ref: 22ca1a9c2e831d15c65a8e8788b0bebc968fb95a
dir: /sys/src/cmd/postscript/psfiles/Nroundpage.ps/
%
% A version of roundpage.ps that assumes a symmetric clipping path. Thanks
% to Matthijs Melchior for the suggestion.
%
/roundpagebbox {
pagebbox dup 0 get pagebbox 2 get add 2 exch put
pagebbox dup 1 get pagebbox 3 get add 3 exch put
pagebbox 0 0 put
pagebbox 1 0 put
} bind def