code: public double computePower(int idx){
  		double r = real[idx];
  		double i = imag[idx];
  		power[idx] = r*r+i*i;
  		return power[idx];
  	}
docs: Calculates, stores and returns the power at the specified index.
  The power is the squared magnitude of the complex number ( cmplx=a+bi  power=a*a+b*b ).
  Subsequent calls to e.g. {@link #getValueP_atIndex(int)} will return the stored result.
  @param idx index
  @return power of pixel at index