问题
If I have a SwiftUI Color:
let col: Color = Color(red: 0.5, green: 0.5, blue: 0.5)
How do I get the RGB components from col?
Like this maybe:
print(col.components.red)
In UIKit, I could use UIColor.getRed but there doesn't seem to be an equivalent in SwiftUI.
回答1:
iOS 14 / macOS 10.16
There is a new initializer that takes a Color and returns a UIColor for iOS or NSColor for macOS now. With the help of those you can implement the following extensions:
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)
}
}
Usage
Color.red.components.red // 0.9999999403953552 // <- SwiftUI Colors are not pure!
回答2:
Waiting for an API I've abused CustomStringConvertible protocol for the simple rgba case where the color description format is #rrggbbaa
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)"
as you can see, things like Color.red just dump "red" but if you are working with simple RGB colors generated by code (ie from a color picker) then this is not too bad
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
}
}
回答3:
The answer is no - there's no API do so (yet), but...
Most of SwiftUI structs have fields that are private, like in Color.
You can use Mirror to extract such informations - but keep in mind it is not efficient.
Here's how to extract the hexadecimal representation of a SwiftUI Color - for educational purpose.
Copy and paste this into a Xcode 11 playground.
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 { $0.label == "provider" }.first
guard let provider = _provider?.value else {
return nil
}
let providerChildren = Mirror(reflecting: provider).children
let _base = providerChildren.filter { $0.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
Colors like .red, .white, etc., don't seem to have many information in them, when dumped.
Just their "system" name.
▿ red
▿ provider: SwiftUI.(unknown context at $1297483bc).ColorBox<SwiftUI.SystemColorType> #0
- super: SwiftUI.(unknown context at $129748300).AnyColorBox
- base: SwiftUI.SystemColorType.red
A Color instantiated with red/blue/green components does instead.
▿ #4C80FFFF
▿ provider: SwiftUI.(unknown context at $11cd2e3bc).ColorBox<SwiftUI.Color._Resolved> #0
- super: SwiftUI.(unknown context at $11cd2e300).AnyColorBox
▿ base: #4C80FFFF
- linearRed: 0.073238954
- linearGreen: 0.21404114
- linearBlue: 1.0
- opacity: 1.0
In the Playground, you will see:
systemColor.hexRepresentationreturningnilcolor.hexRepresentationreturning"#4C80FFFF"
回答4:
You can use UIColor and transform the UIColor to Color after. Code:
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)
}
}
来源：https://stackoverflow.com/questions/56586055/how-to-get-rgb-components-from-color-swiftui