public static void ApplyQuantizationTable(string JpegFilePath, EnumStegoChannel Component = EnumStegoChannel.Y, int ScaleFactor = 50, int[] QuantizationTable = null)
{
var jpds = new jpeg_decompress_struct();
FileStream fileStreamImg = new FileStream(JpegFilePath, FileMode.Open, FileAccess.Read);
jpds.jpeg_stdio_src(fileStreamImg);
jpds.jpeg_read_header(true);
// DCT coefficients
var jBlock = jpds.jpeg_read_coefficients();
jpds.jpeg_finish_decompress();
fileStreamImg.Close();
if (null == QuantizationTable)
{
switch (Component)
{
case EnumStegoChannel.Y:
QuantizationTable = _qLuminance;
break;
case EnumStegoChannel.Cb:
case EnumStegoChannel.Cr:
QuantizationTable = _qChromiance;
break;
}
}
// Get fle info
FileInfo fInfo = new FileInfo(JpegFilePath);
string dir = fInfo.DirectoryName;
string fNane = fInfo.Name;
string stegFName = $"steg_{DateTime.Now.ToString("yyyyMMddHHmm")}_{fNane}";
string stegJpegFilePath = Path.Combine(dir, stegFName);
// Compress process
FileStream fileStream = File.Create(stegJpegFilePath);
jpeg_compress_struct jpcs = new jpeg_compress_struct();
jpcs.jpeg_stdio_dest(fileStream);
jpds.jpeg_copy_critical_parameters(jpcs);
jpcs.jpeg_write_coefficients(jBlock);
jpcs.jpeg_finish_compress();
fileStream.Close();
jpds.jpeg_abort_decompress();
}
/// <summary>
/// For bits 0-63 only the LSB of DCT coefficients is written (it takes the full length of the bits to read). From bit 64 every DCT coefficient is written with the last 2 LSBs.
/// </summary>
/// <param name="jpegFilePath"></param>
/// <param name="bits"></param>
/// <param name="securityLevel"></param>
private static void changeDctCoefficients(string jpegFilePath, BitArray bits, int securityLevel)
{
var jpds = new jpeg_decompress_struct();
FileStream fileStreamImg = new FileStream(jpegFilePath, FileMode.Open, FileAccess.Read);
jpds.jpeg_stdio_src(fileStreamImg);
jpds.jpeg_read_header(true);
// DCT coefficients
var jBlock = jpds.jpeg_read_coefficients();
var bitsLen = bits.Length;
int currentBit = 0;
bool canIterate = true;
int cntAcCoeffNotZero = 0;
// Write on position 0 then 1
// Start with Cr component
int component = (int)EnumStegoChannel.Cr;
while ((component >= 0) && canIterate)
{
int z = 0;
while (canIterate)
{
int countCrRows;
try
{
countCrRows = jBlock[component].Access(z, 1)[0].Length;
}
catch
{
break;
}
int i = 0;
while ((i < countCrRows) && canIterate)
{
// Skip DC coefficients j = 0
int j = 1;
while ((j < 64) && canIterate)
{
short currentVal = jBlock[component].Access(z, 1)[0][i][j];
// Skip bits 0 and dct according to the security level (steps)
if (0 != currentVal) // Set only 1 bit for the first 64 AC coefficients
{
// Define the step of bits to write after 64 bits
if ((0 == cntAcCoeffNotZero % securityLevel) || (currentBit < 64))
{
// Get the current bit
bool bit = bits[currentBit];
// Write the new value in position 0
short newVal = getNewValForComponent(currentVal, bit, 0);
jBlock[component].Access(z, 1)[0][i][j] = newVal;
currentBit++;
canIterate = currentBit < bitsLen;
// Start writing on bit 1 after 64 bits to encode the content length
if (canIterate && currentBit > 64)
{
// Get the current bit
bit = bits[currentBit];
// Write the new value in position 1
newVal = getNewValForComponent(newVal, bit, 1);
jBlock[component].Access(z, 1)[0][i][j] = newVal;
currentBit++;
canIterate = currentBit < bitsLen;
}
}
cntAcCoeffNotZero++;
}
j++;
}
i++;
}
z++;
}
component--;
}
jpds.jpeg_finish_decompress();
fileStreamImg.Close();
// Get file info
FileInfo fInfo = new FileInfo(jpegFilePath);
string dir = fInfo.DirectoryName;
string fName = fInfo.Name;
var docPath = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);
var stegJpegFilePath = $@"{docPath}\StegImageUI\steg_{DateTime.Now.ToString("yyyyMMddHHmmss")}_{fName}";
// Compress process
FileStream fileStream = File.Create(stegJpegFilePath);
jpeg_compress_struct jpcs = new jpeg_compress_struct();
jpcs.jpeg_stdio_dest(fileStream);
jpds.jpeg_copy_critical_parameters(jpcs);
jpcs.jpeg_write_coefficients(jBlock);
jpcs.jpeg_finish_compress();
fileStream.Close();
jpds.jpeg_abort_decompress();
}