Simple swift color picker popover (iOS)

Question

Is there is a simple way to implement a color picker popover in swift? Are there any built-in libraries or UI elements that I could leverage for this purpose? I saw some color pickers written in objective-c, but they were several years old and I was wondering if there was something more recent.

Answer 1

Here's one I made which is as simple as it gets. It's just a lightweight UIView that allows you to specify the element size in case you want blocked regions (elementSize > 1). It draws itself in interface builder so you can set element size and see the consequences. Just set one of your views in interface builder to this class and then set yourself as a delegate. It will tell you when someone either taps or drags on it and the uicolor at that location. It will draw itself to its own bounds and there's no need for anything other than this class, no image required.

Element size=1 (Default)

Element size=10

internal protocol HSBColorPickerDelegate : NSObjectProtocol {
    func HSBColorColorPickerTouched(sender:HSBColorPicker, color:UIColor, point:CGPoint, state:UIGestureRecognizerState)
}

@IBDesignable
class HSBColorPicker : UIView {

    weak internal var delegate: HSBColorPickerDelegate?
    let saturationExponentTop:Float = 2.0
    let saturationExponentBottom:Float = 1.3

    @IBInspectable var elementSize: CGFloat = 1.0 {
        didSet {
            setNeedsDisplay()
        }
    }

    private func initialize() {
        self.clipsToBounds = true
        let touchGesture = UILongPressGestureRecognizer(target: self, action: #selector(self.touchedColor(gestureRecognizer:)))
        touchGesture.minimumPressDuration = 0
        touchGesture.allowableMovement = CGFloat.greatestFiniteMagnitude
        self.addGestureRecognizer(touchGesture)
    }

   override init(frame: CGRect) {
        super.init(frame: frame)
        initialize()
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        initialize()
    }

    override func draw(_ rect: CGRect) {
        let context = UIGraphicsGetCurrentContext()
        for y : CGFloat in stride(from: 0.0 ,to: rect.height, by: elementSize) {
            var saturation = y < rect.height / 2.0 ? CGFloat(2 * y) / rect.height : 2.0 * CGFloat(rect.height - y) / rect.height
            saturation = CGFloat(powf(Float(saturation), y < rect.height / 2.0 ? saturationExponentTop : saturationExponentBottom))
            let brightness = y < rect.height / 2.0 ? CGFloat(1.0) : 2.0 * CGFloat(rect.height - y) / rect.height
            for x : CGFloat in stride(from: 0.0 ,to: rect.width, by: elementSize) {
                let hue = x / rect.width
                let color = UIColor(hue: hue, saturation: saturation, brightness: brightness, alpha: 1.0)
                context!.setFillColor(color.cgColor)
                context!.fill(CGRect(x:x, y:y, width:elementSize,height:elementSize))
            }
        }
    }

    func getColorAtPoint(point:CGPoint) -> UIColor {
        let roundedPoint = CGPoint(x:elementSize * CGFloat(Int(point.x / elementSize)),
                               y:elementSize * CGFloat(Int(point.y / elementSize)))
        var saturation = roundedPoint.y < self.bounds.height / 2.0 ? CGFloat(2 * roundedPoint.y) / self.bounds.height
        : 2.0 * CGFloat(self.bounds.height - roundedPoint.y) / self.bounds.height
        saturation = CGFloat(powf(Float(saturation), roundedPoint.y < self.bounds.height / 2.0 ? saturationExponentTop : saturationExponentBottom))
        let brightness = roundedPoint.y < self.bounds.height / 2.0 ? CGFloat(1.0) : 2.0 * CGFloat(self.bounds.height - roundedPoint.y) / self.bounds.height
        let hue = roundedPoint.x / self.bounds.width
        return UIColor(hue: hue, saturation: saturation, brightness: brightness, alpha: 1.0)
    }

    func getPointForColor(color:UIColor) -> CGPoint {
        var hue: CGFloat = 0.0
        var saturation: CGFloat = 0.0
        var brightness: CGFloat = 0.0
        color.getHue(&hue, saturation: &saturation, brightness: &brightness, alpha: nil);

        var yPos:CGFloat = 0
        let halfHeight = (self.bounds.height / 2)
        if (brightness >= 0.99) {
            let percentageY = powf(Float(saturation), 1.0 / saturationExponentTop)
            yPos = CGFloat(percentageY) * halfHeight
        } else {
            //use brightness to get Y
            yPos = halfHeight + halfHeight * (1.0 - brightness)
        }
        let xPos = hue * self.bounds.width
        return CGPoint(x: xPos, y: yPos)
    }

    @objc func touchedColor(gestureRecognizer: UILongPressGestureRecognizer) {
        if (gestureRecognizer.state == UIGestureRecognizerState.began) {
            let point = gestureRecognizer.location(in: self)
            let color = getColorAtPoint(point: point)
            self.delegate?.HSBColorColorPickerTouched(sender: self, color: color, point: point, state:gestureRecognizer.state)
        }        
    }
}