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maint: Merge default to bytecode-interpreter.
author Markus Mützel <markus.muetzel@gmx.de>
date Tue, 21 May 2024 18:29:03 +0200
parents 2e484f9f1f18
children
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1 ########################################################################
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2 ##
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3 ## Copyright (C) 1994-2024 The Octave Project Developers
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4 ##
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5 ## See the file COPYRIGHT.md in the top-level directory of this
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6 ## distribution or <https://octave.org/copyright/>.
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7 ##
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8 ## This file is part of Octave.
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9 ##
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10 ## Octave is free software: you can redistribute it and/or modify it
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11 ## under the terms of the GNU General Public License as published by
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12 ## the Free Software Foundation, either version 3 of the License, or
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13 ## (at your option) any later version.
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14 ##
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15 ## Octave is distributed in the hope that it will be useful, but
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16 ## WITHOUT ANY WARRANTY; without even the implied warranty of
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17 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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18 ## GNU General Public License for more details.
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19 ##
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20 ## You should have received a copy of the GNU General Public License
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21 ## along with Octave; see the file COPYING. If not, see
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22 ## <https://www.gnu.org/licenses/>.
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23 ##
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24 ########################################################################
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26 ## -*- texinfo -*-
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27 ## @deftypefn {} {@var{I} =} ind2gray (@var{x}, @var{map})
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28 ## Convert a color indexed image to a grayscale intensity image.
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29 ##
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30 ## The image @var{x} must be an indexed image which will be converted using the
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31 ## colormap @var{map}. If @var{map} does not contain enough colors for the
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32 ## image, pixels in @var{x} outside the range are mapped to the last color in
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33 ## the map before conversion to grayscale.
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34 ##
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35 ## The output @var{I} is of the same class as the input @var{x} and may be
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36 ## one of @code{uint8}, @code{uint16}, @code{single}, or @code{double}.
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37 ##
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38 ## Implementation Note: There are several ways of converting colors to
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39 ## grayscale intensities. This functions uses the luminance value obtained
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40 ## from @code{rgb2gray} which is @code{I = 0.299*R + 0.587*G + 0.114*B}.
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41 ## Other possibilities include the value component from @code{rgb2hsv} or
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42 ## using a single color channel from @code{ind2rgb}.
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43 ## @seealso{gray2ind, ind2rgb}
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44 ## @end deftypefn
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45
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46 function I = ind2gray (x, map)
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47
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48 if (nargin != 2)
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49 print_usage ();
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50 endif
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51 [x, map] = ind2x ("ind2gray", x, map);
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52
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53 ## Convert colormap to luminance intensity values
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54 map *= [0.29894; 0.58704; 0.11402];
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55
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56 ## Convert colormap to same class as that of input so that reshape
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57 ## will produce output of the same type as the input.
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58 cls = class (x);
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59 if (isinteger (x))
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60 ## if we later add support for int16 images, this will not work. Look into
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61 ## im2int16 from image package for such case
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62 map *= intmax (cls);
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63 elseif (strcmp (cls, "single"))
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64 map = single (map);
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65 endif
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66
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67 ## Replace indices in the input matrix with the indexed luminance value.
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68 I = reshape (map(x(:)), size (x));
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70 endfunction
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71
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72
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73 %!shared i2g
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74 %! i2g = ind2gray (1:100, gray (100));
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75 %!
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76 %!assert (i2g, 0:1/99:1, eps)
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77 %!assert (gray2ind (i2g, 100), uint8 (0:99))
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78
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79 ## Test input validation
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80 %!error <Invalid call> ind2gray ()
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81 %!error <Invalid call> ind2gray (1)
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82 %!error <X must be an indexed image> ind2gray (ones (3,3,3), jet (64))
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83 %!error <X must be an indexed image> ind2gray (1+i, jet (64))
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84 %!error <X must be an indexed image> ind2gray (sparse (1), jet (64))
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85 %!error <X must be an indexed image> ind2gray (1.1, jet (64))
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86 %!error <X must be an indexed image> ind2gray ({1}, jet (64))
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87 %!error <MAP must be a valid colormap> ind2gray (1, {1})
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88 %!error <MAP must be a valid colormap> ind2gray (1, 1+i)
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89 %!error <MAP must be a valid colormap> ind2gray (1, ones (2,2,2))
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90 %!error <MAP must be a valid colormap> ind2gray (1, ones (2,4))
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91 %!error <MAP must be a valid colormap> ind2gray (1, [-1])
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92 %!error <MAP must be a valid colormap> ind2gray (1, [2])
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93
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94 %!warning <contains colors outside of colormap> ind2gray ([0 1 2], gray (5));
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95 %!warning <contains colors outside of colormap> ind2gray ([1 2 6], gray (5));
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96 %!warning <contains colors outside of colormap> ind2gray (uint8 ([1 2 5]), gray (5));