docs: private void initializeDerivatives(T input) {
  		// reshape derivatives if the input image has changed size
  		if (detector.getRequiresGradient() || detector.getRequiresHessian()) {
  			derivX.reshape(input.width, input.height);
  			derivY.reshape(input.width, input.height);
  		}
  		if (detector.getRequiresHessian()) {
  			derivXX.reshape(input.width, input.height);
  			derivYY.reshape(input.width, input.height);
  			derivXY.reshape(input.width, input.height);
  		}
  	}