docs: public static KernelBase lookupKernelX( DerivativeType type , boolean isInteger) {
  		switch( type ) {
  			case PREWITT:
  				return GradientPrewitt.getKernelX(isInteger);
  
  			case SOBEL:
  				return GradientSobel.getKernelX(isInteger);
  
  			case THREE:
  				return GradientThree.getKernelX(isInteger);
  
  			case TWO_0:
  				return GradientTwo0.getKernelX(isInteger);
  
  			case TWO_1:
  				return GradientTwo1.getKernelX(isInteger);
  		}
  
  		throw new IllegalArgumentException("Unknown kernel type: "+type);
  	}