/// <summary>
/// This function decode and extract the payload from an image
/// </summary>
/// <param name="ImageFileName">Image File Name</param>
/// <param name="OriginalFileName">returns the Decoded Payload File Name</param>
/// <param name="passphrase">Passphrase for data decryption</param>
/// <param name="hash">return the file hash</param>
/// <returns>Payload data</returns>
static public byte[] Decode(string ImageFileName, ref string OriginalFileName, string passphrase, ref byte[] hash)
{
PayloadFile payload = new PayloadFile();
Bitmap Image = new Bitmap(ImageFileName);
payload = GetPayloadFromImage(Image, passphrase);
OriginalFileName = payload.Filename;
hash = payload.hash;
return(payload.data);
}
/// <summary>
/// This Function extract a Payload Data from an RGB Image
/// </summary>
/// <param name="Image">RGB Image Data</param>
/// <param name="passphrase">Passphrase to decrypt data</param>
/// <returns></returns>
static PayloadFile GetPayloadFromImage(Bitmap Image, string passphrase)
{
int height = Image.Height;
int width = Image.Width;
PayloadFile payload = new PayloadFile();
MemoryStream str = new MemoryStream();
for (int i = 0; i < height; i++)
{
for (int j = 0; j < width; j++)
{
Int32 pixel = Image.GetPixel(j, i).ToArgb();
str.WriteByte(GetByteFromPixel(pixel));
}
}
if (passphrase != "")
{
byte[] cipherByte = str.ToArray();
int cipherTextLength = (cipherByte.Length - 32) / 16;
cipherTextLength = (cipherTextLength + 1) * 16;
Array.Resize(ref cipherByte, cipherTextLength);
str = new MemoryStream(Crypto.Decrypt(cipherByte, passphrase));
}
str.Seek(0, SeekOrigin.Begin);
byte[] temp = new byte[4];
str.Read(temp, 0, 4);
UInt32 FileSize = BitConverter.ToUInt32(temp, 0);
str.Read(temp, 0, 4);
UInt32 FileNameLen = BitConverter.ToUInt32(temp, 0);
byte[] buffer = new byte[FileNameLen];
str.Read(buffer, 0, (int)FileNameLen);
payload.Filename = System.Text.ASCIIEncoding.ASCII.GetString(buffer);
payload.data = new byte[FileSize];
str.Read(payload.data, 0, (int)FileSize);
payload.hash = new byte[32];
str.Read(payload.hash, 0, 32);
str.Close();
return(payload);
}
