;+
;
; @file_comments 
; interpolate data from a "regular/rectangular grid" to any grid.
;   2 methods availables: bilinear and imoms3
;   A "regular/rectangular grid" is defined as a grid for which each lontitudes lines have
;   the same latitude and each latitudes columns have the same longitude.
;
; @categories interpolation
;
; @param method {in}{required}  a string defining the interpolation method.
;            must be 'bilinear' or 'imoms3'
; @param datain {in}{required}  a 2D array the input data to interpolate
; @param lonin {in}{optional}  1D or 2D array defining the longitude of the input data
; @param latin {in}{optional}  1D or 2D array defining the latitude of the input data
; @param lonout {in}{optional}  1D or 2D array defining the longitude of the output data
; @param latout {in}{required}  1D or 2D array defining the latitude of the output data
;
; @keyword WEIG (see ADDR)
; @keyword ADDR 2D arrays, weig and addr are the weight and addresses used to
;     perform the interpolation:
;          dataout = total(weig*datain[addr], 1)
;          dataout = reform(dataout, jpio, jpjo, /over)
;     Those keywords can be set to named variables (that are undefined or equal to 0) into which the
;     values will be copied when the current routine exits. Next, they can be used to perform
;     the interpolation whithout computing again those 2 parameters. In that
;     case, lonin, latin, lonout and latout are not necessary.
;
; @keyword NONORTHERNLINE
; @keyword NOSOUTHERNLINE
; activate if you don't want to take into account the northen/southern line
; of the input data when perfoming the interpolation.
;
; @returns 2D array the interpolated data
;
; @restrictions
; We supposed the data are located on a sphere, with a periodicity along the
; longitude.
;
; @examples
;
; IDL> topa = fromreg('bilinear', tncep, xncep, yncep, glamt, gphit)
;
;  or
;
; IDL> t1opa = fromreg('bilinear', t1ncep, xncep, yncep, glamt, gphit, WEIG = a, ADDR = b)
; IDL> help, a, b
; IDL> t2opa = fromreg('bilinear', t2ncep, xncep, WEIG = a, ADDR = b)
;
; @history
;  November 2005: Sebastien Masson (smasson\@lodyc.jussieu.fr)
;
; @version $Id$
;
;-
;----------------------------------------------------------
;----------------------------------------------------------
;
FUNCTION fromreg, method, datain, lonin, latin, lonout, latout $
                  , WEIG = weig, ADDR = addr $
                  , NONORTHERNLINE = nonorthernline $
                  , NOSOUTHERNLINE = nosouthernline
;
  compile_opt idl2, strictarrsubs
;
;---------------
; atmospheric grid parameters
;---------------
    alon = lonin
    alat = latin
    get_gridparams, alon, alat, jpia, jpja, 1, /double
;---------------
; Oceanic grid parameters
;---------------
    olon = lonout
    olat = latout
    get_gridparams, olon, olat, jpio, jpjo, 2, /double
;---------------
; Compute weight and address
;---------------
  IF NOT (keyword_set(weig) AND keyword_set(addr)) THEN BEGIN
    CASE method OF
      'bilinear':compute_fromreg_bilinear_weigaddr, alon, alat, olon, olat, weig, addr, NONORTHERNLINE = nonorthernline, NOSOUTHERNLINE = nosouthernline
      'imoms3':  compute_fromreg_imoms3_weigaddr,   alon, alat, olon, olat, weig, addr, NONORTHERNLINE = nonorthernline, NOSOUTHERNLINE = nosouthernline
      ELSE:BEGIN
        print, ' unknown interpolation method... we stop'
        stop
      ENDELSE
    ENDCASE
  ENDIF
;
  dataout = total(weig*datain[addr], 1)
  dataout = reform(dataout, jpio, jpjo, /over)
;
  RETURN, dataout
END