void large_ps()
{
    auto c1 = new TCanvas("c1","c1",500,500);
    auto box = new TBox(0.1,0.1,0.9,0.9);
    box->SetFillColor(kYellow);
    box->SetFillStyle(1001);
    c1->Add(box);

    TPostScript ps1("large.ps");

    for (int n = 0; n < 1000000; ++n) {
       gVirtualPS->SetFillColor(kRed);
       gVirtualPS->SetLineColor(kGreen);
    }
    c1->Draw();
    ps1.Close();
}