以防有人关心Mark Ransom回答的SCSS版本:

@use 'sass:color' as *;
@use 'sass:math' as *;

@function col_r($color) {
    @if $color <= 0.03928 {
        @return $color / 12.92;
    } @else {
        @return pow((($color + 0.055) / 1.055), (2.4));
    }
}

@function pickTextColorBasedOnBgColorAdvanced(
  $bgColor,
  $lightColor,
  $darkColor
) {
  $r: red($bgColor);
  $g: green($bgColor);
  $b: blue($bgColor);
  $ui_r: $r / 255;
  $ui_g: $g / 255;
  $ui_b: $b / 255;

  $ui_r_c: col_r($ui_r);
  $ui_g_c: col_r($ui_g);
  $ui_b_c: col_r($ui_b);

  $L: (0.2126 * $ui_r_c) + (0.7152 * $ui_g_c) + (0.0722 * $ui_b_c);
  @if ($L > 0.179) {
    @return $darkColor;
  } @else {
    @return $lightColor;
  }
}

根据来自链接的不同输入，使前景颜色黑色或白色取决于背景和这个线程，我为颜色做了一个扩展类，为您提供所需的对比色。

代码如下:

 public static class ColorExtension
{       
    public static int PerceivedBrightness(this Color c)
    {
        return (int)Math.Sqrt(
        c.R * c.R * .299 +
        c.G * c.G * .587 +
        c.B * c.B * .114);
    }
    public static Color ContrastColor(this Color iColor, Color darkColor,Color lightColor)
    {
        //  Counting the perceptive luminance (aka luma) - human eye favors green color... 
        double luma = (iColor.PerceivedBrightness() / 255);

        // Return black for bright colors, white for dark colors
        return luma > 0.5 ? darkColor : lightColor;
    }
    public static Color ContrastColor(this Color iColor) => iColor.ContrastColor(Color.Black);
    public static Color ContrastColor(this Color iColor, Color darkColor) => iColor.ContrastColor(darkColor, Color.White);
    // Converts a given Color to gray
    public static Color ToGray(this Color input)
    {
        int g = (int)(input.R * .299) + (int)(input.G * .587) + (int)(input.B * .114);
        return Color.FromArgb(input.A, g, g, g);
    }
}

这个(JavaScript代码)怎么样?

/**
 * Get color (black/white) depending on bgColor so it would be clearly seen.
 * @param bgColor
 * @returns {string}
 */
getColorByBgColor(bgColor) {
    if (!bgColor) { return ''; }
    return (parseInt(bgColor.replace('#', ''), 16) > 0xffffff / 2) ? '#000' : '#fff';
}

我在@SudoPlz提出的高级函数的基础上做了一个函数，它也考虑了浅色和深色:

function getTextColor (bgColor, lightColor = '#FFFFFF', darkColor = '#000000') {

  const getLuminance = function (hexColor) {
    var color = (hexColor.charAt(0) === '#') ? hexColor.substring(1, 7) : hexColor
    var r = parseInt(color.substring(0, 2), 16) // hexToR
    var g = parseInt(color.substring(2, 4), 16) // hexToG
    var b = parseInt(color.substring(4, 6), 16) // hexToB
    var uicolors = [r / 255, g / 255, b / 255]
    var c = uicolors.map(col => col <= 0.03928 ? col / 12.92 : ((col + 0.055) / 1.055) ** 2.4)

    return (0.2126 * c[0]) + (0.7152 * c[1]) + (0.0722 * c[2]);
  }

  var L = getLuminance(bgColor)
  var L1 = getLuminance(lightColor)
  var L2 = getLuminance(darkColor)

  return (L > Math.sqrt((L1 + 0.05) * (L2 + 0.05)) - 0.05) ? darkColor : lightColor;
}

因此，如果深色文本不是黑色而是栗色，灰色背景上的推荐文本颜色会变成白色:

getTextColor('#808080')
"#000000"

getTextColor('#808080', '#FFFFFF', '#800000')
"#FFFFFF"

这是Mark Ransom的答案的一个快速版本，作为UIColor的扩展

extension UIColor {

// Get the rgba components in CGFloat
var rgba: (red: CGFloat, green: CGFloat, blue: CGFloat, alpha: CGFloat) {
    var red: CGFloat = 0, green: CGFloat = 0, blue: CGFloat = 0, alpha: CGFloat = 0

    getRed(&red, green: &green, blue: &blue, alpha: &alpha)

    return (red, green, blue, alpha)
}

/// Return the better contrasting color, white or black
func contrastColor() -> UIColor {
    let rgbArray = [rgba.red, rgba.green, rgba.blue]

    let luminanceArray = rgbArray.map({ value -> (CGFloat) in
        if value < 0.03928 {
            return (value / 12.92)
        } else {
            return (pow( (value + 0.55) / 1.055, 2.4) )
        }
    })

    let luminance = 0.2126 * luminanceArray[0] +
        0.7152 * luminanceArray[1] +
        0.0722 * luminanceArray[2]

    return luminance > 0.179 ? UIColor.black : UIColor.white
} }

这是马克·兰森的答案的R版本，只使用R基。

hex_bw <- function(hex_code) {

  myrgb <- as.integer(col2rgb(hex_code))

  rgb_conv <- lapply(myrgb, function(x) {
    i <- x / 255
    if (i <= 0.03928) {
      i <- i / 12.92
    } else {
      i <- ((i + 0.055) / 1.055) ^ 2.4
    }
    return(i)
  })

 rgb_calc <- (0.2126*rgb_conv[[1]]) + (0.7152*rgb_conv[[2]]) + (0.0722*rgb_conv[[3]])

 if (rgb_calc > 0.179) return("#000000") else return("#ffffff")

}

> hex_bw("#8FBC8F")
[1] "#000000"
> hex_bw("#7fa5e3")
[1] "#000000"
> hex_bw("#0054de")
[1] "#ffffff"
> hex_bw("#2064d4")
[1] "#ffffff"
> hex_bw("#5387db")
[1] "#000000"