How to control shadow spread and blur?

Question

I have designed UI elements in sketch, and one of them has a shadow with blur 1 and spread 0. I looked at the doc for the views layer property and layer doesnt have anything

Answer 1

For those who are attempting to apply a shadow to a predefined path (Like for a circular view, for instance), here's what I ended up with:

extension CALayer {
    func applyShadow(color: UIColor = .black,
                     alpha: Float = 0.5,
                     x: CGFloat = 0,
                     y: CGFloat = 2,
                     blur: CGFloat = 4,
                     spread: CGFloat = 0,
                     path: UIBezierPath? = nil) {
        shadowColor = color.cgColor
        shadowOpacity = alpha
        shadowRadius = blur / 2
        if let path = path {
            if spread == 0 {
                shadowOffset = CGSize(width: x, height: y)
            } else {
                let scaleX = (path.bounds.width + (spread * 2)) / path.bounds.width
                let scaleY = (path.bounds.height + (spread * 2)) / path.bounds.height

                path.apply(CGAffineTransform(translationX: x + -spread, y: y + -spread).scaledBy(x: scaleX, y: scaleY))
                shadowPath = path.cgPath
            }
        } else {
            shadowOffset = CGSize(width: x, height: y)
            if spread == 0 {
                shadowPath = nil
            } else {
                let dx = -spread
                let rect = bounds.insetBy(dx: dx, dy: dx)
                shadowPath = UIBezierPath(rect: rect).cgPath
            }
        }
        shouldRasterize = true
        rasterizationScale = UIScreen.main.scale
    }
}

I'll post some examples later, but this has worked spot on for circular views for me.