iOS 利用 Metal 实现滤镜与动效滤镜

原始代码：
ImageView.image = originImage
注入滤镜代码：
let filter = C7ColorMatrix4x4(matrix: Matrix4x4.sepia)
ImageView.image = try? originImage.make(filter: filter)

注入边缘检测滤镜
var filter = C7EdgeGlow()
filter.lineColor = UIColor.blue
生成相机采集器
let collector = C7FilterCollector(callback: {
    self.ImageView.image = $0
})
collector.captureSession.sessionPreset = AVCaptureSession.Preset.hd1280x720
collector.filter = filter
ImageView.layer.addSublayer(collector)

public protocol C7FilterProtocol {
     /// 编码器类型和对应的函数名
     ///
     /// 计算需要对应的`kernel`函数名
     /// 渲染需要一个`vertex`着色器函数名和一个`fragment`着色器函数名
     var modifier: Modifier { get }
     /// 制作缓冲区
     /// 设置修改参数因子，需要转换为`Float`。
     var factors: [Float] { get }
     /// 多输入源扩展
     /// 包含 `MTLTexture` 的数组
     var otherInputTextures: C7InputTextures { get }
     /// 改变输出图像的大小
     func outputSize（input size：C7Size）-> C7Size
}

public struct C7SoulOut: C7FilterProtocol {
    /// The adjusted soul, from 0.0 to 1.0, with a default of 0.5
    public var soul: Float = 0.5
    public var maxScale: Float = 1.5
    public var maxAlpha: Float = 0.5
    public var modifier: Modifier {
        return .compute(kernel: "C7SoulOut")
    }
    public var factors: [Float] {
        return [soul, maxScale, maxAlpha]
    }
    public init() { }
}

kernel void C7SoulOut(texture2d<half, access::write> outputTexture [[texture(0)]],
                      texture2d<half, access::sample> inputTexture [[texture(1)]],
                      constant float *soulPointer [[buffer(0)]],
                      constant float *maxScalePointer [[buffer(1)]],
                      constant float *maxAlphaPointer [[buffer(2)]],
                      uint2 grid [[thread_position_in_grid]]) {
    constexpr sampler quadSampler(mag_filter::linear, min_filter::linear);
    const half4 inColor = inputTexture.read(grid);
    const float x = float(grid.x) / outputTexture.get_width();
    const float y = float(grid.y) / outputTexture.get_height();
    const half soul = half(*soulPointer);
    const half maxScale = half(*maxScalePointer);
    const half maxAlpha = half(*maxAlphaPointer);
    const half alpha = maxAlpha * (1.0h - soul);
    const half scale = 1.0h + (maxScale - 1.0h) * soul;
    const half soulX = 0.5h + (x - 0.5h) / scale;
    const half soulY = 0.5h + (y - 0.5h) / scale;
    const half4 soulMask = inputTexture.sample(quadSampler, float2(soulX, soulY));
    const half4 outColor = inColor * (1.0h - alpha) + soulMask * alpha;
    outputTexture.write(outColor, grid);
}

var filter = C7SoulOut()
filter.soul = 0.5
filter.maxScale = 2.0
/// 直接显示在ImageView
ImageView.image = try? originImage.makeImage(filter: filter)

/// 1.转换成BGRA
let filter1 = C7Color2(with: .color2BGRA)
/// 2.调整颗粒度
var filter2 = C7Granularity()
filter2.grain = 0.8
/// 3.调整白平衡
var filter3 = C7WhiteBalance()
filter3.temperature = 5555
/// 4.调整高光阴影
var filter4 = C7HighlightShadow()
filter4.shadows = 0.4
filter4.highlights = 0.5
/// 5.组合操作
let AT = C7FilterTexture.init(texture: originImage.mt.toTexture()!)
let result = AT ->> filter1 ->> filter2 ->> filter3 ->> filter4
/// 6.获取结果
filterImageView.image = result.outputImage()

/// 1.转换成RBGA
let filter1 = C7Color2(with: .color2RBGA)
/// 2.调整颗粒度
var filter2 = C7Granularity()
filter2.grain = 0.8
/// 3.配置灵魂效果
var filter3 = C7SoulOut()
filter3.soul = 0.7
/// 4.组合操作
let group: [C7FilterProtocol] = [filter1, filter2, filter3]
/// 5.获取结果
filterImageView.image = try? originImage.makeGroup(filters: group)

pod 'Harbeth'

pod 'OpencvQueen'