## Copyright (C) 2007 S�ren Hauberg <soren@hauberg.org>
## Copyright (C) 2012 Carn� Draug <carandraug+dev@gmail.com>
##
## This program is free software; you can redistribute it and/or modify it under
## the terms of the GNU General Public License as published by the Free Software
## Foundation; either version 3 of the License, or (at your option) any later
## version.
##
## This program is distributed in the hope that it will be useful, but WITHOUT
## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
## FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
## details.
##
## You should have received a copy of the GNU General Public License along with
## this program; if not, see <http://www.gnu.org/licenses/>.

## -*- texinfo -*-
## @deftypefn {Function File} @var{im2} = im2double(@var{im1})
## @deftypefnx {Function File} @var{im2} = im2double(@var{im1}, "indexed")
## Convert input image @var{im1} to double precision.
##
## The following images type are supported: double, single, uint8, uint16, int16,
## binary (logical), indexed. If @var{im1} is an indexed images, the second
## argument must be a string with the value `indexed'.
##
## Processing will depend on the class of the input image @var{im1}:
## @itemize @bullet
## @item uint8, uint16, int16 - output will be rescaled for the interval [0 1]
## with the limits of the class;
## @item double - output will be the same as input;
## @item single - output will have the same values as input but the class will
## double;
## @item indexed, logical - converted to double class.
## @end itemize
##
## @seealso{im2bw, im2uint16, im2uint8}
## @end deftypefn

function im = im2double (im, ind = false)

  ## Input checking (private function that is used for all im2class functions)
  im_class = imconversion (nargin, "im2double", ind, im);

  switch im_class
    case "double"
      ## do nothing, return the same
    case {"logical", "single"}
      im = double (im);
    case {"uint8", "uint16"}
      if (ind)
        im = double (im) + 1;
      elseif (isind (im))
        im = double (im) / double (intmax (im_class));
      endif
    case "int16"
      im = (double (im) + double (intmax (im_class)) + 1) / double (intmax ("uint16"));
    otherwise
      error ("unsupported image class %s", im_class);
  endswitch
endfunction

%!assert(im2double([1 2 3]), [1 2 3]);                  # double returns the same
%!assert(im2double(uint8([0 255])), [0 1]);             # basic usage
%!assert(im2double(uint8([1 25]), "indexed"), [2 26]);  # test indexed
%!assert(im2double(int16([-32768 32768])), [0 1]);      # test signed integer