Metal每日分享，图像处理色彩丢失和模糊效果

// 色彩丢失和模糊效果
let filter = C7ColorPacking.init(horizontalTexel: 2.5, verticalTexel: 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

/// 色彩丢失/模糊效果
public struct C7ColorPacking: C7FilterProtocol {
    /// The larger the transverse offset, the more the green contour shadow offset to the right.
    public var horizontalTexel: Float
    /// The larger the vertical offset, the more the blue contour shadow offset downward.
    public var verticalTexel: Float
    public var modifier: Modifier {
        return .compute(kernel: "C7ColorPacking")
    }
    public var factors: [Float] {
        return [horizontalTexel, verticalTexel]
    }
    public init(horizontalTexel: Float = 0, verticalTexel: Float = 0) {
        self.horizontalTexel = horizontalTexel
        self.verticalTexel = verticalTexel
    }
}

kernel void C7ColorPacking(texture2d<half, access::write> outputTexture [[texture(0)]],
                           texture2d<half, access::sample> inputTexture [[texture(1)]],
                           device float *texelWidthPointer [[buffer(0)]],
                           device float *texelHeightPointer [[buffer(1)]],
                           uint2 grid [[thread_position_in_grid]]) {
    constexpr sampler quadSampler(mag_filter::linear, min_filter::linear);
    const float width  = outputTexture.get_width();
    const float height = outputTexture.get_height();
    const float texelWidth  = float(*texelWidthPointer / width);
    const float texelHeight = float(*texelHeightPointer / height);
    const float2 textureCoordinate = float2(float(grid.x) / width, float(grid.y) / height);
    const float2 upperLeftTextureCoordinate = textureCoordinate + float2(-texelWidth, -texelHeight);
    const float2 upperRightTextureCoordinate = textureCoordinate + float2(texelWidth, -texelHeight);
    const float2 lowerLeftTextureCoordinate = textureCoordinate + float2(-texelWidth, texelHeight);
    const float2 lowerRightTextureCoordinate = textureCoordinate + float2(texelWidth, texelHeight);
    half upperLeftIntensity = inputTexture.sample(quadSampler, upperLeftTextureCoordinate).r;
    half upperRightIntensity = inputTexture.sample(quadSampler, upperRightTextureCoordinate).r;
    half lowerLeftIntensity = inputTexture.sample(quadSampler, lowerLeftTextureCoordinate).r;
    half lowerRightIntensity = inputTexture.sample(quadSampler, lowerRightTextureCoordinate).r;
    const half4 outColor = half4(upperLeftIntensity, upperRightIntensity, lowerLeftIntensity, lowerRightIntensity);
    outputTexture.write(outColor, grid);
}