code: public static void real( TupleDesc_F64 input , TupleDesc_S8 output ) {
  		double max = 0;
  		for( int i = 0; i < input.size(); i++ ) {
  			double v = Math.abs(input.value[i]);
  			if( v > max )
  				max = v;
  		}
  
  		for( int i = 0; i < input.size(); i++ ) {
  			output.value[i] = (byte)(127.0*input.value[i]/max);
  		}
  	}
docs: Converts a floating point description with real values into the 8-bit integer descriptor by
  dividing each element in the input by the element maximum absolute value and multiplying by 127.
  
  @param input Description with elements that are all positive
  @param output Unsigned 8-bit output