code: public static <I extends ImageGray<I>, D extends ImageGray<D>>
  	AnyImageDerivative<I,D> derivativeForScaleSpace( Class<I> inputType , Class<D> derivType ) {
  		return createAnyDerivatives(DerivativeType.THREE,inputType,derivType);
  	}
docs: Creates an instance of {@link AnyImageDerivative} which is intended for use of calculating scale-spaces.
  It uses {@link DerivativeType#THREE} since it does not blur the image.  More typical operators, such as Sobel and
  Prewitt, blur the image.
  
  @param inputType Type of input image.
  @param derivType Type of derivative image
  @param <I> Image type.
  @param <D> Image derivative type.
  @return AnyImageDerivative