IEnumerable <byte> GetFormatedData(BitStream bitStream, UsedBitCount usedBitCount)
{
int count = 0;
switch (usedBitCount)
{
case UsedBitCount.One:
count = 1;
break;
case UsedBitCount.Two:
count = 2;
break;
}
bool isEnd;
byte shiftedByte;
do
{
// count * 3 nes piksely yra 3 baitai: RGB, o mes naudojam count kiekį bitų vienam baitui
(isEnd, shiftedByte) = ShiftInBytes(bitStream, count * 3);
yield return(shiftedByte);
}while (!isEnd);
}
public string ReadImage(string imageFileName, UsedBitCount usedBitCount)
{
bool pushTwoBitPerByte = false;
switch (usedBitCount)
{
case UsedBitCount.One:
pushTwoBitPerByte = false;
break;
case UsedBitCount.Two:
pushTwoBitPerByte = true;
break;
}
Bitmap bitmap = GetBitmap(imageFileName);
BitCollector bitCollector = new BitCollector();
for (int i = 0; i < bitmap.Width; i++)
{
for (int j = 0; j < bitmap.Height; j++)
{
var pixel = bitmap.GetPixel(i, j);
// alpha chanelis daro kažkokias nesąmones :D. Reiks išsiaiškint
if (pixel.A < ALPHA_CHANNEL_LIMIT)
{
continue;
}
if (pushTwoBitPerByte)
{
bitCollector.PushBit((pixel.R >> 1) & 0b0000_0001);
}
bitCollector.PushBit(pixel.R & 0b0000_0001);
if (pushTwoBitPerByte)
{
bitCollector.PushBit((pixel.G >> 1) & 0b0000_0001);
}
bitCollector.PushBit(pixel.G & 0b0000_0001);
if (pushTwoBitPerByte)
{
bitCollector.PushBit((pixel.B >> 1) & 0b0000_0001);
}
bitCollector.PushBit(pixel.B & 0b0000_0001);
}
}
return(Encoding.ASCII.GetString(bitCollector.GetBuffer()));
}
public void EncodeMessage(string message, string imageFileName, UsedBitCount bitCountToUse)
{
Bitmap bitmap = GetBitmap(imageFileName);
bitmap.Save(imageFileName + ".orig");
BitStream msgData = new BitStream(Encoding.ASCII.GetBytes(message));
//jeigu neužtenka baitų paveikslėlyje
if (bitmap.Width * bitmap.Height < (msgData.Length / (int)bitCountToUse))
{
throw new Exception("image not big enough for message to fit"); //TODO (never :) ) handle dis
}
// j i --->
// |
// *
for (int i = 0; i < bitmap.Width; i++)
{
for (int j = 0; j < bitmap.Height; j++)
{
Color pixelColor = bitmap.GetPixel(i, j);
// alpha chanelis daro kažkokias nesąmones :D. Reiks išsiaiškint
if (pixelColor.A < ALPHA_CHANNEL_LIMIT)
{
continue;
}
var(isEnd, newPixel) = InjectDataIntoPixel(pixelColor, msgData, bitCountToUse);
bitmap.SetPixel(i, j, newPixel);
// jeigu nebeturim daugiau message
if (isEnd)
{
bitmap.Save(imageFileName + ".steg");
return;
}
}
}
}
// byte data naudoja tik (usedBitCount) kiekį duomenų
public (bool end, Color pixel) InjectDataIntoPixel(Color pixelToSet, BitStream data, UsedBitCount usedBitCount)
{
byte shiftInCount = (byte)usedBitCount;
var(end, temp) = ShiftInBytes(data, shiftInCount);
int newR = ZeroOutBottomBits(pixelToSet.R, shiftInCount) | temp;
(end, temp) = ShiftInBytes(data, shiftInCount);
int newG = ZeroOutBottomBits(pixelToSet.G, shiftInCount) | temp;
(end, temp) = ShiftInBytes(data, shiftInCount);
int newB = ZeroOutBottomBits(pixelToSet.B, shiftInCount) | temp;
return(end, Color.FromArgb(pixelToSet.A, newR, newG, newB));
}
