;/* ----------------------------------------------------------------------
;  Find real value of lower or upper bound at a given column.
;  mode=1 : lower bound.
;  mode=2 : upper bound.
;  The lower bound is offset for some orders to align profiles.
;  NOTE: Shifting polynomials by 'yvoff' pixels inward (fudge).. -tab 14mar2017
;*/

function nsxng_find_real_image_row, mode, icol, nso, NCP, SlitOffset
;  common nsx

  if n_params() lt 5 then SlitOffset = 0.
  if n_params() lt 4 then ncp = nsxng_load_ncp()
  
  yvoff_lo = [ 0.d, 0., 0., 2., 1., 0., 0., 0., 0. ]
  yvoff_up = [ 0.d, 0., 0., 5., 4., 3., 3., 3., 0. ]

  if (mode eq 1) then begin
     xv = icol - NCP[nso].xoffa ;
     yv = poly(xv,NCP[nso].coefa) ;
     yv = yv + yvoff_lo[nso]       ;
  endif else begin
     xv = icol - NCP[nso].xoffb            ;
     yv =poly(xv,NCP[nso].coefb) ;
     yv = yv - yvoff_up[nso]        ;
  endelse
  yv = yv + SlitOffset          ;
  return, yv

end