Mercurial > octave
view scripts/image/cubehelix.m @ 33528:6813c5c7e1b9 default tip @
Update to gnulib revision 6213c5bd72d15ca5e1ea9c34122899e02fed448c.
* bootstrap.conf: Update GNULIB_REVISION that contains a fix for a build issue
when targeting Cygwin.
author | Markus Mützel <markus.muetzel@gmx.de> |
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date | Fri, 03 May 2024 16:04:05 +0200 |
parents | d8e5e55c3cf5 |
children |
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######################################################################## ## ## Copyright (C) 2014-2024 The Octave Project Developers ## ## See the file COPYRIGHT.md in the top-level directory of this ## distribution or <https://octave.org/copyright/>. ## ## This file is part of Octave. ## ## Octave 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. ## ## Octave 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 Octave; see the file COPYING. If not, see ## <https://www.gnu.org/licenses/>. ## ######################################################################## ## -*- texinfo -*- ## @deftypefn {} {@var{map} =} cubehelix () ## @deftypefnx {} {@var{map} =} cubehelix (@var{n}) ## @deftypefnx {} {@var{map} =} cubehelix (@var{n}, @var{start}, @var{rots}, @var{hue}, @var{gamma}) ## Create cubehelix colormap. ## ## This colormap varies from black to white going though blue, green, and red ## tones while maintaining a monotonically increasing perception of intensity. ## This is achieved by traversing a color cube from black to white through ## a helix, hence the name cubehelix, while taking into account the perceived ## brightness of each channel according to the NTSC specifications from 1953. ## ## @example ## rgbplot (cubehelix (256)) ## @end example ## ## The argument @var{n} must be a scalar. ## If @var{n} is not specified the length of the current colormap is used. If ## there is no current colormap the default value of 256 is used. ## ## Reference: Green, D. A., 2011, ## @cite{A @nospell{colour} scheme for the display of astronomical intensity ## images}, Bulletin of the Astronomical Society of India, 39, 289. ## ## @seealso{colormap} ## @end deftypefn function map = cubehelix (n, start = 0.5, rots = -1.5, hue = 1, gamma = 1) if (nargin > 0) if (! (isscalar (n) && isreal (n) && n == fix (n))) error ("cubehelix: N must be a scalar integer"); endif n = double (n); else hf = get (0, "currentfigure"); if (! isempty (hf)) n = rows (get (hf, "colormap")); else n = 256; endif endif if (n > 1) coeff = [ -0.14861 -0.29227 1.97294 1.78277 -0.90649 0.00000]; fract = ((0:n-1) / (n-1))'; angle = 2 * pi * (start/3 + 1 + rots*fract); fract .^= gamma; amp = hue * fract .* (1-fract) /2; map = fract + amp .* ([cos(angle) sin(angle)] * coeff); ## Clip values (only in case users have changed values of hue or gamma) map(map < 0) = 0; map(map > 1) = 1; elseif (n > 0) map = [0, 0, 0]; else map = zeros (0, 3); endif endfunction ## A better demo of this colormap would be a 3-D plot in NTSC instead of ## RGB values. That would really show what this colormap is about. %!demo %! ## Show the 'cubehelix' colormap profile and as an image %! cmap = cubehelix (256); %! subplot (2, 1, 1); %! rgbplot (cmap, "composite"); %! subplot (2, 1, 2); %! rgbplot (cmap); %!assert (size (cubehelix ()), [256, 3]) %!assert (size (cubehelix (16)), [16, 3]) %!assert (cubehelix (1), [0,0,0]) %!assert (cubehelix (true), double ([0,0,0])) %!assert (cubehelix (char (1)), double ([0,0,0])) %!assert (cubehelix (int32 (1)), double ([0,0,0])) %!assert (cubehelix (0), zeros (0, 3)) %!assert (cubehelix (-1), zeros (0, 3)) %!assert (cubehelix (2), [0, 0, 0; 1, 1, 1]) %!assert ([cubehelix]([1,end],:), [0, 0, 0; 1, 1, 1]) %!shared a %! a = [0, 0, 0; %! 0.17004232121057959, 0.43679759647517287, 0.22372555555555556; %! 0.82995767878942041, 0.56320240352482713, 0.77627444444444445; %! 1, 1, 1]; %!assert (cubehelix (4), a, eps) %!shared # Clear shared varibles to avoid echo on unrelated test errors. ## Input validation %!error <N must be a scalar integer> cubehelix ("foo") %!error <N must be a scalar integer> cubehelix ([1, 2, 3]) %!error <N must be a scalar integer> cubehelix ({1, 2, 3})