% Copyright (C) 1994-2013 John W. Eaton
% Copyright (C) 2012 Carnė Draug
%
% This file is part of Octave.
%
% Octave 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.
%
% Octave 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 Octave; see the file COPYING.  If not, see
% <http://www.gnu.org/licenses/>.

% private function for the ind2xxx functions which have a lot of code in common

function [x, map] = ind2x (caller, x, map)

  % Check if x is an indexed image.
  % an indexed image is defined has having only 2D, and that's how Matlab
  % behaves.  But we want to support ND images, so we will allow up to 4D
  % and check that the 3rd is a singleton
  if (all (ndims (x) ~= [2 4]) || size (x, 3) ~= 1 || issparse (x) || ...
      (isfloat (x) && ~ isindex (x)) || ...
      ~ any (strcmp (class (x), {'uint8', 'uint16', 'single', 'double'})))
    error ('%s: x must be an indexed image', caller);
  end

  % Check if map is a valid colormap.
  if (~ iscolormap (map))
    error ('%s: MAP must be a valid colormap', caller);
  end

  % Do we have enough colors in the color map?
  % there's an offset of 1 when the indexed image is an integer class so we fix
  % it now and convert it to float only if really necessary and even then only
  % to single precision since that is enough for both uint8 and uint16.
  maxidx = max (x(:));
  if (isinteger (x))
    if (maxidx == intmax (class (x)))
      x = single (x);
    end
    x      += 1;
    maxidx += 1;
  end

  num_colors = rows (map);
  if (num_colors < maxidx)
    % Pad with the last color in the map for Matlab compatibility
    pad = repmat (map(end,:), maxidx - num_colors, 1);
    map(end+1:maxidx, :) = pad;
  end