/**
* Method to embed the message into the cover data
*
* @param msg Message to be embedded
* @param msgFileName Name of the message file. If this value is provided, then the filename
* should be embedded in the cover data
* @param cover Cover data into which message needs to be embedded
* @param coverFileName Name of the cover file
* @param stegoFileName Name of the output stego file
* @return Stego data containing the message
* @throws OpenStegoException
*/
public byte[] embedData(
byte[] msg, String msgFileName, byte[] cover, String coverFileName, String stegoFileName)
throws OpenStegoException {
BufferedImage image = null;
List<int[][]> yuv = null;
DWT dwt = null;
ImageTree dwtTree = null;
ImageTree p = null;
Signature sig = null;
Pixel pixel1 = null;
Pixel pixel2 = null;
Pixel pixel3 = null;
int[][] luminance = null;
int imgType = 0;
int origWidth = 0;
int origHeight = 0;
int cols = 0;
int rows = 0;
int n = 0;
double temp = 0.0;
// Cover file is mandatory
if (cover == null) {
throw new OpenStegoException(null, NAMESPACE, DWTXieErrors.ERR_NO_COVER_FILE);
} else {
image = ImageUtil.byteArrayToImage(cover, coverFileName);
}
imgType = image.getType();
origWidth = image.getWidth();
origHeight = image.getHeight();
image = ImageUtil.makeImageSquare(image);
cols = image.getWidth();
rows = image.getHeight();
yuv = ImageUtil.getYuvFromImage(image);
luminance = yuv.get(0);
sig = new Signature(msg);
// Wavelet transform
dwt = new DWT(cols, rows, sig.filterID, sig.embeddingLevel, sig.waveletFilterMethod);
dwtTree = dwt.forwardDWT(luminance);
p = dwtTree;
// Consider each resolution level
while (p.getLevel() < sig.embeddingLevel) {
// Descend one level
p = p.getCoarse();
}
// Repeat binary watermark by sliding a 3-pixel window of approximation image
for (int row = 0; row < p.getImage().getHeight(); row++) {
for (int col = 0; col < p.getImage().getWidth() - 3; col += 3) {
// Get all three approximation pixels in window
pixel1 = new Pixel(0, DWTUtil.getPixel(p.getImage(), col + 0, row));
pixel2 = new Pixel(1, DWTUtil.getPixel(p.getImage(), col + 1, row));
pixel3 = new Pixel(2, DWTUtil.getPixel(p.getImage(), col + 2, row));
// Bring selected pixels in ascending order
if (pixel1.value > pixel2.value) {
swapPix(pixel1, pixel2);
}
if (pixel2.value > pixel3.value) {
swapPix(pixel2, pixel3);
}
if (pixel1.value > pixel2.value) {
swapPix(pixel1, pixel2);
}
// Apply watermarking transformation (modify median pixel)
temp =
wmTransform(
sig.embeddingStrength,
pixel1.value,
pixel2.value,
pixel3.value,
getWatermarkBit(sig.watermark, n % (sig.watermarkLength * 8)));
// Write modified pixel
DWTUtil.setPixel(p.getImage(), col + pixel2.pos, row, temp);
n++;
}
}
dwt.inverseDWT(dwtTree, luminance);
yuv.set(0, luminance);
image = ImageUtil.cropImage(ImageUtil.getImageFromYuv(yuv, imgType), origWidth, origHeight);
return ImageUtil.imageToByteArray(image, stegoFileName, this);
}
/**
* Method to extract the message from the stego data
*
* @param stegoData Stego data containing the message
* @param stegoFileName Name of the stego file
* @param origSigData Optional signature data file for watermark
* @return Extracted message
* @throws OpenStegoException
*/
public byte[] extractData(byte[] stegoData, String stegoFileName, byte[] origSigData)
throws OpenStegoException {
List<Integer> sigBitList = new ArrayList<Integer>();
BufferedImage image = null;
DWT dwt = null;
ImageTree dwtTree = null;
ImageTree p = null;
Signature sig = null;
Pixel pixel1 = null;
Pixel pixel2 = null;
Pixel pixel3 = null;
int[][] luminance = null;
int cols = 0;
int rows = 0;
int n = 0;
image = ImageUtil.makeImageSquare(ImageUtil.byteArrayToImage(stegoData, stegoFileName));
cols = image.getWidth();
rows = image.getHeight();
luminance = ImageUtil.getYuvFromImage(image).get(0);
sig = new Signature(origSigData);
// Wavelet transform
dwt = new DWT(cols, rows, sig.filterID, sig.embeddingLevel, sig.waveletFilterMethod);
dwtTree = dwt.forwardDWT(luminance);
p = dwtTree;
// Consider each resolution level
while (p.getLevel() < sig.embeddingLevel) {
// Descend one level
p = p.getCoarse();
}
// Repeat binary watermark by sliding a 3-pixel window of approximation image
for (int row = 0; row < p.getImage().getHeight(); row++) {
for (int col = 0; col < p.getImage().getWidth() - 3; col += 3) {
// Get all three approximation pixels in window
pixel1 = new Pixel(0, DWTUtil.getPixel(p.getImage(), col + 0, row));
pixel2 = new Pixel(1, DWTUtil.getPixel(p.getImage(), col + 1, row));
pixel3 = new Pixel(2, DWTUtil.getPixel(p.getImage(), col + 2, row));
// Bring selected pixels in ascending order
if (pixel1.value > pixel2.value) {
swapPix(pixel1, pixel2);
}
if (pixel2.value > pixel3.value) {
swapPix(pixel2, pixel3);
}
if (pixel1.value > pixel2.value) {
swapPix(pixel1, pixel2);
}
// Apply inverse watermarking transformation to get the bit value
sigBitList.add(
invWmTransform(sig.embeddingStrength, pixel1.value, pixel2.value, pixel3.value));
n++;
}
}
sig.setWatermark(convertBitListToByteArray(sigBitList));
return sig.getSigData();
}
