Metal每日分享，图像处理色彩丢失和模糊效果

作者: 弹吉他的少年 | 来源:发表于2022-11-29 09:11 被阅读0次

Metal图像处理——直方图均衡化
Metal每日分享，均值模糊滤镜效果
滤镜
Metal图像处理——颜色查找表（Color Lookup Ta
Metal 渲染视频
高斯模糊
图像模糊处理
图像平滑处理
Metal视频处理——绿幕视频合成
高斯模糊

本案例的目的是理解如何用Metal实现图像包装效果滤镜，用于图像处理色彩丢失和模糊效果；

效果图

WX20221129-145900.png

Demo

HarbethDemo地址

实操代码

// 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

实现原理

过滤器

这款滤镜采用并行计算编码器设计.compute(kernel: "C7ColorPacking")，参数因子[horizontalTexel, verticalTexel]

对外开放参数

horizontalTexel: 横向偏移，越大绿色轮廓虚影向右偏移越多；
verticalTexel: 纵向偏移，越大蓝色轮廓虚影向下偏移越多；

/// 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
    }
}

着色器

纹理坐标和偏移均归一化处理，然后获取到上下左右4个纹理偏移坐标，取出对应的纹理红色值，最后得到像素值；

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);
}

效果图

横行纵向偏移	横向偏移	纵向偏移
1	2	3

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.