如何在 SwiftUI 中从 Color 获取 RGB 分量

Question

如果我有 SwiftUI Color:

let col: Color = Color(red: 0.5, green: 0.5, blue: 0.5)

如何从 col 获取 RGB 分量？
可能像这样：

print(col.components.red)

在 UIKit 中，我可以使用 UIColor.getRed，但在 SwiftUI 中似乎没有等效项。

Answer 1

答案是否 - 还没有API这样做，但是...

大多数 SwiftUI 结构都有 private 的字段，例如 Color.

您可以使用 Mirror 来提取此类信息 - 但请记住它效率不高。

以下是提取 SwiftUI 的十六进制表示的方法 Color - 用于教育目的。

将其复制并粘贴到 Xcode 11 游乐场。

import UIKit
import SwiftUI

let systemColor = Color.red
let color = Color(red: 0.3, green: 0.5, blue: 1)

extension Color {

    var hexRepresentation: String? {
        let children = Mirror(reflecting: color).children
        let _provider = children.filter { [=10=].label == "provider" }.first
        guard let provider = _provider?.value else {
            return nil
        }
        let providerChildren = Mirror(reflecting: provider).children
        let _base = providerChildren.filter { [=10=].label == "base" }.first
        guard let base = _base?.value else {
            return nil
        }
        var baseValue: String = ""
        dump(base, to: &baseValue)
        guard let firstLine = baseValue.split(separator: "\n").first,
              let hexString = firstLine.split(separator: " ")[1] as Substring? else {
            return nil
        }
        return hexString.trimmingCharacters(in: .newlines)
    }

}

systemColor.hexRepresentation
color.hexRepresentation

像.red、.white等颜色，好像没有多少信息，当dumped.

只是他们的 "system" 名字。

▿ red
  ▿ provider: SwiftUI.(unknown context at 97483bc).ColorBox<SwiftUI.SystemColorType> #0
    - super: SwiftUI.(unknown context at 9748300).AnyColorBox
    - base: SwiftUI.SystemColorType.red

用 red/blue/green 组件实例化的 Color 代替。

▿ #4C80FFFF
  ▿ provider: SwiftUI.(unknown context at cd2e3bc).ColorBox<SwiftUI.Color._Resolved> #0
    - super: SwiftUI.(unknown context at cd2e300).AnyColorBox
    ▿ base: #4C80FFFF
      - linearRed: 0.073238954
      - linearGreen: 0.21404114
      - linearBlue: 1.0
      - opacity: 1.0

在 Playground 中，您将看到：

systemColor.hexRepresentation 返回 nil
color.hexRepresentation 返回 "#4C80FFFF"

Answer 2

等待 API 我滥用了 CustomStringConvertible 颜色描述格式为 #rrggbbaa

的简单 rgba 协议

debugPrint(Color.red)
debugPrint(Color(red: 1.0, green: 0.0, blue: 0.0))
debugPrint(Color(red: 1.0, green: 0.3, blue: 0.0))
debugPrint(Color(.sRGB, red: 1.0, green: 0.0, blue: 0.5, opacity: 0.3))
debugPrint(Color(hue: 1.0, saturation: 0.0, brightness: 1.0))
debugPrint(Color(.displayP3, red: 1.0, green: 0.0, blue: 0.0, opacity: 1.0).description)

red
#FF0000FF
#FF4C00FF
#FF00804D
#FFFFFFFF
"DisplayP3(red: 1.0, green: 0.0, blue: 0.0, opacity: 1.0)"

如您所见，Color.red 之类的东西只是转储 "red" 但如果您正在使用由代码生成的简单 RGB 颜色（即来自颜色选择器）那么这还不错

extension SwiftUI.Color {
    var redComponent: Double? {
        let val = description
        guard val.hasPrefix("#") else { return nil }
        let r1 = val.index(val.startIndex, offsetBy: 1)
        let r2 = val.index(val.startIndex, offsetBy: 2)
        return Double(Int(val[r1...r2], radix: 16)!) / 255.0
    }

    var greenComponent: Double? {
        let val = description
        guard val.hasPrefix("#") else { return nil }
        let g1 = val.index(val.startIndex, offsetBy: 3)
        let g2 = val.index(val.startIndex, offsetBy: 4)
        return Double(Int(val[g1...g2], radix: 16)!) / 255.0
    }

    var blueComponent: Double? {
        let val = description
        guard val.hasPrefix("#") else { return nil }
        let b1 = val.index(val.startIndex, offsetBy: 5)
        let b2 = val.index(val.startIndex, offsetBy: 6)
        return Double(Int(val[b1...b2], radix: 16)!) / 255.0
    }

    var opacityComponent: Double? {
        let val = description
        guard val.hasPrefix("#") else { return nil }
        let b1 = val.index(val.startIndex, offsetBy: 7)
        let b2 = val.index(val.startIndex, offsetBy: 8)
        return Double(Int(val[b1...b2], radix: 16)!) / 255.0
    }
}

Answer 3

您可以使用 UIColor 并将 UIColor 转换为 Color。代码：

extension UIColor {
    func hexValue() -> String {
        let values = self.cgColor.components
        var outputR: Int = 0
        var outputG: Int = 0
        var outputB: Int = 0
        var outputA: Int = 1

        switch values!.count {
            case 1:
                outputR = Int(values![0] * 255)
                outputG = Int(values![0] * 255)
                outputB = Int(values![0] * 255)
                outputA = 1
            case 2:
                outputR = Int(values![0] * 255)
                outputG = Int(values![0] * 255)
                outputB = Int(values![0] * 255)
                outputA = Int(values![1] * 255)
            case 3:
                outputR = Int(values![0] * 255)
                outputG = Int(values![1] * 255)
                outputB = Int(values![2] * 255)
                outputA = 1
            case 4:
                outputR = Int(values![0] * 255)
                outputG = Int(values![1] * 255)
                outputB = Int(values![2] * 255)
                outputA = Int(values![3] * 255)
            default:
                break
        }
        return "#" + String(format:"%02X", outputR) + String(format:"%02X", outputG) + String(format:"%02X", outputB) + String(format:"%02X", outputA)
    }
}

Answer 4

iOS 14 / macOS 10.16

有一个新的初始化器，它接受一个 Color 和 returns 一个 UIColor for iOS or NSColor 现在 macOS。在这些人的帮助下，您可以实现以下扩展：

iOS / macOS

import SwiftUI

#if canImport(UIKit)
import UIKit
#elseif canImport(AppKit)
import AppKit
#endif

extension Color {
    var components: (red: CGFloat, green: CGFloat, blue: CGFloat, opacity: CGFloat) {

        #if canImport(UIKit)
        typealias NativeColor = UIColor
        #elseif canImport(AppKit)
        typealias NativeColor = NSColor
        #endif

        var r: CGFloat = 0
        var g: CGFloat = 0
        var b: CGFloat = 0
        var o: CGFloat = 0

        guard NativeColor(self).getRed(&r, green: &g, blue: &b, alpha: &o) else {
            // You can handle the failure here as you want
            return (0, 0, 0, 0)
        }

        return (r, g, b, o)
    }
}

用法

Color.red.components.red // 0.9999999403953552 // <- SwiftUI Colors are not pure!

Answer 5

我发现@Mojtaba Hosseinis 的回答工作正常，除非您在具有明暗外观的资产中声明了颜色。

然后我发现使用 UIColor(self) 时，黑色外观不知何故消失了。这是我想出的解决方法：

请注意，这仅适用于 iOS，因为我的应用仅适用于 iOS，您当然可以像@Mojtaba Hosseini 那样做，并将其调整为 macOS。

extension Color {

    var components: (r: Double, g: Double, b: Double, o: Double)? {
        let uiColor: UIColor
        
        var r: CGFloat = 0
        var g: CGFloat = 0
        var b: CGFloat = 0
        var o: CGFloat = 0
        
        if self.description.contains("NamedColor") {
            let lowerBound = self.description.range(of: "name: \"")!.upperBound
            let upperBound = self.description.range(of: "\", bundle")!.lowerBound
            let assetsName = String(self.description[lowerBound..<upperBound])
            
            uiColor = UIColor(named: assetsName)!
        } else {
            uiColor = UIColor(self)
        }

        guard uiColor.getRed(&r, green: &g, blue: &b, alpha: &o) else { return nil }
        
        return (Double(r), Double(g), Double(b), Double(o))
    }
}

想法是改用 UIColor(named:) 初始值设定项，其中所有外观都是正确的。幸运的是，我们在assets中设置的名称保存在Color的描述中。我们只需要抽象它，因为还有其他信息，即bundle等

Answer 6

根据@Mojtaba 的回答，我想出了一个更短、更灵活的版本：

#if canImport(UIKit)
import UIKit
#elseif canImport(AppKit)
import AppKit
#endif

extension Color {
    #if canImport(UIKit)
    var asNative: UIColor { UIColor(self) }
    #elseif canImport(AppKit)
    var asNative: NSColor { NSColor(self) }
    #endif

    var rgba: (red: CGFloat, green: CGFloat, blue: CGFloat, alpha: CGFloat) {
        let color = asNative.usingColorSpace(.deviceRGB)!
        var t = (CGFloat(), CGFloat(), CGFloat(), CGFloat())
        color.getRed(&t.0, green: &t.1, blue: &t.2, alpha: &t.3)
        return t
    }

    var hsva: (hue: CGFloat, saturation: CGFloat, value: CGFloat, alpha: CGFloat) {
        let color = asNative.usingColorSpace(.deviceRGB)!
        var t = (CGFloat(), CGFloat(), CGFloat(), CGFloat())
        color.getHue(&t.0, saturation: &t.1, brightness: &t.2, alpha: &t.3)
        return t
    }
}

做 asNative.redComponent 等也可能有效，仅供参考。

Answer 7

简单的一行：

print(UIColor(Color.blue).cgColor.components)

你得到 [CGFloat]? 的 [red, green, blue, alpha]。

如何在 SwiftUI 中从 Color 获取 RGB 分量

How to get RGB components from Color in SwiftUI

rgb

colors

swift

swiftui

iOS 14 / macOS 10.16

iOS / macOS

用法