/// <summary>
/// Reads an image from filepath and encrypts its pixel content (This does not encrypt the image header!)
/// Refer MSDN article on BitmapData class for details about reading & writing pixes in an image.
/// Link: https://msdn.microsoft.com/en-us/library/system.drawing.imaging.bitmapdata.aspx#Examples
/// </summary>
/// <param name="filePath"></param>
/// <returns></returns>
public static Bitmap EncryptImage(this string filePath, CipherMode cipherMode)
{
try
{
Bitmap bmp = new Bitmap(Bitmap.FromFile(filePath)); // Pick image from file path
// Lock the bitmap's bits.
Rectangle rect = new Rectangle(0, 0, bmp.Width, bmp.Height);
System.Drawing.Imaging.BitmapData bmpData =
bmp.LockBits(rect, System.Drawing.Imaging.ImageLockMode.ReadWrite,
bmp.PixelFormat);
// Get the address of the first line.
IntPtr ptr = bmpData.Scan0;
// Declare an array to hold the bytes of the bitmap.
int bytes = Math.Abs(bmpData.Stride) * bmp.Height;
byte[] contentBytes = new byte[bytes];
// Copy the content bytes into the array (This does not copy the image header!).
System.Runtime.InteropServices.Marshal.Copy(ptr, contentBytes, 0, bytes);
byte[] modifiedBytes = null;
// Modify the bytes
switch (cipherMode)
{
case CipherMode.CBC:
modifiedBytes = BlockCipher.Encrypt(contentBytes, CipherMode.CBC);
break;
case CipherMode.ECB:
modifiedBytes = BlockCipher.Encrypt(contentBytes, CipherMode.ECB);
break;
default: break;
}
_encryptedBytes = modifiedBytes; // Store the encrypted bytes in memory, for later use in decryption routine.
_bytes = bytes;
// Copy the modified values back to the bitmap
System.Runtime.InteropServices.Marshal.Copy(modifiedBytes, 0, ptr, bytes);
// Unlock the bits.
bmp.UnlockBits(bmpData);
return(bmp);
}
catch (Exception ex)
{
throw ex;
}
}
public static Image DecryptImage(this Bitmap bmp, CipherMode cipherMode)
{
try
{
// Lock the bitmap's bits.
Rectangle rect = new Rectangle(0, 0, bmp.Width, bmp.Height);
System.Drawing.Imaging.BitmapData bmpData =
bmp.LockBits(rect, System.Drawing.Imaging.ImageLockMode.ReadWrite,
bmp.PixelFormat);
// Get the address of the first line.
IntPtr ptr = bmpData.Scan0;
// Fetch the bytes to modify from the content stored during encryption
int bytes = _bytes;
byte[] contentBytes = _encryptedBytes;
// Copy the content bytes into the array (This does not copy the image header!).
// System.Runtime.InteropServices.Marshal.Copy(ptr, contentBytes, 0, bytes);
// Modify the bytes
byte[] modifiedBytes = null;
// Modify the bytes
switch (cipherMode)
{
case CipherMode.CBC:
modifiedBytes = BlockCipher.Decrypt(contentBytes, CipherMode.CBC);
break;
case CipherMode.ECB:
modifiedBytes = BlockCipher.Decrypt(contentBytes, CipherMode.ECB);
break;
default: break;
}
// Copy the modified values back to the bitmap
System.Runtime.InteropServices.Marshal.Copy(modifiedBytes, 0, ptr, bytes);
// Unlock the bits.
bmp.UnlockBits(bmpData);
return(bmp);
}
catch (Exception ex)
{
throw ex;
}
}
