docs: public static <T extends ImageGray<T>,D extends ImageGray<D>>
  	TrackerObjectQuad<T> sparseFlow(SfotConfig config, Class<T> imageType , Class<D> derivType ) {
  
  		if( derivType == null )
  			derivType = GImageDerivativeOps.getDerivativeType(imageType);
  
  		if( config == null )
  			config = new SfotConfig();
  
  		ImageGradient<T, D> gradient = FactoryDerivative.sobel(imageType,derivType);
  
  		SparseFlowObjectTracker<T,D> tracker = new SparseFlowObjectTracker<>(config, imageType, derivType, gradient);
  
  		return new Sfot_to_TrackObjectQuad<>(tracker, imageType);
  	}