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我有一个带有 HSB(Hue, Saturation, Brightness) 值的颜色，我希望将 RBG 直接转换为十六进制字符串。我怎样才能做到这一点？有没有不使用 UIColor API 的方法，我想实现我自己的功能，比如：

    func toHex(h: CGFloat, s: CGFloat, b: CGFloat) -> String {
        var hex: String
        //conversion

        return hex // For example "#02AAFE"
    }
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1 回答 1

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您可以使用 UIColor 初始化程序创建 UIColor，然后使用 UIColor getRed 方法提取 rgb 颜色。然后你只需要将组件值乘以 255 并使用字符串基数初始化器从它们创建一个六进制表示：

extension UIColor {
    var rgb: (red: CGFloat, green: CGFloat, blue: CGFloat)? {
        var r: CGFloat = 0, g: CGFloat = 0, b: CGFloat = 0
        guard getRed(&r, green: &g, blue: &b, alpha: nil) else { return nil }
        return (r,g,b)
    }
    var hexa: String? {
        guard let (r,g,b) = rgb else { return nil }
        return "#" + UInt8(r*255).hexa + UInt8(g*255).hexa + UInt8(b*255).hexa
    }
}

extension UInt8 {
    var hexa: String {
        let value = String(self, radix: 16, uppercase: true)
        return (self < 16 ? "0": "") + value
    }
}

let red = UIColor(hue: 1, saturation: 1, brightness: 1, alpha: 1)
let white = UIColor(hue: 1, saturation: 0, brightness: 1, alpha: 1)
let black = UIColor(hue: 1, saturation: 0, brightness: 0, alpha: 1)
red.hexa    // "#FF0000" red
white.hexa  // "#ffffff" white
black.hexa  // "#000000" black

现在，如果您真的想避免使用 UIColor api，您可以使用这篇文章作为从 HSB 转换为 RGB 的参考：

func toHex<F: BinaryFloatingPoint>(h: F, s: F, b: F) -> String {
    var red, green, blue, i, f, p, q, t: F
    i = (h * 6).rounded(.down)
    f = h * 6 - i
    p = b * (1 - s)
    q = b * (1 - f * s)
    t = b * (1 - (1 - f) * s)
    switch h * 360 {
    case 0..<60, 360: red = b; green = t; blue = p
    case 60..<120: red = q; green = b; blue = p
    case 120..<180: red = p; green = b; blue = t
    case 180..<240: red = p; green = q; blue = b
    case 240..<300: red = t; green = p; blue = b
    case 300..<360: red = b; green = p; blue = q
    default: fatalError()
    return "#" + UInt8(red * 255).hexa + UInt8(green * 255).hexa + UInt8(blue * 255).hexa
}

toHex(h: 1, s: 1, b: 1)         // "#FF0000" red
toHex(h: 1, s: 0, b: 1)         // "#FFFFFF" white
toHex(h: 1, s: 0, b: 0)         // "#000000" black
toHex(h: 0.8333, s: 1, b: 0.5)  // "#7F007F" purple
于 2020-07-13T02:06:09.223 回答