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doc: Periodic grammarcheck of documentation.
author Rik <rik@octave.org>
date Wed, 20 Jan 2016 21:14:47 -0800
parents 3ec8332e0e01
children ecce63c99c3f
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1 ## Copyright (C) 2007-2015 Søren Hauberg
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2 ## Copyright (C) 2012-2015 Carnë Draug
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3 ##
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4 ## This file is part of Octave.
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5 ##
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6 ## Octave is free software; you can redistribute it and/or modify it
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7 ## under the terms of the GNU General Public License as published by
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8 ## the Free Software Foundation; either version 3 of the License, or (at
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9 ## your option) any later version.
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10 ##
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11 ## Octave is distributed in the hope that it will be useful, but
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12 ## WITHOUT ANY WARRANTY; without even the implied warranty of
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13 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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14 ## General Public License for more details.
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15 ##
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16 ## You should have received a copy of the GNU General Public License
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17 ## along with Octave; see the file COPYING. If not, see
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18 ## <http://www.gnu.org/licenses/>.
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19
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20 ## -*- texinfo -*-
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21 ## @deftypefn {} {} im2double (@var{img})
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22 ## @deftypefnx {} {} im2double (@var{img}, "indexed")
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23 ## Convert image to double precision.
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24 ##
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25 ## The conversion of @var{img} to double precision, is dependent
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26 ## on the type of input image. The following input classes are
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27 ## supported:
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28 ##
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29 ## @table @samp
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30 ## @item uint8, uint16, and int16
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31 ## The range of values from the class is scaled to the interval [0 1].
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32 ##
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33 ## @item logical
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34 ## True and false values are assigned a value of 0 and 1 respectively.
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35 ##
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36 ## @item single
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37 ## Values are cast to double.
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38 ##
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39 ## @item double
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40 ## Returns the same image.
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41 ##
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42 ## @end table
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43 ##
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44 ## If @var{img} is an indexed image, then the second argument should be
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45 ## the string @qcode{"indexed"}. If so, then @var{img} must either be
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46 ## of floating point class, or unsigned integer class and it will simply
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47 ## be cast to double. If it is an integer class, a +1 offset is applied.
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48 ##
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49 ## @seealso{double}
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50 ## @end deftypefn
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51
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52 ## Author: Søren Hauberg <soren@hauberg.org>
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53 ## Author: Carnë Draug <carandraug@octave.org>
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54
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55 function img = im2double (img, im_type)
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56 ## "normal" (non-indexed) images
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57 if (nargin () == 1)
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58 switch (class (img))
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59 case "uint8", img = double (img) / 255;
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60 case "uint16", img = double (img) / 65535;
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61 case "int16", img = (double (img) + 32768) / 65535;
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62 case "single", img = double (img);
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63 case "logical", img = double (img);
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64 case "double", # do nothing
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65 otherwise, error ("im2double: IMG is of unsupported class \"%s\"", class (img));
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66 endswitch
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67
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68 ## indexed images
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69 elseif (nargin () == 2)
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70 if (! strcmpi (im_type, "indexed"))
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71 error ("im2double: second input argument must be the string \"indexed\"");
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72 elseif (any (isa (img, {"uint8", "uint16"})))
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73 img = double (img) + 1;
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74 elseif (isfloat (img) || isbool (img))
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75 img = double (img);
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76 else
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77 ## Technically, it could also be of logical class and we do not
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78 ## enforce positive integers for floating for Matlab compatibility.
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79 ## Still, no need to tell that to the user.
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80 error (["im2double: if IMG is indexed, then it must be positive " ...
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81 "integer floating points, or unsigned integer class"]);
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82 endif
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83
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84 else
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85 print_usage ();
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86 endif
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87 endfunction
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88
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89
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90 %!assert (im2double ([1 2 3]), [1 2 3])
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91 %!assert (im2double (single ([1 2 3])), [1 2 3])
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92 %!assert (im2double (uint8 ([0 127 128 255])), [0 127/255 128/255 1])
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93 %!assert (im2double (uint16 ([0 127 128 65535])), [0 127/65535 128/65535 1])
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94 %!assert (im2double (int16 ([-32768 -32767 -32766 32767])),
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95 %! [0 1/65535 2/65535 1])
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96
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97 %!assert (im2double (uint8 ([0 1 255]), "indexed"), [1 2 256])
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98 %!assert (im2double (uint16 ([0 1 2557]), "indexed"), [1 2 2558])
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99 %!assert (im2double ([3 25], "indexed"), [3 25])
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100 %!assert (im2double (single ([3 25]), "indexed"), [3 25])
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101
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102 ## Test for ND input
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103 %!function test_im2double_nd (cls, low, high)
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104 %! in = rand (2, 4, 2, 3, 2);
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105 %! in *= high - low;
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106 %! in += low;
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107 %! in = cast (in, cls);
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108 %! out = zeros (size (in));
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109 %! for n = 1:12
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110 %! out(:,:,n) = im2double (in(:,:,n));
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111 %! endfor
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112 %! assert (im2double (in), out)
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113 %!endfunction
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114
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115 %!test
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116 %! test_im2double_nd ("double", 0, 1);
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117 %! test_im2double_nd ("single", 0, 1);
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118 %! test_im2double_nd ("uint8", 0, 255);
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119 %! test_im2double_nd ("uint16", 0, 6535);
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120 %! test_im2double_nd ("int16", -32768, 32767);
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121
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122 ## Test lack of input check for Matlab compatibility
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123 %!assert (im2double ([0 1 2], "indexed"), [0 1 2])
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124 %!assert (im2double ([0 -1 -2], "indexed"), [0 -1 -2])
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125 %!assert (im2double ([0 -1.5 -2], "indexed"), [0 -1.5 -2])
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126 %!assert (im2double ([0 -1.5 -2i], "indexed"), [0 -1.5 -2i])
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127 %!assert (im2double ([false true], "indexed"), [0 1])
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128
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129 %!error <unsigned integer class> im2double (int16 ([17 8]), "indexed");
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130 %!error <unsigned integer class> im2double (int16 ([-7 8]), "indexed");
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131 %!error <must be the string "indexed"> im2double ([1 2 3], "non-indexed");