function sxig12_zeropix,image0,ext2_hdr1,zeroarr

dummy=where(image0 eq 0, pix_count)

if pix_count gt 0 then begin
  ext2_hdr1=sxi_sxmodpar(ext2_hdr1,'NAXIS2',pix_count)
  zeroarr=intarr(2,pix_count)
  zeroarr(0,*)=dummy mod 512
  zeroarr(1,*)=fix(dummy/512)
endif else begin
  ext2_hdr1=sxi_sxmodpar(ext2_hdr1,'NAXIS',0)
  sxdelpar,ext2_hdr1,'NAXIS1'
  sxdelpar,ext2_hdr1,'NAXIS2'
endelse

return,pix_count

end