docs: public static <I extends ImageGray<I>, D extends ImageGray<D>>
  	DetectLineHoughFootSubimage<I,D> houghFootSub(@Nullable ConfigHoughFootSubimage config ,
  												  Class<I> imageType ,
  												  Class<D> derivType ) {
  
  		if( config == null )
  			config = new ConfigHoughFootSubimage();
  
  		ImageGradient<I,D> gradient = FactoryDerivative.sobel(imageType,derivType);
  
  		return new DetectLineHoughFootSubimage<>(config.localMaxRadius,
  				config.minCounts, config.minDistanceFromOrigin, config.thresholdEdge,
  				config.totalHorizontalDivisions, config.totalVerticalDivisions, config.maxLines, gradient);
  	}