docs: public static void fillBorder(GrayF64 input, double value, int radius ) {
  
  		// top and bottom
  		for (int y = 0; y < radius; y++) {
  			int indexTop = input.startIndex + y * input.stride;
  			int indexBottom = input.startIndex + (input.height-y-1) * input.stride;
  			for (int x = 0; x < input.width; x++) {
  				input.data[indexTop++] = value;
  				input.data[indexBottom++] = value;
  			}
  		}
  
  		// left and right
  		int h = input.height-radius;
  		int indexStart = input.startIndex + radius*input.stride;
  		for (int x = 0; x < radius; x++) {
  			int indexLeft = indexStart + x;
  			int indexRight = indexStart + input.width-1-x;
  			for (int y = radius; y < h; y++) {
  				input.data[indexLeft] = value;
  				input.data[indexRight] = value;
  				
  				indexLeft += input.stride;
  				indexRight += input.stride;
  			}
  		}
  	}