For this you should have to encrypt the image using linear algebra techniques. convert your image in matrix and then reverse this mat for encryption or you have many techniques to encrypt this mat.Some thing like this.
public byte[] getBytesFromBitmap(Bitmap bitmap) {
ByteArrayOutputStream stream = new ByteArrayOutputStream();
bitmap.compress(CompressFormat.JPEG, 70, stream);
return stream.toByteArray();
}
hope this will help.