Metal每日分享，均值模糊滤镜效果

// 均值模糊效果滤镜
let filter = C7MeanBlur.init(radius: 0.5)
// 方案1:
let dest = BoxxIO.init(element: originImage, filter: filter)
ImageView.image = try? dest.output()
dest.filters.forEach {
    NSLog("%@", "\($0.parameterDescription)")
}
// 方案2:
ImageView.image = try? originImage.make(filter: filter)
// 方案3:
ImageView.image = originImage ->> filter

/// 均值模糊效果
public struct C7MeanBlur: C7FilterProtocol {
    public var radius: Float = 1
    public var modifier: Modifier {
        return .compute(kernel: "C7MeanBlur")
    }
    public var factors: [Float] {
        return [radius]
    }
    public init(radius: Float = 1) {
        self.radius = radius
    }
}

kernel void C7MeanBlur(texture2d<half, access::write> outputTexture [[texture(0)]],
                       texture2d<half, access::sample> inputTexture [[texture(1)]],
                       constant float *blurRadius [[buffer(0)]],
                       uint2 grid [[thread_position_in_grid]]) {
    constexpr sampler quadSampler(mag_filter::linear, min_filter::linear);
    const float2 coordinate = float2(float(grid.x) / outputTexture.get_width(), float(grid.y) / outputTexture.get_height());
    const half radius = half(*blurRadius) / 100.0h;
    const half4 sample1 = inputTexture.sample(quadSampler, float2(coordinate.x - radius, coordinate.y - radius));
    const half4 sample2 = inputTexture.sample(quadSampler, float2(coordinate.x + radius, coordinate.y + radius));
    const half4 sample3 = inputTexture.sample(quadSampler, float2(coordinate.x + radius, coordinate.y - radius));
    const half4 sample4 = inputTexture.sample(quadSampler, float2(coordinate.x - radius, coordinate.y + radius));
    const half4 outColor = (sample1 + sample2 + sample3 + sample4) / 4.0h;
    outputTexture.write(outColor, grid);
}