/// <summary>
/// Stenographically hide a file in an image.
/// </summary>
/// <param name="image">The image to hide stuff in.</param>
/// <param name="file">The file to hide in the image.</param>
/// <param name="quality">The number of bits per byte to encode data into. (1-8)</param>
/// <exception cref="OutOfMemoryException"></exception>
/// <example>
/// // Format the image for encoding
/// Image originalImage = Bitmap.FromFile("image.bmp");
/// Bitmap image = new Bitmap(originalImage.Width, originalImage.Height);
/// Graphics g = Graphics.FromImage(image);
/// g.DrawImage(originalImage, 0, 0, originalImage.Width, originalImage.Height);
/// TP_Stenography.EncodeImage(image, new TP_File("secret.txt", "password"), 1);
/// image.Save("output.bmp", System.Drawing.Imaging.ImageFormat.Bmp);
/// </example>
static public void EncodeImage(Bitmap image, TP_File file, int quality)
{
// Prepare the image for direct access
BitmapData bmData = image.LockBits(new Rectangle(0, 0, image.Width, image.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);
int stride = bmData.Stride;
IntPtr Scan0 = bmData.Scan0;
int nOffset = stride - image.Width * 3;
int data; // Represents 3 bytes of input data
byte[] bits = new byte[24]; // Represents 24 bits from the 3 bytes of input data
byte r, g, b; // Pixel color values (in RGB)
int xloc = 0; // The X location of the working pixel in the image
int yloc = 0; // The Y location of the working pixel in the image
int bit = 0; // The bit location we are encoding data into
byte mask = 0x01; // The bit mask for where we are encoding data into
// Make sure the file to encode into the image is padded to groups of 3 bytes
file.PadFileBytes();
// Make sure the image is large enough to hold the data file
if (GetImageCapacity(image) * quality < file.Contents.Length)
{
throw new FileTooLargeForImageException();
}
unsafe // :)
{
// The pointer to the Bitmap pixel data of the image
byte *p = (byte *)(void *)Scan0;
for (int i = 0; i < file.Contents.Length; i += 3)
{
// Read in 3 bytes of data from the file to be hidden as an int
data = file.Contents[i] << 16;
data |= file.Contents[i + 1] << 8;
data |= file.Contents[i + 2];
// Isolate 24 bits (from the 3 bytes) into an array
for (int j = 0; j < 24; j++)
{
bits[j] = (byte)((data >> (24 - j - 1)) & 1);
}
// Loop through the pixels and change the color's low order bit to a data bit
for (int location = 0; location < 8 * 3; location += 3)
{
// Get the RGB parts of the next pixel (It's actually stored as BGR, thus the indices)
r = p[2];
g = p[1];
b = p[0];
// Clear bit we are going to write to
r &= (byte)(0xFF - mask);
g &= (byte)(0xFF - mask);
b &= (byte)(0xFF - mask);
// Set bits to a piece of data
r |= (byte)(bits[location] << bit);
g |= (byte)(bits[location + 1] << bit);
b |= (byte)(bits[location + 2] << bit);
// Save the pixel back to the image
p[2] = r;
p[1] = g;
p[0] = b;
// Increment the location of the pixels we are writing to (3 bytes)
p += 3;
// If we reach the end of a row, adjust the pointer further
xloc++;
if (xloc >= image.Width)
{
p += nOffset;
xloc = 0;
yloc++;
if (yloc >= image.Height)
{
// Start at the beginning of the image again
p = (byte *)(void *)Scan0;
xloc = 0;
yloc = 0;
// Use the next up bit in each pixel
bit++;
mask *= 2;
}
}
}
}
}
image.UnlockBits(bmData);
return;
}
/// <summary>
/// Stenographically hide a file in an image.
/// </summary>
/// <param name="image">The image to hide stuff in.</param>
/// <param name="file">The file to hide in the image.</param>
/// <param name="quality">The number of bits per byte to encode data into. (1-8)</param>
/// <exception cref="OutOfMemoryException"></exception>
/// <example>
/// // Format the image for encoding
/// Image originalImage = Bitmap.FromFile("image.bmp");
/// Bitmap image = new Bitmap(originalImage.Width, originalImage.Height);
/// Graphics g = Graphics.FromImage(image);
/// g.DrawImage(originalImage, 0, 0, originalImage.Width, originalImage.Height);
/// TP_Stenography.EncodeImage(image, new TP_File("secret.txt", "password"), 1);
/// image.Save("output.bmp", System.Drawing.Imaging.ImageFormat.Bmp);
/// </example>
public static void EncodeImage(Bitmap image, TP_File file, int quality)
{
// Prepare the image for direct access
BitmapData bmData = image.LockBits(new Rectangle(0, 0, image.Width, image.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);
int stride = bmData.Stride;
IntPtr Scan0 = bmData.Scan0;
int nOffset = stride - image.Width * 3;
int data; // Represents 3 bytes of input data
byte[] bits = new byte[24]; // Represents 24 bits from the 3 bytes of input data
byte r, g, b; // Pixel color values (in RGB)
int xloc = 0; // The X location of the working pixel in the image
int yloc = 0; // The Y location of the working pixel in the image
int bit = 0; // The bit location we are encoding data into
byte mask = 0x01; // The bit mask for where we are encoding data into
// Make sure the file to encode into the image is padded to groups of 3 bytes
file.PadFileBytes();
// Make sure the image is large enough to hold the data file
if (GetImageCapacity(image) * quality < file.Contents.Length)
throw new FileTooLargeForImageException();
unsafe // :)
{
// The pointer to the Bitmap pixel data of the image
byte* p = (byte*)(void*)Scan0;
for (int i = 0; i < file.Contents.Length; i += 3)
{
// Read in 3 bytes of data from the file to be hidden as an int
data = file.Contents[i] << 16;
data |= file.Contents[i + 1] << 8;
data |= file.Contents[i + 2];
// Isolate 24 bits (from the 3 bytes) into an array
for (int j = 0; j < 24; j++)
bits[j] = (byte)((data >> (24 - j - 1)) & 1);
// Loop through the pixels and change the color's low order bit to a data bit
for (int location = 0; location < 8 * 3; location+=3)
{
// Get the RGB parts of the next pixel (It's actually stored as BGR, thus the indices)
r = p[2];
g = p[1];
b = p[0];
// Clear bit we are going to write to
r &= (byte)(0xFF - mask);
g &= (byte)(0xFF - mask);
b &= (byte)(0xFF - mask);
// Set bits to a piece of data
r |= (byte)(bits[location] << bit);
g |= (byte)(bits[location + 1] << bit);
b |= (byte)(bits[location + 2] << bit);
// Save the pixel back to the image
p[2] = r;
p[1] = g;
p[0] = b;
// Increment the location of the pixels we are writing to (3 bytes)
p += 3;
// If we reach the end of a row, adjust the pointer further
xloc++;
if (xloc >= image.Width)
{
p += nOffset;
xloc = 0;
yloc++;
if (yloc >= image.Height)
{
// Start at the beginning of the image again
p = (byte*)(void*)Scan0;
xloc = 0;
yloc = 0;
// Use the next up bit in each pixel
bit++;
mask *= 2;
}
}
}
}
}
image.UnlockBits(bmData);
return;
}
