private void EmbedWatermark(double[,] data)
{
double[,] watermarkData = new double[_watermarkPixels.Width, _watermarkPixels.Height];
for (int x = 0; x < _watermarkPixels.Width; x++)
{
for (int y = 0; y < _watermarkPixels.Height; y++)
{
watermarkData[x, y] = _watermarkPixels.R[x, y] > 125 ? 255 : 0;
}
}
ParallelHaar.FWT(data, 2);
var subband = LL2(data);
Parallel.For(0, _watermarkPixels.Height, y =>
{
for (int x = 0; x < _watermarkPixels.Width; x++)
{
var block = subband.Submatrix(x * BlockSize, x * BlockSize + BlockSize - 1, y * BlockSize, y * BlockSize + BlockSize - 1);
CosineTransform.DCT(block);
var midbandSum = Math.Max(2, Math.Abs(MidBand(block).Sum()));
var sigma = (watermarkData[x, y] > 125 ? 3 : -3);
block[1, 2] += midbandSum * sigma;
block[2, 0] += midbandSum * sigma;
block[2, 1] += midbandSum * sigma;
block[2, 2] += midbandSum * sigma;
CosineTransform.IDCT(block);
for (int i = 0; i < BlockSize; i++)
{
for (int j = 0; j < BlockSize; j++)
{
subband[x * BlockSize + i, y * BlockSize + j] = block[i, j];
}
}
}
});
BackApplySubBand(data, subband);
ParallelHaar.IWT(data, 2);
}
private WatermarkResult RetrieveWatermark(double[,] data)
{
var origWidth = data.GetUpperBound(0) + 1;
var origHeight = data.GetUpperBound(1) + 1;
if (DiffWidth - origWidth > 0 || DiffHeight - origHeight > 0)
{
var top = (DiffHeight - origHeight) / 2;
var left = (DiffWidth - origWidth) / 2;
var bottom = (DiffHeight - origHeight) - top;
var right = (DiffWidth - origWidth) - left;
data = data.Pad(left, top, right, bottom);
}
double[,] recoveredWatermarkData = new double[_watermarkPixels.Width, _watermarkPixels.Height];
ParallelHaar.FWT(data, 2);
var subband = LL2(data);
var width = subband.GetUpperBound(0) + 1;
var height = subband.GetUpperBound(1) + 1;
Parallel.For(0, _watermarkPixels.Height, y =>
{
for (int x = 0; x < _watermarkPixels.Width; x++)
{
if (x * BlockSize + BlockSize > width)
{
return;
}
if (y * BlockSize + BlockSize > height)
{
return;
}
var block = subband.Submatrix(x * BlockSize, x * BlockSize + BlockSize - 1, y * BlockSize, y * BlockSize + BlockSize - 1);
CosineTransform.DCT(block);
recoveredWatermarkData[x, y] = (MidBand(block).Sum() > 0) ? 255 : 0;
}
});
double similiar = 0;
double total = (width / 4) * (height / 4);
for (int x = 0; x < _watermarkPixels.Width; x++)
{
for (int y = 0; y < _watermarkPixels.Height; y++)
{
var oldValue = _watermarkPixels.R[x, y] > 125 ? 255 : 0;
if (recoveredWatermarkData[x, y] == oldValue)
{
similiar++;
}
}
}
var similarity = Math.Round((similiar / total) * 100);
var recoveredData = new RgbData(recoveredWatermarkData);
var recoveredWatermarkBytes = _imageHelper.SavePixels(recoveredData);
return(new WatermarkResult(similarity, recoveredWatermarkBytes));
}