Metal每日分享，UV去雾滤镜效果

// 去雾效果滤镜
let filter = C7Haze.init(distance: 0.5, slope: 0.5)
// 方案1:
ImageView.image = try? BoxxIO(element: originImage, filters: [filter, filter2, filter3]).output()
// 方案2:
ImageView.image = originImage.filtering(filter, filter2, filter3)
// 方案3:
ImageView.image = originImage ->> filter ->> filter2 ->> filter3

/// 去雾，类似于UV过滤器
public struct C7Haze: C7FilterProtocol {
    /// Strength of the color applied.
    public var distance: Float = 0
    /// Amount of color change.
    public var slope: Float = 0
    public var modifier: Modifier {
        return .compute(kernel: "C7Haze")
    }
    public var factors: [Float] {
        return [distance, slope]
    }
    public init(distance: Float = 0, slope: Float = 0) {
        self.distance = distance
        self.slope = slope
    }
}

kernel void C7Haze(texture2d<half, access::write> outputTexture [[texture(0)]],
                   texture2d<half, access::read> inputTexture [[texture(1)]],
                   constant float *hazeDistance [[buffer(0)]],
                   constant float *slope [[buffer(1)]],
                   uint2 grid [[thread_position_in_grid]]) {
    const half4 inColor = inputTexture.read(grid);
    const half4 white = half4(1.0h);
    const half dd = half(grid.y) / half(inputTexture.get_height()) * half(*slope) + half(*hazeDistance);
    const half4 outColor = half4((inColor - dd * white) / (1.0h - dd));
    outputTexture.write(outColor, grid);
}