🚀 go-pugleaf

I am having a problem generating large postscript images using the image
and imagemask operators repeatedly.  There seems to be some limit to the
number of times I can invoke the image operator onto a given page.
The following fragment is attempting to fill a page with 300 dpi images
from a 32-bit word array by writing out hexadecimal strings (FORTRAN):
 
  open(unit=2,file='bits.ps')
  write(2,'(a)') '%!'
  write(2,'(a)') '18 18 translate 576 6 scale 0 setgray % 25 lines at 300dpi'
  do k=1, iymax, 25
    write(2,'(a)') '2400 25 true [2400 0 0 25]'
    do j=k,k+24
       write(2,'(25z8)') (word(i,j),i=1,ixmax)
    enddo
    write(2,'(a)') '>| 'imagemask 0 1 translate'
  enddo
  write(2,'(a)') 'showpage'
  close(unit=2)
 
The resulting bitmap is printed out from bottom to top. However, if "imagemask"
is invoked more than about 30 times, the page never prints, either on the Apple
Laserwriter II or the IBM Personal Pageprinter II. Is there some limit I am not
aware of in postscript?
 
Please reply to "Gregory A. Neumann" <GOLUX@BROWNVM.BROWN.EDU. Thanks.