public Dictionary<int, byte> Encode(byte[] message, string savePath)
{
List<byte> data = new List<byte>();
data.AddRange(BitConverter.GetBytes(message.Length));
data.AddRange(message);
if (!MessageFitsImage(data)) {
throw new ArgumentException("Message is too big to encode in the image.");
}
BinaryList bits = new BinaryList(data);
if (InvertBits)
bits.Invert();
LockedBitmap lockedBmp = new LockedBitmap(BitmapImage);
lockedBmp.LockBits();
Dictionary<int, byte> changes = new Dictionary<int, byte>();
int bitIndex = 0;
for (int pixelIndex = Seed[0]; pixelIndex <= (BitmapImage.Height * BitmapImage.Width) && bitIndex < bits.Count; pixelIndex += (Seed[bitIndex % Seed.Count] + 1)) {
byte[] pixelValue = lockedBmp.GetPixelArgb(pixelIndex);
BinaryOctet octet = pixelValue[(int)Color];
for (int currBit = 0; currBit < lsb; ++currBit)
octet = octet.SetBit(currBit, bits[bitIndex++]);
if (octet != pixelValue[(int)Color]) {
changes.Add(pixelIndex, pixelValue[(int)Color]);
pixelValue[(int)Color] = octet;
}
lockedBmp.SetPixel(PixelCoord(pixelIndex, BitmapImage.Width), pixelValue);
}
lockedBmp.UnlockBits();
BitmapImage.Save(savePath, ImageFormat.Png);
return changes;
}
private IEnumerable<byte> ReadBits(int byteCount)
{
BinaryList data = new BinaryList();
LockedBitmap lockedBmp = new LockedBitmap(BitmapImage);
lockedBmp.LockBits();
int bitIndex = 0;
for (int pixelIndex = Seed[0]; bitIndex < byteCount * 8; pixelIndex += (Seed[bitIndex % Seed.Count] + 1)) {
BinaryOctet octet = lockedBmp.GetPixelArgb(pixelIndex)[(int)Color];
for (byte currBit = 0; currBit < lsb; ++currBit, ++bitIndex)
data.Add(octet[currBit]);
}
lockedBmp.UnlockBits();
return data.ToBytes(InvertBits);
}