Metal每日分享，调整胶片颗粒感滤镜效果

// 调节胶片颗粒感滤镜
let filter = C7Granularity.init(grain: 0.7)
// 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

/// 调节胶片颗粒感
public struct C7Granularity: C7FilterProtocol {
    public static let range: ParameterRange<Float, Self> = .init(min: 0.0, max: 0.5, value: 0.3)
    /// The grain size is adjusted by adjusting the grain parameter. The grain size ranges from 0.0 to 0.5,
    /// Where 0.0 represents the original image,
    public var grain: Float = range.value
    public var modifier: Modifier {
        return .compute(kernel: "C7Granularity")
    }
    public var factors: [Float] {
        return [grain]
    }
    public init(grain: Float = range.value) {
        self.grain = grain
    }
}

kernel void C7Granularity(texture2d<half, access::write> outputTexture [[texture(0)]],
                          texture2d<half, access::read> inputTexture [[texture(1)]],
                          constant float *grain [[buffer(0)]],
                          uint2 grid [[thread_position_in_grid]]) {
    const half4 inColor = inputTexture.read(grid);
    const float2 textureCoordinate = float2(float(grid.x) / outputTexture.get_width(), float(grid.y) / outputTexture.get_height());
    const float d = dot(textureCoordinate, float2(12.9898, 78.233) * 2.0);
    const half noise = half(fract(sin(d) * 43758.5453h));
    const half4 outColor = half4(inColor - noise * (*grain));
    outputTexture.write(outColor, grid);
}