docs: static public <D extends ImageGray<D>>
  	void direction2( D derivX , D derivY , GrayF32 angle )
  	{
  		if( derivX instanceof GrayF32) {
  			GradientToEdgeFeatures.direction2((GrayF32)derivX,(GrayF32)derivY,angle);
  		} else if( derivX instanceof GrayS16) {
  			GradientToEdgeFeatures.direction2((GrayS16)derivX,(GrayS16)derivY,angle);
  		} else if( derivX instanceof GrayS32) {
  			GradientToEdgeFeatures.direction2((GrayS32)derivX,(GrayS32)derivY,angle);
  		} else {
  			throw new IllegalArgumentException("Unknown input type");
  		}
  	}