xcode – 在Swift中将UIColor转换为十六进制(web颜色)的最佳/最短方法是什么？

我提出了以下解决方案,但想知道是否有人采用更清晰的方法(在 Xcode-Playground中测试)：

let colors = CGColorGetComponents( UIColor.greenColor().CGColor )
let hexCol:String = Nsstring(format: "#%02x%02x%02x",Int(colors[0] * 255.0),Int(colors[1] * 255.0),Int(colors[2] * 255.0))

结果是#00ff00

其中UIColor.greenColor()是任何UIColor的示例.

编辑：
取自莱昂纳多的答案,我觉得有点重构(他的所有测试仍然适用).

extension UIColor {
    typealias RGBComponents = (red: CGFloat,green: CGFloat,blue: CGFloat,alpha: CGFloat)
    typealias HSBComponents = (hue: CGFloat,saturation: CGFloat,brightness: CGFloat,alpha: CGFloat)

    var rgbComponents:RGBComponents {
        var c:RGBComponents = (0,0)

        if getRed(&c.red,green: &c.green,blue: &c.blue,alpha: &c.alpha) {
            return c
        }

        return (0,0)
    }

    var cssRGBA:String {
        return String(format: "rgba(%d,%d,%.02f)",Int(rgbComponents.red * 255),Int(rgbComponents.green * 255),Int(rgbComponents.blue * 255),Float(rgbComponents.alpha))
    }
    var hexRGB:String {
        return String(format: "#%02x%02x%02x",Int(rgbComponents.blue * 255))
    }
    var hexRGBA:String {
        return String(format: "#%02x%02x%02x%02x",Int(rgbComponents.alpha * 255) )
    }

    var hsbComponents:HSBComponents {
        var c:HSBComponents = (0,0)

        if getHue(&c.hue,saturation: &c.saturation,brightness: &c.brightness,0)
    }
}

let v1 = UIColor.redColor().rgbComponents.red
let v2 = UIColor.redColor().cssRGBA
let v3 = UIColor.redColor().hexRGBA
let v4test = UIColor.RGBComponents(red: 0.0,green: 0.0,blue: 0.0,alpha: 0.0)

解决方法

Xcode 8.2•Swift 3.0.2

从UIColor获取红色,绿色,蓝色和Alpha组件：

extension UIColor {
    var rgba: (red: CGFloat,alpha: CGFloat) {
        var r: CGFloat = 0,g: CGFloat = 0,b: CGFloat = 0,a: CGFloat = 0
        if getRed(&r,green: &g,blue: &b,alpha: &a) { 
            return (r,g,b,a)
        }
        return (0,0)
    }

    // hue,saturation,brightness and alpha components from UIColor**
    var hsba: (hue: CGFloat,alpha: CGFloat) {
        var hue: CGFloat = 0,saturation: CGFloat = 0,brightness: CGFloat = 0,alpha: CGFloat = 0
        if getHue(&hue,saturation: &saturation,brightness: &brightness,alpha: &alpha) {
            return (hue,brightness,alpha)
        }
        return (0,0)
    }

    var htmlRGB: String {
        return String(format: "#%02x%02x%02x",Int(rgba.red * 255),Int(rgba.green * 255),Int(rgba.blue * 255))
    }

    var htmlRGBA: String {
        return String(format: "#%02x%02x%02x%02x",Int(rgba.blue * 255),Int(rgba.alpha * 255) )
    }
}

测试它：

HTML颜色

let myWhiteWebColor = UIColor(red: 1,green: 1,blue: 1,alpha: 1).htmlRGBA      // #ffffffff
let myGreyWebColor = UIColor(red: 0.5,green: 0.5,blue: 0.5,alpha: 1).htmlRGBA // #7f7f7fff
let myBlackWebColor = UIColor(red: 0,green: 0,blue: 0,alpha: 1).htmlRGBA      // #000000ff
let myRedWebColor = UIColor(red: 1,alpha: 1).htmlRGBA        // #ff0000ff
let myGreenWebColor = UIColor(red: 0,alpha: 1).htmlRGBA      // #00ff00ff
let myBlueWebColor = UIColor(red: 0,alpha: 1).htmlRGBA       // #0000ffff

let myColorBlack = UIColor.black.htmlRGBA              // #000000ff
let myLghtGrayColor = UIColor.lightGray.htmlRGBA       // #aaaaaaff
let myDarkGrayColor = UIColor.darkGray.htmlRGBA        // #555555ff

let myRedHueWebColor = UIColor(hue: 1,saturation: 1,brightness: 1,alpha: 1).htmlRGBA  //ff0000ff

RGB组件

UIColor.red.rgba        // (1.0,0.0,1.0)
UIColor.red.rgba.red    // 1
UIColor.red.rgba.green  // 0
UIColor.red.rgba.blue   // 0
UIColor.red.rgba.alpha  // 1

UIColor.green.rgba       // (0.0,1.0,1.0)
UIColor.green.rgba.red   // 0
UIColor.green.rgba.green // 1
UIColor.green.rgba.blue  // 0
UIColor.green.rgba.alpha // 1

UIColor.blue.rgba        // (0.0,1.0)
UIColor.blue.rgba.red    // 0
UIColor.blue.rgba.green  // 0
UIColor.blue.rgba.blue   // 1
UIColor.blue.rgba.alpha  // 1

Hue组件

UIColor.red.hsba               // (0.0,1.0)
UIColor.red.hsba.hue           // 1
UIColor.red.hsba.saturation    // 1
UIColor.red.hsba.brightness    // 1
UIColor.red.hsba.alpha         // 1

UIColor.green.hsba             // (0.333333333333333,1.0)
UIColor.green.hsba.hue         // 0.3333333333333333
UIColor.green.hsba.saturation  // 1
UIColor.green.hsba.brightness  // 1
UIColor.green.hsba.alpha       // 1

UIColor.blue.hsba              // (0.666666666666667,1.0)
UIColor.blue.hsba.hue          // 0.666666666666667
UIColor.blue.hsba.saturation   // 1.0
UIColor.blue.hsba.brightness   // 1.0
UIColor.blue.hsba.alpha        // 1.0

UIColor.clear.hsba       // (.0 0,.1 0,.2 0,.3 0)

UIColor.blue.htmlRGB     //"#0000ff"
UIColor.blue.htmlRGBA    //"#0000ffff"