void RootProblem(){

  int argc = 1;
  std::string filename = "/tmp/root2.root";

  if (argc == 2){
    std::cout << "Run with dummy canvas" << std::endl;
    // only one argument given
    // -> create dummy canvas to allow root to open file(!)
    TCanvas* dummyCan = new TCanvas("dummy","dummy",600,400);
  } else if (argc == 3){
    std::cout << "Recreating root file with TH2D in canvas in draw mode \"COLZ\""
	      << std::endl;
    // two arguments
    // recreate root file, store a canvas with a TH2D in draw mode "COLZ"
    TFile* sourceFile =  new TFile(filename.c_str(),"RECREATE");

    TH2D *sourceHis = new TH2D("th2","th2",2,0,2,2,0,2);
  
    sourceHis->Fill(0.,0.,1.);
    sourceHis->Fill(0.,1.,2.);
    sourceHis->Fill(1.,0.,3.);
    sourceHis->Fill(1.,1.,4.);
       
    TCanvas* sourceCan = new TCanvas("can1","can1",600,400);
    
    sourceHis->Draw("COLZ");
    sourceCan->Modified();
    sourceCan->Update();
    sourceCan->Write();
    
    sourceFile->Close();
    delete sourceFile;

    exit(1);
  }

  // read out previously created canvas

  std::cout << "Reading root file" << std::endl;

  TFile* rootFile = new TFile(filename.c_str());

  TCanvas* readCan = 0;
  TH2D* readHis = 0;

  rootFile->GetObject("can1",readCan);
  TPad* pad5 = (TPad*) readCan->GetPad(0);
  readHis = (TH2D*) pad5->FindObject("th2");

  rootFile->Close();
}