Make background color change during scroll

Question

I have an onboarding section of my app with 4 pages the users scrolls through horizontally to get an idea of how to use the app (standard). I want the background color to tr

Answer 1

    var currPage = 0
    let colors: [UIColor] = [.red, .blue, .green, .yellow, .purple, .orange]

    func scrollViewDidScroll(_ scrollView: UIScrollView) {
        // for horizontal scrolling
        let progress = scrollView.contentOffset.x / scrollView.bounds.width
        let page = Int(progress)
        if currPage != page { currPage = page }
        let nextPage = Int(progress + 1)
        let prog = 1 - (CGFloat(Int(progress + 1)) - progress)
        print("\(currPage) \(nextPage) \(prog)")
        if currPage >= 0 && currPage < colors.count && nextPage >= 0 && nextPage < colors.count {
            let interColor = colorBetween(col1: colors[currPage], col2: colors[nextPage], percent: prog)
            scrollView.backgroundColor = interColor.withAlphaComponent(0.5)
        }
    }

    // calculates intermediate color, percent should in between 0.0 - 1.0
    func colorBetween(col1: UIColor, col2: UIColor, percent: CGFloat) -> UIColor {
        let c1 = CIColor(color: col1)
        let c2 = CIColor(color: col2)

        let alpha = (c2.alpha - c1.alpha) * percent + c1.alpha
        let red = (c2.red - c1.red) * percent + c1.red
        let blue = (c2.blue - c1.blue) * percent + c1.blue
        let green = (c2.green - c1.green) * percent + c1.green

        return UIColor(red: red, green: green, blue: blue, alpha: alpha)
    }