Ansi扩展颜色索引中颜色的RGB值(17-255)

一些来源:

urxvt 手册页:

除了默认的前景色和背景色之外,urxvt还可以显示多达88/256种颜色:8种ANSI颜色加上相同的高强度(可能是粗体/闪烁)版本,以及72种(或256种颜色模式中的240种颜色)颜色排列在4x4x4(或6x6x6)彩色RGB立方体加上8(24)彩色灰度渐变.

xterm 手册页:

这些指定256色扩展的颜色.默认资源值用于颜色16到231以制作6x6x6颜色立方体,而颜色232到255用于制作灰度渐变.

关于ANSI转义码的维基百科文章(反过来本身缺乏对该主题的引用)

默认RGB值

从理论上讲,为了获得均匀分布的颜色范围,16 - 231范围内颜色的RGB值可以这样计算:

# example in Python: // is integer divison, % is modulo
rgb_R = ((number - 16) // 36) * 51
rgb_G = (((number - 16) % 36) // 6) * 51
rgb_B = ((number - 16) % 6) * 51

但似乎实际方法不同:

我测试的任何终端仿真器似乎都遵循XTerm并将[0, 1, 2, 3, 4, 5]红色,绿色和蓝色的值映射到[0, 95, 135, 175, 215, 255]RGB颜色轴上的值.(我测试了XTerm(297)URxvt(v9.19),ROXTerm(2.8.1),gnome-terminal(3.6.2)和xfce4-terminal(0.6.3))

可以使用此算法计算给定索引的RGB值:

# example in Python: 'a = b if c else d' is 'a = (c) ? b : d` in C, Perl, etc.
index_R = ((number - 16) // 36)
rgb_R = 55 + index_R * 40 if index_R > 0 else 0
index_G = (((number - 16) % 36) // 6)
rgb_G = 55 + index_G * 40 if index_G > 0 else 0
index_B = ((number - 16) % 6)
rgb_B = 55 + index_B * 40 if index_B > 0 else 0

灰度似乎遵循这个简单的公式:

rgb_R = rgb_G = rgb_B = (number - 232) * 10 + 8

256colres.pl在XTerm源(版本313)的根目录中使用类似的算法生成256colres.h,其中包含256色模式的颜色定义:

$line1="COLOR_RES(\"%d\",";
$line2="\tscreen.Acolors[%d],";
$line3="\tDFT_COLOR(\"rgb:%2.2x/%2.2x/%2.2x\")),\n";

# colors 16-231 are a 6x6x6 color cube
for ($red = 0; $red < 6; $red++) {
    for ($green = 0; $green < 6; $green++) {
    for ($blue = 0; $blue < 6; $blue++) {
        $code = 16 + ($red * 36) + ($green * 6) + $blue;
        printf($line1, $code);
        printf($line2, $code);
        printf($line3,
           ($red ? ($red * 40 + 55) : 0),
           ($green ? ($green * 40 + 55) : 0),
           ($blue ? ($blue * 40 + 55) : 0));
    }
    }
}

# colors 232-255 are a grayscale ramp, intentionally leaving out
# black and white
$code=232;
for ($gray = 0; $gray < 24; $gray++) {
    $level = ($gray * 10) + 8;
    $code = 232 + $gray;
    printf($line1, $code);
    printf($line2, $code);
    printf($line3,
       $level, $level, $level);
}

function termcolors () 
{
    print TERM
    print -P "Foreground: >?<"
    print -P "Background: >%S?%s<\n"

    print "      0 1 2 3 4 5 6 7" 
    for b (0 1)
    do
        printf "%d %2d " $b $(( 8 * b ))
        for r (0 1 2 3 4 5 6 7)
        do
            c=$(( 8 * b + r ))
            print -nP "%K{$c}  %k"
        done
        printf " %2d\n" $(( 8 * b + 7 ))
    done

    print

    print RGB
    for r (0 1 2 3 4 5)
    do 
        print "$r $(( 16 + 36 * r )) - $(( 16 + 36 * r + 35 ))\n       0 1 2 3 4 5"
        for g (0 1 2 3 4 5)
        do
            printf "%d %3d " $g $(( 16 + 36 * r + 6 * g ))
            for b (0 1 2 3 4 5)
            do
                c=$(( 16 + 36 * r + 6 * g + b ))
                print -nP "%K{$c}  %k"
            done
            printf " %3d\n" $(( 16 + 36 * r + 6 * g + 5))
        done
        print
    done

    print

    print GRAY
    for g in $(seq 0 23)
    do
        c=$(( 232 + g ))
        printf "%2d %3d " $g $c
        print -P "%K{$c}  %k"
    done
}

OSC 4; c ; spec BEL
OSC 4; c ; spec ST

echo -en "\e]4;COLOR;SPEC\a"
echo -en "\e]4;COLOR;SPEC\a"

echo -en "\e]4;5;red\a"
echo -en "\e]4;5;#ff0000\e\\"
echo -en "\033]4;5;rgb:ff/00/00\007"

OSC 104 ; c BEL
OSC 104 ; c ST

for c in {0..255}; do
  echo -en "\e]104;$c\a"
done

echo -en "\e]10;red\a"
echo -en "\e]11;green\a"

echo -en "\e]110\a"
echo -en "\e]111\a"