Beispiel #1
0
        public OutputMessage Decode(Bitmap inputImage)
        {
            Bitmap image = new Bitmap(inputImage);

            int colorIndex = 0;

            // last bit position
            const int lastBitIndex = 7;

            StringBuilder textMessage = new StringBuilder();

            OutputMessage outputMessage = new OutputMessage();
            HeaderData    headerData    = new HeaderData();

            // remaining bits to read
            int remainingBits = (int)LSBHeaderConstants.MessageTypeLength;

            bool isTypeDecoded         = false;
            bool isHeaderLengthDecoded = false;
            bool isLengthDecoded       = false;

            bool isImageDimensionsDecoded = false;

            MessageType messageType = MessageType.Plaintext;

            for (int i = 0; i < image.Height; i++)
            {
                for (int j = 0; j < image.Width; j++)
                {
                    Color pixel = image.GetPixel(j, i);

                    for (int n = 0; n < 3; n++)
                    {
                        byte currentColor = 0;

                        switch (colorIndex % 3)
                        {
                        case 0:
                        {
                            currentColor = pixel.R;
                            break;
                        }

                        case 1:
                        {
                            currentColor = pixel.G;
                            break;
                        }

                        case 2:
                        {
                            currentColor = pixel.B;
                            break;
                        }
                        }

                        string bitRep       = TypeConverter.Instance.ByteToString(currentColor);
                        int    lastBitValue = TypeConverter.Instance.CharToInt(bitRep[lastBitIndex]);
                        textMessage.Append(lastBitValue);
                        remainingBits--;

                        colorIndex++;

                        if (remainingBits != 0)
                        {
                            continue;
                        }

                        if (!isTypeDecoded)
                        {
                            messageType = LSBHeaderDecoder.Instance.DecodeMessageType(textMessage.ToString());
                            headerData.SetMessageType(messageType);
                            isTypeDecoded = true;
                            remainingBits = LSBHeaderDecoder.Instance.GetHeaderLengthWithoutMessageType(messageType);
                        }

                        else if (messageType != MessageType.Plaintext && !isImageDimensionsDecoded)
                        {
                            ImageDimensions imageDimensions = LSBHeaderDecoder.Instance.DecodeImageDimensions(textMessage.ToString(), messageType);
                            remainingBits =
                                LSBHeaderDecoder.Instance.GetHeaderLengthWithoutImageDimensions(messageType);
                            isImageDimensionsDecoded = true;

                            headerData.SetImageHeight(imageDimensions.GetImageHeight());
                            headerData.SetImageWidth(imageDimensions.GetImageWidth());
                        }

                        else if (!isHeaderLengthDecoded)
                        {
                            isHeaderLengthDecoded = true;
                            remainingBits         = LSBHeaderDecoder.Instance.DecodeMessageLength(textMessage.ToString(), messageType);
                        }

/*                        else if (!isLengthDecoded)
 *                      {
 *                          isLengthDecoded = true;
 *                          remainingBits = LSBHeaderDecoder.Instance.DecodeMessageLength(inputMessage.ToString(), messageType);
 *                      }*/

                        // inputMessage decoded
                        else
                        {
                            outputMessage.SetHeaderData(headerData);
                            outputMessage.SetContent(textMessage.ToString());
                            return(outputMessage);
                        }
                    }
                }
            }
            return(null);
        }
Beispiel #2
0
        private OutputMessage decodeMessageLeft(Bitmap inputImage, int minIndex, int maxIndex)
        {
            //temporary
            int remainingBits = (int)HSHeaderConstants.MessageTypeLength;

            bool isTypeDecoded            = false;
            bool isHeaderLengthDecoded    = false;
            bool isImageDimensionsDecoded = false;

            int messageIndex = 0;

            int R = 0;
            int G = 0;
            int B = 0;

            int mIndex = 0;

            Color pixel;

            OutputMessage outputMessage = new OutputMessage();
            HeaderData    headerData    = new HeaderData();

            // need to be replaced
            MessageType messageType = MessageType.Plaintext;

            StringBuilder message = new StringBuilder();

            for (int i = 0; i < inputImage.Height; i++)
            {
                for (int j = 0; j < inputImage.Width; j++)
                {
                    pixel = inputImage.GetPixel(j, i);

                    R = pixel.R;
                    G = pixel.G;
                    B = pixel.B;

                    if (R == maxIndex - 1)
                    {
                        message.Append("1");
                        messageIndex++;
                        remainingBits--;
                    }

                    else if (R == maxIndex)
                    {
                        message.Append("0");
                        messageIndex++;
                        remainingBits--;
                    }

                    // header decoding
                    if (remainingBits == 0)
                    {
                        if (isTypeDecoded == false)
                        {
                            messageType = HSHeaderDecoder.Instance.DecodeMessageType(message.ToString());
                            headerData.SetMessageType(messageType);
                            isTypeDecoded = true;
                            remainingBits = HSHeaderDecoder.Instance.GetHeaderLengthWithoutMessageType(messageType);
                        }
                        else if (messageType != MessageType.Plaintext && !isImageDimensionsDecoded)
                        {
                            ImageDimensions imageDimensions = HSHeaderDecoder.Instance.DecodeImageDimensions(message.ToString(), messageType);
                            remainingBits =
                                HSHeaderDecoder.Instance.GetHeaderLengthWithoutImageDimensions(messageType);
                            isImageDimensionsDecoded = true;

                            headerData.SetImageHeight(imageDimensions.GetImageHeight());
                            headerData.SetImageWidth(imageDimensions.GetImageWidth());
                        }
                        else if (!isHeaderLengthDecoded)
                        {
                            isHeaderLengthDecoded = true;
                            remainingBits         = HSHeaderDecoder.Instance.DecodeMessageLength(message.ToString(), messageType);
                        }
                        else
                        {
                            outputMessage.SetHeaderData(headerData);
                            outputMessage.SetContent(message.ToString());
                            return(outputMessage);
                        }
                    }
                }
            }

            return(null);
        }