{ 
   TCanvas *c = new TCanvas("c","transparent pad",200,10,700,500); 
   c->SetFrameFillColor(0);
   c->SetFrameFillStyle(0);
   c->SetFrameBorderMode(0);
   TPad *p = new TPad("p","",0,0,1,1); 
   p->SetFrameFillColor(0);
   p->SetFrameFillStyle(0);
   p->SetFrameBorderMode(0);
   p->Draw(); 
   p->cd(); 
   TH1F* h = new TH1F("h","h",100,-5,5); 
   h->FillRandom("gaus"); 
   h->Draw(); 
   c->SaveAs("trans.pdf");
   c->SaveAs("trans.eps");
   c->SaveAs("trans.png");
}