/**
* Masks a file with an image given a file and image.
*/
public static string[] Mask(string file, string image)
{
//Create a new Bitmap objects and map pixels/bits.
var img = new Bitmap(image);
Color[] pixels = GetPixels(img);
var pixelBits = new int[pixels.Length];
for (int n = 0, length = pixels.Length; n < length; n++)
pixelBits[n] = Util.ColorToBits(pixels[n]);
//Read all bits from the file to mask.
byte[] bytes = File.ReadAllBytes(file);
var bits = new BitArray(bytes);
//Merge bits.
var tour = new Tour(img.Width, img.Height);
pixelBits = Merge(bits, tour, pixelBits);
//Generate pixel colors based on each the merged bits.
for (int n = 0, length = pixelBits.Length; n < length; n++)
pixels[n] = Util.BitsToColor(pixelBits[n]);
Bitmap maskedImage = CreateImage(img.Width, img.Height, pixels);
//Save the new image.
string dir = Path.GetDirectoryName(image);
string name = Path.GetFileNameWithoutExtension(image);
string extension = Path.GetExtension(image);
Benchmark mark = new Benchmark("Time to Write Masked File", true);
maskedImage.Save(dir + "\\" + name + " - Masked" + extension);
mark.Time();
//Generate AES keys and return.
mark = new Benchmark("Time to Generate Encryption Keys", true);
string[] hash = Crypt.Encrypt(Path.GetFileName(file) + ":" + bits.Length + ":" + tour.Export());
mark.Time();
return hash;
}
/**
* Creates a file given an image and a valid hash and key.
*/
public static void Unmask(string image, string hash, string key)
{
//Create a new Bitmap object and decrypt the AES hash.
var img = new Bitmap(image);
string info = Crypt.Decrypt(hash, key);
if (info != null)
{
string name = info.Split(':')[0];
int size = int.Parse(info.Split(':')[1]);
var tour = new Tour(img.Width, img.Height);
Square path = tour.Import(info.Split(':')[2]);
//Get pixel data and extract bits from the data.
Color[] pixels = GetPixels(img);
var pixelBits = new int[pixels.Length];
for (int n = 0, length = pixels.Length; n < length; n++)
pixelBits[n] = Util.ColorToBits(pixels[n]);
var file = new byte[size/8];
Extract(pixelBits, tour, path, size).CopyTo(file, 0);
//Write the bits to a file.
File.WriteAllBytes(Path.GetDirectoryName(image) + "\\" + name, file);
}
}
/**
* Merges colors represented as 32-bit integers with an array of bits
* from a given file.
*/
private static int[] Merge(BitArray bits, Tour tour, int[] pixels)
{
//Clone pixels to prevent destruction.
var newPixels = (int[]) pixels.Clone();
Benchmark mark = new Benchmark("Time to Generate Tour", true);
Square start = tour.CreateTour();
Square current = start;
mark.Time();
mark = new Benchmark("Time to Modify Pixel Channels", true);
for (int n = 0, length = bits.Length; n < length; n += 3)
{
//Calculate the bit depth to use.
int depth = n/newPixels.Length;
//Select the pixel to operate on and get the color channels.
int index = Util.ToIndex(tour.Width, current.X, current.Y);
int pixel = newPixels[index];
//Get channel values and create a bool representation.
int r = (pixel >> 16) & 0xFF;
int g = (pixel >> 8) & 0xFF;
int b = pixel & 0xFF;
bool red = bits[n];
bool green = n + 1 < length && bits[n + 1];
bool blue = n + 2 < length && bits[n + 2];
//Set pixel channel values based on the above bools.
if (red) r = r | 1 << depth;
else r = r & ~(1 << depth);
if (green) g = g | 1 << depth;
else g = g & ~(1 << depth);
if (blue) b = b | 1 << depth;
else b = b & ~(1 << depth);
newPixels[index] = Util.BitsToColor(r, g, b);
//Select the next pixel to manipulate.
current = current.Next ?? start;
}
mark.Time();
return newPixels;
}
/**
* Returns a BitArray object containing the bits extracted from
* the pixel array "bits".
*/
private static BitArray Extract(int[] bits, Tour tour, Square path, int size)
{
var file = new BitArray(size);
Square start = path;
for (int n = 0; n < size; n += 3)
{
int depth = n/bits.Length;
int index = Util.ToIndex(tour.Width, path.X, path.Y);
Color color = Util.BitsToColor(bits[index]);
int r = color.R;
int g = color.G;
int b = color.B;
r = r & 1 << depth;
g = g & 1 << depth;
b = b & 1 << depth;
file.Set(n, Util.IntToBool(r));
if (n + 1 < size) file.Set(n + 1, Util.IntToBool(g));
if (n + 2 < size) file.Set(n + 2, Util.IntToBool(b));
//Select the next pixel to read from.
path = path.Next ?? start;
}
return file;
}
