iOS 14, SwiftUI 2.0, swift 5.1, Xcode beta12

extension Color {
  static func hexColour(hexValue:UInt32)->Color
    {
      let red = Double((hexValue & 0xFF0000) >> 16) / 255.0
      let green = Double((hexValue & 0xFF00) >> 8) / 255.0
      let blue = Double(hexValue & 0xFF) / 255.0
      return Color(red:red, green:green, blue:blue)
    }
}

用十六进制数表示

let red = Color.hexColour(hexValue: 0xFF0000)

我做了一个小函数，把它放在我可以全局使用它的地方，在swift 2.1中工作得很好:

func getColorFromHex(rgbValue:UInt32)->UIColor{
   let red = CGFloat((rgbValue & 0xFF0000) >> 16)/255.0
   let green = CGFloat((rgbValue & 0xFF00) >> 8)/255.0
   let blue = CGFloat(rgbValue & 0xFF)/255.0

   return UIColor(red:red, green:green, blue:blue, alpha:1.0)
}

用法:

getColorFromHex(0xffffff)

Swift 5 (Swift 4, Swift 3) UIColor扩展:

extension UIColor {
    convenience init(hexString: String) {
        let hex = hexString.trimmingCharacters(in: CharacterSet.alphanumerics.inverted)
        var int = UInt64()
        Scanner(string: hex).scanHexInt64(&int)
        let a, r, g, b: UInt64
        switch hex.count {
        case 3: // RGB (12-bit)
            (a, r, g, b) = (255, (int >> 8) * 17, (int >> 4 & 0xF) * 17, (int & 0xF) * 17)
        case 6: // RGB (24-bit)
            (a, r, g, b) = (255, int >> 16, int >> 8 & 0xFF, int & 0xFF)
        case 8: // ARGB (32-bit)
            (a, r, g, b) = (int >> 24, int >> 16 & 0xFF, int >> 8 & 0xFF, int & 0xFF)
        default:
            (a, r, g, b) = (255, 0, 0, 0)
        }
        self.init(red: CGFloat(r) / 255, green: CGFloat(g) / 255, blue: CGFloat(b) / 255, alpha: CGFloat(a) / 255)
    }
}

用法:

let darkGrey = UIColor(hexString: "#757575")

斯威夫特2。x版本:

extension UIColor {
    convenience init(hexString: String) {
        let hex = hexString.stringByTrimmingCharactersInSet(NSCharacterSet.alphanumericCharacterSet().invertedSet)
        var int = UInt32()
        NSScanner(string: hex).scanHexInt(&int)
        let a, r, g, b: UInt32
        switch hex.characters.count {
        case 3: // RGB (12-bit)
            (a, r, g, b) = (255, (int >> 8) * 17, (int >> 4 & 0xF) * 17, (int & 0xF) * 17)
        case 6: // RGB (24-bit)
            (a, r, g, b) = (255, int >> 16, int >> 8 & 0xFF, int & 0xFF)
        case 8: // ARGB (32-bit)
            (a, r, g, b) = (int >> 24, int >> 16 & 0xFF, int >> 8 & 0xFF, int & 0xFF)
        default:
            (a, r, g, b) = (255, 0, 0, 0)
        }
        self.init(red: CGFloat(r) / 255, green: CGFloat(g) / 255, blue: CGFloat(b) / 255, alpha: CGFloat(a) / 255)
    }
}

你可以在UIColor上使用这个扩展，它将你的字符串(十六进制，RGBA)转换为UIColor，反之亦然。

extension UIColor {

  //Convert RGBA String to UIColor object
  //"rgbaString" must be separated by space "0.5 0.6 0.7 1.0" 50% of Red 60% of Green 70% of Blue Alpha 100%
  public convenience init?(rgbaString : String){
      self.init(ciColor: CIColor(string: rgbaString))
  }

  //Convert UIColor to RGBA String
  func toRGBAString()-> String {
    var r: CGFloat = 0
    var g: CGFloat = 0
    var b: CGFloat = 0
    var a: CGFloat = 0
    self.getRed(&r, green: &g, blue: &b, alpha: &a)
    return "\(r) \(g) \(b) \(a)"
  }

  //return UIColor from Hexadecimal Color string
  public convenience init?(hexString: String) {  
    let r, g, b, a: CGFloat

    if hexString.hasPrefix("#") {
      let start = hexString.index(hexString.startIndex, offsetBy: 1)
      let hexColor = hexString.substring(from: start)

      if hexColor.characters.count == 8 {
        let scanner = Scanner(string: hexColor)
        var hexNumber: UInt64 = 0

        if scanner.scanHexInt64(&hexNumber) {
          r = CGFloat((hexNumber & 0xff000000) >> 24) / 255
          g = CGFloat((hexNumber & 0x00ff0000) >> 16) / 255
          b = CGFloat((hexNumber & 0x0000ff00) >> 8) / 255
          a = CGFloat(hexNumber & 0x000000ff) / 255
          self.init(red: r, green: g, blue: b, alpha: a)
          return
        }
      }
    }

    return nil
  }

  // Convert UIColor to Hexadecimal String
  func toHexString() -> String {
    var r: CGFloat = 0
    var g: CGFloat = 0
    var b: CGFloat = 0
    var a: CGFloat = 0
    self.getRed(&r, green: &g, blue: &b, alpha: &a)
    return String(
        format: "%02X%02X%02X",
        Int(r * 0xff),
        Int(g * 0xff),
        Int(b * 0xff))
  }
}

斯威夫特2.0

下面的代码是在xcode 7.2上测试的

import UIKit
extension UIColor{

    public convenience init?(colorCodeInHex: String, alpha: Float = 1.0){

        var filterColorCode:String =  colorCodeInHex.stringByReplacingOccurrencesOfString("#", withString: "")

        if  filterColorCode.characters.count != 6 {
            self.init(red: 0.0, green: 0.0, blue: 0.0, alpha: CGFloat(alpha))
            return
        }

        filterColorCode = filterColorCode.stringByTrimmingCharactersInSet(NSCharacterSet.whitespaceAndNewlineCharacterSet()).uppercaseString

        var range = Range(start: filterColorCode.startIndex.advancedBy(0), end: filterColorCode.startIndex.advancedBy(2))
        let rString = filterColorCode.substringWithRange(range)

        range = Range(start: filterColorCode.startIndex.advancedBy(2), end: filterColorCode.startIndex.advancedBy(4))
        let gString = filterColorCode.substringWithRange(range)


        range = Range(start: filterColorCode.startIndex.advancedBy(4), end: filterColorCode.startIndex.advancedBy(6))
        let bString = filterColorCode.substringWithRange(range)

        var r:CUnsignedInt = 0, g:CUnsignedInt = 0, b:CUnsignedInt = 0;
        NSScanner(string: rString).scanHexInt(&r)
        NSScanner(string: gString).scanHexInt(&g)
        NSScanner(string: bString).scanHexInt(&b)


        self.init(red: CGFloat(r) / 255.0, green: CGFloat(g) / 255.0, blue: CGFloat(b) / 255.0, alpha: CGFloat(alpha))
        return
    }
}

#ffffff实际上是16进制表示法的3个颜色组件——红色ff，绿色ff和蓝色ff。你可以在Swift中使用0x前缀编写十六进制符号，例如0xFF

为了简化转换，让我们创建一个初始化式，它接受整数(0 - 255)值:

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)

如何得到alpha?

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

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

或者你可以在上面的方法中添加一个额外的(可选的)参数:

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
    )
}

(我们不能将参数命名为alpha，因为与现有的初始化式名称冲突)。

称为:

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

为了得到0-255的整数，我们可以

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)

或者是前面几种方法的组合。绝对没有必要使用字符串。