本案例的目的是理解如何用Metal实现调节胶片颗粒感滤镜，通过调整颗粒参数来调整晶粒尺寸来达到颗粒感效果；

Demo

  • HarbethDemo地址

实操代码

// 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

实现原理

  • 过滤器

这款滤镜采用并行计算编码器设计.compute(kernel: "C7Granularity")，参数因子[grain]

对外开放参数

  • grain: 通过调整颗粒参数来调整晶粒尺寸，大小从0.0到0.5不等，其中0.0代表原始图像。
/// 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.valuepublic var modifier: Modifier {return .compute(kernel: "C7Granularity")}public var factors: [Float] {return [grain]}public init(grain: Float = range.value) {self.grain = grain}
}
  • 着色器

对坐标点归一化处理，计算出小数部分noise，最后对每个像素x颗粒度；

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);
}

Harbeth功能清单

最后