pro shift_div, imone, imtwo, xshift, yshift,  imnew, DZV=DIV_ZERO_VAL

; imone gets shifted by xshift and yshift, then divided by imtwo
; any pixels that get divided by zero are given the value DIV_ZERO

  zmask = imtwo eq 0 ; where the zeros are
  nzmask = imtwo ne 0 ; where the non-zeros are

  imtwo_b = imtwo + zmask ; make all the zeros ones

  imnew = shift_im_cbc(imone, xshift, yshift) / imtwo_b ; do the shifting and 
                                                        ; division

  if KEYWORD_SET(DIV_ZERO_VAL) then $
    imnew = imnew * nzmask + (zmask * DIV_ZERO_VAL) $
  else imnew = imnew * nzmask

  imstat, imnew[335:1005, 325:975]

end