Get lighter and darker color variations for a given UIColor

Question

How to get different lighter and darker variations of a given UIColor in Swift?

Answer 1

Swift 4 version that supports RGBA, HSBA, and WB (greyscale)

Here's a variation of TranQuan's answer that also supports greyscale colors like .white and .black. (Note: I removed saturation adjustment because I didn't think it belonged in a simple function like this.)

extension UIColor {
    /**
     Create a ligher color
     */
    func lighter(by percentage: CGFloat = 10.0) -> UIColor {
        return self.adjustBrightness(by: abs(percentage))
    }

    /**
     Create a darker color
     */
    func darker(by percentage: CGFloat = 10.0) -> UIColor {
        return self.adjustBrightness(by: -abs(percentage))
    }

    /**
     Try to adjust brightness and falls back to adjusting colors if necessary
     */
    func adjustBrightness(by percentage: CGFloat) -> UIColor {
        var alpha, hue, saturation, brightness, red, green, blue, white : CGFloat
        (alpha, hue, saturation, brightness, red, green, blue, white) = (0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0)

        let multiplier = percentage / 100.0

        if self.getHue(&hue, saturation: &saturation, brightness: &brightness, alpha: &alpha) {
            let newBrightness: CGFloat = max(min(brightness + multiplier*brightness, 1.0), 0.0)
            return UIColor(hue: hue, saturation: saturation, brightness: newBrightness, alpha: alpha)
        }
        else if self.getRed(&red, green: &green, blue: &blue, alpha: &alpha) {
            let newRed: CGFloat = min(max(red + multiplier*red, 0.0), 1.0)
            let newGreen: CGFloat = min(max(green + multiplier*green, 0.0), 1.0)
            let newBlue: CGFloat = min(max(blue + multiplier*blue, 0.0), 1.0)
            return UIColor(red: newRed, green: newGreen, blue: newBlue, alpha: alpha)
        }
        else if self.getWhite(&white, alpha: &alpha) {
            let newWhite: CGFloat = (white + multiplier*white)
            return UIColor(white: newWhite, alpha: alpha)
        }

        return self
    }
}

Answer 2

Since I use SwiftUI in my current project, I adapted the best answer from Stephen. Tested with Xcode 12.0, SwiftUI 2 and iOS 14.0

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 {
            return (0, 0, 0, 0)
        }
        return (r, g, b, o)
    }
    
    func lighter(by percentage: CGFloat = 30.0) -> Color {
        return self.adjust(by: abs(percentage) )
    }

    func darker(by percentage: CGFloat = 30.0) -> Color {
        return self.adjust(by: -1 * abs(percentage) )
    }

    func adjust(by percentage: CGFloat = 30.0) -> Color {
        return Color(red: min(Double(self.components.red + percentage/100), 1.0),
                     green: min(Double(self.components.green + percentage/100), 1.0),
                     blue: min(Double(self.components.blue + percentage/100), 1.0),
                     opacity: Double(self.components.opacity))
    }
}

Answer 3

Kenji-Tran's answer works fine, as long as your starting color is not black (brightness value 0). With the addition of a few lines of extra code, you can also make black "lighter" (i.e. brighten it to a grayscale or color value).

Note: I wasn't able to add this change using an Edit and I'm not allowed to comment on Kenji-Tran's answer due to my "new boy" rep, therefore I found no other way to share my knowledge on SO then by posting a new answer. I hope that's okay.

extension UIColor {
  /**
   Create a ligher color
   */
  func lighter(by percentage: CGFloat = 30.0) -> UIColor {
    return self.adjustBrightness(by: abs(percentage))
  }

  /**
   Create a darker color
   */
  func darker(by percentage: CGFloat = 30.0) -> UIColor {
    return self.adjustBrightness(by: -abs(percentage))
  }

  /**
   Try to increase brightness or decrease saturation
   */
  func adjustBrightness(by percentage: CGFloat = 30.0) -> UIColor {
    var h: CGFloat = 0, s: CGFloat = 0, b: CGFloat = 0, a: CGFloat = 0
    if self.getHue(&h, saturation: &s, brightness: &b, alpha: &a) {
      if b < 1.0 {
        /**
         Below is the new part, which makes the code work with black as well as colors
        */
        let newB: CGFloat
        if b == 0.0 {
            newB = max(min(b + percentage/100, 1.0), 0.0)
        } else {
            newB = max(min(b + (percentage/100.0)*b, 1.0), 0,0)
        }
        return UIColor(hue: h, saturation: s, brightness: newB, alpha: a)
      } else {
        let newS: CGFloat = min(max(s - (percentage/100.0)*s, 0.0), 1.0)
        return UIColor(hue: h, saturation: newS, brightness: b, alpha: a)
      }
    }
    return self
  }
}

Answer 4

To save anyone typing, the simple practical version is just

extension UIColor {

    var darker: UIColor {

    var h: CGFloat = 0, s: CGFloat = 0, b: CGFloat = 0, a: CGFloat = 0

        guard self.getHue(&h, saturation: &s, brightness: &b, alpha: &a) else {
            print("** some problem demuxing the color")
            return .gray
        }

        let nudged = b * 0.5

        return UIColor(hue: h, saturation: s, brightness: nudged, alpha: a)
    }
}

use like

something.color = .yellow.darker

or

backgroundColor = backgroundColor.darker

On a large project .................

You should definitely extend Apple's pattern:

.withAlphaComponent(_ alpha: CGFloat)

So, have:

.withBrightnessComponent(_ alpha: CGFloat)

and distinctly

.withBrightnessComponentAdjustedBy(percentage: CGFloat)

and/or

.withBrightnessComponentMultipliedBy(factor: CGFloat)

Answer 5

SwiftUI: Color - iOS 14 / macOS 10.16

extension Color {
    public func lighter(by amount: CGFloat = 0.2) -> Self { Self(UIColor(self).lighter(by: amount)) }
    public func darker(by amount: CGFloat = 0.2) -> Self { Self(UIColor(self).darker(by: amount)) }
}

_{Reqires one of the followings (or both) for iOS or (and) macOS}

---

AppKit: NSColor

extension NSColor {
    func mix(with color: NSColor, amount: CGFloat) -> Self {
        var red1: CGFloat = 0
        var green1: CGFloat = 0
        var blue1: CGFloat = 0
        var alpha1: CGFloat = 0

        var red2: CGFloat = 0
        var green2: CGFloat = 0
        var blue2: CGFloat = 0
        var alpha2: CGFloat = 0

        getRed(&red1, green: &green1, blue: &blue1, alpha: &alpha1)
        color.getRed(&red2, green: &green2, blue: &blue2, alpha: &alpha2)

        return Self(
            red: red1 * CGFloat(1.0 - amount) + red2 * amount,
            green: green1 * CGFloat(1.0 - amount) + green2 * amount,
            blue: blue1 * CGFloat(1.0 - amount) + blue2 * amount,
            alpha: alpha1
        )
    }

    func lighter(by amount: CGFloat = 0.2) -> Self { mix(with: .white, amount: amount) }
    func darker(by amount: CGFloat = 0.2) -> Self { mix(with: .black, amount: amount) }
}

---

UIKit: UIColor

extension UIColor {
    func mix(with color: UIColor, amount: CGFloat) -> Self {
        var red1: CGFloat = 0
        var green1: CGFloat = 0
        var blue1: CGFloat = 0
        var alpha1: CGFloat = 0

        var red2: CGFloat = 0
        var green2: CGFloat = 0
        var blue2: CGFloat = 0
        var alpha2: CGFloat = 0

        getRed(&red1, green: &green1, blue: &blue1, alpha: &alpha1)
        color.getRed(&red2, green: &green2, blue: &blue2, alpha: &alpha2)

        return Self(
            red: red1 * CGFloat(1.0 - amount) + red2 * amount,
            green: green1 * CGFloat(1.0 - amount) + green2 * amount,
            blue: blue1 * CGFloat(1.0 - amount) + blue2 * amount,
            alpha: alpha1
        )
    }

    func lighter(by amount: CGFloat = 0.2) -> Self { mix(with: .white, amount: amount) }
    func darker(by amount: CGFloat = 0.2) -> Self { mix(with: .black, amount: amount) }
}

Answer 6

Using lukszar clampled function, I wrote this function for the UIColor extension, using real proportions of RGB values. I hope it is helpful

public extension UIColor {

  public func lighter(by percentage: CGFloat = 30.0) -> UIColor {
    return self.adjustBrightness(by: abs(percentage))
  }

  public func darker(by percentage: CGFloat = 30.0) -> UIColor {
    return self.adjustBrightness(by: -abs(percentage))
  }

  func adjustBrightness(by percentage: CGFloat = 30.0) -> UIColor {

    let ratio = percentage/100

    var red:   CGFloat = 0.0
    var green: CGFloat = 0.0
    var blue:  CGFloat = 0.0
    var alpha: CGFloat = 0.0

    if self.getRed(&red, green: &green, blue: &blue, alpha: &alpha) {
      let newRed =   (red   + ((ratio < 0) ? red   * ratio : (1 - red)   * ratio)).clamped(to: 0.0 ... 1.0)
      let newGreen = (green + ((ratio < 0) ? green * ratio : (1 - green) * ratio)).clamped(to: 0.0 ... 1.0)
      let newBlue =  (blue  + ((ratio < 0) ? blue  * ratio : (1 - blue)  * ratio)).clamped(to: 0.0 ... 1.0)
      return UIColor(red: newRed, green: newGreen, blue: newBlue, alpha: alpha)
    }
    return self
  }
}