Jones was close, but not the best/easiest. Cut the head off first - then with a cutting torch, blow a hole through the center. Use a tip that is big enough so that its done fast and you don't heat the frame much. It doesn,t have to be a very big hole. Yes, the hole weakens the rivet, as such, but the heat with the torch tries to make the rivet expand inside the hole, but it can't because it is restrained by the surrounding frame - so it expands into itself - the hole. Then most important - let it cool. THEN use your BFH and the hammer. They will come out easy as pie.
You guys that think a kitchen hammer is OK - its not. you will do more dammage and cause the rivet to swell. Use at least a 5# hammer. You should only have to hit it once, then just a tap, to drop it out! If it takes more then two hits - go back to rule one, and get the BFH.