docs: public static <T extends ImageGray<T>>
  	T nv21ToGray( byte[] data , int width , int height ,
  				  T output , Class<T> outputType ) {
  
  		if( outputType == GrayU8.class ) {
  			return (T)nv21ToGray(data,width,height,(GrayU8)output);
  		} else if( outputType == GrayF32.class ) {
  			return (T)nv21ToGray(data,width,height,(GrayF32)output);
  		} else {
  			throw new IllegalArgumentException("Unsupported BoofCV Image Type "+outputType.getSimpleName());
  		}
  	}