view scripts/image/ind2rgb.m @ 18578:875f4510d6dc

Accept indexed images with color values below the first colormap entry (bug #41851). Change made for Matlab compatibility. * ind2gray.m: Change %!tests to accept an indexed image with colors below the first entry in the colormap. * ind2rgb.m: Change %!tests to accept an indexed image with colors below the first entry in the colormap. * ind2x.m: Change input validation to accept all floating point images with integer indices. Issue a warning if any of the indices are below the first entry in the colormap. Map all color indices below the first entry to the first color in the colormap.
author Rik <rik@octave.org>
date Mon, 17 Mar 2014 09:10:32 -0700
parents d63878346099
children db92e7e28e1f
line wrap: on
line source

## Copyright (C) 1994-2013 John W. Eaton
##
## 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/>.

## -*- texinfo -*-
## @deftypefn  {Function File} {@var{rgb} =} ind2rgb (@var{x}, @var{map})
## @deftypefnx {Function File} {[@var{R}, @var{G}, @var{B}] =} ind2rgb (@var{x}, @var{map})
## Convert an indexed image to red, green, and blue color components.
##
## The image @var{x} must be an indexed image which will be converted using the
## colormap @var{map}.  If @var{map} does not contain enough colors for the
## image, pixels in @var{x} outside the range are mapped to the last color in
## the map.
##
## The output may be a single RGB image (@nospell{MxNx3} matrix where M and N
## are the original image @var{x} dimensions, one for each of the red, green
## and blue channels).  Alternatively, the individual red, green, and blue
## color matrices of size @nospell{MxN} may be returned.
##
## Multi-dimensional indexed images (of size @nospell{MxNx1xK}) are also
## supported.
##
## @seealso{rgb2ind, ind2gray, hsv2rgb, ntsc2rgb}
## @end deftypefn

## Author: Tony Richardson <arichard@stark.cc.oh.us>
## Created: July 1994
## Adapted-By: jwe

function [R, G, B] = ind2rgb (x, map)

  if (nargin != 2)
    print_usage ();
  endif
  [x, map] = ind2x ("ind2rgb", x, map);

  ## Compute result
  sz = size (x);
  R = reshape (map(x(:), 1), sz);
  G = reshape (map(x(:), 2), sz);
  B = reshape (map(x(:), 3), sz);

  ## Use ND array if only one output is requested.
  if (nargout <= 1)
    if (ndims (x) == 2)
      R = reshape ([R(:); G(:); B(:)], [sz, 3]);
    elseif (ndims (x) == 4)
      R = permute (reshape ([R(:); G(:); B(:)], [sz(1) sz(2) sz(4) 3]), [1 2 4 3]);
    else
      ## we should never reach here since ind2x() should filter them out
      error ("ind2rgb: an indexed image must have 2 or 4 dimensions.");
    endif
  endif

endfunction


%!shared img, map, ergb, rgb, r, g, b
%! img = [2 4 5; 3 2 5; 1 2 4];
%! map = [0.0  0.0  0.0
%!        0.2  0.4  0.6
%!        0.4  0.4  0.5
%!        0.3  0.7  1.0
%!        0.1  0.5  0.8];
%! ergb(:,:,1) = [0.2 0.3 0.1; 0.4 0.2 0.1; 0.0 0.2 0.3];
%! ergb(:,:,2) = [0.4 0.7 0.5; 0.4 0.4 0.5; 0.0 0.4 0.7];
%! ergb(:,:,3) = [0.6 1.0 0.8; 0.5 0.6 0.8; 0.0 0.6 1.0];
%! ## test basic usage with 1 and 3 outputs
%! [rgb] = ind2rgb (img, map);
%! [r, g, b] = ind2rgb (img, map);
%!
%!assert (ergb, rgb)
%!assert (ergb, reshape ([r(:) g(:) b(:)], [size(img) 3]))
%!test
%! ## test correction for integers
%! img = uint8 (img - 1);
%! [rgb] = ind2rgb (img, map);
%! assert (ergb, rgb);
%!test
%! ## Check that values below lower bound are mapped to first color value 
%! rgb = ind2rgb ([-1 0 2], gray (64));
%! assert (rgb(:,1:2,:), zeros (1,2,3));
%! assert (rgb(:,3,:), 1/63 * ones (1,1,3));

%% Test input validation
%!error ind2rgb ()
%!error ind2rgb (1,2,3)
%!error <X must be an indexed image> ind2rgb (ones (3,3,3), jet (64))
%!error <X must be an indexed image> ind2rgb (1+i, jet (64))
%!error <X must be an indexed image> ind2rgb (sparse (1), jet (64))
%!error <X must be an indexed image> ind2rgb (1.1, jet (64))
%!error <X must be an indexed image> ind2rgb ({1}, jet (64))
%!error <MAP must be a valid colormap> ind2rgb (1, {1})
%!error <MAP must be a valid colormap> ind2rgb (1, 1+i)
%!error <MAP must be a valid colormap> ind2rgb (1, ones (2,2,2))
%!error <MAP must be a valid colormap> ind2rgb (1, ones (2,4))
%!error <MAP must be a valid colormap> ind2rgb (1, [-1])
%!error <MAP must be a valid colormap> ind2rgb (1, [2])

%!warning <contains colors outside of colormap> ind2rgb ([-1 1], jet (64));
%!warning <contains colors outside of colormap> ind2rgb ([0 1 2], gray (5));
%!warning <contains colors outside of colormap> ind2rgb ([1 2 6], gray (5));
%!warning <contains colors outside of colormap> ind2rgb (uint8 ([1 2 5]), gray (5));