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);
}
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);
}
