octave-image 2.2.2-1 / usr / share / octave / packages / image-2.2.2 / wavelength2rgb.m

This file is indexed.

/usr/share/octave/packages/image-2.2.2/wavelength2rgb.m is in octave-image 2.2.2-1.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below. 

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
## Copyright (C) 2011 William Krekeler <WKrekeler@cleanearthtech.com>
## Copyright (C) 2012 Carnë Draug <carandraug+dev@gmail.com>
##
## This program 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.
##
## This program 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
## this program; if not, see <http://www.gnu.org/licenses/>.

## -*- texinfo -*-
## @deftypefn  {Function File} {@var{rgb} =} wavelength2rgb (@var{wavelength})
## @deftypefnx {Function File} {@var{rgb} =} wavelength2rgb (@var{wavelength}, @var{class})
## @deftypefnx {Function File} {@var{rgb} =} wavelength2rgb (@var{wavelength}, @var{class}, @var{gamma})
## Convert wavelength in nm into an RGB value set.
##
## Given a N-dimensional matrix @var{wavelength} with color values in nm, returns
## a RGB image with N+3 dimensions.
##
## @group
## @example
## wavelength2rgb (400)
##     @result{} [0.51222 0.00000 0.70849]
##
## wavelength2rgb ([400 410])
##     @result{(:,:,1)} 0.51222   0.49242
##     @result{(:,:,2)} 0         0
##     @result{(:,:,3)} 0.70849   0.85736
## @end example
## @end group
##
## The @var{rgb} class can be specified with @var{class}.  Possible values are
## double (default), single, uint8, uint16, and int16.
##
## @group
## @example
## wavelength2rgb (400)
##     @result{} 0.51222  0.00000  0.70849
##
## wavelength2rgb (400, "uint8")
##     @result{} 131    0  181
## @end example
## @end group
##
## The luminance of colors can be adjusted with @var{gamma} which must a scalar
## value in the range [0 1]. Defaults to 0.8.
##
## Reference:
## @itemize @bullet
## @item @uref{http://stackoverflow.com/questions/2374959/algorithm-to-convert-any-positive-integer-to-an-rgb-value}
## @item @uref{http://www.midnightkite.com/color.html} per Dan Bruton
## @end itemize
## @end deftypefn

function rgb = wavelength2rgb (wavelength, out_class = "double", gamma = 0.8)

  if (nargin < 1 || nargin > 3)
    print_usage;
  elseif (!isnumeric (wavelength) || any (wavelength <= 0))
    error ("wavelength2rgb: wavelength must a positive numeric");
  elseif (!ischar (out_class) || all (!strcmpi (out_class, {"single", "double", "uint8", "uint16", "int16"})))
    error ("wavelength2rgb: unsupported class `%s'", char (out_class));
  elseif (!isnumeric (gamma) || !isscalar (gamma) || gamma > 1 || gamma < 0)
    error ("wavelength2rgb: gamma must a numeric scalar between 1 and 0");
  endif

  ## initialize rgb. One extra dimension of size 3 for RGB. Later on, we will
  ## use ndims and when input is a scalar, ndims still returns 2 which means
  ## output would be 1x1x3. Check this and adjust later on
  if (isscalar (wavelength))
    rgb = zeros (1, 3);
    size_adjust = 1;
  else
    rgb = zeros ([size(wavelength), 3]);
    size_adjust = 0;
  endif

  ## this RGBmask's will be used for broadcasting later
  Rmask = Gmask = Bmask = false ([ones(1, ndims (wavelength) - size_adjust) 3]);
  Rmask(1)  = true;
  Gmask(2)  = true;
  Bmask(3)  = true;

  ## for each group of wavelengths we calculate the mask, expand for the 3
  ## channels and use Rmask, Gmask and Bmask with broadcasting to select the
  ## right one. Will skip some channels since their values would be zero and
  ## we already initialized the matrix with zeros()
  get_rgb_mask = @(mask) repmat (mask, [ones(1, ndims (mask) - size_adjust) 3]);

  warning ("off", "Octave:broadcast", "local");

  mask    = wavelength >= 380 & wavelength < 440;
  rgbmask = get_rgb_mask (mask);
  rgb(rgbmask & Rmask) = -(wavelength(mask) - 440) / 60; # 60 comes from 440-380
  ## skiping green channel (values of zero)
  rgb(rgbmask & Bmask) = 1;

  mask    = wavelength >= 440 & wavelength < 490;
  rgbmask = get_rgb_mask (mask);
  ## skiping red channel (values of zero)
  rgb(rgbmask & Gmask) = (wavelength(mask) - 440) / 50; # 50 comes from 490-440
  rgb(rgbmask & Bmask) = 1;

  mask    = wavelength >= 490 & wavelength < 510;
  rgbmask = get_rgb_mask (mask);
  ## skiping red channel (values of zero)
  rgb(rgbmask & Gmask) = 1;
  rgb(rgbmask & Bmask) = -(wavelength(mask) - 510) / 20; # 20 comes from 510-490

  mask    = wavelength >= 510 & wavelength < 580;
  rgbmask = get_rgb_mask (mask);
  rgb(rgbmask & Rmask) = (wavelength(mask) - 510) / 70; # 70 comes from 580-510
  rgb(rgbmask & Gmask) = 1;
  ## skiping blue channel (values of zero)

  mask    = wavelength >= 580 & wavelength < 645;
  rgbmask = get_rgb_mask (mask);
  rgb(rgbmask & Rmask) = 1;
  rgb(rgbmask & Gmask) = -(wavelength(mask) - 645) / 65; # 65 comes from 645-580
  ## skiping blue channel (values of zero)

  mask    = wavelength >= 645 & wavelength <= 780;
  rgbmask = get_rgb_mask (mask);
  rgb(rgbmask & Rmask) = 1;
  ## skiping green channel (values of zero)
  ## skiping blue channel (values of zero)

  ## all other wavelengths have values of zero in all channels (black)

  ## let intensity fall off near the vision limits
  ## set the factor
  factor        = zeros (size (wavelength));
  mask          = wavelength >= 380 & wavelength < 420;
  factor(mask)  = 0.3 + 0.7*(wavelength(mask) - 380) / 40; # 40 = 420 - 380
  mask          = wavelength >= 420 & wavelength <= 700;
  factor(mask)  = 1;
  mask          = wavelength > 700 & wavelength <= 780;
  factor(mask)  = 0.3 + 0.7*(780 - wavelength(mask)) / 80; # 80 = 780 - 700
  ## for other wavelengths, factor is 0

  ## expand factor for the 3 channels
  factor = repmat (factor, [ones(1, ndims (factor) - size_adjust) 3]);

  ## correct rgb
  rgb = (rgb .* factor) .^gamma;

  ## scale to requested class
  switch tolower (out_class)
    case {"single"}   rgb = im2single (rgb);
    case {"double"}   ## do nothing, already class double
    case {"uint8"}    rgb = im2uint8  (rgb);
    case {"uint16"}   rgb = im2uint16 (rgb);
    case {"int16"}    rgb = im2int16  (rgb);
    otherwise         error ("wavelength2rgb: unsupported class `%s'", out_class)
  endswitch
endfunction

%!demo
%!
%! ##draw RGB values for wavelengths between 350 and 800 nm
%! RGB = wavelength2rgb (350:800);
%! rgbplot (squeeze (RGB), "composite");
%! axis off;

APT Browse - Built by Thomas Orozco.