/// <summary>
/// decrypts an image
/// </summary>
/// <param name="image">the image that will be dencrypted</param>
/// <param name="roIs">the Region of Interests</param>
/// <param name="password">the password used for decryption</param>
/// <param name="cryptoFlags">determines which encryption mode will be applied</param>
/// <param name="errorCode">if an error occurs this value will be set is not 0</param>
/// <returns>returns an decrypted image</returns>
public static Image DecryptJPG(Image image, IList <RoI> roIs, string password, CryptoFlags cryptoFlags, out EnumErrorCode errorCode)
{
// create JpegOperation from business logic
IBusinessLogic businessLogic = BLFactory.CreateBusinessLogic();
IJpegOperation jpegOperation = businessLogic.CreateJpegOperationBL();
// convert Image to byte array
byte[] in_jpegToDecrypt = jpegOperation.ConvertImageToByteArray(image);
Int32 in_size = in_jpegToDecrypt.Length;
// convert RoIs to the correct format
int counter = 0;
Int32[] in_roiArray = new Int32[roIs.Count() * 4];
foreach (RoI roi in roIs)
{
in_roiArray[(counter * 4) + 0] = roIs[counter].X;
in_roiArray[(counter * 4) + 1] = roIs[counter].Y;
in_roiArray[(counter * 4) + 2] = roIs[counter].Width;
in_roiArray[(counter * 4) + 3] = roIs[counter].Height;
counter++;
}
Int32 in_roiArraySize = roIs.Count() * 4;
// create MD5 hash of the password
MD5 md5 = new MD5CryptoServiceProvider();
byte[] textToHash = Encoding.Default.GetBytes(password);
byte[] in_decryptionKey = md5.ComputeHash(textToHash);
Int32 in_decryptionKeySize = in_decryptionKey.Length;
// convert crypto flags
byte in_cryptoFlags = cryptoFlags.ToByte();
// get memory for the decrypted image
byte[] out_jpegDecrypted = new byte[in_size * 2];
byte[] out_statistics = new byte[in_size];
IntPtr out_jpegDecryptedSize = new IntPtr();
int[] ia2 = new int[1];
GCHandle gch1 = GCHandle.Alloc(ia2);
out_jpegDecryptedSize = Marshal.UnsafeAddrOfPinnedArrayElement(ia2, 0);
// create a pointer for the error code (will be set from C-code)
int[] ia = new int[1];
IntPtr out_errorCode = new IntPtr();
GCHandle gch = GCHandle.Alloc(ia);
out_errorCode = Marshal.UnsafeAddrOfPinnedArrayElement(ia, 0);
// try to decrypt the image
try
{
decJpeg(
in_jpegToDecrypt,
in_size,
in_roiArray,
in_roiArraySize,
in_decryptionKey,
in_decryptionKeySize,
in_cryptoFlags,
out_jpegDecrypted,
ref out_jpegDecryptedSize,
ref out_errorCode
);
// get the error code
errorCode = ConvertIntToErrorCode(out_errorCode.ToInt32());
// truncate byte array
out_jpegDecrypted = out_jpegDecrypted.Take(out_jpegDecryptedSize.ToInt32()).ToArray();
}
catch
{
throw new EncryptionException("Error while decrypting!");
}
return(jpegOperation.ConvertByteArrayToImage(out_jpegDecrypted));
}
