;+
;
; @file_comments
; add land points on a 2D land-sea mask
;
; @categories
; Grid
;
; @param TAB {in}{required}
; a 2D land-sea mask, with 1 on sea and 0 on land
;
; @keyword CELLSIZE
; size (in pixel) of the square
; representing one point of the mask
;
; @returns
; the new 2D land-sea mask
;
; @examples
;
;   IDL> a = changemsk(tmask[*,*,0])
;
;  to add ocean points
;   IDL> a = 1 - changemsk(1 - tmask[*,*,0])
;
; @history
;      Sebastien Masson (smasson\@lodyc.jussieu.fr)
;      June 2006
;
; @version
; $Id$
;
;-
FUNCTION changemsk,tab, CELLSIZE=cellsize
;
  compile_opt idl2, strictarrsubs
;
   newmsk = -1
   taille = size(tab)
   if taille[0] NE 2 then return, newmsk
   newmsk=byte(tab)
   if keyword_set(cellsize) THEN cellsize = long(cellsize) $
   ELSE cellsize = long(2)
   window,xsize=taille[1]*cellsize,ysize=taille[2]*cellsize
   tvscl, congrid(newmsk, taille[1]*cellsize, taille[2]*cellsize)

   if NOT keyword_set(nouseinfos) then begin
    print, 'left button  : use it twice to define the diagonal of the rectangle to be set to 0 (land)'
    print, 'middle button: put 0 (land) on the clicked point'
    print, 'right button : quit'
  endif

  cursor,x1,y1,/device, /up
   while (!mouse.button ne 4) do begin
      case !mouse.button of
         0:return, newmsk
         1:BEGIN
            cursor,x2,y2,/device, /up
            x = [x1, x2]
            x = x[sort(x)]
            x = round(x/cellsize)
            y = [y1, y2]
            y = y[sort(y)]
            y = round(y/cellsize)
            newmsk[x[0]:x[1], y[0]:y[1] ] = 0
            tvscl, replicate(0,(x[1]-x[0]+1)*cellsize $
                             ,(y[1]-y[0]+1)*cellsize) $
             ,x[0]*cellsize,y[0]*cellsize
         end
         2:BEGIN
            x1 = round(x1/cellsize)
            y1 = round(y1/cellsize)
            newmsk[x1, y1] = 0
            tvscl,replicate(0,cellsize,cellsize) $
             ,x1*cellsize,y1*cellsize

          END
         ELSE:
      endcase
      cursor,x1,y1,/device, /up
   endwhile

   return, newmsk
end