');
  }
  for (int i = 0; i < getEncoderCapacity(img); ++i) {
    encodedImg[i] = encodeOnePixel(img[i], paddedMsg[i]);
  }
  imglib.Image editableImage = imglib.Image.fromBytes(
      req.original.width, req.original.height, encodedImg.toList());
  Image displayableImage =
      Image.memory(imglib.encodePng(editableImage), fit: BoxFit.fitWidth);
  Uint8List data = Uint8List.fromList(imglib.encodePng(editableImage));
  EncodeResponse response =
      EncodeResponse(editableImage, displayableImage, data);
  return response;
}