PointXYZRGB to CIELab conversion

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I get this error:

/home/dinesh/catkin_ws_pcl/src/my_pcl_tutorial/src/godgift.cpp:48:41: error: no matching function for call to ‘pcl::NormalEstimation<pcl::PointXYZRGB, pcl::Normal>::setInputCloud(pcl::PointCloud<pcl::PointXYZRGB>&)’
    normalEstimation.setInputCloud(output);

when i try to run below code:

void
cloud_cb (const sensor_msgs::PointCloud2ConstPtr& input)
{

    pcl::PointCloud<pcl::PointXYZRGB> output;
    pcl::fromROSMsg(*input,output);
    pcl::PointCloud<pcl::Normal>::Ptr normals;
     pcl::PointCloud<pcl::SHOT1344>::Ptr descriptors;
pcl::PointXYZRGB p[400][400];

for(int i=0;i<400;i++)
{
  for(int j=0;j<400;j++)
    {
      p[i][j] = output.at(i,j);

  }
 }



pcl::NormalEstimation<pcl::PointXYZRGB, pcl::Normal> normalEstimation;



normalEstimation.setInputCloud(output);
        normalEstimation.setRadiusSearch(0.03);
      pcl::search::KdTree<pcl::PointXYZRGB>::Ptr kdtree;
     normalEstimation.setSearchMethod(kdtree);
            normalEstimation.compute(*normals);
     pcl::SHOTColorEstimation<pcl::PointXYZRGB, pcl::Normal, pcl::SHOT1344> shot;
        shot.setInputCloud(output);
        shot.setInputNormals(normals);
 shot.setRadiusSearch(0.02);

        shot.compute(*descriptors);
  std::cout<<"rgb"<<"\t"<<p[200][200].x<<"\t"<<p[200][200].r<<std::endl;
}

which i got from pcl forum but, i dont understand how do i use this. I want to somehow access lab values of color instead of rgb. Im using ros indigo, this are for the computer vision purpose. I also tried this methode but the values only comes zero.

    pcl::PointCloud<pcl::PointXYZRGB> output;
    pcl::fromROSMsg(*input,output);
    pcl::PointCloud<pcl::PointXYZLAB> cloud;
    pcl::copyPointCloud(output,cloud);

    pcl::PointXYZLAB  p;
 p = output.at(400,300);
 std::cout<<p.L<<"\t"<<p.a<<"\t"<<p.b<<std::endl;