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########################################################################
##
## Copyright (C) 1994-2024 The Octave Project Developers
##
## See the file COPYRIGHT.md in the top-level directory of this
## distribution or <https://octave.org/copyright/>.
##
## 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
## <https://www.gnu.org/licenses/>.
##
########################################################################
## -*- texinfo -*-
## @deftypefn {} {[x, map] =} ind2x (@var{caller}, @var{x}, @var{map})
##
## Private function for the ind2XXX functions which have a lot of code in
## common.
## @end deftypefn
function [x, map] = ind2x (caller, x, map)
## Check if X is an indexed image.
## An indexed image is defined has having only 2 dimensions, and that's how
## Matlab behaves. But we want to support N-D images, so we will allow up to
## 4-D and check that the 3rd dimension is a singleton.
if (all (ndims (x) != [2 4]) || size (x, 3) != 1
|| iscomplex (x) || issparse (x)
|| ! (isfloat (x) && all (x(:) == fix (x(:)))
|| (isinteger (x) && intmin (x) == 0)))
error ("%s: X must be an indexed image", caller);
endif
## Check if map is a valid colormap.
if (! iscolormap (map))
error ("%s: MAP must be a valid colormap", caller);
endif
## Any color indices below the lower bound of the color map are modified
## to point to the first color in the map (see bug #41851).
if (isfloat (x))
invalid_idx = x < 1;
if (any (invalid_idx(:)))
warning (["Octave:" caller ":invalid-idx-img"],
[caller ": indexed image contains colors outside of colormap"]);
x(invalid_idx) = 1;
endif
endif
## Switch to using 1-based indexing.
## It is possible that an integer storage class may not have enough room
## to make the switch, in which case we convert the data to single.
maxidx = max (x(:));
is_int = isinteger (x);
if (is_int)
if (maxidx == intmax (x))
x = single (x);
endif
x += 1;
endif
## When there are more colors in the image, than there are in the map,
## pad the colormap with the last color in the map for Matlab compatibility.
num_colors = rows (map);
if (num_colors - is_int < maxidx)
warning (["Octave:" caller ":invalid-idx-img"],
[caller ": indexed image contains colors outside of colormap"]);
if (numel (x) > maxidx - num_colors + is_int)
## The image is large. So extend the map.
pad = repmat (map(end,:), maxidx - num_colors + is_int, 1);
map(end+(1:rows (pad)), :) = pad;
else
## The map extension would be large. So clip the image.
x(x > rows (map)) = rows (map);
endif
endif
endfunction
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