How to convert detected mouth region in gray-scale and binary in android ?

Here is my code, i am not able to covert the mouth region into grayscale please help me...i have tried everything available on internet Mat innerWindow = mRgba.submat(moutharea); Imgproc.cvtColor(innerWindow, innerWindow,Imgproc.COLOR_RGB2GRAY); Imgproc.threshold( innerWindow, innerWindow,70, 255,Imgproc.THRESH_BINARY);