Problem with iText decodePredictor(byte in[], PdfObject dicPar)

Hi

I am trying to decompress a stream with filter=flatedecode and decodeparms=[predictor 12 columns 4].
I decoded the stream with FlateDecode(byte in[]) first.
Then the output is pass in to decodePredictor(byte in[], PdfObject dicPar).

I have checked that dicPar is correct.

However, the resulting byte[] from decodePredictor is incorrect (i'm expecting some readable strings).

Please help!!!!!