# create a canvas and save as png

    void pad2png()
    {
       // Create a canvas and save as png.

       TCanvas *c = new TCanvas;
       TH1F *h = new TH1F("gaus", "gaus", 100, -5, 5);
       h->FillRandom("gaus", 10000);
       h->Draw();

       gSystem->ProcessEvents();

       TImage *img = TImage::Create();

       //img->FromPad(c, 10, 10, 300, 200);
       img->FromPad(c);

       img->WriteImage("canvas.png");

       delete h;
       delete c;
       delete img;
    }