docs: private void createSparseDerivatives() {
  		Kernel1D_F32 kernelD = new Kernel1D_F32(new float[]{-1,0,1},3);
  
  		Kernel1D_F32 kernelDD = KernelMath.convolve1D_F32(kernelD, kernelD);
  		Kernel2D_F32 kernelXY = KernelMath.convolve2D(kernelD, kernelD);
  
  		derivXX = FactoryConvolveSparse.horizontal1D(GrayF32.class, kernelDD);
  		derivXY = FactoryConvolveSparse.convolve2D(GrayF32.class, kernelXY);
  		derivYY = FactoryConvolveSparse.vertical1D(GrayF32.class, kernelDD);
  
  		ImageBorder<GrayF32> border = FactoryImageBorder.single(GrayF32.class, BorderType.EXTENDED);
  
  		derivXX.setImageBorder(border);
  		derivXY.setImageBorder(border);
  		derivYY.setImageBorder(border);
  	}