グラデーションアニメーション

ContentView.swift

import SwiftUI

extension [Color] {
    static func rainbow(hue: Double = 0, count: Int) -> Self {
        (0..<count).map { i in
            var value = hue + Double(i) / Double(count)
            value -= floor(value)
            return Color(hue: value, saturation: 1/4, brightness: 1)
        }
    }
}

struct ContentView: View {
    let date = Date()

    var body: some View {
        TimelineView(.animation) { context in
            let time = context.date.timeIntervalSince(date)
            Image(systemName: "apple.logo")
                .resizable()
                .aspectRatio(contentMode: .fit)
                .foregroundStyle(
                    LinearGradient(
                        colors: .rainbow(hue: time/5, count: 256).reversed(),
                        startPoint: .topTrailing,
                        endPoint: .bottom
                    )
                )
                .animation(.spring(duration: 1.5)) { view in
                    view.scaleEffect(Int(time) % 2 == 0 ? 1 : 1.08)
                }
        }
        .padding(40)
    }
}

#Preview {
    ContentView()
}