public static void StegBinary(string PngFilePath, BitArray Bits, int SecurityLevel)
{
var bitmap = new Bitmap(PngFilePath);
var imgHelper = new ImageHelper(bitmap);
imgHelper.LockBits();
var bytes = imgHelper.Pixels;
var bitsLen = Bits.Length;
// Count all bytes useful for embedding (2 bits per slot = byte)
var slots = 2 * imgHelper.Pixels.Length;
if (slots < bitsLen)
{
throw new Exception("Content too large for the selected image.");
}
// If ok continue
int currentBit = 0;
int byteCount = 0;
bool canIterate = true;
while (canIterate)
{
// Define the step of bits to write according to security level
if ((0 == byteCount % SecurityLevel) || (currentBit < 64))
{
// Get the current color component value
byte currentVal = bytes[byteCount];
// Get the current bit
bool bit = Bits[currentBit];
// Write the new value in position 0
byte newVal = getNewValForComponent(currentVal, bit, 0);
currentBit++;
canIterate = currentBit < bitsLen;
// If still bits write on the 1st position after the first 64 bits
if (canIterate && currentBit > 64)
{
// Get the current bit
bit = Bits[currentBit];
// Write the new value in position 1
newVal = getNewValForComponent(newVal, bit, 1);
currentBit++;
canIterate = currentBit < bitsLen;
}
// Set the new value for the color component
bytes[byteCount] = newVal;
}
byteCount++;
}
imgHelper.UnlockBits();
var flPath = System.IO.Path.GetDirectoryName(PngFilePath);
var filename = PngFilePath.Remove(0, string.Concat(flPath, "\\").Length);
var docPath = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);
var newFileNameAndPath = $@"{docPath}\StegImageUI\steg_{DateTime.Now.ToString("yyyyMMddHHmmss")}_{filename}";
bitmap.Save(newFileNameAndPath, ImageFormat.Png);
}
/// <summary>
/// Return the available slots for embedding.
/// </summary>
/// <param name="TifFilePath"></param>
/// <returns></returns>
public static int GetAvailableSlots(string TifFilePath)
{
Bitmap bitmap = new Bitmap(TifFilePath);
var ih = new ImageHelper(bitmap);
ih.LockBits();
var slots = ih.Pixels.Length;
ih.UnlockBits();
// TIF: 2 bits per byte
return(slots * 2);
}
/// <summary>
/// Return the available slots for embedding.
/// </summary>
/// <param name="PngFilePath"></param>
/// <returns></returns>
public static int GetAvailableSlots(string PngFilePath)
{
var bitmap = new Bitmap(PngFilePath);
var imgHelper = new ImageHelper(bitmap);
int byteCount = 0;
imgHelper.LockBits();
byteCount = imgHelper.Pixels.Length;
imgHelper.UnlockBits();
// Check slots availability
// Count all bytes useful for embedding (2 bits per slot = byte)
var slots = 2 * byteCount;
return(slots);
}
public static StegStruct UnstegBinary(string PngFilePath)
{
var ssRet = new StegStruct();
int iter = 0;
var bitmap = new Bitmap(PngFilePath);
var imgHelper = new ImageHelper(bitmap);
imgHelper.LockBits();
var bytes = imgHelper.Pixels;
imgHelper.UnlockBits();
// Read the content length
BitArray baTotLength;
try
{
baTotLength = readAllBitArray(bytes, iter, 32, oneBitReading: true);
}
catch (Exception ex)
{
_log.Debug(ex.Message);
throw new Exception("No data embedded in this image or the image is corrupted.");
}
// If data is correct, continue
int totalBits = baTotLength.ToInteger();
ssRet.TotalSize = totalBits;
// Read the security level: int => 32 bits (2 bits per component)
iter += 32;
BitArray baSecLev;
try
{
baSecLev = readAllBitArray(bytes, iter, 32, oneBitReading: true);
}
catch (Exception ex)
{
_log.Debug(ex.Message);
throw new Exception("No data embedded in this image or the image is corrupted.");
}
// If data is correct, continue
int secLev = baSecLev.ToInteger();
ssRet.SecurityLevel = secLev;
// Read all steg bits step by security level
// Start from index 16 for every DCT coeff 2 bits to take => end DCT index is 64
iter += 32;
// The security level bitrun has to excluded
var bits2Read = totalBits - 32;
// Get the byte array with the required data
BitArray stegBits;
try
{
stegBits = readAllBitArray(bytes, iter, bits2Read, secLev);
}
catch (Exception ex)
{
_log.Debug(ex.Message);
throw new Exception("No data embedded in this image or the image is corrupted.");
}
// If data is correct, continue
ssRet.ContentFull = baTotLength.Append(baSecLev).Append(stegBits);
// Start reading the bit array struct --------------------------------------------------
// Read if it is a string or file
ssRet.IsFile = stegBits[0];
// Read all the content
int idx = 1;
int lng = stegBits.Length - idx;
var baTmp = readBitArrayData(stegBits, idx, lng);
ssRet.Content = baTmp;
ssRet.ContentSize = ssRet.Content.Length;
return(ssRet);
}
