currentpoint			% b l r t
exch					% b l t r
newpath					% b l t r
4 2 roll				% t r b l
2 copy					% t r b l b l
/Mleft exch def			% t r b l b
/Mbottom exch def		% t r b l
3 -1 roll				% t b l r
sub neg					% t b r-l
/Mwidth exch def		% t b
sub neg					% b-t
/Mheight exch def		% -