シェーダー関数でモザイク

Mosaic.metal

#include <metal_stdlib>
#include <SwiftUI/SwiftUI.h>
using namespace metal;

[[ stitchable ]] half4 mosaic(
    float2 position,
    SwiftUI::Layer layer,
    float scale
) {
    position = floor(position / scale) * scale;
    return layer.sample(position);
}

Mosaic.swift

import SwiftUI

struct ContentView: View {
    @State private var start = Date()

    var body: some View {
        TimelineView(.animation) { context in
            let time = context.date
                .timeIntervalSince(start)
            let scale = 1 + 30 * (sin(time) + 1)
            Image("waterwheel")
                .layerEffect(
                    mosaic(scale: scale),
                    maxSampleOffset: .zero
                )
        }
    }

    func mosaic(scale: Double) -> Shader {
        ShaderLibrary
            .mosaic(.float(scale))
    }
}

#Preview {
    ContentView()
}