Metal每日分享,图像处理色彩丢失和模糊效果

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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;


Demo

效果图

横行纵向偏移横向偏移纵向偏移
WX20221129-145900.pngWX20221129-145951.pngWX20221129-145924.png

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);
}

最后

  • 慢慢再补充其他相关滤镜,喜欢就给我点个星🌟吧。

✌️.