如何使用十六进制颜色值 [英] How to use hex color values

问题描述

我正在尝试在Swift中使用十六进制颜色值，而不是UIColor允许您使用的一些标准颜色值，但是我不知道该怎么做.

I am trying to use hex color values in Swift, instead of the few standard ones that UIColor allows you to use, but I have no idea how to do it.

示例:我将如何使用#ffffff作为颜色?

Example: how would I use #ffffff as a color?

推荐答案

#ffffff实际上是十六进制表示的3种颜色分量-红色ff，绿色ff和蓝色ff.您可以使用0x前缀(例如0xFF

#ffffff are actually 3 color components in hexadecimal notation - red ff, green ff and blue ff. You can write hexadecimal notation in Swift using 0x prefix, e.g 0xFF

为简化转换，让我们创建一个采用整数(0-255)值的初始化程序:

To simplify the conversion, let's create an initializer that takes integer (0 - 255) values:

extension UIColor {
   convenience init(red: Int, green: Int, blue: Int) {
       assert(red >= 0 && red <= 255, "Invalid red component")
       assert(green >= 0 && green <= 255, "Invalid green component")
       assert(blue >= 0 && blue <= 255, "Invalid blue component")

       self.init(red: CGFloat(red) / 255.0, green: CGFloat(green) / 255.0, blue: CGFloat(blue) / 255.0, alpha: 1.0)
   }

   convenience init(rgb: Int) {
       self.init(
           red: (rgb >> 16) & 0xFF,
           green: (rgb >> 8) & 0xFF,
           blue: rgb & 0xFF
       )
   }
}

用法:

let color = UIColor(red: 0xFF, green: 0xFF, blue: 0xFF)
let color2 = UIColor(rgb: 0xFFFFFF)

如何获取Alpha?

根据您的用例，您可以简单地使用本机UIColor.withAlphaComponent方法，例如

Depending on your use case, you can simply use the native UIColor.withAlphaComponent method, e.g.

let semitransparentBlack = UIColor(rgb: 0x000000).withAlphaComponent(0.5)

或者您可以在上述方法中添加其他(可选)参数:

Or you can add an additional (optional) parameter to the above methods:

convenience init(red: Int, green: Int, blue: Int, a: CGFloat = 1.0) {
    self.init(
        red: CGFloat(red) / 255.0,
        green: CGFloat(green) / 255.0,
        blue: CGFloat(blue) / 255.0,
        alpha: a
    )
}

convenience init(rgb: Int, a: CGFloat = 1.0) {
    self.init(
        red: (rgb >> 16) & 0xFF,
        green: (rgb >> 8) & 0xFF,
        blue: rgb & 0xFF,
        a: a
    )
}

(由于与现有初始化程序的名称冲突，我们无法命名参数alpha).

(we cannot name the parameter alpha because of a name collision with the existing initializer).

称为:

let color = UIColor(red: 0xFF, green: 0xFF, blue: 0xFF, a: 0.5)
let color2 = UIColor(rgb: 0xFFFFFF, a: 0.5)

要获取Alpha作为0-255的整数，我们可以

To get the alpha as an integer 0-255, we can

convenience init(red: Int, green: Int, blue: Int, a: Int = 0xFF) {
    self.init(
        red: CGFloat(red) / 255.0,
        green: CGFloat(green) / 255.0,
        blue: CGFloat(blue) / 255.0,
        alpha: CGFloat(a) / 255.0
    )
}

// let's suppose alpha is the first component (ARGB)
convenience init(argb: Int) {
    self.init(
        red: (argb >> 16) & 0xFF,
        green: (argb >> 8) & 0xFF,
        blue: argb & 0xFF,
        a: (argb >> 24) & 0xFF
    )
}

称为

let color = UIColor(red: 0xFF, green: 0xFF, blue: 0xFF, a: 0xFF)
let color2 = UIColor(argb: 0xFFFFFFFF)

或上述方法的组合.完全不需要使用字符串.

Or a combination of the previous methods. There is absolutely no need to use strings.

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