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scripts/image/hsv2rgb.m

changeset 10289: 4b124317dc38
parent:cadc73247d65
author: John W. Eaton <jwe@octave.org>
date: Tue Feb 09 20:58:55 2010 -0500 (62 minutes ago)
permissions: -rw-r--r--
description: base_properties::set_children: account for hidden children 
     1## Copyright (C) 1999, 2000, 2001, 2002, 2004, 2005, 2006, 2007, 2008, 2009

     2##               Kai Habel

     3##

     4## This file is part of Octave.

     5##

     6## Octave is free software; you can redistribute it and/or modify it

     7## under the terms of the GNU General Public License as published by

     8## the Free Software Foundation; either version 3 of the License, or (at

     9## your option) any later version.

    10##

    11## Octave is distributed in the hope that it will be useful, but

    12## WITHOUT ANY WARRANTY; without even the implied warranty of

    13## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

    14## General Public License for more details.

    15##

    16## You should have received a copy of the GNU General Public License

    17## along with Octave; see the file COPYING.  If not, see

    18## <http://www.gnu.org/licenses/>.

    19

    20## -*- texinfo -*-

    21## @deftypefn {Function File} {@var{rgb_map} =} hsv2rgb (@var{hsv_map})

    22## Transform a colormap or image from the hsv space to the rgb space. 

    23## @seealso{rgb2hsv}

    24## @end deftypefn

    25

    26## Author: Kai Habel <kai.habel@gmx.de>

    27## Adapted-by: jwe

    28

    29function rgb_map = hsv2rgb (hsv_map)

    30

    31## Each color value x = (r,g,b) is calculated with

    32## x = (1-sat)*val+sat*val*f_x(hue)

    33## where f_x(hue) is a piecewise defined function for

    34## each color with f_r(hue-2/3) = f_g(hue) = f_b(hue-1/3).

    35

    36  if (nargin != 1)

    37    print_usage ();

    38  endif

    39

    40  ## If we have an image convert it into a color map.

    41  if (ismatrix (hsv_map) && ndims (hsv_map) == 3)

    42    is_image = true;

    43    Sz = size (hsv_map);

    44    hsv_map = [hsv_map(:,:,1)(:), hsv_map(:,:,2)(:), hsv_map(:,:,3)(:)];

    45    ## Convert to a double image.

    46    if (isinteger (hsv_map))

    47      C = class (hsv_map);

    48      low = double (intmin (C));

    49      high = double (intmax (C));

    50      hsv_map = (double (hsv_map) - low) / (high - low);

    51    endif

    52  else

    53    is_image = false;

    54  endif

    55

    56  if (! ismatrix (hsv_map) || columns (hsv_map) != 3)

    57    error ("hsv2rgb: argument must be a matrix of size nx3");

    58  endif

    59

    60  ## set values <0 to 0 and >1 to 1

    61  hsv_map = (hsv_map >= 0 & hsv_map <= 1) .* hsv_map \

    62      + (hsv_map < 0) .* 0 + (hsv_map > 1);

    63

    64  ## fill rgb map with v*(1-s)

    65  rgb_map = kron ([1, 1, 1], hsv_map(:,3) .* (1 - hsv_map(:,2)));

    66

    67  ## red(hue-2/3)=green(hue)=blue(hue-1/3)

    68  ## apply modulo 1 for red and blue 

    69  t = hsv_map(:,1);

    70  tp = t';

    71  hue = [(tp - 2/3 - floor (t - 2/3)');

    72         tp;

    73         (tp - 1/3 - floor (t - 1/3)')]';

    74

    75  ## factor s*v -> f

    76  f = kron ([1, 1, 1], hsv_map(:,2)) .* kron ([1, 1, 1], hsv_map(:,3));

    77

    78  ## add s*v* hue-function to rgb map

    79  rgb_map = rgb_map +  f .* (6 * (hue < 1/6) .* hue

    80			     + (hue >= 1/6 & hue < 1/2)

    81			     + (hue >= 1/2 & hue < 2/3) .* (4 - 6 * hue));

    82

    83  ## If input was an image, convert it back into one.

    84  if (is_image)

    85    rgb_map = reshape (rgb_map, Sz);

    86  endif

    87

    88endfunction