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);
}
