public FileModel Demux(IImageWrapper source)
{
Pixel[,] dataSet = new Pixel[source.Width, source.Height];
for (var x = 0; x < source.Width; ++x)
{
for (var y = 0; y < source.Height; ++y)
{
Pixel p = new Pixel();
p.R = source.GetRedAtPosition(x, y);
p.G = source.GetGreenAtPosition(x, y);
p.B = source.GetBlueAtPosition(x, y);
dataSet[x, y] = p;
}
}
return(demuxxImage(dataSet));
}
private Pixel[,] muxxImageAndFile(FileModel fileModel, IImageWrapper container)
{
// warning, this is very verbose code.
// i could have written this in linq much more elegantly,
// however i wrote this so that others can pick it up without needing to know c# / linq / lambdas
if (!this.encryptionFeasible(fileModel, container))
{
throw new Exception("image is too small to hide this file in");
}
int byteSpread = this.getByteSpread();
int bitShiftCount = (BITS_PER_CHANNEL - BITS_USED_PER_CHANNEL);
int maxValue = (0x01 << BITS_PER_CHANNEL) - 0x01;
int partMask = maxValue >> bitShiftCount;
int visibleMask = (byte)(maxValue << (0x08 - bitShiftCount));
var header = new EncryptionHeader();
header.FileName = fileModel.FileName;
header.FileSize = (int)fileModel.FileContents.Length;
var headerBytesUnspread = header.ToBytes();
var fileBytesUnspread = new byte[fileModel.FileContents.Length];
fileModel.FileContents.Read(fileBytesUnspread, 0, (int)fileModel.FileContents.Length);
var unspreadBytes = new byte[headerBytesUnspread.Length + fileBytesUnspread.Length];
var spreadBytes = new byte[unspreadBytes.Length * byteSpread];
int unspreadIndex = 0;
for (var i = 0; i < headerBytesUnspread.Length; ++i)
{
unspreadBytes [unspreadIndex] = headerBytesUnspread [i];
++unspreadIndex;
}
for (var i = 0; i < fileBytesUnspread.Length; ++i)
{
unspreadBytes [unspreadIndex] = fileBytesUnspread [i];
++unspreadIndex;
}
int spreadIndex = 0;
for (var i = 0; i < unspreadBytes.Length; ++i)
{
var toSpread = unspreadBytes [i];
for (var s = 0; s < byteSpread; ++s) // going least significant bit to most
{
var spreadShift = s * BITS_USED_PER_CHANNEL;
var shifted = toSpread >> spreadShift;
var masked = shifted & partMask;
spreadBytes [spreadIndex] = (byte)masked;
++spreadIndex;
}
}
// sanity check
var maxSpreadValue = (0x01 << (BITS_USED_PER_CHANNEL)) - 1;
for (var i = 0; i < spreadBytes.Length; ++i)
{
var sb = spreadBytes [i];
if (sb > maxSpreadValue)
{
throw new Exception("the author is a moron");
}
}
Pixel[,] dataSet = new Pixel[container.Width, container.Height];
var numberOfChannels = Enum.GetValues(typeof(LosslessFileMuxxer.ByteOrder)).GetLength(0);
var channelIndex = 0;
spreadIndex = 0;
var rand = new Random(Guid.NewGuid().GetHashCode());
var randomiseNonDatasetBytes = false;
for (var x = 0; x < container.Width; ++x)
{
for (var y = 0; y < container.Height; ++y)
{
Pixel p = new Pixel();
p.R = container.GetRedAtPosition(x, y);
p.G = container.GetGreenAtPosition(x, y);
p.B = container.GetBlueAtPosition(x, y);
if (spreadIndex < spreadBytes.Length)
{
for (var c = 0; c < numberOfChannels; ++c)
{
if (spreadIndex < spreadBytes.Length)
{
var byteToHide = spreadBytes [spreadIndex];
var whichChannel = (ByteOrder)channelIndex;
switch (whichChannel)
{
case ByteOrder.Red:
p.R = (byte)(((int)p.R & visibleMask) + byteToHide);
break;
case ByteOrder.Green:
p.G = (byte)(((int)p.G & visibleMask) + byteToHide);
break;
case ByteOrder.Blue:
p.B = (byte)(((int)p.B & visibleMask) + byteToHide);
break;
}
channelIndex = channelIndex == numberOfChannels - 1 ? 0 : channelIndex + 1;
++spreadIndex;
}
else
{
if (randomiseNonDatasetBytes)
{
// not a data pixel, give it a random value
var newVal = rand.Next(0, maxSpreadValue);
p.R = (byte)(((int)p.R & visibleMask) + newVal);
newVal = rand.Next(0, maxSpreadValue);
p.G = (byte)(((int)p.G & visibleMask) + newVal);
newVal = rand.Next(0, maxSpreadValue);
p.B = (byte)(((int)p.B & visibleMask) + newVal);
}
}
}
}
else
{
if (randomiseNonDatasetBytes)
{
// not a data pixel, give it a random value
var newVal = rand.Next(0, maxSpreadValue);
p.R = (byte)(((int)p.R & visibleMask) + newVal);
newVal = rand.Next(0, maxSpreadValue);
p.G = (byte)(((int)p.G & visibleMask) + newVal);
newVal = rand.Next(0, maxSpreadValue);
p.B = (byte)(((int)p.B & visibleMask) + newVal);
}
}
dataSet [x, y] = p;
}
}
return(dataSet);
}
