Metal每日分享，连环画滤镜和油画滤镜效果
本案例的目的是理解如何用Metal实现连环画滤镜和油画滤镜，将图像处理成连环画和油画效果；
Demo
HarbethDemo地址
实操代码
// 连环画效果 let filter = C7ComicStrip.init() // 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 复制代码
连环画实现原理
过滤器
这款滤镜采用并行计算编码器设计.compute(kernel: "C7ComicStrip")
/// 连环画滤镜 public struct C7ComicStrip: C7FilterProtocol { public var modifier: Modifier { return .compute(kernel: "C7ComicStrip") } public init() { } } 复制代码着色器
获取到红色值abs(g - b + g + r) * r绝对值，绿色abs(b - g + b + r) * r，蓝色abs(b - g + b + r) * g，最后获取到像素颜色；
kernel void C7ComicStrip(texture2d<half, access::write> outputTexture [[texture(0)]], texture2d<half, access::read> inputTexture [[texture(1)]], uint2 grid [[thread_position_in_grid]]) { const half4 inColor = inputTexture.read(grid); const half r = inColor.r; const half g = inColor.g; const half b = inColor.b; const half R = half(abs(g - b + g + r) * r); const half G = half(abs(b - g + b + r) * r); const half B = half(abs(b - g + b + r) * g); const half4 outColor = half4(R, G, B, inColor.a); outputTexture.write(outColor, grid); } 复制代码油画实现原理
过滤器
这款滤镜采用并行计算编码器设计.compute(kernel: "C7OilPainting")，参数因子[radius, Float(pixel)]
对外开放参数
radius: 模糊半径；pixel: 像素颗粒度；
/// 油画滤镜 public struct C7OilPainting: C7FilterProtocol { public var radius: Float = 3.0 public var pixel: Int = 1 public var modifier: Modifier { return .compute(kernel: "C7OilPainting") } public var factors: [Float] { return [radius, Float(pixel)] } public init(radius: Float = 3.0, pixel: Int = 1) { self.radius = radius self.pixel = pixel } } 复制代码着色器
kernel void C7OilPainting(texture2d<half, access::write> outputTexture [[texture(0)]], texture2d<half, access::sample> inputTexture [[texture(1)]], constant float *radius [[buffer(0)]], constant float *pixel [[buffer(1)]], uint2 grid [[thread_position_in_grid]]) { constexpr sampler quadSampler(mag_filter::linear, min_filter::linear); const float2 size = float2(*pixel) / float2(outputTexture.get_width(), outputTexture.get_height()); const float2 textureCoordinate = float2(grid) / float2(outputTexture.get_width(), outputTexture.get_height()); const float r = float(*radius); const float n = float((r + 1.0) * (r + 1.0)); float3 m0 = float3(0.0); float3 m1 = float3(0.0); float3 s0 = float3(0.0); float3 s1 = float3(0.0); float3 color = float3(0.0); for (float j = -r; j <= 0.0; ++j) { for (float k = -r; k <= 0.0; ++k) { color = float3(inputTexture.sample(quadSampler, textureCoordinate + float2(k,j) * size).rgb); m0 += color; s0 += color * color; } } for (float j = -r; j <= 0.0; ++j) { for (float k = 0.0; k <= r; ++k) { color = float3(inputTexture.sample(quadSampler, textureCoordinate + float2(k,j) * size).rgb); m1 += color; s1 += color * color; } } half4 outColor = half4(0.0h); float min_sigma2 = 100.0; m0 /= n; s0 = abs(s0 / n - m0 * m0); float sigma2 = s0.r + s0.g + s0.b; if (sigma2 < min_sigma2) { min_sigma2 = sigma2; outColor = half4(half3(m0), 1.0h); } m1 /= n; s1 = abs(s1 / n - m1 * m1); sigma2 = s1.r + s1.g + s1.b; if (sigma2 < min_sigma2) { min_sigma2 = sigma2; outColor = half4(half3(m1), 1.0h); } outputTexture.write(outColor, grid); } 复制代码效果图
| 原图 | 连环画 | 油画 |
|---|---|---|
Harbeth功能清单
支持ios系统和macOS系统
支持运算符函数式操作
支持多种模式数据源 UIImage, CIImage, CGImage, CMSampleBuffer, CVPixelBuffer.
支持快速设计滤镜
支持合并多种滤镜效果
支持输出源的快速扩展
支持相机采集特效
支持视频添加滤镜特效
支持矩阵卷积
支持使用系统 MetalPerformanceShaders.
支持兼容 CoreImage.
滤镜部分大致分为以下几个模块：
Blend：图像融合技术
Blur：模糊效果
Pixel：图像的基本像素颜色处理
Effect：效果处理
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: 系统 MetalPerformanceShaders.
作者：茶底世界之下
链接：https://juejin.cn/post/7172371363641229326