Program Listing for File generate_rgb.m

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%
%> Compute Rgb triple for given CSS color name. The function returns the RGB
%> (Red-Green-Blue) triple corresponding to the color name by the CSS3
%> proposed standard [1], which contains 139 different colors (an RGB triple
%> is a 1x3 vector of numbers between 0 and 1). The input color name is case
%> insensitive, and for gray colors both spellings (gray and grey) are allowed.
%>
%>   **Usage:**
%>   - c = Indigo.Utils.generate_rgb('DarkRed'): returns c = [0.5430 0 0].
%>   - c = Indigo.Utils.generate_rgb('Green'): returns c = [0 0.5 0].
%>   - plot(x, y, 'color', generate_rgb('Orange')): plots an orange line through
%>     x and y.
%>   - Indigo.Utils.show_colors(): shows all the available colors.
%>
%>   **Background:**
%>     The color names of [1] have already been ratified in [2], and
%>     according to [3] they are accepted by almost all web browsers and are
%>     used in Microsoft's .net framework. All but four colors agree with
%>     the X11 colornames, as detailed in [4]. Of these the most important
%>     clash is green, defined as [0 0.5 0] by CSS and [0 1 0] by X11. The
%>     definition of green in Matlab matches the X11 definition and gives a
%>     very light green, called lime by CSS (many users of Matlab have
%>     discovered this when trying to color graphs with 'g-'). Note that
%>     cyan and aqua are synonyms as well as magenta and fuchsia.
%>
%>   **About:**
%>     This program is public domain and may be distributed freely.
%>     Author: Kristjan Jonasson, Dept. of Computer Science, University of
%>     Iceland (jonasson@hi.is). June 2009.
%>
%>   **References:**
%>     [1] "CSS Color module level 3", W3C (World Wide Web Consortium)
%>         working draft 21 July 2008, http://www.w3.org/TR/css3-color
%>     [2] "Scalable Vector Graphics (SVG) 1.1 specification", W3C
%>         recommendation 14 January 2003, edited in place 30 April 2009,
%>         http://www.w3.org/TR/SVG
%>     [3] "Web colors", http://en.wikipedia.org/wiki/Web_colors
%>     [4] "X11 color names" http://en.wikipedia.org/wiki/X11_color_names
%>
%> \param str Color string name.
%>
%> \return Red-Green-Blue triple.
%
function out = generate_rgb( str )

  CMD = 'Indigo.Utils.generate_rgb(...): ';

  % First time rgb is called
  [num, name] = Indigo.Utils.get_colors();
  name = lower(name);
  num  = reshape(hex2dec(num), [], 3);

  % Divide most numbers by 256 for "aesthetic" reasons (green = [0 0.5 0])
  I = num < 240;

  % Interpolate F0-FF linearly from 240/256 to 1.0
  num(I)  = num(I)/256;
  num(~I) = ((num(~I) - 240)/15 + 15)/16; % + 240;

  % Show colors chart
  if strcmpi(str, 'chart')
    Indigo.Utils.show_colors()
  else
    k = find(strcmpi(str, name)); %#ok<STLOW>
    if isempty(k)
      error([CMD, 'invalid color ''', str, '''.']);
    else
      out = num(k(1), :);
    end
  end
end