question: private Object [ ] invWmSubBand ( Image img , double [ ] wm , int n , double threshold ) { int m = 0 ; double z = 0.0 ; double v = 0.0 ; for ( int i = 0 ; i < img . getWidth ( ) * img . getHeight ( ) ; i ++ ) { if ( img . getData ( ) [ i ] > threshold ) { z += ( img . getData ( ) [ i ] * wm [ i % n ] ) ; v += Math . abs ( img . getData ( ) [ i ] ) ; m ++ ; } } return new Object [ ] { m , z , v } ; }
target:  Extracts the watermark data from subband