Mercurial > octave-libtiff
view scripts/image/cubehelix.m @ 30564:796f54d4ddbf stable
update Octave Project Developers copyright for the new year
In files that have the "Octave Project Developers" copyright notice,
update for 2021.
In all .txi and .texi files except gpl.txi and gpl.texi in the
doc/liboctave and doc/interpreter directories, change the copyright
to "Octave Project Developers", the same as used for other source
files. Update copyright notices for 2022 (not done since 2019). For
gpl.txi and gpl.texi, change the copyright notice to be "Free Software
Foundation, Inc." and leave the date at 2007 only because this file
only contains the text of the GPL, not anything created by the Octave
Project Developers.
Add Paul Thomas to contributors.in.
author | John W. Eaton <jwe@octave.org> |
---|---|
date | Tue, 28 Dec 2021 18:22:40 -0500 |
parents | 7854d5752dd2 |
children |
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######################################################################## ## ## Copyright (C) 2014-2022 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 unspecified, the length of the current colormap, or 64, 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)) error ("cubehelix: N must be a scalar"); endif n = double (n); else hf = get (0, "currentfigure"); if (! isempty (hf)) n = rows (get (hf, "colormap")); else n = 64; 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 3D 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);