Rounded opaque buttons for iOS

RoundedButton.swift

// Rounded opaque buttons for iOS
// Drop-in replacement for UIButton with Interface Builder support
// UIButton.buttonType type should be set to .custom
// Color is chosen based on the tint color. Supports highlighted and selected states
// Assumes that tint color has high brightness and saturation (e.g. not white or black)
// Written for iOS 12 with Swift 4.2

import  UIKit

let kRoundedButtonDefaultFont = UIFont.systemFont(ofSize: 14.0, weight: .medium)
let kRoundedButtonDefaultCornerRadius: CGFloat = 4.0
let kRoundedButtonDefaultVerticalMargin: CGFloat = 6.0
let kRoundedButtonDefaultHorizontalMargin: CGFloat = 12.0

@IBDesignable class RoundedButton: UIButton {
    @IBInspectable var highlightDimmingFactor: CGFloat = 0.85 {
        didSet { updateColors() }
    }
    @IBInspectable var backgroundSaturationFactor: CGFloat = 0.1 {
        didSet { updateColors() }
    }
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        setDefaultValues()
    }
    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        setDefaultValues()
    }
    
    func setDefaultValues() {
        titleLabel?.font = kRoundedButtonDefaultFont
        cornerRadius = kRoundedButtonDefaultCornerRadius
        verticalMargin = kRoundedButtonDefaultVerticalMargin
        horizontalMargin = kRoundedButtonDefaultHorizontalMargin
        
        updateColors()
    }
    
    @IBInspectable var cornerRadius: CGFloat {
        get { return layer.cornerRadius }
        set {
            layer.cornerRadius = newValue
            layer.masksToBounds = newValue > 0
        }
    }
    
    @IBInspectable var verticalMargin: CGFloat {
        get { return contentEdgeInsets.top }
        set {
            contentEdgeInsets.top = newValue
            contentEdgeInsets.bottom = newValue
        }
    }
    
    @IBInspectable var horizontalMargin: CGFloat {
        get { return contentEdgeInsets.left }
        set  {
            contentEdgeInsets.left = newValue
            contentEdgeInsets.right = newValue
        }
    }
    
    func updateColors() {
        let primaryColor = tintColor!
        let desaturatedColor = tintColor.multipliedHSBColor(1.0, backgroundSaturationFactor, 1.0)
        
        let customTextColor = isSelected ? .white : primaryColor
        setTitleColor(customTextColor, for: .normal)
        setTitleColor(customTextColor.multipliedHSBColor(1.0, 1.0, highlightDimmingFactor), for: .highlighted)
        
        let currentDimmingFactor = isHighlighted ? highlightDimmingFactor : 1.0
        let customBackgroundColor = isSelected ? primaryColor : desaturatedColor
        
        backgroundColor = customBackgroundColor.multipliedHSBColor(1.0, 1.0, currentDimmingFactor)
    }
    
    override var isHighlighted: Bool {
        didSet { updateColors() }
    }
    
    override var isSelected: Bool {
        didSet { updateColors() }
    }
    
    override func tintColorDidChange() {
        super.tintColorDidChange()
        updateColors()
    }
}

extension UIColor {
    func multipliedHSBColor(_ hueFactor: CGFloat, _ saturationFactor: CGFloat, _ brightnessFactor: CGFloat) -> UIColor {
        var h: CGFloat = 0.0
        var s: CGFloat = 0.0
        var b: CGFloat = 0.0
        var a: CGFloat = 0.0
        getHue(&h, saturation: &s, brightness: &b, alpha: &a)
        h = clamp(h * hueFactor, in: 0.0...1.0)
        s = clamp(s * saturationFactor, in: 0.0...1.0)
        b = clamp(b * brightnessFactor, in: 0.0...1.0)
        return UIColor(hue: h, saturation: s, brightness: b, alpha: a)
    }
}

public func clamp<T>(_ value: T, in range: ClosedRange<T>) -> T where T : Comparable {
    return min(max(value, range.lowerBound), range.upperBound)
}