Metal每日分享，3×3矩阵卷积滤镜效果-六虎

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本案例的目的是理解如何用Metal完成3×3卷积矩阵作用滤镜，取像素点周边九个区域半径点像素rgb值进行矩阵运算获取新的rgb值;

现在有如下几款卷积核供运用，

default：空卷积核
identity：原始卷积核
edgedetect：边际检测卷积核
embossment：浮雕滤波器卷积核
embossment45：45度的浮雕滤波器卷积核
morphological：腐蚀卷积核
laplance：拉普拉斯算子，边际检测算子
sharpen：锐化卷积核
sobel：边际提取卷积核，求梯度比较常用

Demo

HarbethDemo地址

实操代码

// 锐化卷积作用滤镜
let filter = C7ConvolutionMatrix3x3(convolutionType: .sharpen(iterations: 2))
// 计划1:
let dest = BoxxIO.init(element: originImage, filter: filter)
ImageView.image = try? dest.output()
dest.filters.forEach {
  NSLog("%@", "\($0.parameterDescription)")
}
// 计划2:
ImageView.image = try? originImage.make(filter: filter)
// 计划3:
ImageView.image = originImage ->> filter

完成原理

过滤器

这款滤镜选用并行计算编码器规划.compute(kernel: "C7ConvolutionMatrix3x3")，参数因子[Float(convolutionPixel)]

对外开放参数

convolutionPixel: 卷积像素

/// 3 x 3卷积
public struct C7ConvolutionMatrix3x3: C7FilterProtocol {
    public enum ConvolutionType {
        case `default`
        case identity
        case edgedetect
        case embossment
        case embossment45
        case morphological
        case sobel(orientation: Bool)
        case laplance(iterations: Float)
        case sharpen(iterations: Float)
        case custom(Matrix3x3)
    }
    /// Convolution pixels, default 1
    public var convolutionPixel: Int = 1
    private var matrix: Matrix3x3
    public var modifier: Modifier {
        return .compute(kernel: "C7ConvolutionMatrix3x3")
    }
    public var factors: [Float] {
        return [Float(convolutionPixel)]
    }
    public func setupSpecialFactors(for encoder: MTLCommandEncoder, index: Int) {
        guard let computeEncoder = encoder as? MTLComputeCommandEncoder else { return }
        var factor = matrix.to_factor()
        computeEncoder.setBytes(&factor, length: Matrix3x3.size, index: index + 1)
    }
    public init(matrix: Matrix3x3) {
        self.matrix = matrix
    }
    public init(convolutionType: ConvolutionType) {
        self.init(matrix: convolutionType.matrix)
    }
    public mutating func updateConvolutionType(_ convolutionType: ConvolutionType) {
        self.matrix = convolutionType.matrix
    }
    public mutating func updateMatrix3x3(_ matrix: Matrix3x3) {
        self.matrix = matrix
    }
}
extension C7ConvolutionMatrix3x3.ConvolutionType {
    var matrix: Matrix3x3 {
        switch self {
        case .identity:
            return Matrix3x3.Kernel.identity
        case .edgedetect:
            return Matrix3x3.Kernel.edgedetect
        case .embossment:
            return Matrix3x3.Kernel.embossment
        case .embossment45:
            return Matrix3x3.Kernel.embossment45
        case .morphological:
            return Matrix3x3.Kernel.morphological
        case .sobel(let orientation):
            return Matrix3x3.Kernel.sobel(orientation)
        case .laplance(let iterations):
            return Matrix3x3.Kernel.laplance(iterations)
        case .sharpen(let iterations):
            return Matrix3x3.Kernel.sharpen(iterations)
        case .custom(let matrix3x3):
            return matrix3x3
        default:
            return Matrix3x3.Kernel.`default`
        }
    }
}

着色器

取像素点周边九个区域半径点像素，然后归一化处理，然后取出每个像素对应rgb，再进行卷积矩阵运算得到卷积之后的rgb值，生成新的像素色彩；

kernel void C7ConvolutionMatrix3x3(texture2d<half, access::write> outputTexture [[texture(0)]],
                                   texture2d<half, access::sample> inputTexture [[texture(1)]],
                                   constant float *pixel [[buffer(0)]],
                                   constant float3x3 *matrix3x3 [[buffer(1)]],
                                   uint2 grid [[thread_position_in_grid]]) {
    constexpr sampler quadSampler(mag_filter::linear, min_filter::linear);
    const float x = float(grid.x);
    const float y = float(grid.y);
    const float w = float(inputTexture.get_width());
    const float h = float(inputTexture.get_height());
    const float l = float(x - *pixel);
    const float r = float(x + *pixel);
    const float t = float(y - *pixel);
    const float b = float(y + *pixel);
    // Normalization
    const float2 m11Coordinate = float2(l / w, t / h);
    const float2 m12Coordinate = float2(x / w, t / h);
    const float2 m13Coordinate = float2(r / w, t / h);
    const float2 m21Coordinate = float2(l / w, y / h);
    const float2 m22Coordinate = float2(x / w, y / h);
    const float2 m23Coordinate = float2(r / w, y / h);
    const float2 m31Coordinate = float2(l / w, b / h);
    const float2 m32Coordinate = float2(x / w, b / h);
    const float2 m33Coordinate = float2(r / w, b / h);
    const half4 centerColor = inputTexture.sample(quadSampler, m22Coordinate);
    const half3 m11Color = inputTexture.sample(quadSampler, m11Coordinate).rgb;
    const half3 m12Color = inputTexture.sample(quadSampler, m12Coordinate).rgb;
    const half3 m13Color = inputTexture.sample(quadSampler, m13Coordinate).rgb;
    const half3 m21Color = inputTexture.sample(quadSampler, m21Coordinate).rgb;
    const half3 m22Color = centerColor.rgb;
    const half3 m23Color = inputTexture.sample(quadSampler, m23Coordinate).rgb;
    const half3 m31Color = inputTexture.sample(quadSampler, m31Coordinate).rgb;
    const half3 m32Color = inputTexture.sample(quadSampler, m32Coordinate).rgb;
    const half3 m33Color = inputTexture.sample(quadSampler, m33Coordinate).rgb;
    const float3x3 matrix = (*matrix3x3);
    half3 resultColor = half3(0.0h);
    resultColor += m11Color * (matrix[0][0]) + m12Color * (matrix[0][1]) + m13Color * (matrix[0][2]);
    resultColor += m21Color * (matrix[1][0]) + m22Color * (matrix[1][1]) + m23Color * (matrix[1][2]);
    resultColor += m31Color * (matrix[2][0]) + m32Color * (matrix[2][1]) + m33Color * (matrix[2][2]);
    const half4 outColor = half4(resultColor, centerColor.a);
    outputTexture.write(outColor, grid);
}

其他卷积核

extension Matrix3x3 {
  /// 常见 3x3 矩阵卷积内核，考线性代数时间
  /// Common 3x3 matrix convolution kernel
  public struct Kernel { }
}
extension Matrix3x3.Kernel {
  /// 原始矩阵，空卷积核
  /// The original matrix, the empty convolution kernel
  public static let `default` = Matrix3x3(values: [
    0.0, 0.0, 0.0,
    0.0, 1.0, 0.0,
    0.0, 0.0, 0.0,
  ])
  public static let identity = Matrix3x3(values: [
    1.0, 0.0, 0.0,
    0.0, 1.0, 0.0,
    0.0, 0.0, 1.0,
  ])
  /// 边际检测矩阵
  /// Edge detection matrix
  public static let edgedetect = Matrix3x3(values: [
    -1.0, -1.0, -1.0,
    -1.0, 8.0, -1.0,
    -1.0, -1.0, -1.0,
  ])
  /// 浮雕矩阵
  /// Anaglyph matrix
  public static let embossment = Matrix3x3(values: [
    -2.0, 0.0, 0.0,
    0.0, 1.0, 0.0,
    0.0, 0.0, 2.0,
  ])
  /// 45度的浮雕滤波器
  /// A 45 degree emboss filter
  public static let embossment45 = Matrix3x3(values: [
    -1.0, -1.0, 0.0,
    -1.0, 0.0, 1.0,
    0.0, 1.0, 1.0,
  ])
  /// 腐蚀矩阵
  /// Matrix erosion
  public static let morphological = Matrix3x3(values: [
    1.0, 1.0, 1.0,
    1.0, 1.0, 1.0,
    1.0, 1.0, 1.0,
  ])
 
  /// 拉普拉斯算子，边际检测算子
  /// Laplace operator, edge detection operator
  public static func laplance(_ iterations: Float) -> Matrix3x3 {
    let xxx = iterations
    return Matrix3x3(values: [
      0.0, -1.0, 0.0,
      -1.0, xxx, -1.0,
      0.0, -1.0, 0.0,
    ])
  }
 
  /// 锐化矩阵
  /// Sharpening matrix
  public static func sharpen(_ iterations: Float) -> Matrix3x3 {
    let cc = (8 * iterations + 1)
    let xx = (-iterations)
    return Matrix3x3(values: [
      xx, xx, xx,
      xx, cc, xx,
      xx, xx, xx,
    ])
  }
 
  /// Sobel矩阵图像边际提取，求梯度比较常用
  /// Sobel matrix image edge extraction, gradient is more commonly used
  public static func sobel(_ orientation: Bool) -> Matrix3x3 {
    if orientation {
      return Matrix3x3(values: [
        -1.0, 0.0, 1.0,
        -2.0, 0.0, 2.0,
        -1.0, 0.0, 1.0,
      ])
    } else {
      return Matrix3x3(values: [
        -1.0, -2.0, -1.0,
        0.0, 0.0, 0.0,
        1.0, 2.0, 1.0,
      ])
    }
  }
 
  /// BT.601, which is the standard for SDTV.
  public static let to601 = Matrix3x3(values: [
    1.164, 1.164, 1.164,
    0.000, -0.392, 2.017,
    1.596, -0.813, 0.000,
  ])
 
  /// BT.601 full range (ref: http://www.equasys.de/colorconversion.html)
  public static let to601FullRange = Matrix3x3(values: [
    1.0, 1.000, 1.000,
    0.0, -0.343, 1.765,
    1.4, -0.711, 0.000,
  ])
 
  /// BT.709, which is the standard for HDTV.
  public static let to709 = Matrix3x3(values: [
    1.164, 1.164, 1.164,
    0.000, -0.213, 2.112,
    1.793, -0.533, 0.000,
  ])
}

作用图

常见核卷积图

边际检测矩阵	浮雕矩阵	45度的浮雕滤波器

锐化矩阵	拉普拉斯算子	Sobel矩阵图像边际提取

Harbeth功能清单

支撑ios体系和macOS体系
支撑运算符函数式操作
支撑多种模式数据源 UIImage, CIImage, CGImage, CMSampleBuffer, CVPixelBuffer.
支撑快速规划滤镜
支撑兼并多种滤镜作用
支撑输出源的快速扩展
支撑相机收集特效
支撑视频添加滤镜特效
支撑矩阵卷积
支撑运用体系 MetalPerformanceShaders.
支撑兼容 CoreImage.
滤镜部分大致分为以下几个模块：
- Blend：图像融合技能
- Blur：含糊作用
- Pixel：图像的根本像素色彩处理
- Effect：作用处理
- Lookup：查找表过滤器
- Matrix: 矩阵卷积滤波器
- Shape：图像形状大小相关
- Visual: 视觉动态特效
- MPS: 体系 MetalPerformanceShaders.

最后

关于3×3矩阵卷积作用滤镜介绍与规划到此为止吧。
渐渐再补充其他相关滤镜，喜爱就给我点个星吧。
滤镜Demo地址，现在包括100+种滤镜，一起也支撑CoreImage混合运用。
再附上一个开发加速库KJCategoriesDemo地址
再附上一个网络根底库RxNetworksDemo地址
喜爱的老板们能够点个星，谢谢各位老板！！！

✌️.

Metal每日分享，3×3矩阵卷积滤镜效果

Demo

实操代码

完成原理

其他卷积核

作用图

Harbeth功能清单

最后

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