Swift：如何根据 slider 的值更改 UISlider 上拇指图像的大小？

Question

I haven't found an answer for this in Swift.

I have a UISlider that changes the value of a brush size for a drawing app I'm making. I want the size of the thumb image to update depending on the value of the slider's thumb position.

Here's a screenshot of the slider for some context:

I set the initial image of the thumb in viewDidLoad()

self.brushSizeSlider.setThumbImage(UIImage(named: "black"), forState: UIControlState.Normal)

and have an IBAction for the slider as follows:

    @IBAction func brushSizeSliderChanged(sender: UISlider) {
    if sender == brushSizeSlider {
        self.brushWidth = CGFloat(sender.value)
        println("the size of the brush is: \(self.brushWidth)")
    }
}

What should I add to brushSizeSliderChanged to change the size of it's thumb image depending on the value of brushSizeSliders thumb position / value?

Answer 1

var ratio : CGFloat = CGFloat ( sender.value + 0.5)
var thumbImage : UIImage = UIImage(named: "yourImage")!
var size = CGSizeMake( thumbImage.size.width * ratio, thumbImage.size.height * ratio )
self.setThumbImage( self.imageWithImage(thumbImage, scaledToSize: size), forState: UIControlState.Normal )

Add this code to your action method

Answer 2

You can use a more recent API

extension UIImage {

/// Непропорциональное масштабирование к указанному размеру
/// - Parameter size: конечный размер изображения
/// - Parameter displayScale: масштаб, в котором создаётся итоговое изображение
/// - Returns: изображение необходимого размера
func scaled(to size: CGSize, scale displayScale: CGFloat = UIScreen.main.scale) -> UIImage {
    let format = UIGraphicsImageRendererFormat.preferred()
    format.scale = displayScale
    return UIGraphicsImageRenderer(size: size, format: format).image { _ in
        draw(in: CGRect(origin: .zero, size: size))
    }
}