function [X map] = rgb2ind(R,G,B)

# Convert and RGB image to an octave indexed image.
#
# [X map] = rgb2ind(R,G,B)
#
# SEE ALSO: ind2rgb, rgb2ntsc.
#
# Bugs: The color map may have duplicate entries.

  if(nargin != 3)
    usage ("[X, map] = rgb2ind(R,G,B)");
  endif

  [hi wi] = size(R);

  X = zeros(hi,wi);

  map = zeros(hi*wi,3);

  pref = do_fortran_indexing;

  unwind_protect

    do_fortran_indexing = "true";

    map(:,1) = R(:);
    map(:,2) = G(:);
    map(:,3) = B(:);

    X(:) = 1:(hi*wi);

  unwind_protect_cleanup
    do_fortran_indexing = pref;
  end_unwind_protect

endfunction