如何将颜色名称转换为3元素RGB矢量？

Question

在许多MATLAB绘图功能中,您可以将颜色指定为字符串或直接列出红色,绿色和蓝色值的3元素矢量.

例如,这两个陈述是等价的:

plot(x, y, 'Color', 'r');
plot(x, y, 'Color', [1 0 0]);

有8种颜色可以用字符串值指定:'r','g','b','c','m','y','k','w'.是否有MATLAB内置函数将这些字符串转换为等效的RGB矢量？

Answer 1

我在MathWorks文件交换中找到了这个通用的替代方法,它甚至可以处理MATLAB中默认值为8的颜色字符串:

• rgb.m由本·米奇

如果您只关注默认8色字符串的转换,这里是我自己编写的一个函数,用于在RGB三元组和短颜色名称(即单个字符)之间来回转换:

function outColor = convert_color(inColor)

  charValues = 'rgbcmywk'.';  %#'
  rgbValues = [eye(3); 1-eye(3); 1 1 1; 0 0 0];
  assert(~isempty(inColor),'convert_color:badInputSize',...
         'Input argument must not be empty.');

  if ischar(inColor)  %# Input is a character string

    [isColor,colorIndex] = ismember(inColor(:),charValues);
    assert(all(isColor),'convert_color:badInputContents',...
           'String input can only contain the characters ''rgbcmywk''.');
    outColor = rgbValues(colorIndex,:);

  elseif isnumeric(inColor) || islogical(inColor)  %# Input is a numeric or
                                                   %#   logical array
    assert(size(inColor,2) == 3,'convert_color:badInputSize',...
           'Numeric input must be an N-by-3 matrix');
    inColor = double(inColor);           %# Convert input to type double
    scaleIndex = max(inColor,[],2) > 1;  %# Find rows with values > 1
    inColor(scaleIndex,:) = inColor(scaleIndex,:)./255;  %# Scale by 255
    [isColor,colorIndex] = ismember(inColor,rgbValues,'rows');
    assert(all(isColor),'convert_color:badInputContents',...
           'RGB input must define one of the colors ''rgbcmywk''.');
    outColor = charValues(colorIndex(:));

  else  %# Input is an invalid type

    error('convert_color:badInputType',...
          'Input must be a character or numeric array.');

  end

请注意,此功能允许您输入字符串或 N-by-3数字或逻辑数组(RGB值从0到1或0到255),并返回相反的颜色表示.它还使用ISMEMBER函数进行转换.

Answer 2

万一没有，我就一起黑了一个

function rgbvec = char2rgb (charcolor)
%function rgbvec = char2rgb (charcolor)
%
%converts a character color (one of 'r','g','b','c','m','y','k','w') to a 3
%value RGB vector
%if charcolor is a string (vector of chars), the result is a Nx3 matrix of
%color values, where N is the length of charcolor

if (~exist(charcolor,'var') || ~ischar(charcolor))
    warning('RGB2VEC:NOTC', 'You must pass a character (rgbcmykw)');
    rgbvec = [0 0 0];
    return;
end
rgbvec = zeros(length(charcolor), 3);
charwarning = false;
for j = 1:length(charcolor)
    switch(lower(charcolor(j)))
        case 'r'
            rgbvec(j,:) = [1 0 0];
        case 'g'
            rgbvec(j,:) = [0 1 0];
        case 'b'
            rgbvec(j,:) = [0 0 1];
        case 'c'
            rgbvec(j,:) = [0 1 1];
        case 'm'
            rgbvec(j,:) = [1 0 1];
        case 'y'
            rgbvec(j,:) = [1 1 0];
        case 'w'
            rgbvec(j,:) = [1 1 1];
        case 'k'
            rgbvec(j,:) = [0 0 0];
        otherwise
            charwarning = true;
    end
end

if (charwarning)
    warning('RGB2VEC:BADC', 'Only r,g,b,c,m,y,k,and w are recognized colors');
end

Answer 3

我认为在matlab中没有为此功能。我建议您使用Marcs函数或单行代码。

C = rem(floor((strfind('kbgcrmyw', C) - 1) * [0.25 0.5 1]), 2); 

Answer 4

从 R2020b 开始，您可以使用validatecolor此功能。