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/octave-3.6.2/scripts/image/gray2ind.m

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Objective C | 61 lines | 56 code | 5 blank | 0 comment | 13 complexity | 156167dcabc65a1c5ef50fd9bc56b0b4 MD5 | raw file
 1## Copyright (C) 1994-2012 John W. Eaton
 2##
 3## This file is part of Octave.
 4##
 5## Octave is free software; you can redistribute it and/or modify it
 6## under the terms of the GNU General Public License as published by
 7## the Free Software Foundation; either version 3 of the License, or (at
 8## your option) any later version.
 9##
10## Octave is distributed in the hope that it will be useful, but
11## WITHOUT ANY WARRANTY; without even the implied warranty of
12## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13## General Public License for more details.
14##
15## You should have received a copy of the GNU General Public License
16## along with Octave; see the file COPYING.  If not, see
17## <http://www.gnu.org/licenses/>.
18
19## -*- texinfo -*-
20## @deftypefn {Function File} {[@var{img}, @var{map}] =} gray2ind (@var{I}, @var{n})
21## Convert a gray scale intensity image to an Octave indexed image.
22## The indexed image will consist of @var{n} different intensity values.  If not
23## given @var{n} will default to 64.
24## @end deftypefn
25
26## Author: Tony Richardson <arichard@stark.cc.oh.us>
27## Created: July 1994
28## Adapted-By: jwe
29
30function [X, map] = gray2ind (I, n = 64)
31  ## Check input
32  if (nargin < 1 || nargin > 2)
33    print_usage ();
34  endif
35  C = class(I);
36  if (! ismatrix (I) || ndims (I) != 2)
37    error ("gray2ind: first input argument must be a gray scale image");
38  endif
39  if (! isscalar (n) || n < 0)
40    error ("gray2ind: second input argument must be a positive integer");
41  endif
42  ints = {"uint8", "uint16", "int8", "int16"};
43  floats = {"double", "single"};
44  if (! ismember (C, {ints{:}, floats{:}}))
45    error ("gray2ind: invalid data type '%s'", C);
46  endif
47  if (ismember (C, floats) && (min (I(:)) < 0 || max (I(:)) > 1))
48    error ("gray2ind: floating point images may only contain values between 0 and 1");
49  endif
50
51  ## Convert data
52  map = gray (n);
53  ## If @var{I} is an integer matrix convert it to a double matrix with values in [0, 1]
54  if (ismember (C, ints))
55    low = double (intmin (C));
56    high = double (intmax (C));
57    I = (double (I) - low) / (high - low);
58  endif
59  X = round (I*(n-1)) + 1;
60
61endfunction