Get Slightly Lighter and Darker Color from UIColor

user_1342945 0
Viewed 61434

I was looking to be able to turn any UIColor into a gradient. The way I am intending to do this is by using Core Graphics to draw a gradient. What I am trying to do is to get a color, lets say:

[UIColor colorWithRed:0.5 green:0.5 blue:0.5 alpha:1.0];

and get a UIColor which is a few shades darker and a few shades lighter. Does anyone know how to do this? Thank you.

gradient uicolor core-graphics objective-c ios
19 Answers

Swift 5

extension UIColor {

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

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

func adjust(by percentage:CGFloat=30.0) -> UIColor? {
    var r:CGFloat=0, g:CGFloat=0, b:CGFloat=0, a:CGFloat=0;
    if self.getRed(&r, green: &g, blue: &b, alpha: &a) {
        return UIColor(red: min(r + percentage/100, 1.0),
                       green: min(g + percentage/100, 1.0),
                       blue: min(b + percentage/100, 1.0),
                       alpha: a)
    } else {
        return nil
     }
   }
}
user_64492920

Tested in Xcode 10 with Swift 4.x for iOS 12

Start with your color as a UIColor and pick a darkening factor (as a CGFloat)

let baseColor = UIColor.red
let darkenFactor: CGFloat = 2

The type CGColor has an optional value components which break down the color into RGBA (as a CGFloat array with values between 0 and 1). You can then reconstruct a UIColor using RGBA values taken from the CGColor and manipulate them.

let darkenedBase = UIColor(displayP3Red: startColor.cgColor.components![0] / darkenFactor, green: startColor.cgColor.components![1] / darkenFactor, blue: startColor.cgColor.components![2] / darkenFactor, alpha: 1)

In this example, each of the RGB valuse were divided by 2, making the color half as dark as it was before. The alpha value remained the same, but you could alternatively apply the darken factor on the alpha value rather than the RGB.

user_91845070

A Swift extension based on @Sebyddd answer:

import Foundation
import UIKit

extension UIColor{
    func colorWith(brightness: CGFloat) -> UIColor{
        var r:CGFloat = 0, g:CGFloat = 0, b:CGFloat = 0, a:CGFloat = 0

        if getRed(&r, green: &g, blue: &b, alpha: &a){
            return UIColor(red: max(r + brightness, 0.0), green: max(g + brightness, 0.0), blue: max(b + brightness, 0.0), alpha: a)
        }

        return UIColor()
    }
}
user_44211000

for darker color, this is the simplest: theColor = [theColor shadowWithLevel:s]; //s:0.0 to 1.0

user_9066130
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